Friday, July 30, 2010
PROJECT PROFILE: Using GIS to model how climate change and land use will affect the abundance of common ragweed
The big picture of the project I am working in is to model how climate change and difference in land use will affect the allergenic potency of Artemisia artemissifolia, better known as common ragweed. This is the first year of a four-year study, so creating a database that will work for the rest of the project is indispensable. I am working on developing part of a geodatabase containing a myriad of GIS shape files, from “all roads” layers to layers containing parcel owner information and population densities.
Using GIS, my team has created a layer that combines three different land cover categories (Forest, Open and Developed) with three different averaged temperatures. This combination gives us nine categories (E.g. Open, Low Temperature). We have up to 10 plots created randomly in each category, and I have created maps that facilitate us access to our plots by collecting detailed information such as addresses and land use. We have surveyed most of our plots in Massachusetts, New York, Connecticut, and New Jersey, and we expect to go to Vermont and New Hampshire in the next few weeks.
Once we are at our plots, we also look for factors, other than temperature and land cover, that might affect ragweed distribution at a finer scale. For example, we’ve been in plots under the same category, but completely different land uses. One might be a baseball field and the other an agricultural field. Or even if both are agricultural fields, plowing practices and distance to right-of-ways might affect ragweed population per plot, so we have to be careful when collecting data to pay attention to those details.
Building a bridge between environmental and social factors is essential to understand how ragweed will affect human populations in the future, and that is exactly what I am trying to do. With the collected data, I am going to do a spatial distribution model showing ragweed abundance using the characteristics mentioned before as parameters, and linking them to socio-economic variables and human population density.
Thursday, July 29, 2010
Two weeks from now, all 33 summer REU students will be speaking in a two-day Symposium at Harvard Forest. They will have 15 minutes to discuss their research projects from this summer. For some, this will be their first public presentation.
In preparation for their talks, David Orwig, Senior Ecologist at Harvard Forest, gave a seminar Tuesday night, “How to Give a Good Scientific Presentation”. Orwig discussed how the framework for a scientific presentation should parallel the structure for a scientific paper by including sections on objectives, methods, results, discussion, and conclusions. He emphasized to students to think about which 2-3 main points they want their audience to remember, and to make sure those points are made clearly throughout the talk. He provided several useful tips, such as:
- Acknowledge co-authors in your opening remarks
- State your objectives clearly and concisely
- When describing methods, be precise but not exhaustive. Include maps of study locations, photos of your research site, study organism, and equipment used, but don’t go into every detail of how you collected and analyzed data.
- When displaying a graph of results, make sure to explain the components of the graph. Tell the audience what the axes are, which colors or bars represent which data, and why you drew certain results from the graph.
- Use tables and graphics that only have information you want the audience to see. Statements like “I know this is hard to read, but I really just want to point out this section” are frustrating to an audience. Edit your tables and graphics to have only the sections you want to discuss.
- In your discussion and conclusion, remember to emphasize the 2-3 main points you want your audience to remember. A conclusion should be quick; it is your last opportunity to reinforce your main idea.
- Include an acknowledgment slide at the end of your talk to identify key personnel and funders.
In addition to discussing how students should structure their presentations, he also provided several good tips on presentation skills:
- When speaking, be enthusiastic and smile!
- Do not read your slides verbatim; talk with your audience, not to the screen.
- Practice transitions between sections and slides
- Create slides that are simple and easy to read. Use consistence colors and backgrounds.
- Try to make “color-blind-friendly” slides by not mixing reds and greens in figures (use this for assistance)
- Practice your talk; finish on time; tailor your talk to your audience.
The bottom line for a good scientific presentation? Be organized, speak clearly, and be enthusiastic! If your audience remembers your 2-3 main take-home points, your talk has been a success!
Tuesday, July 27, 2010
Here at the Harvard Forest, I am working on the effects of soil warming on various hardwoods. There has already been an experiment to test the effects of global warming on soil. The 20-year-long experiment found that with increased soil temperatures there was an increase in microbial activity. This increase in microbial activity led to more usable nitrogen in the system. Nitrogen is the limiting nutrient in tree growth; with more nitrate and ammonium availability, trees can continue to grow. Ammonium can easily be made into many amino acids, proteins, which the tree can use. However, nitrate, the other form of nitrogen, cannot be used to make proteins. Nitrate needs to be broken down into ammonium. Trees make this enzyme, called nitrate reductase, which reduces nitrate to ammonium. My project this summer is measuring the amount of nitrate reductase enzymes in Oak, Sugar Maple, Red Maple, and Birch. My mentors and I measure trees at Barre Woods where there are two twenty meter plots, one heated and one controlled. This summer we started measuring trees grown with different fertilizer treatments in the greenhouse. We measured both the roots and the leaves to compare nitrate reductase activity.
