Abstract
Abstract. Stem respiration is an important, but poorly studied component of total forest ecosystem respiration. Stem CO2 efflux was investigated with an open gas exchange system while stand microclimate and stem temperature were continuously monitored in a Schima superba plantation in South China for several days in August and December 2010. The temperature response of respiration in the different seasons, the vertical variation in stem CO2 efflux along the stem, and the stand-level stem CO2 efflux were examined. Stem volume was identified as the better correlate for stem CO2 efflux and was used as the scalar for the stand-level estimates of stem CO2 efflux in this S. superba plantation. Volume-based stem CO2 efflux was higher at 2 m than at 1.3 m. Mean stem CO2 efflux was 268.9 and 104.6 μmol m−3 s−1 in August and December, respectively, indicating a dramatic seasonal variation of stem CO2 efflux. The temperature response of stem CO2 efflux remained constant during our study period with Q10 values of 1.9 and 1.8. In this subtropical S. superba plantation, stem CO2 efflux per unit ground area averaged 3.36 and 1.26 μmol m−2 s−1 based on the measurement data at 1.3-m height of the stem in August and December, respectively. Our results suggest that stem CO2 efflux has a constant temperature response, and the seasonal variation in stem CO2 efflux is mainly controlled by stem temperature, and the vertical variation in stem CO2 efflux needs to be considered in the stand-level estimation.
Highlights
Forest carbon storage is an important carbon pool in the terrestrial ecosystem
Our results suggest that stem CO2 efflux has a constant temperature response, and the seasonal variation in stem CO2 efflux is mainly controlled by stem temperature, and the vertical variation in stem CO2 efflux needs to be considered in the stand-level estimation
Since woody tissue constitutes the largest part of forest biomass, its respiration makes an important contribution to the carbon balance of forest ecosystems (Kramer and Kozlowski, 1979; Harris et al, 2008)
Summary
Forest carbon storage is an important carbon pool in the terrestrial ecosystem. Respiration is the dominant physiological process accounting for the variations in ecosystem production, and autotrophic respiration can consume 30–70 % of net primary production (Valentini et al, 1996; Ryan et al, 1997; Litton et al, 2007; Tang et al, 2008). Recent studies emphasize the utility of in situ chamber measurements for stand-level estimation, but woody tissue respiration is usually measured only at a given point of the stem (Ryan, 1990; Sprugel, 1990; Harris et al, 2008; Robertson et al, 2010). One of the main problems involved in scaling up the chamber measurements to the forest is the difficulty in measuring stem surface area or stem volume at the stand level due to the different tree structures of tree species (Lavigne et al, 1996; Ryan et al, 1996; Levy and Jarvis, 1998; Kim et al, 2007). It is very essential to consider the spatial changes in woody tissue respiration when estimating
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