Trees have stories to tell, their annual growth rings cataloging changes in the environment, including climate. Many tree-ring scientists focus on conifers, but Neil Pederson, a scientist at Lamont-Doherty Earth Observatory, believes that the less-studied broadleaf trees in temperate forests, such as magnolia, tulip-poplar, maple and birch, have much to teach us.
I walked out of the house Thursday morning when my nose detected it – a forest fire! Having worked for two years in the piney woods of southwest Georgia, I had become accustomed to and, actually, come to love forest fires. That classic line kept coming into my mind, “the scent of fire in the morning reminds me of healthy forests.” The scent can be better than a campfire. It can be a little sweeter. That morning, it filled the entire town. Firefighters were just beginning to quench the fire. As of Saturday night, it had burned about 40 ha (ca 100 acres), but was still uncontained on its northern end. I might have been one of the few people to be thrilled to be in a smoke-filled town. It reminded me that we lived in a heavily forested area, and an active ecological event was playing out just up the hill.
It was fascinating to see the coverage of this fire. There were many resources thrown at it. It is understandable. Clausland Mountain is beautiful, beautiful enough that it is ringed by expensive houses. Twenty-six fire units, composed of about 150 firefighters, were actively fighting the fire (about one fire unit for every 1.5 hectares (3.8 acres)). Two helicopters were brought in to douse the flames. The breathless words of the reporter are fascinating as well, “remote areas” and “extremely dangerous.”
The large response is what happens in the wildland-urban interface, especially outside of one of the largest cities in the world. The conflict between humans and ecological processes has been on the rise as we move out into natural areas and as we become more aware of important ecological processes that maintain ecosystems and the services they provide for humanity. Fire is one of these processes.
So, Sunday we went on a hike to see the impact of the fire. Bushwhacking, we went into the northern end where the fire was still smoldering (though the fire took care of many bushes). It is steep and the ash makes the slope a bit slippery. Much of the leaf litter was consumed, though not completely. In some places, logs were consumed down to the mineral soil. Death shadows are evident. The potentially severe rainstorms approaching from the west should put out the fire. (Update: they did.)
It will be interesting to see how the forest responds. Fire is an important ecological process. It reduces the disease and pest load in an ecosystem; it is an antiseptic in a way. It favors some plants more than others. Like me, fire favors blueberries! Oak trees in the eastern United States do not seem to be regenerating very well over the last 40-50 years. The re-introduction of fire is today’s response to a lack of oak regeneration. Much money is being spent on prescribed fires and education about fire. The lack of oak regeneration seems complex. It is said that the rise of mesophytic species, the species “taking the place” of oak, is changing the forest in such a way that it ecologically dampens the forest, making it hard for fire to take hold. However, the re-introduction of fire doesn’t seem to be having its hypothesized impact – oaks still do not seem to be regenerating in experiments employing fire, while mesophytic species seem to be handling the fire pretty well. Important for the context of this ecological scenario, many changes have occurred in the forest over the last 50-100 years, all of which could be a factor of a reduction in oak regeneration – increased deer populations, loss of important megafauna, and changing land-use and cultural patterns (Hello Smoky Bear!). And, climate change might be playing a direct role in the “mesophication” of the East.
One physical mechanism has been detected – flammability of and differential drying of forest fuels (leaves). Fire is a very physical process. The variation in forest fuels, especially the finer fuels that carry fire in wetter regions, plays an important role in flammability. Thinner leaves absorb moisture more easily. Large, curling leaves, especially lobed leaves, dry faster. Curling leaves make the duff (or “litter”*), the fuel layer, fluffier, allowing better oxygenation of fire, to literally fuel the fire even more. One hypothesis for why eastern forests burn less is the loss of the great American icon, the American chestnut tree. Research by Morgan Varner supports this hypothesis.
It will be especially interesting to see how the Clausland forest responds to this fire. It is getting much wetter in this part of the world. Deer populations are high because of the high human density and the amount of forest preserve in the county (there is no hunting in the area, and deer have learned home gardens are a smörgåsbord). And, the diversity in this little patch of woods is pretty amazing. On our 0.5-mile hike, if that (our 2-year-old doesn’t hike great yet), I spotted 13 major broadleaf tree species, one conifer, the fading eastern hemlock, and two small tree species (I wasn’t even trying to seek out species; there must be more). Amazingly, yellow birch, a boreal species more common to the Adirondacks, New England and southeastern Canada, is mixed in with pignut hickory and sweet birch, species more common to Virginia.
The understory might respond a little differently, though in the little patch we hiked, the wineberry looked just fine. Guess we’ll have to go back out and hike a little more next spring. Shucks.
A pictorial of the aftermath of the November 2013 Clausland Mountain fire.
We met a colleague and his wife on the trail. They were out to check out the fire. They live near the burn and watched the fire grow and the efforts to stop the fire. She noted that it was like a ring of fire. Absolutely!
* = really? Can we get rid of the term “litter”? Fallen leaves, twigs, branches, bud scales, etc., enrich the soil by returning nutrients back to the Earth and increasing the soil’s ability to retain moisture. If that is “litter,” call me trash.
It was midday. It was dark. It was June! It was pouring. We were sitting in my folk’s cabin in the Adirondacks when my dad groaned, “This is depressing”. Later on that same day, a hometown friend made a similar exclamation. Elizabeth’s update triggered a deluge of similar sentiments. During that discussion, she made reference to The Long Rain. It was the perfect comparison. Judging from the sentiment in our cabin, in the newspapers, and on Facebook, Central New York was on the edge of insanity because of the unrelenting rain.
It was too early in the season to write this post. Predicting future rainfall is like trying to predict Dennis Rodman’s next career move: It will move in a new direction, but no one can pinpoint the trajectory. But now, as Cortland and Macoun apples grace us with their presence, we can now safely say that summer is over (I do not care what the tilt of the Earth says. It is apple season!). In fact, the Northeast Regional Climate Center and NOAA have completed an early overview of this past summer’s climate. Their conclusion regarding precipitation in the Northeastern US? The Pluvial continues.
Actually, these overviews typically discuss climate of just the most recent month or season year or versus the “climate normal.” While useful, these summaries do not paint the full picture. Consider this: A climate normal is often based on a recent 30-year period, like 1970-2000. Now consider this: Instrumental records for the Northeastern U.S. (below) and analyses for the Catskills region and southern New York State, here and here, indicate that since the 1960s drought, the region has seen a substantial increase in precipitation; in fact, hydroclimate seems quite unusual since 2000. Now really consider this: A tree-ring reconstruction of moisture availability indicates that the recent wetting comes at the end of a 120-180 year trend (and maybe longer). So, the daily comparisons on TV or other media sources are typically based upon recent climate and ignore the past. Thus, based upon paleo records, the full picture indicates that we are sitting in one of the more unusually wet periods of the last 500 years.
I return to this topic because of: 1) the many implications of this climatic shift and, most importantly, 2) what seems to be a limited amount of public awareness of how wet it has become in recent decades (though this awareness is growing). The substantial change in moisture across the Northeastern U.S. (the draft of the 2013 3rd assessment is here) is more commonly known in the scientific literature, but it seems to be less well-known outside of that community. For example, under the tab “Climate Change” on the Northeast Regional Climate Center’s excellent web resource, one can only find minimum and maximum temperatures when seeking to understand how much the climate has changed. An increasing trend in precipitation just doesn’t seem to grip the attention of most people like an intense heat wave or drought. In fact, an editor remarked to a freelance writer that they’d only do a story on the change in precipitation in the NYC region if “they were painting the lawns green on Staten Island.”
For the people in Vermont, the Catskills, Mohawk Valley, and those wishing to use beaches in the summer along the coast, this seems a bit short-sighted. Excess rain is costly. It costs the people still trying to rebuild in the Catskills from the flooding of 2011 (and it isn’t just the two tropical storms that triggered the flooding – new research indicates that because the soils were saturated, the impact of Irene and Lee were worse than they might have been in other times). It costs people in Vermont wanting to rebuild their cultural heritage. It will cost all of us in NY State if tax breaks are given to expand flood relief measures in five counties and restoration and reconstruction of managed water systems; climatic change disregards political boundaries. It might cost us if we are managing forests for a long-gone climatic era. It further erodes trust between country and city folk as well as citizens and their government. Tragically, it costs lives.
So, as we become aware of the impacts of additional rainfall (and certainly there are additional costly impacts than what is listed above), we need to know that precipitation is likely to increase over the coming century. Model projections indicate it is likely that the Northeast will get wetter and have more extreme rain events. This doesn’t mean we will not experience droughts in the future, nor does it mean each summer will be like 2011 or 2013. And, these model projections could be wrong. But, our state of knowledge indicates that these Long Rain conditions could become more common.
This shouldn’t be viewed as more environmental doom and gloom. Humans have enormous brains and know how to use them! See: Klaus Jacob. We have the ability to prepare for potential adversity. And, if it isn’t clear by now, humans are one of the more adaptable and flexible animals on the planet. Heck, we might even celebrate wetter conditions with some enormous fun. And, from my Broadleaf perspective, the Northeast could become a temperate rainforest with bigger trees and a denser forest.* Folks spend enormous money to experience such things.
