CO2 efflux from decomposing leaf litter stacks is influenced by the vertical distribution of leaf litter water content and its temporal variation
2015
Ataka, M. (Kyoto University, Kyoto (Japan). Graduate School of Agriculture, Division of Environmental Science and Technology, Laboratory of Forest Hydrology) | Kominami, Y. | Jomura, M. | Yoshimura, K. | Miyama, T. | Kosugi, Y. | Tani, M.
We evaluated the temporal changes in the vertical distribution of leaf litter respiration (Rsub(LL)) due to changes of leaf litter water content (Wsub(LL)) within the leaf litter layer (L layer) using in situ direct measurements. To investigate the vertical distribution of Rsub(LL) and Wsub(LL) within the leaf litter layer over a time-series, we measured the Rsub(LL) and Wsub(LL) of 10 separate layers in vertical leaf litter stacks fixed to the forest floor using wire pins. Measurements were conducted for 30 stacks in a temperate broad-leaved secondary forest between May 2008 and January 2009. In the warm season, high Rsub(LL) was observed at high Wsub(LL), while low Rsub(LL) was observed at low Wsub(LL). Rsub(LL) was comparatively lower during the cool season than during the warm season regardless of the magnitude of Wsub(LL). The temperature sensitivity of Rsub(LL) differed depending on Wsub(LL); temperature increases under low-moisture conditions had small effects on Rsub(LL), while under higher-moisture conditions, Rsub(LL) was more responsive to temperature increases. Small differences in position within the leaf litter stack affected the vertical variation of Wsub(LL) and, consequently, there was large distribution in Rsub(LL) during the wet period and small distribution in Rsub(LL) (totally small values) during the dry period. Thus, CO2 efflux from the net L layer was strongly affected by Rsub(LL) distribution induced by the local wetting within the L layer. In estimating CO2 efflux from the L layer using water content of the L layer, monitoring of the water content of the L layer, which takes into account the vertical distribution in Wsub(LL) within the L layer, is necessary.
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