Walking through a forest, one can often smell the characteristic scents of decomposing vegetation - fragrances from the many natural chemicals (volatile organic compounds or VOCs) that are released as vegetation breaks down. These compounds not only give decomposing leaves their characteristic odor, they are also important to the chemistry of the atmosphere, and to underlying soils, where they can influence soil fertility and alter the types of organisms residing in soil. Hundreds of different VOCs can also be released by the microbes that consume vegetation on the forest floor, and microbial decay of leaves and branches from different plant species produces distinct VOCs during decomposition, contributing to the different smells of a pine versus an oak forest, for example. Scientists do not yet understand how the types and amounts of these substances vary as plant matter decomposes. Researchers also need to understand how the release of VOCs will be altered as forest composition shifts seasonally with changes in the environment. This research will not only address these knowledge gaps, it will also determine the importance of VOCs to underlying soils; how they may promote the storage of carbon in forest soils, and how they can influence soil fertility by altering nitrogen cycling and the types of microorganisms found in soils. This project will be conducted by a team of researchers both at the University of Colorado and at Virginia Tech where the project will train undergraduate and graduate students in cutting-edge research. In addition, researchers at these universities will use the research results to introduce high school students to key concepts and tools in the study of soils and their roles in sustaining ecosystems.
All decomposing plant litter emits VOCs, and the total amount of carbon (C) released as VOCs can be surprisingly high, with some litters emitting VOCs at rates approaching that of C emissions as carbon dioxide. The proposed research will use a series of field and laboratory-based studies to determine 1) how the amounts and types of VOCs emitted vary as litter decomposition progresses, 2) the sensitivity of these emissions to changes in moisture and temperature regimes, 3) the degree to which the VOCs produced during litter decomposition represent a source of organic C to underlying soils, and 4) how these VOCs impact microbial communities and key nitrogen cycling processes in soil. Together, the proposed work will improve model representations of VOC fluxes from terrestrial ecosystems, an important objective given that some of these litter-derived VOCs can promote the formation of ozone and secondary organic aerosols in the atmosphere. In addition, this research will explore an understudied mechanism by which leaf litter can influence the biotic and abiotic characteristics of underlying soils. Ultimately this research could lead to the development of novel strategies to manage soil by identifying specific VOCs that could reduce soil pathogen loads or alter the rates of specific microbial processes that are critical to the maintenance of soil fertility.
