Tree photosynthesis modulates soil respiration on a diurnal time scale

TitleTree photosynthesis modulates soil respiration on a diurnal time scale
Publication TypeJournal Article
Year of Publication2005
AuthorsTANG, JIANWU, Baldocchi Dennis D., and Xu Liukang
JournalGlobal Change Biology
Pagination1298 - 1304
Date Published08/2005
Keywordscarbon cycle, CO2 efflux, CO2 sensor, eddy covariance, savanna

To estimate how tree photosynthesis modulates soil respiration, we simultaneously and continuously measured soil respiration and canopy photosynthesis over an oak-grass savanna during the summer, when the annual grass between trees was dead. Soil respiration measured under a tree crown reflected the sum of rhizosphere respiration and heterotrophic respiration; soil respiration measured in an open area represented heterotrophic respiration. Soil respiration was measured using solid-state CO2 sensors buried in soils and the flux-gradient method. Canopy photosynthesis was obtained from overstory and understory flux measurements using the eddy covariance method. We found that the diurnal pattern of soil respiration in the open was driven by soil temperature, while soil respiration under the tree was decoupled with soil temperature. Although soil moisture controlled the seasonal pattern of soil respiration, it did not influence the diurnal pattern of soil respiration. Soil respiration under the tree controlled by the root component was strongly correlated with tree photosynthesis, but with a time lag of 7–12 h. These results indicate that photosynthesis drives soil respiration in addition to soil temperature and moisture.