* unless future warming overwhelms our rain wealth and stunts the future forest…. apologies. It is hard to avoid all of the potential doom and gloom…
By Ana Camila Gonzalez
When we walked into the Sheraton in Springfield, Massachusetts we were greeted by none other than a wall full of cross sections from trees perfectly sanded to reveal the rings.
“No way” I say. “I forgot the camera!” says Neil.
We were just walking into the Northeast Natural History Conference, along with Dario and Jackie from the Tree Ring Lab. When I pictured my freshman year of college last summer, I pictured a lot of things. I did not picture getting to go to a conference to present a poster on my own research.
On the first day we listened to talks given by people who dealt with everything from conservation science to birds and berries and beetles. I’ve gone to multiple talks at Lamont, but those talks are mostly geared towards graduate students, so I’m always the slightest bit lost listening to them. This conference seemed to be geared towards a wider audience: I could actually understand the talks. I couldn’t believe it at first. After the first day I knew a little more about a wide range of topics: I can now tell you about the reproductive cycle of a lobster, what kind of fruits allow birds to fly farther during migration and even the life cycle of an Emerald Ash Borer in a tree.
I also learned more about the research process, since many people were presenting research projects that we weren’t already familiar with. I thought there was only a specific set of proxies for climate, but I found that people are continually finding more and more. I listened as someone described how they were using a mountainside as a proxy for climate change, and I realized that one of the great things about environmental science is that you can use the world as your lab, in many cases literally.
That afternoon during lunch we were told to make sure our GPS systems were safely hidden in our car. We were warned that we had to realize that we were now in a “big city.” We joked at our table—all being from New York—about how Springfield didn’t seem like a big city at all. I liked the thought, however, of a field of science where so many people are able to work in small rural towns that they do see Springfield as a big city. Want to know a secret? As much as I like school in the Big Apple, and I see myself living the city life for a while after school, I don’t see myself living anywhere with a population over five thousand after that.
Everyone in the lab was scheduled to present the next day. I was scheduled to give a poster, but Jackie, a Senior undergrad at Columbia, was scheduled to give a talk: we were both freaking out in the hotel room that night, but she probably had more justification. That night Jackie, Neil and Dario went through their talks while I made a big deal over how to cut my poster. Jackie ended up cutting it for me; my hands were too shaky. I must have asked a million questions to prepare that no one ever actually asked me, but by the end of that night I felt ready. “At least I’m not giving a talk!” That didn’t really calm Jackie’s nerves.
The next morning we had an awesome breakfast, I bought a piece of flan for no apparent reason, and we headed to the conference. I set up my poster and less than a half hour later sat to watch Jackie, Dario and Neil give their talks back to back. They were all wonderful, and some questions were asked that sparked some good conversation. Someone made a comment about baldcypress, and my ears turned up at the corners. She was mentioning how incredibly sensitive it was to drought, and I have to admit I got a little too excited. I talked to her afterwards: “That makes so much sense! I’ve been trying to cross-date this batch of baldcypress for so long, and it seems like every drought year thus far has produced either a narrow, missing or micro ring, and yeah, like you mentioned, isn’t it crazy that they’re so sensitive…” yeah, I was a little over-excited. It worked out well, because I had to go stand by my poster directly afterwards.
This is it. I’m standing by my poster. Someone comes up to me. THEY’RE GOING TO ASK ME SOMETHING I CAN’T ANSWER… THEY’RE GOING TO… “Hey, so can you tell me a bit about what you did?”
Wait. Really? I can do that!
The rest of the poster session went well. I was asked more than “can you tell me about your poster,” but it wasn’t half as bad as I had imagined. There were many questions I could answer, and there were many that I couldn’t. I ended up liking the questions I couldn’t answer more, however, because they told me what to do next. The same scientist who I had talked to previously about the baldcypress caught me off guard when she told me she’d look forward to reading about my findings in a paper. I hadn’t thought about it before, but I guess that’s my next step: take the unanswerables and answer them.
All in all, I learned more than I ever thought I could at the North East Natural History Conference, and walked away with much more than just natural history. I’m more excited than ever for what’s to come.
Ana Camila Gonzalez is finally out of the woods. She has, essentially, completed her first-year as a student in environmental science and creative writing at the Tree Ring Laboratory of Columbia University and Lamont-Doherty Earth Observatory. She has completed her blogging on the process of tree-ring analysis, from field work to scientific presentations…for now. We are happy to announce that she will be working with us for Summer 2013.
By Ana Camila Gonzalez
“You can do math on excel?” I ask. I immediately imagine a face-palm response, but Dario, one of my advisors, is nice enough to hide it. I’ve collected tree core samples, I’ve prepared them and cross-dated them. Now what?
Oh, right. The Science.
I guess I never really understood there could be so much involved in answering a question. When I imagine the scientific method I’ve learned since the sixth grade, I somehow imagine a question that can be answered with a yes or no. If I let go of this apple, will it fall to the ground? Hypothesis: yes, it will. Experiment: yes, it does. Conclusion: yes, it will. To the credit of my high school science teachers, it’s not that they didn’t make it perfectly clear that the why and the how are just as important as the yes or the no. I just couldn’t imagine that you’d have to explain why the apple falls with four different figures: haven’t you seen an apple fall too?
Dario is helping me understand how to analyze the data from the black oak samples I have already been working with for some time now. I know these samples. Or at least I think I know these samples. I’m learning there’s more to know about them than I initially thought.
We’re analyzing the climate response, which proves to be exactly what it sounds like. We have recorded measurements of climate (precipitation records, temperature records) and a proxy for tree growth (our ring width measurements!) and by comparing those we can see how a tree population responds to a range of climactic conditions. Alright. I can do this. I’ve made graphs before.
“So we’re going to find correlations,” says Dario.
“Click on an empty cell.” I start to make a scatter plot; I think what we’re going to do is look at the slope of a line of best fit.
“So we’re going to see if the correlation is positive or negative?” I ask.
“Yes, but we also have to see if the correlations are significant.” Isn’t any correlation higher than a zero significant? They’re showing a relationship.
Dario continues, “Any correlation above a 0.2 or so is significant for the hundred years of ring width and climate that you have for this analysis.” I learn how to use the =correl function to compare the populations to temperature and I have to say I’m disappointed. I thought 0.2 sounded so low, but some of my data is showing a much lower correlation, and the data that is significant only ranges from about really close to 0.2 to 0.38 or so. I wanted to see a 0.5 correlation like I did between tree samples within a species as I was cross-dating. Comparing precipitation to ring width gives me slightly higher correlations, a few in the 0.3 range, but I’m still feeling underwhelmed.
“No, but it’s still significant! It matters!” Dario tells me to make a scatter plot comparing precipitation to ring-width measurements over time at both sites. At first it looks like a ball of yarn, but as I mask the plot out I can see why those 0.3 correlations are significant. I follow each curve, visually skateboarding up and down the peaks and valleys and noticing that I’m going up and down a lot of very similar hills as I do so. What’s most rewarding is looking for years I know are drought years (1966 and 1954 were big droughts) and seeing relatively low measures of precipitation and ring width during those years. I knew while I was cross-dating that those years were important when I saw how small the rings were, but now I can prove it. Like the apple falling, I can’t just say that because I see the rings are small those were dry years. I have to compare it to precipitation records, temperature records, and, dare I say it, the Palmer Drought Severity Index (I have to admit I don’t entirely understand the mechanics behind the index, but I understand that dryness is a composite of precipitation and temperature forcings).
Dario, over multiple days, teaches me a few more nuances of Excel and helps me understand the ARSTAN program and how we use it to make our ring-width measurements more effective as proxies for tree growth. He mentions this would all be easier if I knew how to use R. I make a mental note: learning R is the next step. If I thought that was scary, now I have to put this information on a poster. That real people will see. At a real conference.
Neil shows me a few poster examples, and the message is clear. Show your data instead of describing it in words. That also means I’ll have to explain my data by actually… talking… about it. Gulp. The North East Natural History Conference is next weekend, but I feel like I’m ready. I understand the why and how after analyzing my data. At least I understand it enough to give an answer better than yes or no.
Ana Camila Gonzalez is a first-year environmental science and creative writing student at Columbia University at the Tree Ring Laboratory of Lamont-Doherty Earth Observatory. She will be blogging on the process of tree-ring analysis, from field work to scientific presentations.
By Ana Camila Gonzalez
Ever since I’ve started learning to cross-date tree core samples, I’ve learned I have a type. I prefer my tree cores to be black oaks, middle-aged, with some nice big rings to show me. Alright, fine, I can deal with some smaller rings every now and then. As long as they’re some nice marker rings.
Unfortunately, the trees don’t seem to be trying to impress me.
I was told on a fifth grade field trip that you could tell the age of a tree by chopping it down and counting from the ring on the outside, which represents the current year, to the inside ring, which represents the year it started to grow. I’m coming to learn at the Tree Ring Laboratory of Lamont-Doherty Earth Observatory that there are a few problems with that statement.
