Peatlands in the far north store a very large amount of carbon in their cold (sometimes frozen) and wet soils. While the cold, wet environment is clearly important, the biological factors that cause so much peat to accumulate in these ecosystems are not entirely understood. This project will study how changes in peat carbon cycling at the Bonanza Creek Long-Term Ecological Research site vary with nutrient availability. Researchers will conduct experiments to test hypotheses concerning the importance of algae and the food web of insects and invertebrates that algal production supports, to accumulation of carbon in peatlands. Food webs are a poorly know aspect of peatland ecology, and a better understanding of what controls biotic interactions within them will have profound implications for understanding the global carbon cycle. In addition to charting new conceptual ground in ecosystem science, this project will support two early career researchers, involve undergraduate students from under-represented groups, and train two graduate students.
This Early-concept Grant for Exploratory Research (EAGER) project challenges the notion that energy flow within the food web of boreal peatlands is limited to detrital pathways. Through a contribution of carbon subsidies and by modifying redox potential for heterotrophic microorganisms, the investigators propose that algal photosynthesis fuels a microbial loop and contributes to ecosystem carbon and nitrogen fluxes. The research will evaluate the relative importance of bottom-up versus top-down effects (and their interactions) on boreal peatland food webs using a factorial experiment to test three hypotheses: 1) Under low nutrient availability, algal biomass is constrained and decomposition is primarily regulated by detrital pathways. 2) Increasing nutrient availability promotes algal biomass and the transfer of energy to grazers, releasing higher trophic levels from resource limitation. 3) The presence of a second energy pathway in algae (edible vs. inedible) mutes the trophic cascade, leading to greater stability (i.e., lower coefficients of variance) in food web structure than would be expected with strong top-down control of a homogenous edible community.
