Respiration from coarse wood litter in central Amazon forests

Respiration from coarse litter (trunks and large branches > 10 cm diameter) was studied in central Amazon forests. Respiration rates varied over almos t two orders of magnitude (1.003-0.014 mug C g(-1) C min(-1), n = 61), and were significantly correlated with wood density (r(adj)(2) = 0.42), and moi sture content (r(adj)(2) = 0.39). Additional samples taken from a nearby pa sture indicated that wood moisture content was the most important factor co ntrolling respiration rates across sites (r(adj)(2) = 0.65). Based on avera ge coarse litter wood density and moisture content, the mean long-term carb on loss rate due to respiration was estimated to be 0.13 yr(-1) (range of 9 5% prediction interval (PI) = 0.11-0.15 yr(-1)). Comparing mean respiration rate with mean mass loss (decomposition) rate from a previous study, respi ratory emissions to the atmosphere from coarse litter were predicted to be 76% (95% PI = 65-88%) of total carbon loss, or about 1.9 (95% PI = 1.6-2.2) Mg C ha(-1) yr(-) (1). Optimum respiration activity corresponded to about 2.5 g H2O g(-1) dry wood, and severely restricted respiration to < 0.5 g H2 O g(-1) dry wood. Respiration from coarse litter in central Amazon forests is comparable in magnitude to decomposing fine surface litter (e.g. leaves, twigs) and is an important carbon cycling component when characterizing he terotrophic respiration budgets and net ecosystem exchange (NEE).