Primarily, you don’t have to chop the tree down. I learned while doing fieldwork that coring a tree does not damage it at all. More importantly however, you can’t always find the exact age of a tree by simply counting the rings backwards. One has to verify the years you assigned to each ring against other samples, and, occasionally, against known climatic or ecological events. Sometimes a ring can be missing, possibly from either a very dry year or insect defoliation that causes a lack of growth on the side of the tree you’re looking at. Sometimes a ring is there, but it’s tiny; so small you need a microscope to see it: a micro ring. And this is where cross dating comes in.
I sit down to cross date my first batch of samples, black oaks from 2003, with rings I can see without using a microscope. I use the microscope regardless, of course, because sometimes what looks like a ring from far away can actually be a false ring: an “extra” late wood growth caused by an early freeze, early warming, or some disruption to ‘normal’ seasonal weather. The microscope helps me see whether these bands have defined edges or seem to fade, and I’ll know that only the truly defined ones are rings.
I seem to be lucky, however, as none of the Black Oaks seem to have any false rings. I’m actually eager to find some missing rings and micro rings, but I don’t find any of those either; missing rings in oak are so rare that you’ll likely be able to plant your own oak forest and watch it grow to maturity before you find one. This is so easy, I think. I feel like I have it in the bag.
I finish measuring the rings on my samples and labeling them with the years I assigned hypothetically to each ring from my cross dating. Now I’m ready to run the measurements through COFECHA, a program that gives me the correlations between individual samples and finally the correlation between all of the samples. When I first run the program with every sample, I’m told something between 0.5 and 0.6 is the expected correlation for ‘good’ black oaks (in other words, there is a 50 to 60 percent chance that given the ring-width measurements on one sample, you’d be able to predict the measurements on a second sample from the same batch). I get a 0.3 correlation. What could I have possibly done wrong?
I soon find that although Black Oaks don’t usually produce missing rings, micro rings or false rings, it is still a possibility, for reasons I didn’t understand at that time. There is also the possibility of human error resulting from mounting the samples incorrectly, missing pieces of the sample after coring and so on. (Editor’s note: one of the biggest issues dating oaks is jumping from one side of a ray to another while moving down an increment core. Sometimes the rings that are aligned across this division are not!).
What I was doing up until this point was just writing down the years where I found narrow and wider rings as marker rings and trying to find a pattern with everything I wrote down. It was helpful, but I needed to learn more about cross dating to make a few problem samples correlate with the population.
First, I was told I could take a step back and get my nose off of the microscope. By holding up a problem sample to one with a good correlation, I could try and find where patterns aligned visually, and this was usually more helpful than just trying to find the patterns in a sea of numbers I had written down. Second, I was focusing too much on individual samples and not remembering that multiple cores are often taken from the same tree: before a sample can correlate well with an entire forest it is easier to make sure it correlates against the others from the same tree. Finally, I learned that some trees—the very young, the very old, and the trees that constantly get outcompeted for resources—just don’t conform: the rebels, the grumpy old men, the proud nerds. Very suppressed rings won’t correlate well with a series, and neither will very wide rings that signal a release from competition from neighboring giants. Sometimes a 0.3 or a 0.4 correlation is the best you can get for a sample, and I had to learn how to know whether to accept that or keep trying further.
That first batch took me a week and a half to finally cross-date. You should’ve seen the look on my face when I saw my first correlation in the 0.5 range.
And that was just the black oak.
I decided to continue coming to the Tree Ring Lab over winter break, and at first it was incredibly peaceful. A few days of sanding and stabilizing some pines really put me in the Christmas spirit. And then I met Baldcypress, which made me more of a Grinch.
At first, baldcypress and I were really only going to be a one-time thing. I was only told to measure three or four batches from the 80s as a side project, but after I logged all the measurements the COFECHA results were cringe-worthy. I was told I had to try my hand at cross dating the cypress.
If I thought the black oak population had trouble samples, I reconsidered. While Quercus velutina hardly ever displays missing rings, false rings or micro rings, Taxodium distichum seems to want to flaunt them. My first batch had mostly been false rings, but I also learned what a micro ring actually looked like.
I remember staring at a set of what should have been ten rings for 20 minutes, but only seeing nine. I finally asked my advisor and then watched as Neil marked a band relatively darker than its surroundings a cell wide as a ring. If any ring could be called a marker ring, it was this one. Sometimes finding a micro ring where I knew, from the chronology, that a narrower ring should be, was actually a relief. 1966, a heavy drought year for most of the Northeastern US, quickly (and morbidly) became my favorite year.
I dealt with so many false rings that I felt like I was five and my fingers were all turning green (I’m glad no one ever showed me this; I always felt like a princess). Every time I thought a sample couldn’t have any more missing rings I found more. I started thinking everything was a micro ring.
The black oak took a week and a half. I’ve gotten through three batches of baldcypress, and I’m on my fourth: I started over winter break and it is currently spring break. Of course, I’ve been working on other things as well, including a poster presentation on my black oak samples for the Northeast Natural History Conference, but it feels as if the baldcypress just doesn’t want to leave me alone.
Yes, I do have a type. I like real rings, I like big rings and I like rings that conform. In the end, however, I’ve learned more from the “problem children” than the ones that worked out like I wanted them to. I might even admit that the baldcypress has been much more rewarding to work through.
Shhh, don’t tell the black oak.
Ana Camila Gonzalez is a first-year environmental science and creative writing student at Columbia University at the Tree Ring Laboratory of Lamont-Doherty Earth Observatory. She will be blogging on the process of tree-ring analysis, from field work to scientific presentations.
By Daniel D. Douglas
“Are you using this idea for your thesis research?”
I heard this as I stood in front of a classroom full of old-growth forest ecology students. The question had come from Neil Pederson, who was sitting directly in front of me. He was asking this question because I had just spent the past 12 minutes discussing the intricacies of land snail biology and ecology that would make them great organisms to use for ecological modeling in regards to disturbance. Things such as their lack of mobility, susceptibility to desiccation and sudden change that would occur because of major disturbance make their preferences for habitat similar to the defining characteristics of old-growth. Neil looked at me with the excitement of a small child on Christmas morning because he knew that I could potentially be on to something.
So, you can imagine his dismay when I answered his question with “No, I hadn’t really given it any thought.” I know I winced (at least on the inside, if not physically) after I answered because I had suddenly realized that I could be passing up a golden opportunity. I remember walking back to my apartment that night, thinking about what had just happened. I thought about it another hour or so after I arrived home and then emailed Neil to discuss the potential that my presentation had for being used as a master’s research project. Long story short, we developed a research plan of attack with the help of David Brown, my co-advisor, to study how anthropogenic disturbance* can shape land snail communities.
Not many people study land snail ecology. I had the fortune of working under someone that did, Ron Caldwell, while I was an undergraduate at Lincoln Memorial University. I had become deeply interested in these ignored and overlooked organisms. So, as I entered graduate school in biological sciences at Eastern Kentucky University, I had a fairly strong background in “snailology”, aka malacology. I had been unsuccessful in finding a graduate program where I could continue to work with land snails and was wandering the halls of EKU uncertain about what I was going to do for a graduate research project.
What happened in Neil’s class that semester was really fate telling me this is what I should be doing. A year and a half later, I found myself sitting on my back porch sifting through leaf litter samples, picking out micro-snails, excitedly thinking “I’ve got something here.” It was clear that these organisms could be indicators of past human disturbance.
This research took me to some of the most memorable places that I’ve ever been. Since the availability of old-growth in Kentucky is sparse, my sampling sites were limited. The first place I sampled, Floracliff Nature Sanctuary, was just a few miles north in the Bluegrass Region of Kentucky and, oddly enough, a few miles outside of Lexington. It’s crazy to think that a place with trees hundreds of years old exists right outside a fairly large municipal area, but it does.
Floracliff rests on the Kentucky River Palisades in a very rugged, deeply dissected network of gorges cut by streams over eons of geologic time. It also has some of the most spectacular examples of old-growth trees you’ll find in Kentucky, including the oldest known tree in Kentucky to date: a 400+ year old Chinqaupin Oak.
Though this wasn’t true old-growth, it gave me some of the best results I got for the entire study: there was a clear separation of the land snail communities between old and young forest sites. In fact, abundance, richness, and species diversity, were all greater in the older sites. This is also the site where I found the most new county records (i.e. never documented from that county). These results only whet my appetite for more data from different forests.
The next stop was EKU Natural Areas‘ Lilley Cornett Woods Appalachian Ecological Research Station, a small patch of prime mesophytic old-growth forest in Letcher County. It’s bizarre to think that forests like this exists in the Cumberland Plateau portion of Kentucky, due to the fact that our countries insatiable thirst for natural resources has left the region in one kind of an ecological ruin. I was deeply impressed by this forest as wandered around. The snails at LCW did not disappoint either. I saw the same patterns as in Floracliff: old-growth forest had greater abundance, richness, and diversity. The highest species richness for the entire study came from LCW as well, which is something that I did not expect. The evidence was beginning to stack up.
My final study site was Blanton Forest State Nature Preserve. This preserve is over 1200 hectares and contains the largest tract of old-growth forest in Kentucky. Dominated mostly by oak and hemlock, the forest is very rugged and it had more rhododendron than I care to remember. Nevertheless, it is impressive. Comparing Blanton to a nearby young forest didn’t necessarily give me the same exact results, statistically speaking, but I still saw the same trend of higher abundance, richness, and diversity of microsnails in old-growth forest.
