Research Project Descriptions for Summer Research Program in Ecology - 2005
Invasive Plants, Pests & Pathogens
Invasives
Ecological and historical aspects of invasion in the exotic species, Alliaria petiolata in New England.
Researchers Involved: Kristina Stinson
Summer Supervisor: Kristina Stinson
Locations: Harvard Forest, Berkshires, other sites in Massachusetts.
This project investigates landscape, community, and population - level interactions between the exotic plant, Alliaria petiolata, and native plants in New England Forest habitats. We will conduct a comparative demographic survey of populations across sites with different land use history and habitat characteristics to test the idea that successful invasion into intact forests is a product of combined effects of historical, ecological, and evolutionary mechanisms. Field sampling will include comparisons of heavily- and sparsely-invading populations in two contrasting (open and closed) forest canopy environments. We will also continue research that seeks to determine whether populations in high light habitats are more important sources of population growth in spread than those in low light habitats, using data on plant performance in the two habitats. This work involves field observations and a reciprocal transplant design. The work will simultaneously test theoretical questions about the role of population dynamics in invasion and inform conservation management and policy decisions. Our results will help identify links between land use and the presence/abundance of non-natives; develop predictive models of invasion based on historical and present-day levels of anthropogenic and natural disturbance; and identify evolutionary potential for further spread within invading populations.
Students working on this project will employ comparative methods, vegetation sampling, experimental design and field identification of native and invasive plant species. Mentees will measure plant and environmental variables at several different field sites, make regular observations of experimental plants and monitor long term research plots. Opportunities for independent research include but are not limited to soil fungi community sampling, mapping sites using GPS, analyzing spatial data with GIS, leaf chemistry analysis. Students are expected to assist with data entry and analysis, with direction from the mentor. Summer supervisor will meet with student one to three times per week.
Disturbance histories as a predictor of habitat invasibility in a mosaic landscape: Cape Cod National Seashore
Researchers Involved: Betsy Von Holle, David R. Foster, Glenn Motzkin
Summer Supervisor: Betsy Von Holle
Research Location: Cape Cod National Seashore
Non-native species are a major threat to native species and ecosystems. We are trying to understand why certain upland habitats in Cape Cod are invaded by nonnative species while others are not. We employ a multi-scale technique, where we determine landscape-level influences on exotic species invasion and further investigate these influential factors with patch-scale analyses. This study attempts to separate the various contributions that historical natural and human-caused disturbances have on exotic species presence and abundance in the varied landscape of Cape Cod National Seashore. This year we are setting up a heathland restoration project that will simulate different historical disturbance types and colonization intensities to understand the resistance of this system to invasion by nonnative species. Additionally, we are exploring the factors that limit invisibility to into the rare, coastal heathland habitats.
The student will assist myself and one or two other summer students to set up a heathland restoration and to maintain and complete two community-level experiments on nonnative species invasions in heathland and black locust habitats. We will be gathering data 5 days a week, and will have long hours in the field setting up experiments (which will involve planting and weeding the assembled communities, identifying plant species and maintaining the experiments). We will be working occasionally in adverse conditions. In addition, the student will have the option of designing a small experiment within the context of the larger project. The independent project options are to 1. Explore the impact of one of the major non-indigenous species on ecosystem or community properties of Cape Cod National Seashore (CCNS), or 2. Explore the impact of Black Locust, Robinia pseudoacacia, on the understory plant community. The student will meet daily with Betsy Von Holle.
Hemlock Woolly Adelgid
Life History Parameters and Range Expansion of Hemlock Woolly Adelgid Infestations
Principal Investigators: Scott Costa, Joe Elkinton, Aaron Ellison and Paul Moorcroft
Graduate Student: Ann Paradis (Major Professor - J. Elkinton)
Summer Supervisors: Scott Costa and Joe Elkinton
Research Location: Harvard Forest
The hemlock woolly adelgid, Adelges tsugae, is an invasive insect that is decimating hemlock forests in the Eastern United States. The invasion front has passed through Massachusetts and has entered Maine, New Hampshire and probably Vermont. The extent that trees are infested within localized areas continues to increase; yet the dynamics of HWA spread is poorly studied. Factors such as tree health, population density and insect sensitivity to environmental extremes may interact to influence changes in expansion of the vertical and horizontal distribution of HWA infestations. We are seeking to increase our understanding of these processes through documentation and modeling of changes in HWA distribution, development and survival.
