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Research Component

Overview and project descriptions

The research component will focus on topics drawn from four nodes of study representing the variety of research areas at Hubbard Brook Experimental Forest (HBEF.) Students will choose a topic and work with a team of mentors to develop questions, then design and conduct sampling and experiments able to test their hypotheses.  In addition, participants will gain a broad understanding of a number of major areas of research on the Hubbard Brook ecosystem through project presentations and discussions led by the research mentors and other guest scientists. All research projects are interdisciplinary and largely field-based. 

The research nodes, and examples of topics, are as follows: (Mentors or mentor teams are listed in parentheses after each project example).

Animal Ecology: Studies of animal ecology at HBEF were initiated in 1969 and have focused primarily upon birds and small mammals. Scientists at Hubbard Brook have developed a detailed record of bird population dynamics and food web interactions which provide an ideal context for undergraduate research projects. This node will support REU projects examining influences on the population dynamics of vertebrates through investigation of competition for food resources and animal behavior. Two example animal ecology projects are described below:

1. Role of climate in mediating interspecific competition for prey species (one student): Caterpillars are a critical food resource for numerous migratory bird species of northern hardwoods forest, affecting fecundity and population regulation. What regulates the abundance of this critical resource for birds is not clear. Studies at the HBEF have demonstrated that the abundance of caterpillars is sensitive to climate and to inter-annual variation in weather, as well as predation by birds and insects. The relative effects of insect predation remain unexplored and are likely to be sensitive to climate. Students working on this project will have the opportunity to design a project to test the hypothesis that climate affects the distribution, abundance, and activity of vespid wasps that prey on caterpillars in northern hardwoods forest. Results of this study will allow assessment of the potential for competition between birds and predaceous arthropods inhabiting forest foliage, and they will make a significant new contribution to the study of food web interactions within the HBEF. (Dr. Nick Rodenhouse)

2. Population dynamics of vertebrates (one student): This project will be geared toward understanding how behavior limits and regulates the population dynamics of birds throughout the annual cycle. Students working on this project will gain extensive experience with census techniques, capturing, measuring and banding birds, the use of mist nets, behavioral observations, data management, and data analysis. Students can conduct research on parental care and investment, patterns of breeding behavior, demography and habitat selection, and examining the role of changing food resources over the season in driving reproductive success. (Dr. Peter Marra).

Biogeochemistry: Air pollution is an important disturbance to eastern forests, altering the structure and function of forest and aquatic ecosystems in sensitive areas. Acidic deposition is one such disturbance which has received much research, as well as outreach, attention at Hubbard Brook. While acidic deposition has recently decreased in the United States due to controls on emissions of sulfur dioxide and nitrogen oxides from electric utilities, many of the impacts persist, including alteration of the acid-base status of soils and stream water and accumulation of reactive nitrogen in ecosystems. The research infrastructure at Hubbard Brook is excellent for further research on these topics, and the broader White Mountain region provides opportunities for testing hypotheses developed at Hubbard Brook on broader, regional scales. Two example projects are described below:

1. Influence of climate on the fate of nitrogen in forest soils (one or two students): Despite high deposition of nitrogen in the northeastern U.S. during the past several decades, streams at Hubbard Brook and throughout the broader region have generally shown declines in concentrations of stream water nitrate. Most of the nitrogen losses in stream water occur during the winter months, when plant uptake is minimal, yet the mechanisms of nitrogen retention/loss during this time of year are not well-established. A new, three-year study has recently been funded by the Andrew W. Mellon Foundation to investigate how soil frost influences plant nitrogen uptake, net primary productivity, and nitrogen losses in leachates.  An REU project will be developed as part of this larger study. The students will choose a research topic, examining how soil frost, induced the previous winter, may alter the quantity and forms of nitrogen in leachates, gases, or soils during the growing season. Students will also have an opportunity to use long-term field measurements from Hubbard Brook (e.g., stream chemistry, soil frost, snow depth, air temperature, etc.) to assess more broadly how climate change may influence soil frost and nutrient cycling. (Drs. Pamela Templer & John Campbell)

2. Reponses to atmospheric deposition in alpine and subalpine environments (one or two students): The White Mountains have received decades of acidic deposition, including significant amounts of reactive nitrogen. Hubbard Brook has a very detailed record of both the deposition of acidic compounds and their effects on the ecosystem, but the records from the broader region are more sporadic. Specifically, both tundra systems and Wilderness Areas all have received surveys relating to ecosystem effects of atmospheric deposition, yet many of these sites have not been resampled for years. Over this time the watersheds at Hubbard Brook have shown surprising responses. Students working on this project will have the opportunity develop hypotheses on ecosystem response from the long-term data at Hubbard Brook and test them by sampling and analyzing historical data from remote ecosystems. (Drs. Charley Driscoll & Christy Goodale)

Hydrology and Soils: The movement and composition of water dictates the rates by which physical, chemical and biological processes occur within the earth’s biosphere.  These processes may be sensitive to changes in the hydrologic cycle considering predictions for a warmer and potentially wetter climate in New England.  This node will support REU projects that focus on the interactions between soils and water, which are important for governing the generation of streamflow, soil and stream chemistry, and surface water and groundwater exchanges.