On a day-to-day basis, my activities vary between working in the lab to working in the field. It is the perfect mix for me since I am majoring in chemistry, but plants are my passion. In the lab, I measure the amount of nitrate reductase by using an indicator and a spectrophotometer. Out in the field, I collect samples and take soil cores. In the greenhouse, I fertilize, water, and deal with pests. In the beginning I did a lot of reading to formulate a protocol for testing roots since it had never been done before in the experiment.
The project is in its second year of testing. In future years they will continue to test nitrate reductase activity to see if there is any pattern between species or the different plots. There might be a competitive advantage among species if the tree is capable of using nitrate. For the rest of the summer, I will be analyzing the various data I have collected to see if there is any correlation.
Monday, July 26, 2010
We have spent the summer happily crawling around in the forest, bruising ourselves under mountain laurel in pursuit of the holy Grail of our project, moose poop. We are studying the impact of deer and moose browsing on the regeneration of forests, specifically looking at hemlock and oak seedlings. This research is particularly important since the number of white tailed deer continues to increase, and moose recently reappeared in Massachusetts after being extirpated since the mid-19th century.
All the same, you don't have to be very knowledgeable about forest life to know that moose don't fit under mountain laurel, so why would we look under those plants? We have been hiking, rain or shine, out into the wilderness to set up plots on points in state-owned lands that are randomly generated by a computer. This often means that our points are in the least convenient places possible, under mountain laurel, on mountain tops, or at the ends of roads that have restricted access because they are associated with a local jail. Once we have managed to get to a site, we establish 20x20 plots in which we look for deer and moose signs. We also take note of the trees and shrubs in order to gain some understanding of the prevalence of deer and moose at a location and their impact on the forest composition.
This data collection is part of a larger project that also incorporates exclosure plots. The exclosure plots are set up in a recent clear cut and consist of a full exclosure (keeps both deer and moose out using fences), a partial exclosure (keeps moose out but allows deer to crawl in through a two foot gap along the bottom of the fence), and a control where there are no fences.
Mickey is interested in the impact of these clear cuts on the level of deer and moose browsing activity not only within the clear cut, but also in the surrounding area. It is known that a larger number of young trees and shrubs growing up in the recently cut plots provide a greater amount of food in a small area, thus attracting a greater concentration of ungulates. He hopes to identify the impact of the clear cut on the surrounding area, seeing how far into the forest the effect of the clear cut can be seen on browsing levels.
Carlyn's individual project is focused on oak regeneration. She'll be looking at oak regeneration in response to all the variables we measure at the plots (overstory characteristics, shrub cover, soil, deer and moose sign, red maple browse index, and physical characteristics of the site). She is also going to use existing GIS data to examine patterns in oak regeneration from a broader land use perspective, taking into consideration ecoregions, habitat fragmentation, and proximity to clearcuts and development.
Tuesday, July 20, 2010
Helping the Wood Turtles and Learning About Passion: REU Students Participate in Annual Service and Career Day
Last week, all 33 REU students got to take a day off from their regular research projects in order to participate in Service and Career Day, an annual event held each summer for the Program.
For 4 hours in the morning, the students worked for The Trustees of Reservations (TToR), a land trust established in 1891. On the Brooks Woodland Preserve, just a few miles from Harvard Forest, TToR is restoring habitat to be suitable for wood turtles, a threatened species. The turtles need to be able to travel between a small creek in the woods and a newly-created opening in the forest where they will lay their eggs. However, significant amounts of woody debris (such as fallen limbs and branches) accumulated on the ground when the meadow was restored. The REU students were tasked with moving this debris so that it would not prevent the wood turtles from arriving at their mating sites. “We’re building a turtle highway to turtle sex heaven!”, as one student summarized.
“Think like a turtle. Get on your hands and knees, if you like, to try to see what might be a barrier for a wood turtle along this corridor,” Walker Korby, North Quabbin Superintendent of TToR, told the students.
