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Summer Research Project 2020

• Title: Three Decades of Forest Change: The Simulated Hurricane Experiment
• Group Project Leader: Timothy Whitby
• Mentors: Audrey Barker Plotkin
• 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.
  
  
  The Simulated Hurricane Experiment Project
  2 students
  Primary mentor: Audrey Barker Plotkin
  
  Wind disturbance profoundly shapes temperate forests but few studies have evaluated patterns and mechanisms of long-term forest dynamics following major windthrows. In 1990, we initiated a large hurricane simulation experiment in a 0.8-ha manipulation (pulldown) and 0.6-ha control area of a maturing oak-maple forest in New England. We toppled 276 trees in the pulldown, using a winch and cable, in the northwesterly direction of natural treefall from major hurricanes. Eighty percent of canopy trees and two-thirds of all trees 5 cm dbh (diameter at breast height) suffered direct and indirect damage.
  
  Based on the patch size and disturbance magnitude, we expected pioneer tree and understory species to drive succession. The first decade of analyses emphasized tree seedling establishment and sprouting by damaged trees as the dominant mechanisms of forest recovery in this extensive damaged area. However, the few large oaks and birch seedlings that survived the disturbance controlled longer-term forest development. There were shifts in understory vegetation composition and cover, but few species were gained or lost after 20 years. Stand productivity rebounded quickly, but we predict that biomass in the pulldown will lag the control for decades to come. Although the scale and intensity of damage were great, abundant advance regeneration, understory vegetation, and damaged trees remained, allowing the forest to resist changes in ecosystem processes and invasion by new species.
  
  Two students will work with Audrey Barker Plotkin to conduct the year-30 inventories of trees, shrubs, herbs, and dead wood, to test whether the trends observed after 20 years continue. The experimental site is located 3 miles from the main buildings at Harvard Forest (a short drive plus a 10-minute walk), and students will work in the field 3-4 days per week. In addition, students will use spreadsheets and R to process and analyze this summer’s data along with the full 30-year record from this experiment. This is a field-based study, with the joys and challenges associated with it, including biting insects, ticks, and the typical extremes of New England summer weather. Forest measurements skills and the ability to work with large, long-term datasets will be developed. Students are welcome to develop an independent project in the context of the overall 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: Large Experiments and Permanent Plot Studies, Group Projects, Soil Carbon and Nitrogen Dynamics, Forest-Atmosphere Exchange, Ecological Informatics and Modelling