The intern working on this project will use existing sampling plans to monitor population increase and small-scale range expansion of HWA in hemlock stands at Harvard Forest and the surrounding area. Observation of tree health and its relationship to adelgid density and rate of range expansion will be examined. Additionally, the intern will work closely with Ann Paradis in evaluating the vertical distribution, development, density and survival of HWA on individual trees.
The intern will meet with either summer supervisor (Costa and Elkinton) or Ann Paradis weekly basis. We expect that the intern will work closely with Ann several days/week during different times of the project.
Ecosystem Analyses of Hemlock Woolly Adelgid Outbreaks in Southern New England
Principal Investigator: David Orwig
Research Assistant: Heidi Lux
Supervisor: David Orwig
Research Location: Harvard Forest
Our research includes a multi-scale project investigating the response of ecosystem processes to stress and mortality caused by the introduced hemlock woolly adelgid. This forest pest migrated into southern New England in the mid-1980s, and has since caused widespread hemlock mortality and reduced tree vigor throughout Connecticut and southern portions of Massachusetts. We are interested in examining how the decline and mortality of hemlock due to either HWA or logging (the primary management response to HWA) will affect the timing and extent of nitrogen cycling changes. We will be investigating how changes in ecosystem function are manifested in an urban park setting in Boston as well as in forests in Central Massachusetts and Connecticut.
David Orwig will have primary responsibility of supervising and advising one student, but will be assisted by Heidi Lux. David will meet weekly with the student and with Heidi daily. The student should become familiar with HWA background information and have interest in landscape, ecosystem, and soil analyses.
Student responsibilities will include weekly travel to field sites in Connecticut and Massachusetts, to collect vegetation and soils data from permanent plot locations as well as temperature data. The student will be encouraged to select and design an independent research topic within the framework of the overall project, perform appropriate data analyses, and present results orally and in written form at the annual summer student symposium.
Background readings can be found at the following website: http://harvardforest.fas.harvard.edu/research/hwa.html
The influence of recent forest harvesting and historical land-use on forest composition and invasive species distributions
Researchers Involved: Glenn Motzkin, David Foster, Michael Bank, Rob McDonald
Research Location: Harvard Forest
This study investigates the ecological influence of forest harvesting across central and western Massachusetts. Summer researchers will conduct extensive field sampling to: (1) evaluate harvesting impacts on critical ecological characteristics, including tree regeneration, invasive species distribution, and native plant species richness and composition; and (2) determine whether the impact of recent cutting activity differs according to prior land use (e.g., does invasive species establishment after harvesting depend on whether a site was formerly used for agriculture?). The study involves active collaboration of Harvard Forest researchers with staff from The Nature Conservancy. The study is based at Harvard Forest, but field crews will also spend a few weeks during the summer at field stations close to sampling locations.
Michael Bank and Glenn Motzkin will have primary supervisory responsibilities. We are seeking summer research assistants and field crew leaders with interest in and knowledge of the vegetation, soils, and disturbance history of forests of the northeastern U.S. Applicants should be in good physical condition and enjoy field work in a range of forest conditions. Summer researcher responsibilities will include daily travel to field sites across central and western Massachusetts to collect vegetation and soils data. Summer assistants will also assist in laboratory analyses such as soil sieving, drying, plant identification, data entry and analysis.
Landscape-level dynamics of hemlock woolly adelgid dispersal and establishment
Principal Investigators: Joe Elkinton, Aaron Ellison, Dave Orwig, Evan
Preisser
Summer Supervisors: Evan Preisser and Dave Orwig
Research Location: Hemlock transect from southern Connecticut to northern
Massachusetts.
The hemlock woolly adelgid is a major threat to Eastern hemlocks and the ecological communities that these trees support, but little is known about how this invasive insect spreads across the landscape and establishes new populations. This project focuses on adelgid dispersal, establishment, and hemlock resistance to this invasive pest, and complements the project on adelgid life history and range expansion.