After a few hours of moving fallen limbs and raking down piles of dirt, Korby led the students through an interesting exercise in using peripheral vision. The students all formed a circle, shoulder-to-shoulder, and then practiced using their peripheral vision by focusing on their hands, which they held out to the sides of their faces. Once used to focusing sideways, the students tried to throw a ball to each other, across the circle. The exercise taught the students how they actually can see much more of their surroundings using this type of vision, rather than our instinctive mode facing forward.
The purpose of this restoration project took some time for the students to understand. They learned about land restoration and discussed different philosophies on conservation and wilderness protection while working on this service project. In the end, most students felt like they had contributed to the goals of TToR, and all were grateful to spend the day with their friends in the sun.
“Service Day introduced me to a local land trust that I didn't know very much about before, and let us explore beautiful, local, preserved woodland that I don't think any of us knew existed.” – Megan Jones
"Service day really taught me the meaning of friendship. I really enjoyed working together with the other REU students. Although our work was not the most exciting, working side by side with other students who share my passion was." – Kristen Schipper
“For service day, we were supposed to scatter piles of broken branches to make it easier for wood turtles to cross the woods from the pond towards the clearing. It became an interesting and fun exercise for us to figure out how it would be easiest from a wood turtle's perspective to navigate the debris. Another exercise we did was using our peripheral vision to determine the extent of our visual ranges. Using this vision, we practiced throwing balls and trying to catch them without following them with our eyes (i.e. using peripheral vision).” – Sarah Fouzia Choudhury
In the afternoon, the students participated in Career Day. Five panelists came to Harvard Forest to discuss their personal careers and the paths they had taken throughout their lives to get to where they are today. The speakers included Betsy Colburn (Aquatic Ecologist at Harvard Forest), Stephen DeStefano (USGS MA Cooperative Fish and Wildlife Research Unit & University of Massachusetts), Elizabeth Farnsworth (New England Wildflower Society), Wayne Petersen (Massachusetts Audubon), and David Graham Wolf (Mt. Grace Land Trust).
The speakers first spent about an hour introducing themselves to the REU group. All speakers discussed the importance of passion and finding jobs and careers which you enjoy. Many of the speakers had taken circuitous career paths to their current jobs and spoke about how, even though they had times in their lives of uncertainty, job opportunities always had a way of arising at the right time. The students then broke into five smaller groups and each had a chance to talk in depth with each of the five speakers.
Almost all of the students found Career Day to be immensely valuable, in large part because the speakers demonstrated how “choosing a career” does not mean having to choose one interest and to relinquish the rest. People find ways to be artists, writers, lawyers, teachers, and businessman, and still have careers working in ecology, conservation, and the natural resources.
“The speakers at Career Day were striking examples of how attached people can become to the New England landscape, and how this attachment to place can shape a person's future l also learned more about the work done by land trusts, and about the different way research and advocacy can be integrated.” – Megan Jones
"Each of the speakers at career day provided us with enlightening and interesting information about careers in the ecology and natural resources fields. The most important thing I took away from career day is that it is okay to blend your interests for future endeavors, even if they seem quite different, such as art and science or business and ecology. I greatly value the knowledge and information I took away from career day at Harvard Forest." – Autumn Amici
“It was most gratifying to see so many bright young faces potentially interested in the biological and environmental sciences, all willing to spend a hot summer afternoon listening to others talk about their own experiences and careers. I felt that the attention and enthusiasm exhibited by the students, as well as by my fellow colleagues on the panel, was exemplary and I was very pleased to have been part of such a distinguished group. I hope everyone else profited from the experience as much I did!” – Wayne Petersen, Director, Massachusetts Important Bird Areas (IBA) Program, Massachusetts Audubon
Monday, July 19, 2010
We are working with Dr. Andrew Richardson and two of his postdocs, Koen Hufkins and Oliver Sonnentag, to investigate ways of monitoring and measuring the phenology (recurring life cycle events, such as flowering, spring green-up or senescence) of North American forests using webcams and digital imaging. This project is highly analytical and employs the use of computer programming languages such as R and MatLab. These programs let us process thousands of images so we can isolate ideal conditions in which to measure the vegetation indices for a given day or season. There are a multitude of variables that can confound our results such as individual camera settings, weather conditions, and positioning of camera. This work is part of a larger effort involving a national phenological observation webcam network, Phenocam, which includes webcams at National Parks, research sites, and other locations around the country.