You may be asking, “What does this all mean” or, “Well, he found that there is better habitat for these organisms in undisturbed forests. That’s doesn’t really seem novel.” In reality, this is novel. Better, it is important.
First, I documented that a minimum of several decades, if not more than a century, is needed for land snail populations to recover to a point that resembles what their assemblages looked like before human disturbance. As an important part of forested ecosystems in terms of nutrient cycling, organic material decomposition, calcium sequestration, and food sources for many other animals, it is vital that we know things like this so that we can better manage our forests for everything that lives there, starting from the ground up. Second, all of you must know that everything in an ecosystem is interconnected and, once one thing is removed, it can have cascading effects throughout the ecosystem. Better management practices will help us maintain ecological integrity of forests. Third, my findings also indicate the need for locating and protecting remnants of old-growth forests. As I have shown, old forests, whether true old-growth or lightly logged by humans a century or more ago, are biodiversity hotspots and therefore deserve protection beyond their representation of how complex forests are at great ages. And finally, my findings also indicate that land snails have great potential for being used as indicators of old-growth. This is something that many scientists, especially citizen scientists, have been chasing after for decades.
For myself personally? This means that I have a lot more work to do. Despite the fact that there are people out there that study land snails, they remain poorly understood. I feel as if it is my job to bridge that gap in the knowledge. I also hope that what I have accomplished with this research will open the door for future studies on not just land snails, but other non-charismatic fauna. I also hope that my work enables people to look at more than just the trees in old-growth forests. The trees are wonderful, and we are lucky to still have them, but there is a lot going on underneath those trees that we don’t know much about.
* = the linked article is open access and free for downloading – download away!
Daniel Douglas earned his master’s degree in biological science from Eastern Kentucky University in 2011 studying terrestrial snails, important, but less charismatic creatures.
By Ana Camila Gonzalez
“But can’t you see the rings already?” I ask, wondering why I’ve been asked to sand a sample- it sounds to me like one would damage a sample by subjecting it to the mechanical screech of a sander.
“Yes, but under the microscope they look foggy if you don’t sand them. Also, you’re looking at a black oak sample. You wouldn’t see any rings before sanding if you were looking at a Maple, for example.” Jackie responds. She shows me a maple core sample that she explains has been hand-sanded down to a 1200 grit. It’s smooth and shiny as can be; yet I can barely see what seem to be hairlines.
“Oh. That makes sense.” I secretly hope I won’t have look at another maple sample for a while.
I approach the machine. I look like a character from BioShock or a WWII soldier in the trenches, as I am wearing a respiration mask, goggles and ear muffs. Seemed a little excessive to me at first- once I turned the machine on and I saw the mushroom cloud of sawdust come off the banshee-screeching sander, however, I realized I’d be better off looking like a biohazard worker than having to bring an inhaler and hearing aid to work.
I place my first sample down on the sander, but it flies off and hits the wall… I guess I can hold it tighter and push it down a little harder. I try again but this time my sample stops the belt from spinning. Definitely too hard. Eventually I get just the right amount of pressure, and I realize I can tell because my sample looks clearer every time I take it off the belt. I start humming to myself, singing something along the lines of I can see clearly now, the rings are there… As I go to higher and higher grits and my sample starts developing a cloudless luster, I realize I enjoy this a little too much.
To me, sanding is a process full of Zen. It’s a process I can focus on while still letting my mind wander, and my thoughts usually get pretty philosophical- I have this foggy, unclear sample and slowly I take off its layers and layers of disparities. What results is a core in its purest form ready to tell the story of its life, and after a few hours of sanding I’m ready to listen.
Ana Camila Gonzalez is a first-year environmental science and creative writing student at Columbia University at the Tree Ring Laboratory of Lamont-Doherty Earth Observatory. She will be blogging on the process of tree-ring analysis, from field work to scientific presentations.
By Ana Camila Gonzalez
My feet are soaking wet and I’m playing a game of Marco Polo, but I’m nowhere near a pool. It’s my second day on the job. It’s my second week of college. I have no idea what to expect.
I’m a first year undergraduate student at Columbia University, and I just began to work at the Tree Ring Lab at the Lamont-Doherty Earth Observatory after being told by a few upperclassmen that the Lamont campus “just isn’t for freshmen”.
On Friday, September 21st, several members of the lab headed to New Paltz, NY to do some field sampling for a project aiming to uncover particularly major ecological events in the Eastern United States in the past three hundred years. I had just started to understand the basic concepts of differing tree rings. When I was told we’d be coring trees and identifying them, I smiled and nodded my head enthusiastically. You should see my poker face.
We get to the town of New Paltz and drive right through the center, heading towards Minnewaska State Park.
After a deceivingly easy one mile hike on road-like paths, we get to the entrance point for the plot that was pre-designated Jackie, Dario, and Neil earlier in the spring. From that point on, I get to witness the transition from a suburban hike to what seems to be the set of Jurassic Park. We’re heading into the area surrounding a ravine, and my feet remind me that I’m not wearing waterproof boots. At some points I feel like I’m in a maze, and I start yelling MARCO! At that point I start remembering that I took the job because I wanted some hands-on experience in the field of environmental science. Grabbing the four-foot fern in front of me, I feel that I’ve made the right choice.
After some strolling, climbing and maneuvering, we finally reach the plot. Here I finally get to see what the overall project is really about.
While some forest ecosystems in the Western United States recycle nutrients and move through successional cycles at fairly large scales through natural and necessary fires, these processes are much slower and do not seem to occur at larger scales in the temperate forests of the Northeast. Trees experiencing suppressed growth only receive the necessary sunlight, water, and nutrients to experience quicker growth when surrounding competing trees perish, either through logging, disease, windstorms, or similar ecological processes. One can see this change as a drastic change in the width of tree rings: once a previously suppressed tree becomes dominant, the increased growth results in relatively wider tree rings.
When this drastic change is seen not only in the rings of one or two trees but across an entire forest ecosystem, a major ecological event is likely the cause. This project is aiming to find the causes of a few suspected major ecological events in the Eastern United States.
In New Paltz in particular, this project encountered a roadblock- some people believed our study forest in Minnewaska State Park was an old-growth forest, but so far the samples brought back have found evidence of logging in the late 1800s. The first samplings, using plots with a radius of 20 meters, returned few older trees that would be useful to the project. The radius was thus increased to 30 meters, and only trees with diameter greater than 40cm were cored past the 20 meter mark. After this adjustment, the second sampling returned double the amount of older trees. The real science can begin.
So here I am, learning all of this for the first time, and I’m fascinated. Another new student and I learn to core a tree, and we realize how physically strenuous it is, laughing about having to lift weights to get in shape for future fieldwork. Like that’s ever going to happen. We’re introduced to a few different tree species during the process, and we begin to learn how to identify them. For the past few days I’ve walked around trying to identify every tree in Morningside Park.
At the end of the day, I’m feeling pretty fulfilled. The way back to the trail isn’t as cinematic as my entrance through Jurassic Park, but I still feel like I won’t get up after sitting down in the car.
That night, I got a rare chance to talk to my cousin, a botanist in Cuba. I told him about my day and he told me that if I start beginning to enjoy science, and the general act of finding answers to questions others might not have thought of asking, it becomes an obsession. He told me I wouldn’t be able to get away from it. I think I’m starting to get a sense of that. I was hoping to land a job at the LDEO that would just let me begin to get my feet wet in environmental science. So far they’ve gotten soaked, but I have a feeling I’ve only started to dip my feet in the water.
This is the first in a series of guest posts by Ana Gonzalez, a first-year environmental science and creative writing student at Columbia University. Ana is a research assistant at the Tree Ring Laboratory of Lamont-Doherty Earth Observatory who will be blogging on the process of tree-ring analysis starting off with the joys of field work.
2012 is turning out to be an exceptional year in the eastern US. Starting out with what was essentially a #YearWithoutaWinter, followed by a heat wave in March, a hot summer, Macoun and Cortland apples coming in 2-3 weeks early, and the continuation of a severe drought in the Southern US that expanded into the Midwest and Northeast, this year’s climate doesn’t appear ‘normal’. From a 500-year perspective, this year’s drought in the northeast should actually feel like an exception for 58.2% of its people. While there have been droughts in the Northeast over the last 44 years, trees informed us that, as of 2011, we were living one of the wettest 43-year periods since 1531. It is shocking to see towns flood or covered bridges float away during tropical storms in the northeast. But, our new record suggests that the buildup of soil moisture prior to these storms might make these unusual[?] storms the norm.
Immediately preceding this epic pluvial (a period of increased precipitation) was the 1960s drought, one of the most intense droughts of the last 500 years. Having lived only during this epic pluvial, I cannot fathom this drought. Pluvial is my norm. So, every time I lead a hike or lab tour on campus, like during Lamont’s great Open House, I always ask if someone was alive during the 1960s drought. Heads tilt back, eyes come alive, and the stories pour out. People talk about tough times and odd events like a landfill catching on fire. I then congratulate them for surviving one of the worst droughts of the last 500 years. Then I have to say, “Uh, but it has been worse. Much worse.”