The student working on this project will travel extensively within a latitudinal transect extending from southern CT to northern MA. Over the past six years, hundreds of hemlock stands have been surveyed in this transect for adelgid presence, density, and forest health indicators. The student will work with the supervisors and other students to re-sample these stands and document changes in adelgid density and forest health since the last sample. The student will also examine sites devastated by the adelgid for surviving Eastern hemlock trees, helping to test the commonly-held (but unproven) notion that Eastern hemlocks do not exhibit resistance to the adelgid.
The student will meet with at least one of the summer supervisors (Preisser or Orwig) on a weekly basis. Because of the extensive field time required for this project, the student must be comfortable working in a variety of forest environments.
Plant Biology, Population and Community Ecology
Evolutionary Ecology and Genetics
Plant population biology and evolutionary ecology
Researchers Involved: Kathleen Donohue, Kristina Stinson, Lauren Griffen, EunSuk Kim
Principal Investigator: Kathleen Donohue
Post Doc: Kristina Stinson
Graduate Students: Lauren Griffen, EunSuk Kim
Summer Supervisor: Kristina Stinson
Locations: Harvard Forest, Concord Field Station, Cambridge campus
This summer's research will contribute to three research programs. The first project concerns the ecological and genetic basis of variation in germination in Arabidopsis thaliana, a model genetic organism. Field studies in an old-field environment will be combined with germination assays under controlled conditions in order to identify particular environmental cues associated with important germination and life-history variation expressed in the field.
The second project is a study of invasive garlic mustard and its population demography. This is in collaboration with Kristina Stinson, another mentor in the summer research program. We have begun studies of population ecology and evolutionary genetics in order to study what limits or enhances the geographic distribution and population growth rates of this invasive understory species.
The third project is a comparison of the development and morphology of fruits of different members of the Brassiceae, a tribe of mustards that comprises important weeds and crop species. Students will explore the functional significance of fruit variation and characterize the developmental basis for functionally important variation in fruit structure.
Students will participate in one of the research programs described above, including helping to design and execute experiments; collect, manage, and analyze data; and present data at the student symposium. Independent projects can be designed within each research programs. Students attend weekly lab meetings and meet often with their mentors.
Community Assembly
Who eats whom? Structure of food webs and nutrient dynamics of carnivorous pitcher plants.
Researchers Involved: Aaron Ellison, Nicholas Gotelli, and Jess Butler
Primary Supervisors: Jess Butler and Aaron Ellison
Location: Harvard Forest
A primary focus of our research is to understand how anthropogenic stressors (e.g., climate change, acid deposition) alter dynamics of food webs and alter patterns of species distribution and abundance (community assembly). We use the food web of invertebrates that live within the water-filled leaves of carnivorous plants (pitcher plants) as a model system for studies of food web dynamics and community structure.
The students involved in this project will conduct greenhouse and field experiments with the mentor and a research assistant designed to determine how the structure of the invertebrate food web alters growth and form of the pitcher plant, and how these shifts are related to nutrient budget of the plant. The students will be responsible for field collections of invertebrates, maintenance of experiments (with the mentor and research assistant), and ecophysiological measurements of the plants and invertebrates. Students should expect to spend 1-2 days/week in the field and 2-3 days/week in the greenhouse and lab. There should be opportunities for students to develop independent research projects associated with this larger project. The students will meet with Aaron and/or Jess weekly during the summer.
Long Distance Transport in Plants
Ion mediated variation of xylem hydraulic resistance
Researchers involved: Brendan Choat and Michele Holbrook
Research Location: Harvard Forest
In vascular plants water is transported through dead cells known as xylem vessels or tracheids. Until recently it was believed that this water transport pathway was entirely passive, ie. that plants had no ability to effect short term changes in the resistance of this pathway. However, it was recently revealed that the hydraulic resistance of the xylem is directly related to the concentration of ions in the xylem sap such as calcium and potassium. Changes in hydraulic resistance related to variation in ion concentration are large in magnitude and can occur over a very short time scale. This process is of enormous potential benefit to plants as a means of modifying xylem hydraulic resistance in response to environmental variation. In this project we will investigate how changes in ionic concentration of xylem sap may alter the distribution of hydraulic resistance in the canopy of sugar maple trees. Diurnal variation in concentrations of xylem sap ions will be measured in mature trees growing at Harvard Forest. We will also quantify changes in ionic concentration in potted saplings with respect to light availability, photosynthetic rate and water stress. These measurements will be combined with measurements of flow enhancement in detached branches to determine the extent to which resistance is modified under natural conditions.
