OOS 22

Dead Roots: The Dark Side of the Carbon Cycle

Soil is the largest reservoir of terrestrial organic carbon and as such represents a major carbon sink. Contributors to soil carbon include decomposition byproducts of litter, microbes, fungi and animals. Despite likely being a major contributor to soil carbon, a largely unexplored source is dead roots buried in the soil. In this sense, the reference of root decomposition as the ‘dark side’ of the carbon cycle is two-fold: the roots are in the dark, given that they decompose below ground, and ecologists are also ‘in the dark’ with our lack of knowledge of this important process. 50% of primary production in many ecosystems is belowground and as such roots represent both a major source of soil carbon and a potential carbon sink. Although there has been much study on species variation in and environmental effects on leaf litter decomposition, root decomposition may not be parallel to these patterns. Environmental controls over decomposition may be different for roots than for leaves because of the vastly different environment in which this litter decomposes. Roots grow in direct contact with the soil where they die, unlike leaf litter, which experiences ultraviolet radiation and rapid temperature and moisture fluctuations. As most of our information on environmental effects on litter turnover comes from leaf decomposition studies, the effects of global change on root carbon turnover are greatly unknown. This session aims to present our current understanding of root decomposition and identify knowledge gaps. The presentations will offer how root decomposition and soil carbon are linked and present findings from studies that test the effect of different environmental factors and root traits on decomposition. Presenters will include novel methods to study root decomposition and identify key factors that affect root carbon turnover. This session is appealing to ecosystem ecologists, biogeochemists, and microbial ecologists alike.