Often when looking deeper into Earth history, we see things that send shivers up our spine. For those who lived through the 1960s drought, our new record should send shivers up your spine. Our lab’s first study showed the 1960s drought to be the worst since 1700. However, when looking back almost another 200 years, we can say things like, “Yeah, the 1960s drought was bad, but it was only six years in duration.” [six years of below average conditions in our new record] Six years of drought is tough. It must have felt like a decade. But, how might we feel about 23 years of drought? How might a 23-year drought feel when the preceding 11 years had only a few years of average to above average precipitation? [shivers].
The current epic pluvial caps a 150-year wetting trend for the Northeastern US. This trend, however, is not limited to the Northeast. Much of the entire Eastern US has become wetter over the last 150 years. Only the Deep South has trended towards drought over the last 20-30 years.
For more on the development of our new record and some of the implications of what we found, go here. The rest of this post focuses on the contribution of biodiversity and broadleaf species to the new record.
Biodiversity, Broadleaf Species, & Tree-ring Reconstructions in Humid Regions
An interesting result of our study was that the use of a greater number of species can improve a tree-ring based reconstruction (for more examples, see here, here, here, here). Reconstructions have been made using multiple species in humid regions like southeastern NY State since the beginning, so the use of multiple species in not groundbreaking. But, our initial analysis indicates that using 10 records drawn from 10 species outperforms the 10 best chronologies regardless of species (best is defined as the strongest correlation to the climate data used for reconstruction). It seems biodiversity is not only good for life, it can be good for reconstructions of past climate.
We are not exactly sure why increased diversity might improve reconstructions. My pet hypothesis is that each species has a different sensitivity to its environment and that by combining multiple species, differing responses are filtered out, resulting in a more accurate common signal. Some of this is driven by genetics. Some of it could be driven by the ecology of the sites where trees live. Think of it in human terms: some people can eat whatever they want and never gain weight. Some of us look at a banana split and gain two pounds. We might disagree on what we want for dessert, but when offered a fine blueberry pie, or for us sweet tooths – maple cream pie, we can generally agree if it is righteous. I imagine trees have a similar response.
“Remember 1972? Wow, that was a good water year!”
“ Yes, that was a good year, but I really liked 1989.”
“Oh yeah, that was a good year. But what about 1833?”
All 27 records chime in chorus, “Most righteous. Water. Ever!!”
These findings bode well as tree-ring scientists move into new regions of study – say the rich, temperate, broadleaf forests of Asia, for example. Regions with a vast array of tree species could be a boon for the future of dendroclimatology (the reconstruction of climate from tree rings).
Thinking about how we can improve reconstructions is important. Many scientists are exploring new statistical techniques to extract a chorus of solidarity from trees. From a biological perspective, though, the rate of extinction (literal and functional) is a real threat to our science. Hemlock woolly-adelgid is wiping out hemlock trees, a stalwart species and one of the backbones of the North American Drought Atlas. The loss of hemlock and other important species will thus diminish future reconstructions. Replacements species are needed.
Of the 12 species used in our study, eight are broadleaf species. We found that tuliptree or tulip-poplar (Liriodendron tulipifera) is one of the best species to replace hemlock*. Not only is it drought-sensitive, it has shown to be long-lived: a 512 years old specimen was recently found. Amazingly, only about half of its radius was recovered, as the tree was hollow. I would guess this species can live 600 to 700 years, if not more.
Our study also found other broadleaf species suitable for dendroclimatic research. These species include: black birch (for Yanques, but sweet birch for Southerners; Betula lenta), pignut and shagbark hickory (Carya glabra and Cary ovata, respectively), and northern red oak (Quercus rubra). While these trees do not live as long as hemlock or tulip, they are proving to live longer than expected. Continued exploration of species in the diverse eastern North American forest for maximum ages and climatic sensitivity should help dendroclimatological research as species are lost.
* Tuliptree is quickly becoming one of my favorite trees. It great longevity is a real treat. It is now the tallest documented tree in eastern North America now, too. But, it is how it handles drought that is so fun. Tuliptree is a drought-deciduous species, meaning that, during drought, it cannot close its stomata as well as other species to staunch the loss of water from its leaves. Therefore, it drops leaves to reduce water loss. If you paid attention to this tree in 2012, you would have noticed yellow leaves in July, a more common leaf color in September.
The really, really cool thing about this species, however, is that it also has indeterminate growth. This means that, unlike many temperate trees, its growth is not limited or set prior to the growing season. I once saw tuliptrees putting on new leaves in September following a dry August. This plasticity is awesome. It also suggests that September Song is not necessarily mournful for tuliptrees.
I have to call myself out. Earlier I had professed to being a former coniferphile. That was, of course, silly. I like coniferous trees very much. Half of my business is made from this lovely branch of the tree family. This introduction is a lead in to say that this blog will be quieter while my gig in Mongolia continues. A team of us are off to Mongolia to recover an millennia or two of xylemite. My focus in August and September will be on the development of a tasty and long record of drought from central Mongolia. You can follow these adventures here. Before I make that switch, I wanted to make a brief update on a good, busy summer.
Update #1: I caught a tweet that indicated that angiosperms have the ability to adapt a wee bit quicker than conifers. Looking forward to that line of work!
Update #2 – This summer our lab hosted two Lamont Summer Interns. Jackie Testani worked with me and Dario Martin-Benito on understanding the long-term forest dynamics of the Palmaghatt Ravine in the mid-Hudson Valley, NY. When first viewed from the west, the Palmaghatt made me think that if I re-labeled the image below as Borneo, folks would ooh and ahh. The light-green pyramidal crowns of the tuliptrees (Liriodendron tulipifera) gave me the feeling many people have about tropical forests: luscious, wild forest.
Jackie has completed some impressive work this summer. A history major with an interest in medical sciences and Africa, she has taken to tree rings like nobody’s business. Most impressively, Jackie slew the zombie maples. See, a small, but not insignificant proportion red maple in the northeastern US tend to not produce growth rings in the decade or two prior to coring. This on top of red maple’s diffuse-porous rings makes it difficult to work. The cause for the zombie’ness is not yet so clear. But, it happens. Often. Jackie’s work matches an independent collection of red maple from the 1980s. Both show some trees missing 5-6 rings in the decade or two prior to coring. This has important implications for all kinds of tree-ring based research.
And, to finish this update (as we approach the Christmas season), we also found a porcupine in a birch tree.
Update #3 – We has also gotten some preliminary dates on the samples from Turkey. Dr. Nesibe Kose and her students have done a nice job in making their way through the collection. A spruce and fir tree is more than 200 years old. The limited beech forests that we could reach during fieldwork are wicked-fast growers and not too old – 100-180 years old. The oaks look to date to the mid to late-1700s. The coolest thing is that the umbrella pine have a large age range, from ~100 years to >210 years of age. So, these ages suggest this stand was not planted by Russians in the late-1800s. However, when in Eurasia, you can never be too sure this stand was not planted at some point in time. If these ages hold, it suggests that, regardless of their origin, they comprise a functioning stand with little stand-scale disturbance.
Update #4 – I will use this blog to call attention to some neat pieces of the literature in broadleaf forests. Bob Booth and colleagues have a 2012 paper indicating that changes in moisture availability in the Great Lakes region, a relatively humid region, plays a strong role in forest dynamics. Particularly, changes in moisture lead to a long-term decline in American beech. There is also some indication that snowpack is beneficial to sugar maple. You like maple syrup? If so, let’s hope that the snowless 2012-2013 Winter does not become a climatic habit.
Update #5 – Speaking of drought, the drought in the southern US has crept its way into the northeast Maybe The South will rise again? ;). The US drought monitor for July 24, 2012 shows drought across much of the US. Here in NY, the drought came fast and seems exacerbated with the successive heat waves this summer. This year’s growing-season drought is in stark contrast to 2011, one of the wetter years since 1531 (a paper just accepted in the Journal of Climate). If you are lucky to live in the range of tuliptree, however, you do not need an internet connection to know the severity of drought in your area. Go seek the tulip tree. Being a drought-deciduous tree, some of its leaves yellow and fall during drought. It almost seems like a 10% increase in the ratio of yellow leaves to green leaves equals one unit of the Palmer Drought Severity Index.
Finally, update #6 – I just came across a paper by the White Lab suggesting that southern Magnolia (Magnolia grandiflora), or bull bay, is becoming naturalized to the north and west of its range (The South will rise again, II?). The implications in the paper is that warmer winters are allowing this iconic Tree of the South to expand its range. If you find yourself near Auburn, AL, find your way to the Bartram Trail. It will take you through some spectacular forest-grown southern Magnolia. They look much different than the ones you see in people’s yards. When in this form, it is one of my favorite trees.
No, of course not. Do not suggest anything like that to Alaskans, or Europeans where hundreds have died, or Inner Mongolians, or Koreans. But, turning the clock back to December and January for the New York City region, it was not apparent that winter would arrive as it ‘normally’ does. Yes, we have had significant snowfall events. While snow in late October is not unusual, Dr. Jeff Masters had to go back to the 1804 snow hurricane to find something similar (BTW, I love the word I learned in Vermont for these events: snow’icane). And, the late January snowstorm was significant, but honestly, I did not bother to shovel. Temperatures were expected to hit the 50’s F two days later. The Sun and warmth rescued my back and melted that snow away in just a couple of days.