Mentee Responsibilities: Measurement of xylem sap ion concentration in mature trees and saplings. Upper branches in mature trees will be accessed using a canopy lift. Collection of branches and lab based measurement of flow rates in branches. Brendan will meet with the student daily.
Aging in large woody stems: the loss of water transport capacity in inner sapwood
Researchers Involved: Rachel Spicer (6th yr graduate student and primary contact; Missy Holbrook, PI).
Relevant website: http://www.oeb.harvard.edu/faculty/holbrook/people/rachel/spicerweb.htm
Summer Supervisor: Rachel Spicer
Research Location: Harvard Forest, with possible occasional trips to labs at Harvard University, Cambridge, MA
This research project forms an integral part of ongoing work on aging in the sapwood of woody stems, which includes respiration, cell death, and water relations components. The 'decommissioning' of sapwood to form heartwood, which is physiologically inactive, is relevant for both whole tree carbon dynamics and ecosystem-level carbon exchange. As the respiration component of this work concludes, we are shifting gears to focus on water relations - specifically, we are considering what might cause water to stop flowing in the inner sapwood of a woody stem. This would be the focus of the proposed work for the summer of 2005
The mentee would be trained to make measurements of flow and/or vulnerability to cavitation in small regions of wood (= xylem) of large stem segments. The mentee will also be trained in techniques to measure the water potential of woody tissue taken from large increment cores. The field work component (about 25% of total time) would include extracting increment cores from trees and assisting in moving stem segments from the field to the laboratory. Both of these tasks are physically demanding (requiring some lifting and physical strength), but anyone reasonably fit should be capable of the work. The laboratory component (about 75% of total time) will require some manual dexterity (the mentee will need to work with fine tools, possibly under a dissecting microscope - steady hands would be great!), and in general good attention to detail. This is a fairly self-contained project and is expected to form the mentee's independent project. After considerable training with the supervisor at the start of the summer, work will become increasingly independent. An interest in forest tree physiology and/or plant water relations is desirable; anyone with a background in plant physiology is especially encouraged to apply.
Rachel will meet with the student daily for the first few weeks, with continued meetings two to three times per week for the remainder of the summer.
Large Experiments and Permanent Plot Studies
Removal of Hemlock by Logging or Adelgid
Ant diversity in southern New England: Effects of Hemlock Decline and Hemlock Removal
Researchers Involved: Aaron Ellison and Nicholas Gotelli
Primary Supervisor: Aaron Ellison
Research Location: Harvard Forest
The goal of this summer's ant project is to document changes in ant species diversity in hemlock stands that were logged in January 2005 or experimentally girdled in May 2005 to simulate loss of hemlock due the infestation by the invasive hemlock woolly adelgid. We will also explore the relationship between local (stand-level) and regional (tract-level) species competition, and how ants may alter ecosystem properties in the manipulated stands. The focus on hemlock stands is part of a Harvard Forest-wide project on the response of northeastern forests to the impending loss of hemlock resulting from the invasion of the woolly adelgid.
The students involved in this project will be responsible for field collections of ants using a variety of standard methods (pitfall traps, baits, vegetation sampling, artificial nests) and sorting and identifying ants in the laboratory (involves microscope work). Field work will be done in the experimental plots at the Simes Tract of the Harvard Forest. Students should expect to spend 2-3 days/week in the field, and 2-3 days/week in the lab. The students will meet with Aaron at least weekly. During the first few weeks, there will be additional focused sessions on field methods and ant identification.
