Environmental control of mean residence time (MRT) of labile plant C at the ecosystem level

Oak Ridge Experiment	Biosphere 2
Duke Forest

Recent experimental evidence has shown very fast rates of plant C cycling at the ecosystem level. The causes (rate of photosynthesis or growth) or the environmental controls (temperature, moisture, CO₂) of this fast C cycle are not known. We are doing a series of satble isotope pulse-chase experiments in FACE facilities and in mesocosms at Biosphere2 to deconvolute ecosystem and climatic controls on plant carbon cycling at the ecosystem level. This way we will calculate MRT of photosynthate in forests grown at ambient and elevated CO₂. To understand the climatic contorls on ecosystem carbon cycle pulse-chase experiments at biosphere2 are being done in three different mesocosms: rainforest, cottonwood plantation and desert where both photosynthesis and climate are monitored and controlled. We are studying the effects of tempertaure, moisture and seasonality on plant C cycle. These experiments are done in collaboration with Guanghui Lin, Dan Yakir, Barry Osmond and Joe Berry.