Adam and Andrea are involved with writing computer code (mainly in R) that generates graphical output, downloading images from different sites all over the country, filtering these images and classifying them by weather conditions (clear, overcast, snow, etc.). So far a dozen sites have been analyzed in some way or another for a variety of vegetation indices and time series plots have been generated. Adam and Andrea, having little programming experience coming into the program, have “enjoyed” a steep learning curve when it comes to computer programming. So it is fair to say that they have learned quite a bit.
Cory, probably the most tech-savvy of the group, spent most of the beginning of the summer configuring cameras, some of which are essentially small, programmable computers. Currently, Cory is working on expanding the Phenocam website, which shows only current images, to display relevant data including current time series of phenological activity both from images collected at the site and satellite data. This will allow researchers to more easily compare phenological data collected via various methods, one of the main goals of our research.
One of our more interesting projects this summer was the installation of 14 webcams at the top of the EMS tower. We set up these cameras as an experiment to compare and contrast how different cameras influence measure the phenological response that are ultimately extracted from the collected image files. The cameras range from sophisticated surveillance systems to game cameras used by hunters. We assisted our postdoc mentors, Koen and Oliver, with building a weather-proof box (“Mr. Mad Scientist Box”) to contain a power source and data logger and with installing the cameras on top of the tower. This required carrying a 10’ board up the narrow tower, along with all the cameras and tools. It ended up being three long days of work, but was a great chance to see how the cameras all over the country that we are using data from are set up and all the hard work that goes into this research.
On a day to day basis we are glued to our computers programming, downloading and isolating images, researching phenology, conducting image analysis, and taking regular tea/coffee/hot cocoa breaks. We do get out of the office occasionally to help researchers doing related field work or to check up on our newly set up row of cameras and "Mr. Mad Scientist Box."
There is still more work to be done with images we have downloaded and all the information they encompass, but we are aware that we are working on a new and unique project in the field of ecology. This adds to our enthusiasm for working at Harvard Forest this summer.
Friday, July 16, 2010
We are working in the clearcut up on Prospect Hill near the fire tower. Previously, this area was a spruce plantation, but 2 years ago, it was deforested and timber was harvested. This area is now used as a research site to highlight the effects of large-scale deforestation efforts. A flux-tower was set up in the middle of the area to help capture the carbon, water, and energy fluxed between the land and the air. The data we are collecting will be used to put the flux tower measurements into context to better understand the effects of climate variability on carbon sequestration and release from ecosystems (US Forest Service 2009).
To get a snapshot of the landscape, we must employ many different types of data collection methods. Throughout the summer, we’ve been measuring woody debris and vegetation. We have 5 transects that extend from the flux tower, and each transect measures 50m. We identified over 39 different types of vegetation along these transects and also recorded vegetation abundance. Fine woody debris data will also be collected along these transects. We also have 12, 20m x 20m plots between the transects (3 between each transect) where we identified and measured seedlings and saplings as well as collected all coarse woody debris measurements. So far we have completed our vegetation survey comprised of a botanical inventory, vegetation transects, and seedling and sapling plots.
Currently, we are working on finishing up collection of woody debris data so that we can resample our vegetation transects to record vegetation growth and capture any differences in vegetation composition. For our individual projects, we are both focusing on different aspects of the clearcut data we‘ve collected.
Angie will be using the woody debris data and, based on the decay rates proposed in scientific papers, will predict the rate of decay in this specific clear cut in order to better understand the rate at which carbon is released from the debris.
Crystal will perform analysis on the data gathered from the vegetation transects and seedling/sapling plots to characterize the vegetation found in the clear cut as well as its composition in the site. She will also be using Audrey Barker Plotkin’s (Harvard Forest Site Coordinator) previously collected data on the plantation before it was harvested to compare pre- and post-harvest data to record changes in vegetation inventory, growth, and composition.
It gets pretty warm in the clearcut during the summer months, but we are rewarded with an endless supply of berries and a nice farmer’s tan. All of our hard work has been well worth it and will continue to reward us well into the future. We will not only come out of this experience with data to be used for our own research endeavors at our home institutions next semester, but we’ll also have mastered valuable field methods and the opportunity to perform data analysis on data we singlehandedly collected and compiled . As a student, you aren’t always afforded the chance to play such a significant role in each phase of the scientific process, and we definitely are experiencing that here at Harvard Forest, which is extremely rewarding.