And, that is the thing about winter this year in the eastern US: when living with the weather and not the calendar, all the signs of spring were present in December and January. Plants were starting to bud, especially in the Deep South, and there was a warm, wetness in the air more typical of March. We opened windows in late December and early January to exchange the air in our house, which is a spring ritual for me. It has been a freakish winter – it snowed in Libya and a colleague cut a Skype session short with me because of heavy snow in Istanbul. A multitude of temperature records were broken from late December through January (including 875 record highs between late-December and January 6th, 2012). Historical climatologist, Dr. Cary Mock of the University of South Carolina, compared this winter’s warmth to the winter of 1827-1828. There was a rare tropical disturbance in early February 2012. Syracuse basketball fans tailgated prior to a late January game and Oswego, NY, at the leading edge of the Lake Ontario lake effect snowbelt, had to use ‘saved snow’ for its snow festival. I saw some red maple trees in bloom on February 5th. This species typically blooms in mid to late March in the lower Hudson Valley.
All of this gave me pause to wonder if this wasn’t an abstract picture of the future. If so, what would this mean for the trees and forests? While many folks were concerned with the exposed blooms and buds, the potential for real damage of a mild winter is actually hidden away from our senses.
The potential threat to most trees this winter in eastern North America is the one aspect of winter many people are relieved to be without: snow. Snow is important to ecosystem function. Perhaps the most temperature sensitive part of a tree is its root system. Snow is a great insulator for the ‘feet’ of trees.
A study conducted in the White Mountains of New Hampshire found that the lack of snow significantly increased the overwinter mortality of the fine roots of trees. A couple of things amazed me about this study. First, that they had enough money to pay people to shovel snow all winter in the middle of the woods. I imagine some of the conversations during the hiring process went something like this, “For reals?” or “hahahah…what? For reals?” or “I got the job? What do I have to do again? Um thanks, but no thanks.” Second, the years during which this study was conducted were not that cold. The elevated mortality during a warm winter (temperatures were generally around the freezing temperature) made me wonder what would happen during a cold, snowless winter.
I am aware of this study because I was pondering some of my own fresh research at the time the snow & fine roots study was being published. I had created a network of six southern tree species distributed throughout much of the Hudson Valley. Based upon prior work by Ed Cook, Paul Krusic and others, I expected populations of trees at the northern end of the study region, trees closer to their northern range margin, to be more sensitive to winter temperatures. I found the opposite and wasn’t sure what to make of the findings until seeing a lecture about the White Mountain Study. I could only conclude that the regular and persistent snow pack in the northern Hudson Valley made trees less sensitive to winter temperatures than trees closer to New York City and the southern Hudson Valley.
This year’s snow drought and the oncoming cold front could trigger significant damage in living trees. Research by Dr. Colin Beier indicates that yellow-cedar is particularly susceptible to decline in the Pacific Northwest due to a lack of snow and freeze-thaw cycles. Subsequent independent research supports this concept.
And, do you like real maple syrup? Research indicates that sugar maple seems to benefit more from increased snowfall than eastern hemlock of beech. This might not be a good year for maple syrup, eh?
Because we are talking about ecology, however, not all the impacts will be doom and gloom. Nature adapts. Some species in certain areas will likely benefit from warming winters. Almost all of the radial growth of the six species I studied would benefit from warmer temperatures. Like the loblolly pine study mentioned above, conifers will likely benefit more as they as more sensitive to winter temperatures. When the temperature is above freezing, conifers can take advantage of sunlight and conduct low levels of photosynthesis. Over the course of a mild winter, this can result in extra energy for the coming growing season. I suspect that trees in regions with shallow and ephemeral snowpacks will benefit from warmer winters as well since they most likely deal with substantial fine root mortality every year. Warmer temperatures for trees in these regions will likely be a relief to their annual winter stress.
It is truly hard to know exactly what will happen as our winters change. Winter ecology is complex and might not be as well studied as that of other seasons (although there is a textbook on this topic). For now, I am enjoying the unseasonably warm days while my mind quietly ponders if we are seeing an example of the future today.
While the New Jersey bill failed, it is going to be discussed in New Jersey’s Senate Environment Committee on Monday, January 30, 2012. The discussion is not yet over regarding New Jersey’s public forests.
The discussion about ecosystem productivity over time also continues in the forum of the Native Tree Society. Specifically, this post was picked up here. Dr. Lee Frelich, director of the Center for Forest Ecology at the University of Minnesota and active contributor to the Native Tree Society, reminded me/us that ecosystems do experience retrogression. Ecosystem retrogression is the concept that “ecosystem properties such as net primary productivity, decomposition, and rates of nutrient cycling undergo substantial declines“.
Dr. Frelich explained the concept in many ways, including:
“Returning to the issue of increasing carbon storage in older forests, inevitably, if old forests continue to accumulate C, especially in the soil, it will lead to a high C:N ratio and other effects that will stall increased production, and without rejuvenating disturbance, in many cases to ecosystem retrogression. This might take hundreds of years (especially in northern hardwoods), so for now, many forests will continue to increase carbon, an important ‘transient’ dynamic”
I have a tendency to forget about this concept. One of the first papers describing ecosystem retrogression that I recall was the work of Peter Vitousek at Hawaii. In a wonderfully designed study, it was shown that ecosystems do regress over the course of thousands of years. This time scale slips my mind when thinking about old-growth forests and forest management.
Dr. Frelich pointed out a newer study summarizing our knowledge of ecosystem retrogression that surveyed multiple ecosystems. The concept seems to apply to most ecosystems over the course of thousands of years.
I followed up Dr. Frelich’s post by asking, might “the application of the information on ecosystem regression to forest management go something like: ecological justification for logging a forest to ‘save its health’ (prevent ecosystem regression) is on the order of every 100-150 years or less in the absence of fire in boreal systems and on the order of several hundred years to thousands of years for temperate forest types?”
Dr. Frelich responded by saying that “rejuvenating disturbance is necessary at much longer intervals to prevent retrogression. However, I am not sure that logging would be a good agent to prevent retrogression.”
So, yes, ecosystems do regress and decline in productivity. Except for boreal forests with balsam fir, this happens at time scales that are 3-6 times the typical longevity of most trees (200-300 years).
BTW, check out the discussion on the NTS board. Finer points and clarifications of the ecosystem retrogression concept are on-going.
In the previous post, I outlined the argument lighting up parts of the New Jersey legislature and the human elements of its ecological communities. Briefly, one reason some people are using to promote logging on public lands is the perception that old trees and forests are dying of old age. While there are other arguments as a part of the bill, like the fact that because forested ecosystems are maturing, species that use younger forests are declining, this “old trees are in decline” argument has led to much logging of old forests. I would argue it doesn’t have to be that way.
I will spare you many of the details from the scientific literature. But there is a plethora of papers indicating old trees and forests are dying of anything but old age.
An early paper that cemented the age-related decline concept was put forth in the journal Science by the excellent ecologist, Eugene Odum. The main figure of the paper that sticks in many people’s mind that summarizes the concept can be found here. Google Scholar estimates this paper has been cited 3,349 times. The idea was mostly based upon a paper focusing upon short-term leaf biomass production of two coniferous plantations (~18 & 36 yrs) and a 70-year-old forest. Odum described the idea that forest respiration increased as the forest aged such that they released more carbon dioxide than what they took in. It makes sense when you think about biological aging.
Eileen Carey pretty much put the first, evidenced-based blow into the aging forest concept. She strapped monitors onto young and old trees and found that increased respiration might not be the case in old trees. In a wonderfully titled article published in 2001, “Are old forests underestimated as global carbon sinks?,” she put forth the idea that the concept of ecosystem decline with time in the Odum paper might be flawed. Unfortunately, Carey’s article has only been cited 100 times, according to Google Scholar.
Testing the concept at the ecosystem level, which is an important consideration for the argument here, is that there is growing evidence that: 1) ecosystems accumulate carbon as they age, especially temperate forests, and 2) old-growth forests actively take up more carbon every year. Sebastiaan Luyssaert noted in the journal Nature, “Old-growth forests therefore serve as a global carbon dioxide sink, but they are not protected by international treaties, because it is generally thought that aging forests cease to accumulate carbon.” His 2008 article was a part of a small groundswell indicating that old-growth forests are much more important to the carbon cycle than previously presumed. Want more proof? Try here and most of the chapters in this 2009 book. There is more out there.
Better, if you live near Black Rock Forest (a consortium including Columbia University) in the southern Hudson Valley, you can see physical proof that age does not slow carbon uptake. By studying almost every facet of the trees and forest, Cheng-Yuan Xu and others found that, contrary to the long-standing belief that growth (productivity) was the cause of the age-related decline in forest biomass accumulation, it might be increased tree mortality that reduced ecosystem productivity, especially with the mortality of big trees. It might be the ecology, not the physiology of trees, silly.
Of course, there were hints to the idea that old trees might not age as people expect.
