Harvard Forest >

Summer Research Project 2020

• Title: Three Decades of Forest Change: Soil Warming Experiment
• Group Project Leader: Timothy Whitby
• Mentors: Kristen DeAngelis
• Collaborators: Seeta Sistla
• Project Description:

  Please note: This project will work in collaboration as a group project with other projects listed under "Three Decades of Forest Change"
  
  Overall Theme
  Forests operate at multiple scales of time and space. How forests respond to stress and disturbance events in the first few years may not predict long-term consequences. Thirty years ago, the Harvard Forest joined the Long-Term Ecological Research (LTER) program, bringing together ecologists studying organisms from microbes to trees, and processes that operate within a teaspoon of soil to the New England region. The initial focus of the Harvard Forest LTER was a set of experiments designed to contrast forest response to natural disturbance and anthropogenic stress, along with continual monitoring of forest carbon exchange via the Environmental Measurement Site (EMS) flux tower and associated forest plots. Now, three decades later, these experiments and studies continue to reveal new insights.
  
  This summer, five students will work at the EMS, the Simulated Hurricane Experiment, and the Soil Warming Experiment. Hurricanes are infrequent but major natural disturbances that shape long-term trajectories of forest development in New England. Soil warming is a prominent symptom of anthropogenic climate change. In each experiment, early results gave way to surprisingly different trajectories of change over time. At the EMS tower, predictions that the forest would reach equilibrium as it matured were not realized; after 30 years, carbon uptake remains strong. However, recent trends in mortality have the potential to slow net carbon uptake. The long-term changes in each of these studies - growth, decay, evolution - inform our understanding of global climate change and forest resilience to disturbance.
  
  Each sub-project will operate independently, but we will come together weekly as a group to discuss common challenges, share insights, and consider the experiments in the context of the LTER program.
  
  
  Soil Warming Experiment Project
  2 students
  Primary Mentor: Kristen DeAngelis; Collaborator: Seeta Sistla
  
  Microbes are key players in biogeochemical cycling, and genetic information is a rich source of microbial signals in soil with further potential to guide the forecast of microbial systems. Gene markers, genomic markers and phylogenetic markers are currently used as proxies for microbial functions and feedbacks in ecosystem models. But ecosystem models span decades to a century, which is certainly enough time for molecular evolution of microbes to contribute to community acclimation to stress. Microbial adaptation to climate stress is a source of soil self-reinforcing feedbacks to the climate system that can either be stabilizing (negative) or destabilizing (positive). Evolutionary adaptation of soil microbes is suggested as an effect of climate stress. This project will explore changes in microbial fitness due to long-term warming, and work to incorporate molecular evolutionary theory into microbial parameters of climate models.
  
  This proposed research has two specific goals: (1) perform comparative analysis of microbes to estimate fitness gains in adaptation to long-term warming, and (2) develop new parameters for existing trait-based models that incorporate time-delayed microbial adaptations. Students will measure fitness gains as changes in culturable cells (as colony forming units), cell counts (by microscopy), and culture-independent cell counts (by quantitative PCR) of microbes after incubation in microbial cages for three months (to be installed in April 2020). Simultaneously, students will work on incorporating an eco-evolutionary parameter as a biomass allocation fraction into the model MIMICS, a trait-based model of soil carbon optimized for the Harvard Forest sites, coded in R. This new temperature dependent parameter will reflect ongoing adaptation over time, and students will have the opportunity to run simulations of long-term warming to predict the effects of molecular adaptation on ecosystem carbon cycling.
  
  Two students will work with Kristen DeAngelis and Seeta Sistla collaboratively on the field, lab and computer activities associated with this sub-project. The experimental site is located 1 mile from the main buildings at Harvard Forest (a short drive or a 15-minute walk), and students will work in the field 1 day per week or less. Students will mainly split their time between analyzing microbial fitness data from the field experiment in the labs, with some lab work to be conducted in the DeAngelis microbiology lab at UMass Amherst; and between conducting data analysis and modeling studies in R. Data analysis skills, sterile technique, and molecular skills will be developed during this project, and students are welcome to develop an independent project within the context of this study.
  
  
  General requirements for all overall project:
  The students should expect to help one another with the different sub-projects, gaining exposure to all aspects of the overall project and developing the ability to negotiate priorities and scheduling. A clean driving record (2 years or more) is helpful, but not every student needs to drive. Student should have or develop a basic understanding of R for graphical and statistical analysis.The ability to walk 1-2 miles off-trail with a day pack is required, along with stamina and humor to work collaboratively in sometimes challenging conditions (whether they be in the field, lab, or computer).

• Readings:

  Abs, Elsa,, Scott R. Saleska, Regis Ferriere. Microbial evolution reshapes soil carbon feedbacks to climate change. bioRxiv 641399; doi: https://doi.org/10.1101/641399
  
  Barker Plotkin, A., Foster, D. R., Carlson, J, Magill, A. H. 2013. Survivors, not invaders, control forest development following simulated hurricane. Ecology 94: 414-423.
  
  Foster, D. R., Aber, J. D., Melillo, J. M., Bowden, R. D., Bazzaz, F. A. 1997. Forest response to disturbance and anthropogenic stress. Rethinking the 1938 Hurricane and the impact of physical disturbance vs. chemical and climate stress on forest ecosystems. BioScience 47: 437-445.
  
  Liu, W. H., D. M. Bryant, L. R. Hutyra, S. R. Saleska, E. Hammond-Pyle, D. Curran, and S. C. Wofsy. 2006. Woody debris contribution to the carbon budget of selectively logged and maturing mid-latitude forests. Oecologia 148:108–117.
  
  Melillo, Jerry M., Serita D. Frey, Kristen M. DeAngelis, William J. Werner, Michael J. Bernard, Francis P. Bowles, Grace Pold, Melissa A. Knorr, and A. Stuart Grandy. Long-term pattern and magnitude of soil carbon feedback to the climate system in a warming world. Science 358, no. 6359 (2017): 101-105.
  
  Wieder, W. R., A. S. Grandy, C. M. Kallenbach, P. G. Taylor, and G. B. Bonan. Representing life in the Earth system with soil microbial functional traits in the MIMICS model" Geoscientific Model Development 8, no. 6 (2015): 1789-1808.
  

• Research Category: Soil Carbon and Nitrogen Dynamics, Large Experiments and Permanent Plot Studies, Group Projects, Forest-Atmosphere Exchange, Ecological Informatics and Modelling