Thursday, July 15, 2010
Last Sunday, three students and I went whale-watching. Again. Several weeks ago, we had driven to Gloucester, MA, and spent four hours on a boat, in the midst of a cold, thick fog, and returned to shore with no whale sightings. Lucky for us, Cape Ann Whale Watch gave us vouchers to come back on a boat trip at no additional cost since they guarantee whale sightings on their trips. We knew we would be missing the final game of the World Cup, but we had high hopes it would be a good day for whales. And boy, did we have some sightings! It was a beautiful, warm day on deck of the Hurricane II, and with the high visibility, the boat powered out much faster to the whales. Almost immediately, we happened upon two humpback whales, a mother and her calf. The two whales approached our boat closely at first, and for the next 45 minutes, we would wait 5-8 minutes to see them surface for a minute before diving deeper in the water again.
There are three species of whales commonly seen off the coast of Massachusetts: humpback whales, fin whales, and Minke whales. Humpbacks are easily identifiable because their pectoral fins are white, so even when they are below the surface of the water, you can see them swimming. Also, humpback whales are the most likely to lift their tail flukes completely out of the water when they dive more deeply. Researchers name new whales when they are 2-3 years old, usually based on the pattern on their flukes. Whales are never given common “human” names, nor are they given gender-specific names, since the actual sex of the whales is very difficult to determine (except for mothers who are swimming with their calves!).
Once we lost sight of the humpback whales, we continued on our boat trip. We were treated to a rare close sighting of three fin whales. Fin whales, the second largest animal on the planet after the Blue whale, swim faster than other species, so they are often only seen from farther away. After watching the humpback whales for so long, the Fin whales seemed huge! They seemed to be floating directly under the surface of the water, and periodically, they would lift their blowhole out of the water, round their backs until their dorsal fin broke the surface, and then re-submerge. After the excitement of the humpbacks, everyone on board seemed quietly impressed at the great size of the Fin whales.
As the Hurricane II returned to Gloucester, bouncing along on the waves like an amusement park ride, we all enjoyed soaking up the sun on deck. Another delicious meal of New England clam chowder and Bailey’s Cheesecake at a local restaurant completed our trip!
"The whale watching trip was so much fun and was made even better by the fact that we saw three different species of whale along with a mother and calf. It was also great that we were standing next to someone who was getting World Cup updates, so we didn't miss anything at all. It was spectacular!" – ANDREA GARCIA
"This trip was amazing and the weather could not have been better! Although I was quite dazed by the Bonine (which I am so glad I took), it was awesome seeing the three fin whales traveling together. It made me feel so small out there on the ocean. Even more amazing was seeing the mama humpback with her calf only feet away from where I was standing! We wanted to name the baby 'Rose' (to match the mama's name, 'Dusky') but we then realized that the name violated all three naming rules. So, there is a baby whale out there somewhere that is currently nameless. Another huge upside of the trip was getting homemade Bailey’s cheesecake at Halibut Point [a restaurant in Gloucester]. You can't beat that for a Sunday adventure." – MORGAN VIGIL
Wednesday, July 14, 2010
My project this summer is looking at the urban-to-rural gradient between downtown Boston and Harvard Forest. This research is a small piece of a larger project that is looking at the differences in a variety of factors along the gradient. These factors can include changes in the concentration of atmospheric CO2, nitrogen levels in the soil and in tree leaves, and pollution. My personal project is looking at how changes in all of these factors between the two endpoints of the gradient impact the growth rates of two trees: red oak (a tree that is native to Massachusetts) and the tree of heaven (an invasive that was brought over from China over 200 years ago).
Red oaks are fairly common throughout Massachusetts, so finding trees in the Forest and in the Arnold Arboretum in Boston was not particularly difficult. However, while the tree of heaven can be found almost anywhere in Boston, for a highly problematic invasive species, it has been quite difficult to locate anywhere near the Forest. I finally found one large tree and a few saplings in a nearby town. Since locating all of the trees I needed for my research, I have been spending most of my time coring those trees and measuring their growth rings to get a sense of how fast these trees grow. The remainder of that time has been spent learning how to use the program, R, to analyze my data and to convert giant tables of ring width and climate data into friendly graphs.
