Decomposition and carbon cycling of dead trees in tropical forests of the central Amazon

Decomposition rare constants were measured for holes of 155 large dead tree s (>10 cm diameter) in central Amazon forests. Mortality data from 21 ha of permanent inventory plots, monitored for 10-15 years, were used to select dead trees for sampling. Measured rate constants varied by over 1.5 orders of magnitude (0.015-0.67 year(-1)), averaging 0.19 year(-1) with predicted error of 0.026 year. Wood density and bole diameter were significantly and inversely correlated with rate constants. A tree of average biomass was pre dicted to decompose at 0.17 year(-1). Based on mortality data, an average o f 7.0 trees ha(-1) year(-1) died producing 3.6 Mg ha(-1) year(-1) of coarse litter (>10 cm diameter). Mean coarse litter standing-stocks were predicte d to be 21 Mg ha(-1) with a mean residence time of 5.9 years, and a maximum mean carbon flux to the atmosphere of 1.8 Mg C ha(-1) year(-1). Total litt er is estimated to be partitioned into 16% fine wood, 30% coarse wood, and 54% non-woody litter (e.g., leaves, fruits, flowers). Decomposition rate co nstants for coarse litter were compiled from 20 globally distributed studie s. Rates were highly correlated with mean annual temperature, giving a resp iration quotient (Q(10)) of 2.4 (10 degrees C-1).