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Summer Research Project 2018

  • Title: Group Project (Megaplot): Effects of tree community composition on soil and rhizosphere processes
  • Group Project Leader: Fiona Jevon
  • Mentors: Fiona Jevon
  • Collaborators: Aaron Ellison; John Grady; Fiona Jevon; Sydne Record
  • Project Description:

    Important Note: This position is partly funded by Wellesley College and is therefore only open to students who are currently enrolled there.rnrnBiotic, abiotic and anthropogenic disturbances that alter community composition in Northeastern temperate forests can have significant, lasting effects on diversity. In experimental grasslands, higher plant diversity increases not only the aboveground productivity, but also belowground ecosystem function. Both above and below ground, a variety of strategies for growth and survival among different species produces “niche complementarity”; coexistence that is facilitated by a diverse mixture of plants and belowground communities. In Northeast temperate forests, individual trees create feedbacks with soils through differences in root exudation and mycorrhizal associations, phenological influences on soil microclimate, and variable litter chemistry. Work on monospecific stands has shown that not only do different tree species have different strategies for growth and nutrient acquisition, but they are associated with distinct soil and litter microbial communities that reflect those strategies. However, whether mixtures of tree species result in niche complementarity or not remains unclear, as does the overall effect of aboveground diversity on carbon cycling. rnrnThe goal for this project is to continue measuring soil respiration at a variety of sites within the Harvard Forest ForestGEO Megaplot that are surrounded by either all one species of tree or a mixture of species. In addition, the REU student will take novel measurements of root respiration of each of the focal species in this study, in order to assess the contribution of rhizosphere processes to total soil carbon efflux and look for the effects of neighborhood composition on soil and rhizosphere processes and ecosystem function. The work will consist of measuring CO2 fluxes from both collars and roots in the field, as well as harvesting some roots and soil for analysis in lab. The student will learn how to use an ultra-portable greenhouse gas analyzer, to identify forest tree species, and basic soil and root processing protocols in lab. A typical week will primarily be composed of field work (~80%), with some time spent on data analysis and lab work (~20%). Additionally, the student will compile and graphically analyze data in Excel and R, and present their research findings at the end of summer symposium. rnrnThe student working on this project will be mentored by Fiona Jevon, a PhD student at Dartmouth College, who will regularly visit Harvard Forest during the summer. Fiona will meet with the student at least once per week, and help with the field and lab work. This project is part of a larger group project/collaboration within the Megaplot with students working on forest seedlings and energetics with Drs. Grady and Record and students working on ant biodiversity with Dr. Ellison. There will be opportunities throughout the summer to collaborate with this larger Megaplot group, particularly on the collection of seedling survey data. There will also be opportunities to develop an independent project that can be extended into a year-long independent study or a senior thesis. rnrnGeneral Requirements: The student working on this project must be willing torn1. Participate actively in field studies, including ~8 hours per field day carrying heavy equipment through the forest (without trails) with biting insects and hot, humid conditions. rn2. Be able to hike with scientific gear (30-45 lb. pack) in rough, forested terrain. The field site is ~ 1 mile one way from the main buildings at Harvard Forest.rn3. Be willing to collect soil and roots for analysis in the lab.rn4. Be willing to collaborate with the larger Megaplot group on field work and data analyses.rn5. Have, or be willing to develop, a basic understanding of Excel and R for graphical and statistical analysis. rn6. Think critically about theoretical issues in forest demographics and community ecology and link them to field work and data analyses. rnrn

  • Readings:

    Zak, D. R., Holmes, W. E., White, D. C., Peacock, A. D., Tilman, D., Zak, D. R., Holmes, W. E., White, D. C., Peacock, A. D. and Tilman, D. (2003) ‘Plant Diversity, Soil Microbial Communities, and Ecosystem Function : Are There Any Links?’, Ecology, 84(8), pp. 2042–2050.rnrnLaganiere, J., Pare, D., Bergeron, Y. and Chen, H. Y. H. (2012) ‘The effect of boreal forest composition on soil respiration is mediated through variations in soil temperature and C quality’, Soil Biology and Biochemistry, 53, pp. 18–27. rnrnAbramoff, R. Z. and Finzi, A. C. (2016) ‘Seasonality and partitioning of Root allocation to rhizosphere soils in a midlatitude forest’, Ecosphere, 7(11).rn

  • Research Category: Large Experiments and Permanent Plot Studies, Forest-Atmosphere Exchange