1. Spatial patterns of soils and soil development (one or two students): Spatial patterns of soils and soil development processes have broad implications for hydrology, element cycling and stream water quality. At Hubbard Brook, soil development patterns are being used to provide insight to hydrologic and other processes that govern the cycling of elements essential for forest nutrition in an acidic forest ecosystem. An REU project will build on previous research on the interactions between soil development and hydrologic flowpaths in headwater watersheds by exploring soil processes and patterns associated with seeps and wet areas along topographic gradients. (Drs. Scott Bailey & Kevin McGuire)

2. Hydrologic controls on patterns of stream chemistry (one student): The understanding of headwater contributions to downstream water quality is complicated by poorly understood processes that give rise to spatial patterns in stream chemistry throughout headwater tributaries. These processes include groundwater and surface interaction, dynamic wetting and drying patterns associated with storms, and zones of connectivity between uplands and soils adjacent to the stream channel where chemical contributions from upland subsurface flow are likely to change. An REU project will explore controls on the patterns of stream chemistry in a small headwater watershed during low flow and before/after storm events. This project will build on results from a previous REU project and contribute to a larger effort aimed at understanding solute generation, cycling and transport in small acidic forested watersheds. (Drs. Kevin McGuire & Scott Bailey)

Forest Vegetation and Carbon Cycling: Forest vegetation in the northeastern U.S. is undergoing unusually rapid change as a result of a variety of forces including exotic pests and pathogens, atmospheric pollution, climatic change and land-use activities. Long-term records of forest biomass and composition from the HBEF and adjacent forest sites provide an exceptional resource for quantifying and understanding these patterns of change and their implication for the provision of a variety of human services, including ecosystem carbon storage. Major changes in the composition, growth, and biomass of regional forests will have important implications for ecosystem C sequestration and storage as well as consequent effects on feedbacks to global climate change. This node will support REU projects on forest dynamics and carbon cycling, including population and community studies as well as process-level work on forest carbon fluxes.  Some specific project examples are described below:

1. Vegetation change across ecotones (one or two students):  Changes in vegetation community composition in the White Mountains is dominated by the elevational gradient, yet within that gradient many environmental variables change simultaneously. Climate change is likely to influence these variables in different ways, making vegetation responses difficult to predict. Students working on this project will investigate tree community responses to environmental changes across distinct vegetation boundaries. Possible study areas include the fir forest – tundra ecotone at high elevations or the hardwood – spruce/fir boundary. (Drs. Patrick Bourgeron & Tim Fahey)

2. Respiration and ecosystem carbon budgets (one or two students): In terms of climate warming and ecosystem carbon (C) budgets, among the least understood but possibly most responsive fluxes, is plant tissue respiration. A recent comprehensive overview of the C cycle at the HBEF estimated that autotrophic respiration comprised 52% of gross primary productivity; however, no direct measurements have been made and the temperature responses of tissue respiration for the HBEF vegetation is poorly known. Students in this program area would be introduced to advanced field techniques for measuring tree tissue respiration (i.e., attaching chambers to leaves, branches, stems and roots and monitoring CO2 efflux using an infrared gas analyzer) to test hypotheses about environmental and biotic factors influencing this key ecosystem C flux. (Dr. Michele Pruyn)

3. The importance of belowground carbon storage in forest growth (one student): Forest growth is widely advertised as a means of carbon sequestration, but its potential has sometimes been exaggerated. Until now, it has been difficult to measure the rate of carbon storage belowground, which is important to assessing the value of forest management practices to carbon mitigation. New tools now make it possible to collect deep soil cores through rocks and woody roots, enabling the measurement of belowground carbon storage. The proposed project is to sample roots, including coarse roots, which make up the majority of belowground biomass, in young and old forest stands, making it possible to describe the rate of carbon accumulation over time in regrowing forests. The sites are part of a larger long-term project that will eventually assess nutrient limitation to forest growth across a number of sites. This larger context will provide opportunities to interact with graduate students and principle investigators involved in varied aspects of the project. (Drs. Ruth Yanai & Christine Goodale)