Eventually, I hope to be able to do several things with these data. First, I want to compare growth rates between species growing in the same location to see how they behave under similar conditions. Next, I want to look at differences within each species when they are grown in urban versus rural environments. Then, I can compare those differences between species (particularly considering that red oak is a native species and tree of heaven is an invasive). I also plan to look at how growth rates impact carbon sequestration: the faster trees produce new wood, the faster they sequester carbon, but the amount of carbon sequestered in each ring that I measure depends on a lot of variables, including the species of tree and the age/size of that tree. All in all, I hope to do make many manipulations with the data I am collecting, and hopefully by the end of the summer, I will have an interesting story to tell about what’s going on with trees growing in very different places in Massachusetts.
Friday, July 9, 2010
"There was a lot of fun to be had on the 4th of July weekend, including rock climbing, contra dancing, and tacos. I even got to spend some time with Joe and Maddy during their brief return visit. [Joe and Maddy are two REU students spending six weeks collecting data in New Hampshire and Maine]. Even though I didn't go see any fireworks, I didn't feel like I missed anything. I wish I could have more weekends like this." – Andrea Garcia
"This last weekend I headed home for a wedding and then on Sunday and Monday, Meredith, Carlyn, and Erik came up to my lake cabin [in Maine]. We relaxed in the sun, went fishing, tubing, and skiing, and had a bonfire. It was a great time; the night of the 4th, there were fireworks going off all over the lake." – Angie Marshall
"Over the Fourth of July weekend, I went to hang out at Queen Lake, just a few miles from Harvard Forest, for the first time and it was amazing. The beach was clean; the water was clear, and the water-temp to air-temp ratio was perfect. Swimming out to the blueberry island was definitely a fun, appetite-inducing challenge. I also hiked out to the fire tower to watch the sunset on a clear day. It was breathtaking. And the hike back was beautiful between the dusk and fireflies. And the blueberries in the clear cut were definitely a major plus!" – Morgan Vigil
Wednesday, July 7, 2010
Lianna and I are working on the Simulated Hurricane Long Term Ecological Research project out on the Tom Swamp tract of the Harvard Forest. As a part of this project we are collecting another year's worth of data and information on how the original trees are fairing as well as documenting new canopy regeneration and understory dynamics. This summer specifically we’ve worked on recording the current status of the original trees, quantifying the amount of dead wood, mapping new trees that have grown to 5cm Dbh, analyzing leaf liter, and observing understory vegetation make-up and coverage. The pull down and control plots are both quite large (160mx50m and 120mx50m respectively) and most sapling methods require several measurements, so we work our way through the plots together for each of the various phases of data collection. We’re currently working on mapping in the new trees and will then move on to our understory survey.
Here is a timeline of a day in the life of a hurricane researcher:
8am: wake up and head down to Shaler Hall for breakfast
8:45: meet with Audrey Barker-Plotkin (our mentor) and psych ourselves up to go out to the field
9:15: arrive at the Hurricane Plot
9:15-9:20: suit up for going into the woods: apply ample amounts of bug spray, mosquito netting and gloves
9:20-12:00pm: collect data for whatever phase of the project we’re on, i.e. do dead wood transects or map in trees
12:00-1:00pm: head back to Shaler for a delicious lunch and to recuperate our mental strength
1:00-4:00pm: continue the day’s work
So far we have learned the following tid bits:
• Tree tags almost always mysteriously vanish
• Spiders always tend to make their webs at face level
• Hurricanes are actually an important disturbance cycle for New England forests
• No amount of bug spray or mosquito netting will keep you from getting bug bites
• Trees grow back from being damaged in cooler ways than you could imagine
• Chipmunks love playing on the downed wood
• The forest structure has actually changed quite dramatically since the “hurricane”
Where will our project go from here?
After the data we collect this summer are analyzed, we will know a lot more about how the forest has regenerated from the hurricane disturbance which occurred 20 years ago. In the future, scientists can continue to look at this site as a means of understanding the important role wind damage plays in New England forests.
