Carbon Fine Root Allocation and Transfer at Ecosystem Scales (Graduate Project)

Research Team: Durwin Carter (Graduate Student), Dr. Robert J. Mitchell (Scientist), Dr. Joe Hendricks (State University of West Georgia), Dr. Dali Guo (Postdoctoral Associate), and Nancy N. Higginbothem (Research Technician)

Net primary production (NPP) is perhaps the most fundamental ecological characteristic of terrestrial ecosystems. Insight into the basic patterns and mechanistic controls of NPP has been hindered, however, by a poor understanding of belowground dynamics. In particular, uncertainty pertaining to the effects of soil resource availability on the production, mortality, nutrient retranslocation, and decomposition dynamics of fine roots and mycorrhizae has contributed to the development of two diametrically opposed hypotheses regarding soil resource controls on NPP allocation patterns. The overall goal of this study is to assess the mechanistic controls of soil resource availability on NPP in longleaf pine-wiregrass ecosystems. The specific objectives of our research program are to: 1) assess the independent and interacting effects of soil resource availability on above- and belowground NPP, 2) gain a clearer picture of the mechanistic controls of soil resource availability on fine root mortality, 3) determine if an improved understanding of the rates and controls of fine root mortality, nutrient retranslocation, and decomposition will reduce the differences in estimates of fine root NPP obtained using a variety of methods, and 4) test a conceptual model of soil resource control that was developed to explain fine root and foliage dynamics. We are using combinations of natural resource availability gradients and experimental gradients created in a field realistic manner to assess the direct and interaction effects of water and nutrient availability on NPP. In addition, we are examining fine root production, mortality, nutrient retranslocation, and decomposition to provide insight into the reliability of the techniques and, consequently, the rates and controls of these fine root processes. In turn, this information will facilitate more integrated assessments of ecosystem structure and function, which are essential for development of ecologically sound management regimes.

Research in progress, publications forthcoming.

Funded by: USDA NRI Ecosystems