Time-lags Between Canopy Photosynthesis and Soil Respiration in a Temperate Deciduous Forest

The translocation of photosynthates from canopy to roots is a crucial link between the above- and belowground carbon (C) cycles. There is much uncertainty regarding our quantitative understanding of how photosynthesis, in combination with environmental conditions, regulates soil respiration. Improving the prediction accuracy of soil C cycling and respiratory fluxes is critically important for projecting the fate of the terrestrial C cycle and global climate change. The purpose of this research was to examine environmental controls and photosynthetic regulation of respiratory fluxes (total soil, and hetero- and autotrophic components), with emphasis on how drought modulates the coupling of canopy photosynthesis with belowground respiratory fluxes at a drought-prone Quercus-Carya (oak-hickory) forest. We focus on examining the time delay between photosynthesis and soil respiration i.e., how long does it take for photosynthates to be translocated to roots? To address this problem, we synthesized measurements of canopy sun-induced chlorophyll fluorescence as a proxy for photosynthesis in conjunction with a trenching experiment designed to partition soil respiration into its heterotrophic and autotrophic components.