Tree rings, for quite some time, have shown that old trees are capable of “good” growth rates. Val Lamarche and others found evidence of increased growth rates in old bristlecone pine and speculated in a 1984 Science magazine article that the cause was the result of carbon dioxide (I will not get into the CO2 fertilization controversy here). This was followed up in 1989 by Lisa Graumlich and others that showed a trend of increased ecosystem-level productivity in the Cascade Mountains. Soon the floodgates opened here, here, here, here, pgs. 143-156 here, here, here, here, here, here. Most recently, a paper by Matthew Salzer indicates that bristlecone pine 1,000 yrs old or older are growing faster than perhaps ever in their entire life and that this is likely the result of warming. These are but a few papers showing this pattern.
Complementing these studies is an ecophysiological study that indicates there is no difference between the physiological processes in young vs old bristlecone pines. In a study in Experimental Gerontology by Ronald Lanner and Kristina Connor, the question is asked, “Does bristlecone pine senesce?” They “conclude that the concept of senescence does not apply to these trees,” which is very different than us humans.
One new finding in plant ecophysiology that makes trees more like humans is that size matters. It seems that it might be difficult for bigger trees to maintain physiological processes. In a nice series of papers, Maurizio Mencuccini provides some evidence that size mediates tree vigor and that “after the first few years of a tree’s life, size-mediated factors largely prevail over age-mediated factors in determining tree growth rates.” Bigger trees, in this way, do not grow as well as smaller trees.
We find that in nature as well. Bryan Black reviewed of hundreds of trees of various types in North America and found that the oldest trees currently in the landscape were smaller at 100 years of age than younger trees currently in the landscape. A brand new study in Italy by Alfredo Di Filippo finds that lifespan in beech is greater in trees with slower growth and for trees living in areas with shorter growing seasons. They go on to suggest that global warming might reduce longevity of trees. I’m not ready to go there, but if caloric intake is related to biological longevity, perhaps that is correct. Size matters.
Why might size matter for trees? Large, heavy limbs catch much snow, ice and rain. The tallest trees literally become lightening rods. There are advantages to being a large tree, but there are disadvantages when tough times arrive.
You get the point, correct? There is much evidence here against the claim that old trees die of old age. Big trees have some longevity-related issues. Old trees do not seem to be threatened by their great ages. Why trees die is a complex, perplexing and a very active field of research.
So, I promised I’d take you on the way-back machine and show that the concept that old trees decline with age is not even supported by “ancient” forestry literature. Whenever I get on this subject, I always let the late, great Bob Marshall have the last words (not only did they name a wilderness after him, he was a Stumpy, dendrochronologist and A1 scientist with ideas that were decades ahead of his time). After conducting some pretty radical tree-ring analysis for his times, he created the following figure:
Towards the end of his 1927 paper in the Journal of Forestry, Vol 25 (yes! it is finally online!!), he wrote:
It does not take long to see from this picture that the good old growth curve is a delusion.
“There is unrest in the forest, there is trouble with the trees“…I will mostly spare you one of the more ecologically correct, forest ecology rock tunes (the next two lines, however, “For the maples want more sunlight, and the oaks ignore their pleas,” written in 1978, seem incredibly prescient given that one of the first oak-to-maple succession papers was published in 1984. Of course, Rush is that awesome. Why they aren’t in the rock & roll hall of fame…). But, recent developments in the management of public forests in neighboring New Jersey push me to unexpectedly blog again. Oddly, there is a new bill being considered that is pitting forest ecologists against the Audubon Society. There is no unusual unrest in the forest–it is among the people.
The bill being considered would allow forest management, specifically logging, in some of New Jersey’s public forests. One of the main thrusts of this bill is that the older public forests in N.J. need management. I’ll state here that I have no problem with forestry, especially long-minded forestry that considers the entire ecosystem for generations (of trees, animals and people); I marked trees for logging for nearly a year. There are places where you could take most people and they would never know that the forest had been logged for more than 50 years. Of course, Leon Neel is an exceptional human and the forest he manages reflects his soul. (Don’t let “art” in the book title fool you. Neel is an exceptional naturalist with the patience of Job and a highly scientific mind).
What pushes me to write is one of the reasons being used to justify the cutting of trees. It is this, “Supporters of the estimated $2.7 million program say it would help the state nurse its 800,000 acres of land back to health by removing trees and allowing sunlight to feed new growth, creating new habitats and reducing the risk of fires.” The risk of fire is a bit of a red herring given overall forest composition and the recent trend to wetter conditions.
Another provocative passage supporting this bill comes from the N.J. Forestry Association in its spring 2011 newsletter:
“The New Jersey Forestry Association and other professional groups with practical experience need to keep showing that trees need to be managed and harvested to make the most of what nature has provided. A well managed forest will go on forever, while a forest left to its own devices will die and become useless to anyone, as are the pines in Atlantic County where they have lost their needles and are now rotting from the infiltration of pine bark beetles.”
It is true that conifers are highly susceptible to insects, especially in low-diversity ecosystems, and the loss of the pitch pine is a loss of economic output. But, it is unlikely that all the pitch pine are dead. If they are, how did this species survive for centuries in N.J. prior to the arrival of modern forest management?
The line preceding the above quote, beginning on page 3 of the newsletter, states, “Fortunately, there is a potential answer to the anger shown by the public toward the subject of forest management. The remedy is education. Many of the opponents were obviously educated in school and were probably well-meaning, although sometimes intemperate, but they evidenced no schooling in forest management or the overall state of our natural ecosystem.”
Sadly, this is a very true statement.
Education is the answer, but perhaps not in the direction the author implies. It is not the opposition’s lack of “schooling in forest management” that is the source of pushback to the bill. If I could bring Neel to the podium to speak on the issue of natural resource education, he might say something he once said to me, “Do you know what the problem is with forestry in schools these days? They don’t teach forestry!” By this, Mr. Neel meant that what dominates education in modern forestry schools is centered on economic timber production and that there is not enough emphasis on the ecology of ecosystems. He should have this insight. Neel obtained a BS in forestry from the University of Georgia in 1951. By the end of this two part post, ironically, I will show you that, while most of the scientific evidence that old trees and forests do not die of old age, the first publication I can find suggesting that old age is not the source of tree decline is an article published in the Journal of Forestry in 1927. The conflict here is partly a straying from what foresters learned and knew during the first half of the 20th century and partly what forest ecologists have learned during the most recent decades.
Sure. Why not? Why would trees be different than elephants, pandas, whales or humans for that matter. I mean, trees are charismatic megaflora. Why wouldn’t the laws of biology or the laws of life apply to them? For example, Jonny Flynn or Michael Jordan will not be able to replicate their athletic dunks when they are 80 (btw, did you see Michael’s first dunk over Tree Rollins?). Shoot, they will not be able to replicate these feats when they are half that age! So, why wouldn’t trees die simply of old age?
This human perception is understandable. When you go into a true old-growth forest you will notice many dead trees on the forest floor. This is a classic characteristic of an old-growth forest. You might notice several rotten trees, too, including living trees with cubicle butt rot (look to your right and scan the image at the end of this post). To the untrained eye, it might not look pretty. Even to the trained eye it might not look pretty, especially when compared to neatly managed plantations of straight and tall conifers.
So, this human observation is relayed early and often in many classical forestry classrooms, making it feel legitimate (Confession, I attended two forestry schools. I heard this concept frequently). It is so deeply embedded in the fabric of forestry education that the Inter-governmental Panel on Climate Change (IPCC) espoused this belief as recently as 2001. An IPCC publication stated “Overmature forest stands take up carbon from the atmosphere at slower rates, but even as the growth increment of the trees approaches zero,….”….sigh….If folks read this post, I expect some pushback along the lines of, “We don’t really think that anymore…that is an old idea,” which I know is true. The idea is fading. It is overmature. Unfortunately, where the rubber hits the road, where forest management decisions are made, it is a concept very much still in play. This is where things are in New Jersey (and many other places, honestly. Not picking on N.J. here).
In part two of this post, I will lay out the evidence countering the perception that age matters in terms of tree and ecosystem productivity.
There was a nice article in the NY Times on the Adirondack State Park whose title initially focused readers on how climate change could alter the park’s ecosystems. However, by the time you get to the end of the article, and luckily for us, you get to know Jerry Jenkins, one of the best naturalists I’ve ever met. It might be that only recently did this researcher become known outside the region and outside the legion of naturalists in the northeastern United States. For many reasons, I was thrilled to see this article. Primarily, the Adirondacks are my ecological home. It houses the forest that must have shaped my feelings for trees (while finalizing this post, I received a snail-mail from my mom with a clipping of the NYT article). Mostly, it is great to see Jenkins get his due.
The Adirondack State Park is one of the oldest and largest preserves in the lower 48 states; as the Clinton Administration was in its last throes, a larger preserve was created in the American Southwest. The Adirondacks have been a vacationland for the rich, famous, and otherwise since the 19th century. It was never, and I sincerely mean never, much of a home for those who wanted to make a living off of the land. This was especially true for locavores.
See, one of the best interpretations of the word “adirondack” or “adirondac” is “bark-eater.” Apparently, it was a cool nickname for first nation people living outside the Blue Line.
As you see in the N.Y. Times article, the region is also the place to study it all if you consider Nature at all. Jerry Jenkins is one of those people. You will not find his name name on a faculty roster at any college or university. But, what he says about our environment should be given the same weight as the words of any full professor. Like any good naturalist, he’s been out there for a long time. Not only has he been out there, he has been paying attention to what he sees. And better, he thinks about what he sees.
