Climate change and food web resilience project summary
Hubbard Recreation & Natural Area
Annise Dobson, PhD
We have completed our first year of a project that examines the impacts of climate change on food webs. We are testing the ability of predators (spiders) and prey (grasshoppers) to adapt their behavior and physiology in response to climate change. How these players in a food web respond to climate change has implications for agricultural and forestry pests, conservation, ecosystem service, carbon storage, and beyond. We are a group of students, professors, and postdoctoral researchers from Yale and Northeastern University. The project is funded by the National Science Foundation (NSF) and is ongoing at eight sites between South Burlington and the Flanders Nature Center in Connecticut.
Site setup: This year we set up mesh cages for our experiment. We removed any existing insects from the cages before sealing them. This approach allows us to control the variables we are interested in (predators and prey), while still having a real natural environment.
Soil: We took small soil cores from within each of the cages to assess current soil fertility and the functioning of soil microbes to understand the link between soil carbon storage, nutrient cycling, and decomposition rates. We will re-measure these functions at the end of the experiment to examine how our variables (climate and food web structure) interact to impact soils. We took some additional site-level samples to characterize soil bulk density, pH, and texture, which will help explain the results.
Vegetation: We measured the species composition of the plant community within each of the cages, and took small leaf samples to understand current nutrient content. We will measure these variables again at the end of the experiment to see how climate and food web structure interact to impact the plant community.
Grasshoppers: To understand whether and how grasshoppers (prey) are changing over time in response to climate change, we need to hatch an initial group of grasshoppers from each of our eight sites, under the same environmental conditions. Within the large cages we placed 10 grasshoppers and three sand trays, hoping the grasshoppers would mate and oviposit their eggs into the trays. We observed this on a few sunny days in August and brought those egg trays back to the Yale lab in early October. We are hopeful we will be able to hatch the eggs this spring!
Grasshopper Behavior: One of our two main hypotheses is that grasshoppers from northern sites (with colder, more variable temperatures) deal with climatic stress by changing their behavior. We did a preliminary test of that this year at all eight sites, by observing grasshopper habitat use within a (much smaller) mesh cage every 20 minutes over a 10 hour period. Preliminary analysis supports our hypothesis, but we will continue to monitor grasshopper behavior annually.
Grasshopper Physiology: Our other main hypothesis is that grasshoppers from southern sites (with hotter, less variable temperatures) deal with climatic stress by changing their metabolism. We brought a small number of grasshoppers back to the Yale lab from all eight sites and measured their metabolic rate under different temperatures. We are in the process of evaluating those results.
Community Outreach: Dr Annise Dobson, postdoctoral researcher on the project led a group of community members on an interpretive hike entitled ‘Climate Change Impacts in Field to Forest at Hubbard Recreation & Natural Area.’ In addition to this formal programming we had positive and productive interactions with community members, from young children with bug nets to dog walkers and homeowners in adjacent properties. We look forward to participating in future programming and community engagement at Hubbard Recreation & Natural Area.
We are immensely grateful to the City of South Burlington for allowing us to use the field. We would like to thank Holly Rees, Paul Conner, and Ashley Parker in particular for their efforts in facilitating this research and engaging community members. Finally, we would like to thank the South Burlington community for always making us feel welcome.