Hemlock Removal Experiment: Initial Responses
Researchers Involved: Aaron Ellison, Audrey Barker Plotkin, David Orwig, David Foster
Summer Supervisor: Audrey Barker Plotkin
Research Location: Harvard Forest
Links:
http://harvardforest.fas.harvard.edu/research/hwa.html
http://harvardforest.fas.harvard.edu/research/hemlock.html
The dynamics of hemlock forests in New England are changing rapidly with the invasion of the hemlock woolly adelgid (Adelges tsugae), an exotic insect pest that kills hemlock trees and is moving into central New England. Layered onto this regional-scale disturbance is the pre-emptive logging that many landowners are doing in anticipation of hemlock mortality. We have begun a large-scale experiment to simulate the effects of hemlock removal from the forest ecosystem by adelgid and by logging. Our goals for Summer 2005 are to monitor overstory tree response to girdling and assess immediate vegetation response after logging. We also will be continuing an effort to map all trees within the study plots.
Skills used will include vegetation measurement and surveying techniques. This is a field-based project, so prospective students should enjoy working in the outdoors under various conditions. Audrey Barker Plotkin will train students and meet with them regularly, but students should be comfortable working independently in the field. Students will have an option of developing an independent project or to work with the large data set generated by the survey.
Hurricane Experiment
Fifteen years of vegetation response to an experimental hurricane
Researchers Involved: David Foster, Audrey Barker Plotkin
Summer Supervisor: Audrey Barker Plotkin
Research Location: Harvard Forest
The hurricane experiment at Harvard Forest was designed to simulate the impacts of a catastrophic storm like the 1938 New England Hurricane to mature red oak - red maple forest. In October 1990, canopy trees were pulled over using a winch, resulting in direct and indirect damage to nearly 70% of the stand. Despite massive structural reorganization, the site maintained biogeochemical function and resisted major change in understory species composition. In year 15 of this study, we will be looking at long-term survival, sprouting and growth of the original overstory, and doing a final survey of herbaceous and shrub flora in the paired experimental and control plots.
This is a field-based study, so students should be comfortable working in the outdoors under various conditions. Skills in identifying New England trees, shrubs, and understory flora will be developed, as well as basic tree vigor rating and forest measurements. Audrey Barker Plotkin will work with the student in the field. The student will have an option of developing an independent project or to work with the long-term data set.
Temperate Forest Responses to Climate Warming
Researchers Involved: Jerry Melillo, Jacqueline Mohan, Joseph Blanchard
Summer Supervisor: Jacqueline Mohan
Research Location: Harvard Forest
Will temperate forests of the globe shift from being net "sinks" of atmospheric carbon dioxide (CO2) to becoming sources of CO2, thus increasing the rate of climate warming? What are the implications of warming for future reproduction and species compositions? Two of the major results of our original soil warming study were that: (1) warming stimulated the decay of a labile soil carbon pool thus increasing the rate of CO2 efflux to the atmosphere, and (2) warming increased the availability of soil nitrogen to plants. Because of the small size of the original warming plots an important question we have not been able to answer is: Has the increase in available nitrogen led to an increase in growth of the trees - and if so, what is the balance between the carbon lost from the soil and the carbon stored in the vegetation in response to soil warming? We are now addressing these questions with a new, larger warming experiment in Harvard Forest. This study is one of the only warming experiments in the world to take place in a natural forest setting. Pre-treatment data was collected in 2002, and the soil warming treatment commenced May 2003 in a 900 m2 forest tract which is heated to 5 oC above an adjacent control plot .
Growing season measurements that students will be involved with include soil nitrogen mineralization rates, trace gas fluxes (CO2, CH4, N2O - all greenhouse gases), canopy tree growth (using dendrometer bands), chemical analyses of plant foliage (C:N ratios, concentrations of secondary compounds), lysimetry (a method to quantify dissolved nutrients in soil water that may leach out of the system), and light availability in the forest understory (using hemispherical photography). In addition, understory growth, survivorship and reproduction will be monitored to access evolutionary, population, and community-level implications of climate warming. In 2005 we plan to initiate two new projects to address: (1) Possible belowground responses to warming (fine roots and root respiration), and (2) Potential mechanisms linking reproductive responses to altered plant tissue chemistries. REU students are encouraged to take an active role in the development of this new research and to collaborate in future research publications. Students will meet with the Summer Supervisor several times a week.
