Harvard Forest >

Summer Research Project 2020

• Title: Three Decades of Forest Change: Long-term Forest Carbon Balance
• Group Project Leader: Timothy Whitby
• Mentors: J. William Munger; Timothy Whitby
• Collaborators:
• 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.
  
  
  Long-term Forest Carbon Balance Project
  1 student
  Primary mentors: Timothy Whitby and Bill Munger
  
  The background rate of tree mortality is a continual, low-intensity disturbance that changes the total amount and rate of carbon uptake at Harvard Forest. The Environmental Measurement Site (EMS) flux tower has the longest continuous record of forest-atmosphere CO2 exchange of its kind, starting in 1991. The net carbon flux measured by eddy covariance quantifies the balance between photosynthetic uptake and autotrophic and heterotrophic respiration from plants and soils respectively. In addition to flux estimates, we track the carbon balance of the forest with permanent plots that measure intra-annual live above-ground biomass growth and tree mortality. By comparing the plot-based measures of carbon balance to the flux-tower estimates, we can better understand where carbon is accumulating and how the annual carbon balance is influenced by tree species demographics and succession. The student on this sub-project would benefit from incorporating data from multiple sites with variety of history, and the whole group of students looking at demographics in plots would benefit from incorporating the growth and mortality in the EMS as a shifting baseline for comparison.
  
  The fieldwork component of the project would track the fate of dead stems (Coarse Woody Debris - CWD) by resurveying the EMS permanent plots for standing and downed coarse wood using the planar-intercept method. This data will be compared to previous surveys that occur on ~3 year intervals dating back to 2000. Density measurements from woody-debris subsamples spanning a wide range of known ages will provide empirical data to evaluate models of annual decay rates that were made from short-term observations. Additionally, students will assist with other ongoing permanent plot measurements such as dendrometer-band measurements of live aboveground biomass. The student will be trained in standard forest inventory techniques including running transects with a compass, measuring diameter at breast height, and tree height with a clinometer. As time allows, the CWD measurements can be extended to additional stands that are impacted by different disturbances. The student should be prepared to spend approximately 75% of their time in the field, with the other portion reading relevant research papers and performing data analysis in R. There will be ample opportunity to assist with other sub-projects in the field and vice versa. Timothy Whitby will be the daily point of contact for the REU student and train the student in all field and data-analysis techniques. Bill Munger will be available for mentoring and feedback regarding overarching goals of the research project, interpreting data, and presenting results.
  
  
  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