You are here:
SOIL CO2 EFFLUX FROM ISOTOPICALLY LABELED BEECH AND SPRUCE IN SOUTHERN GERMANY
Citation:
ANDERSEN, C. P., T. E. GRAMS, J. GREGG, AND R. MATYSSEK. SOIL CO2 EFFLUX FROM ISOTOPICALLY LABELED BEECH AND SPRUCE IN SOUTHERN GERMANY. Presented at Fourth International Symposium on Dynamics of Physiological Processes in Roots of Woody Plants, Wales, UK, September 16 - 20, 2007.
Impact/Purpose:
To evaluate the timing and extent of carbon allocation belowground and respiratory release in a mature forest.
Description:
• Carbon acquisition and transport to roots in forest trees is difficult to quantify and is affected by a number of factors, including micrometeorology and anthropogenic stresses. The canopies of mature European beech (Fagus sylvatica) and Norway spruce (Picea abies) were exposed to a source of CO2 depleted in 13C from background (δ 13C = -47 vs -10 ‰) to evaluate the timing and extent of carbon allocation belowground and respiratory release in a mature forest. • Specialized soil gas sampling wells were placed at 8 and 15 cm in the soil prior to the experiment, and soil CO2 was sampled daily during a 15 day labeling period in August, 2006. • At both 8 and 15 cm depths, δ13C signature of soil CO2 was variable from day to day, reflecting the effect of Vapor Pressure Defficit (VPD) on the δ13C of photosynthates subsequently available for root respiration. In Beech, δ13C of soil CO2 at 8 cm decreased more than 1 ‰ below controls within 48 hrs of exposure, reflecting rapid translocation of fixed C to roots and subsequent release as respiratory substrate. Continued labeling resulted in a 2 ‰ decrease at 8 cm within 7 days after exposures began, and remained lower until the end of the 17 day exposure. The pattern of response was similar at 15 cm in beech, however differences between control and labeled trees were less, which may reflect fewer respiring roots and/or less dependence of deeper roots on current photosynthate. Soil CO2 was highly variable under spruce and did not show a clear pattern in δ 13C ratio during the measurement period. • The results show that carbon fixed in the canopy rapidly reaches respiring roots in beech forests, and illustrates the dependence of shallow fine roots on recently fixed carbon to meet respiratory requirements. idly reaches respiring roots in beech forests, and illustrates the dependence of shallow fine roots on recently fixed carbon to meet respiratory requirements.