Historical and Retrospective Studies
Paleoecology
Long-term history of vegetation in New England
Researchers involved: David Foster, Wyatt Oswald
Summer supervisor: Wyatt Oswald
Research location: Harvard Forest
By analyzing microscopic plant and animal fossils that accumulate in sedimentary environments such as ponds, wetlands, and organic soils, it is possible to reconstruct past changes in vegetation, plant and animal communities, environmental conditions, and disturbance processes. A variety of paleoecological approaches, including analyses of pollen, charcoal, and plant macrofossils, are used at Harvard Forest in conjunction with modern and historical studies to investigate fundamental ecological questions and to provide background for conservation and land management. Harvard Forest researchers are currently focused on studies exploring the long-term history of hemlock in Massachusetts, changes in northeastern US coastal plant communities during the past 2000 years, and landscape changes associated with European settlement.
The student will participate in many aspects of the Harvard Forest paleoecological research program, including fieldwork (collection of sediment cores) and laboratory work (analyses of pollen, charcoal, and plant macrofossils). In addition, the student will develop a summer project within the framework of the overall research. The student will work closely with Wyatt several days each week.
Atmospheric Chemistry and Soil Carbon and Nitrogen Dynamics
Long term soil respiration at the Harvard Forest
Researchers Involved: Eric Davidson and Kathleen Savage
Summer Supervisors: Eric Davidson and Kathleen Savage
Locations: Harvard Forest and Woods Hole Research Center
Soil respiration, which is the combination of respiration by roots and by soil microorganisms, is an important component of the annual carbon balance of forests. We have been measuring rates of soil respiration, temperature and moisture since 1995. This long-term record allows us to examine both seasonal and annual variations in respiration rates and to relate those variations to temperature and soil moisture content. Understanding environmental controls on soil respiration helps us to understand how potential changes in climate may affect soil respiration and the exchange of carbon between the forest and the atmosphere. Research related website is http://www.whrc.org/science/neforest/neforest.htm.
The summer student will be responsible for making weekly measures of soil respiration, carbon dioxide concentrations within the soil profile, temperature and soil moisture. The student will also be responsible for data entry, some data analysis, and maintaining up-to-date notes. Students will be encouraged to undertake an independent research project. Student will meet weekly with at least one of their summer supervisors.
Effects of management on forest carbon storage
Principal Investigator: Steven Wofsy
Senior Research Fellow: Willam Munger
Research Assistants: John Budney, Christine Jones
Summer Supervisors: John Budney and Christine Jones
Location: Harvard Forest
Since 1989, the research group led by Steven Wofsy has continuously monitored the exchange of carbon dioxide (CO2) between Harvard Forest and the atmosphere using the eddy-covariance method. In conjunction, we make ground based measurements of biological components of carbon (C) cycling at Harvard Forest. This entails frequent measurements of tree growth, leaf or litter production, soil respiration and associated soil and climate factors. Starting in 1999, ground-based measurements were extended to a portion of privately owned land adjacent to Harvard Forest, in anticipation of a selective harvest, which occurred in 2001. Comparing current measurements in logged site with contemporary measurements in the adjacent Prospect Hill tract allows us to examine the effects of the harvest on carbon flux and storage. More details on this project may be found at: http://www-as.harvard.edu/chemistry/index.html
The student's research project for the summer of 2005 will involve investigating the effects of selective harvesting on carbon cycling in coarse woody debris pools. Previous studies have indicated temperature and moisture content as two major factors governing coarse woody debris respiration rates. Disturbance of the forest canopy caused by selective harvesting effects both temperature and moisture levels, while increasing the amount of coarse woody debris on the forest floor. This could have significant implications for coarse woody debris respiration. The student will assist in implementing an automated measurement system designed to monitor temperature and moisture levels for both coarse woody debris and the surrounding environment. Measurements will include air temperature, relative humidity, soil temperature and moisture, log temperature and moisture, and net radiation flux. Studies will be conducted in both the Prospect Hill tract and in the adjacent tract of selectively harvested land. After an intensive training on the workings of the measurement system, students will responsible for monitoring the measurements and retrieving data. Regular fieldwork can be expected collecting log moisture data, as this will be not be part of the automated system.
