PARENT SESSION
Oral Session # 68: Soil Ecology I: Communities, Respiration, and Nutrient Cycling.
Presiding: C Rumbaitis-del Rio
Thursday, August 7. 8:00 AM to 11:30 AM, SITCC Meeting Room 106.
Separating root respiration from soil respiration in a ponderosa pine plantation in the Sierra Nevada.
Tang, Jianwu*,1, Qi, Ye1, Goldstein, Allen1, 1 University of California at Berkeley, Berkeley, CA
ABSTRACT- Partitioning soil respiration into autotrophic and heterotrophic respiration is of critical importance for building process-based soil carbon models since these components respond differently to abiotic and biotic drivers and have different spatial and temporal variations. To remove the influence of root autotrophic respiration from total soil respiration, we trenched a 3m x 3m plot in a ponderosa pine plantation in the Sierra Nevada. We measured soil CO2 efflux in the trenched plot as well as two non-trenched plots between August 2001 and October 2002. We used multivariate regression with independent variables of soil temperature and moisture to analyze measurement data of soil respiration and heterotrophic respiration. We estimated root respiration as the difference between total soil respiration and heterotrophic respiration. In addition to environmental variables, root respiration is affected by plant physiology, phenology, and photosynthesis. The annual accumulations of total soil respiration, heterotrophic respiration, and autotrophic respiration between October 1, 2001 and September 30, 2002 were 78.2 mol m-2 year-1, 52.2 mol m-2year-1, and 26.0 mol m-2 year-1, respectively. Total soil respiration, heterotrophic respiration, and autotrophic respiration peaked in June. The ratio of autotrophic respiration to total soil respiration (Fa/F) is not a constant seasonally with an annual average of 0.33. In the growing seasons between May and October Fa/F averaged 0.37 while in non-growing seasons Fa/F averaged 0.28. We used aerial photos, image analysis, and GIS to study the spatial variation of soil respiration. The spatial variation of soil respiration is mainly explained by root density, and also influenced by soil nitrogen content and soil carbon content.
Key words: root respiration, soil respiration, partition, carbon model