Erik Lilleskov

I study how communities of soil organisms and the ecosystems they inhabit influence each other, and how these interactions are affected by human-induced changes such as air pollution, climate change, or invasive species. In one area of my research I am trying to understand how communities of symbiotic, tree-root associated fungi, called mycorrhizal fungi, are altered by changing atmospheric chemistry, in particular increased nitrogen deposition, ozone, and carbon dioxide. I am especially interested in whether changing communities of mycorrhizal fungi buffer or increase the effects of environmental change. In addition, I am studying the effect of invasive soil organisms on forest ecosystems. By their consumption and mixing of soil organic matter, changes in movement of soil water, alteration of soil food webs, and consumption of roots, they have large effects on forests. We are studying both the distribution and effects of non-native soil organisms including non-native earthworms, isopods, weevils, ground beetles, termites and ants. Another area of focus is understanding how humans affect peatland ecosystems around the world. Peatlands store vast quantities of carbon, and continue to be sinks for carbon under most conditions. However, disturbances like drainage, fire, or long-term drying can cause these ecosystems to degrade and lose carbon to the atmosphere, causing our climate to warm.

Here is a sampling of future project ideas:

• Understand the effect of suites of invasive soil organisms on native biodiversity and ecosystem function;
• Define the role of mycorrhizal fungal presence and community composition and structure in soil carbon formation;
• Partition the roles of free living decomposers, ectomycorrhizal fungi and ericoid mycorrhizal fungi in peatland carbon cycling
• Determine the potential for peatland restoration as a Natural Climate Solution in the US and tropical Latin America

Soil organisms have a strong influence on the way ecosystems function. They process soil organic matter, releasing nutrients critical for forest productivity, and affect greenhouse gases via storage of organic carbon. Bacteria, fungi and soil invertebrates also make up a large part of the biodiversity that resides in them. Hundreds of species of symbiotic fungi are associated with each tree species. Most of the wild mushrooms seen in northern forests are the fruiting structures of these symbiotic fungi, providing a window into belowground diversity, contributing to both above- and belowground food webs. Many insects, salamanders, small mammals, birds and their predators rely on soil organisms as links in their food webs. Alterations in the abundance and diversity of soil organisms can thus have ripple effects throughout forest ecosystems. Soil organisms also provide important non-timber forest products such as wild edible and medicinal mushrooms. Thus, it is critical that we understand how soil organisms interact with our changing forest ecosystems.

Peatlands are important for many reasons. In the context of climate change, they are critical reservoirs of soil carbon, storing about 30% of soil carbon on about 3% of the land surface. Soil carbon is the largest terrestrial pool of carbon. This peatland carbon has been accumulating for millenia, and under pre-industrial climates and land use would continue to remove carbon dioxide from the atmosphere and store it as dead organic matter that makes up peat. However, climate warming, drainage, and intensive land uses such as grazing can cause peatlands to be net sources of climate-warming greenhouse gases. Therefore it is critical to assess the condition of these peatlands, and develop sustainable land use practices that can restore peatland functioning.