The student will assist in all aspects of fieldwork, data entry, and statistical analysis. The student will be responsible for making some measurements independently after extensive training and managing and evaluating the data for the summer. Other fieldwork will be done together with other members of our research group in addition to their project work.
John Budney and Christine Jones will be responsible for field training and direct supervision of weekly measurements. Steve Wofsy will also personally meet with the student from time to time, including at the outset and preparation of the student's presentation. After an initial intensive training, the student will be expected to do some fieldwork independently. Other measurements will be done alongside Christine and other members of our group. Our projects are fieldwork intensive and students can expect to spend a good portion of each day in the field. John Budney and Christine Jones will all assist with independent projects, though Steven Wofsy will be responsible for overall supervision and design and implementation of the project. The student will be expected to meet with Steve Wofsy, John and Christine on a regular basis to discuss the project.
Carbon and water exchange of eastern hemlock and deciduous forests: Differences between forest types, responses to climate, and probable effects of hemlock mortality
Researchers Involved: Julian Hadley, Paul Kuzeja
Summer Supervisor: Julian Hadley
Research Location: Harvard Forest
My research is designed to identify differences between forest types in their use of water and in the amount of carbon dioxide they remove from the atmosphere. I am currently working in two very different forest types; a deciduous forest less than 60 years old near a hilltop, and a coniferous eastern hemlock forest with trees over 200 years old, in a relatively flat area bordering a swamp. These forests are apparently very different in their physiology, as well as in topography and dominant trees species. The deciduous trees use relatively large amounts of water and store carbon rapidly in the summer, whereas the hemlocks use relatively little water and store carbon more slowly, but during spring and fall as well as summer. My research will show how much carbon each forest type stores annually in the current climate, and what is likely to happen as climate changes. It will also give an indication of what will happen to water use and carbon storage if the hemlock forest dies, as it may do in the next 10-20 years as a result of attack by an exotic insect, the hemlock woolly adelgid.
The mentee will be responsible for helping in measurements of soil respiration, and will have a requirement to do an independent project relating to carbon storage or water use of forests. Possible projects include (but are not restricted to) studies of CO2 production by roots and soil microbes, CO2 uptake and water loss by trees, and carbon stored in wood production by trees. I will meet with the mentee 2-3 times per week at a minimum.
Temperate Forest Responses to Climate Warming
Aquatic Studies
Forecasting Stream Ecosystem Responses to a Regional Landscape Disturbance: Indirect Ecological Consequences of the Removal of Eastern Hemlock from New England Forests
Principal Investigators: Bill Sobczak and Betsy Colburn
Summer Supervisors: Bill Sobczak and Betsy Colburn
Research Locations: Central and Western MA including Harvard Forest, Mt. Wachusett, several MA state forests; southern Connecticut; some lab work at College of the Holy Cross.
The hydrology, water quality, energy flow, and food-web structure in streams are tightly associated with the contributing watershed, and forest composition is an important variable. Eastern hemlock dominates many New England forests and stream-side riparian areas and influences the supply of detritus, availability of light, and temperature in many forest streams. The loss of this species to the hemlock woolly adelgid, an exotic forest pest that has killed hemlocks from the middle-Atlantic states into southern New England and is moving rapidly into Massachusetts, will result in an array of ecological consequences. Terrestrial ecosystem responses are just now being documented, yet aquatic ecosystem responses to regional changes in forest composition are less certain. We are investigating the potential effects of hemlock decline on stream ecosystems, including streamflow, water chemistry, carbon sources and cycling, functional feeding groups of biota, and species composition of the biological community. Study areas include streams dominated by eastern hemlock or hardwood. A major emphasis this summer will be on identifying streams that are appropriate for long-term study, and collecting baseline data on these streams. In addition to participating in this baseline study, the student is expected to work on an independent project that complements the broader research effort.