Hi! I’m Fiona, and I work for Leland Werden, Bill Munger, and the Wofsy Group at Harvard University. The project that I am involved with this summer is looking at the influence of understory vegetation on carbon sequestration in the Harvard Forest. This is one small part of a much larger project, which has been going on here for the last 20 years, centered on the eddy flux tower. Over the past two decades, this tower has been collecting data on the amount of carbon that is released and absorbed by the surrounding forest. This summer, I’m focusing on how the understory affects the finding that the Harvard Forest is in fact a sink for carbon, and has been absorbing a larger magnitude of carbon every year since the study began.
Daily, my job is to continue taking physical measurements in the plots surrounding the tower, in order to support the carbon data from the tower. This involves measuring tree growth, maintaining leaf litter traps and dendrometers, and taking LAI (leaf area index) measurements in each of the 34 plots. For my specific project, I have recently completed an understory survey of all woody plants in the plots measuring 1 cm to 10 cm DBH (diameter at breast height), which is over 1500 plants! Next, I will be measuring photosynthetic rate of some of these understory plants, using a LI-6400.
So far this summer, I have learned so much about the way in which scientists collect their data, and how seemingly simple measurements can take a serious amount of work. I have learned how to make and put on dendrometers, to identify the majority of woody plants in the Harvard Forest, to use an LAI and a LI-6400, and of course, I have also learned the basics of how an eddy flux tower works. It is especially interesting for me to be a part of an ongoing project, because I get to see how far we have come in understanding the factors that effect carbon sequestration, but also how much is left for us to discover.
Friday, July 2, 2010
We are studying tree hydraulics; specifically, we’re measuring sap flow in trees to understand at a fundamental level how trees get water from their roots to their canopy. A large component of this project is to understand the methodology used to assess sap flow, which includes the granier and the pulse system. Furthermore, we are also interested in evaluating the effectiveness of the method and the best way to calibrate the data. We are currently collecting and analyzing the data that is coming in from the granier and the pulse system that we have installed. There is some de-bugging we have been doing with the systems, and we are also in the process of inserting more probes into trees to get more data points.
On a day-to-day basis, we have largely been setting up the granier system and preparing for data analysis by taking tree measurements. To set up a good granier system, we have been spending a lot of time making probes, which are very expensive to purchase. Making probes involves a lot of sawing, wire cutting, and soldering. We work with many power tools, thermal couple wires, and super glue. It is very hardcore! We also do a lot of wiring, screwing, and labeling in the field to get the relevant trees connected to the right systems. In addition, we sometimes drive and ride on the “Buckey,” which is a truck similar to a cherry picker that can take us up to the canopy of the forest.
(By Lisa Chen): I have learned a lot about tree physiology and electronics. With the right materials, I can now make $500 granier probes. (A skill which could provide an interesting career alternative if my future plans don’t work out!) In addition, I can now identify a number of different trees such as maples, oaks, and hemlocks, which I wasn’t able to do before this summer. Jim Wheeler (one of our mentors), Sarah, and I spent a long time trying to identify the first chestnut tree we came across, and I am proud to say that I can now identify chestnut trees by sight. In addition, I can operate the “Buckey,” and I think that is an incredibly cool skill.
(By Sarah Fouzia Choudhury): We spent most of the first few weeks making probes, which were surprisingly time consuming to make, but it was useful for learning how they work. We have only processed data for a short while, and have had to wade through a lot of junk data since some of the probes get “creative” with the data they collect. But it would only make it so much more worthwhile when a probe was reading properly and providing interesting results. One of the patterns we have noticed is that the bole of the tree (the part of the tree nearest the ground) often shows a lag of some time. One hypothesis (assuming this is not an artifact of the granier heat dissipation method) is that the tree is acting as a sponge, so the crown of the tree starts to draw water before the roots pull water out of the soil, and it then recharges through the day. We used photosynthetically active radiation (PAR) as a proxy for the amount of solar radiation reaching the trees and stimulating stomatal opening and sap flow.
This Wednesday, we put more probes in the crown of a maple and a pine. For this, we had to raise the jib, and move ourselves into position with the finesse of a parking expert. However, our attempts at doing so were a little less than par, and involved a few broken branches. This delicate maneuver was followed by drilling into the tree, pushing in the probes, and making the required electrical connections.
From here, we hope to continue analyzing the sap flow data and finding meaningful results. We are also interested in measuring photosynthesis rates and the amount of water that is present in the sun leaves of several species to understand tree hydraulics better.