Jenkins was the first one I heard say that there has been no sugar maple regeneration in certain areas of the Adirondacks and that this is likely due to acid rain arising from the coal-fired power plants in the midwestern United States. When a person in the seminar audience asked why he thought that, he said that on sites with high pH (more basic soils), there was plenty of sugar maple regeneration. On sites with low pH (high acidity), there was no regeneration. He figured that the high pH sites buffered the calcium-loving sugar maple from the ravages of acid rain (acid rain leaches calcium from soils. High pH soils generally have more calcium). That care in observation and experimental design (comparing acidic sites to higher pH sites) is what all scientists strive to replicate in their research. I was lucky to talk to him at this meeting. His knowledge and logic were humbling.
Jenkins is not alone as a New England naturalist in terms of quality and intensity. I was reading a grad student’s poster on the damage and regeneration of old-growth forest in the western Adirondacks at this same meeting when Dr. Charlie Cogbill walked up. Like Jenkins, Cogbill is a “free-lance ecologist,” to borrow Cogbill’s term. As the student was explaining the project’s results, Charlie started nodding and said, “Yes, that is correct.” When the conversation proceeded, a question arose about a particular species. Cogbill reached into his backpack, pulled out a worn, spiral-bound notebook and pulled out his raw data from the SAME place where the student had conducted research. Not only did Cogbill have the same data, he has a ream of data from the same area from about a decade prior to that day. My mind marveled at that data set.
The natural history research that he and Jenkins conduct is of high value. It can aid in solving modern ecological issues and inform modern Earth-system models, which is what their massive data sets are doing. Natural history is not dead!
So, why are the Adirondacks such an attraction? It is hard to quantify, though I will give it a shot. The combination of water, mountains and intact forest is nearly unmatched. I’ve been fortunate to have visited and lived in many areas of the globe. Nothing seems to match the Adirondack region in the ratio of water to woods to mountains. Vermont is lovely, but it does not have the wetlands and waterways of the Adirondacks. As Jenkins notes in the Times article, it is this combination of ecosystems that makes it unique. From the boreal forests and wetland ecosystem that are home to the re-surging moose population to the oak and hickory forests like Virginian forests on warm, southern slopes in the southern Adirondacks, the Adirondack region has a wide variety of biota. I’ve even seen American chestnut saplings in the Adirondacks.
The impetus for the creation of the Adirondacks is likely the result of many factors: preservation of watershed for downstream communities, preservation of forest from the onslaught of industrial-scaled logging during the late-1800s, preservation of wilderness. In fact, the Adirondacks are preserved in New York State’s constitution as “Forever Wild.” It would take a majority of New York citizens to vote for any change to the Adirondacks (somewhere in the neighborhood of a 3/4ths vote).
The clause was so effective that the Adirondacks contains the largest amount of old-growth forest in the northeastern United States. In fact, the late Barbara McMartin thought that if you considered areas of the park that were lightly picked at by coniferphiles as old-growth forest, areas where only a handful of spruce, pine and fir were logged before preservation, there could be significantly more old-growth forest than what is currently recognized. In today’s human-dominated landscape, perhaps we can overlook these small-scale intrusions.
Thus, given the significant disturbance in the late-1800s and subsequent preservation soon after, the Adirondacks might be one of the best natural laboratories for the study of “natural” ecosystems. Natural is in quotes because it is time for northern North Americans to recognize humans as a part of Nature. And, in local proximity of uncut ecosystems, people can compare how ecosystems recover after heavy logging over the course of 100 years. There are few places in the eastern United States where such large tracts of forest can be studied in the same way.
The Adirondack natural laboratory also seems like a factory for the production of Earth scientists. At one point during the end of my dissertation I was attending a workshop for students who were part of the Department of Energy’s Global Change Fellowship program. Through that program I met approximately four other students who grew up within 2-3 hours of the Adirondacks and spent a significant time in the park either at a family cabin or through hiking and camping. At around the same time I met another young Earth scientist at Lamont-Doherty whose parent’s cabin was less than a 15-minute drive from my folk’s cabin. It is likely that our connections to the Earth in the Adirondacks influenced our direction as we moved through school. Obviously there is value in natural areas beyond ecotourism and wilderness for their own sake.
OK, I love the place and have gone on far too long, much longer than planned.
What about the title of this post and the focus of this blog? While Adirondack Forest is loved for its piney, boreal and coniferous atmosphere, they are truly loved in autumn for the often spectacular show they give us. That colorful show comes from the graces of broadleaf species: orange to yellow sugar maple leaves, red to yellow red maple leaves, yellow birch leaves, yellow to purplish ash leaves, etc. See for yourself in the untouched picture below.
I will admit it, there was a time when I loved conifers. Like, I was truly fanatical about coniferous trees. The first time I felt that way was upon walking among the great eastern white pine trees in the Adirondack State Park as an undergraduate research assistant and student. My first exposure to some truly impressive pumpkin pine was in the grove of old trees at the Pack Forest. These trees, charismatically represented by the Grandmother Tree, are truly impressive if you are seeing old-growth forests in northeastern North America for the first time. Soon after, I was taken on a hike to see a few large eastern white pine at the ranger school on Cranberry Lake. I was enamored.
As my educational path careened southward, I was brought to the large and old loblolly pines in the Congaree National Park in South Carolina. It was just a few years post-Hurricane Hugo and about half of the dense, massive loblollies were blown over. But, there were, and are, patches in the upper Coastal Plain that can give you a sense of how tree-mendous this forest was preio to Hugo. While not ancient, these trees are old for their species (the oldest tree was confirmed alive just a few days ago, making it at least 246 years old!). Please, go see these trees before they topple, especially in the heat of the summer. The scent they emit in the southern heat is savory.
My next stop was over the course of two years in the great longleaf pine ecosystem of the Deep South. The tree that is the foundation species of this highly diverse system is beyond charismatic. It is long-lived, has a phenomenal tap root that can look like another whole tree below ground, and long needles arranged like a basketball at the end of its twig. It is a glorious tree and ecosystem that deserves our attention and careful restoration across most of the Coastal Plain.
Not long after I finally landed in the Tree Ring Laboratory of Lamont-Doherty Earth Observatory for the first time, I was whisked away to the other side of the world to far, western Mongolia. Toward the end of that first, epic trip (think serious water illness; an outbreak of Black Plague; breaking out of the city quarantine at dawn; sharing a room with dead marmots, carriers of Black Plague; an overbooked plane back to the capital because of the plague; being wrongly held up at the border on the way home and missing our return flight….), we found what is still the oldest tree that I have personally cored: a 752-year-old Siberian larch in the Altai Mountains.
The next year I was on an expedition to the northernmost trees on Earth, the larch on the Taymir Peninsula. The scraggly small trees that were 400-600 years old were just lovely from so many perspectives…
Jeez, I’ve gone off-track here. I admit it. I still have the fever for conifer trees.
The point of all this preamble and this blog, however, is to point out that, yes, conifers are cool trees and while I will mostly ignore them on this blog, I dig them. However, I contend that the research field on the study of most broadleaf tree species is ripe, especially from a dendronchronological perspective. And, for this reason, but perhaps more for the fabulous diversity of leaf shape, bark texture, flower arrangement, autumn leaf color and overall funkiness of broadleaf species, I have moved on to adore broadleaf species.
Scientifically, we generally know much more about conifers than broadleaf species. Why this might be, I am not certain. I would think that conifers are the most studied type of tree for many reasons. Here are three:
1) They are highly valuable forestry species; foresters have been studying their natural history or life-history traits for centuries.
2) They live in extreme environments; forest ecologists and dendrochronologists trying to understand long-term climatic and ecological change focus on trees and forests in environments that are perceived to be the most sensitive to environmental change.
3) They live longer than hardwood trees; so, for many of the same reasons in #2 above, conifers are generally targeted by tree-ring scientists.
The goal of this blog, therefore, is at least twofold. First, it will be a champion for the wonderful, overlooked broadleaf species and their associated forests in the eastern United States and abroad. Of course, overlooked might be too strong of a word. For example, Liriondendron tulipifera (tuliptree, yellow-poplar, tulip-poplar) was an early species described by foresters as they began to scientifically study eastern forests. However, as will be demonstrated, our general knowledge of broadleaf species, including tuliptree, is much more limited than many coniferous species.
Second, as natural history is much less of a focus in modern ecological research, despite its necessity for long-term biological conservation, this blog will serve as an outlet for the natural history of broadleaf species learned through dendrochronology. While conducting paleoclimatological and paleoecological research through the examination of old-growth trees and forests, we often learn much about the natural history of individual species. However, this particular type of information rarely makes it into the scientific literature, as it is rarely the focus of our work (you would be so lucky to sit at a bar sometime with a handful of experienced dendrochronologists — the depth of their natural history knowledge is great). Because natural history appears to be dying out at American universities, the uncertainty around simple questions like, “How long can a tuliptree live?” and “How long might the shade-intolerant tuliptree persist in shade?” is high. This blog will serve as one place to answer some of these questions.
This blog will also serve up some of my favorite images of broadleaf species and forests. To close off the first post, here are some delightful images of the appropriately-named bigleaf Magnolia.