CO₂ efflux from decomposing leaf litter stacks is influenced by the vertical distribution of leaf litter water content and its temporal variation

Abstract

We evaluated the temporal changes in the vertical distribution of leaf litter respiration (R LL ) due to changes of leaf litter water content (W LL ) within the leaf litter layer (L layer) using in situ direct measurements. To investigate the vertical distribution of R LL and W LL within the leaf litter layer over a time-series, we measured the R LL and W 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 R LL was observed at high W LL , while low R LL was observed at low W LL . R LL was comparatively lower during the cool season than during the warm season regardless of the magnitude of W LL. The temperature sensitivity of R LL differed depending on W LL ; temperature increases under low-moisture conditions had small effects on R LL, while under higher-moisture conditions, R LL was more responsive to temperature increases. Small differences in position within the leaf litter stack affected the vertical variation of W LL and, consequently, there was large distribution in R LL during the wet period and small distribution in R LL (totally small values) during the dry period. Thus, CO 2 efflux from the net L layer was strongly affected by R LL distribution induced by the local wetting within the L layer. In estimating CO 2 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 W LL within the L layer, is necessary.

Comparison of litter-bag and chamber methods for measuring CO₂ emissions from leaf litter decomposition in a temperate forest

“…Reportedly, moisture conditions influence CO 2 emissions through leaf litter decomposition Kim et al, 2005b . Particularly, the vertical moisture distribution in the litter layer affects the decomposition Ataka et al, 2015 . Although the effect of mesh on moisture was not measured in this study, the presence of the mesh can underestimate the decomposition rate.…”

Recent advances in the understanding of ecosystem processes at eddy covariance CO<SUB>2</SUB> flux sites in East Asian forest ecosystems: a review

“…Among the AsiaFlux sites, intensive work on R h has been conducted at Yamashiro YMS , which is located in a warm-temperate forest in Japan. Ataka et al 2014Ataka et al , 2015 assessed microscale spatiotemporal variation of leaf litter decomposition due to changes in litter water content. Respiration from leaf litter decomposition just after rainfall events within 1 day became 8.6-fold larger than that prior to rainfall Ataka et al, 2014 , which indicates that precipitation strongly controlled decomposition.…”

“…Respiration from leaf litter decomposition just after rainfall events within 1 day became 8.6-fold larger than that prior to rainfall Ataka et al, 2014 , which indicates that precipitation strongly controlled decomposition. Furthermore, the vertical position within the litter layer also significantly affected leaf litter respiration; respiration from the top position was almost threefold larger than that from the bottom position Ataka et al, 2015. Jomura et al 2007 directly measured respiration from coarse woody debris of a variety of species using a closed-chamber method and developed a comprehensive decomposition function accounting for several coarse woody debris characteristics wood density and diameter at the YMS site.…”