Assessing above-ground woody debris dynamics along a gradient of elevation in Amazonian cloud forests in Peru: balancing above-ground inputs and respiration outputs

Background: Dead biomass, including woody debris (WD), is an important component of the carbon cycle in tropical forests.Aims: This study analyses WD (>2 cm) and other above-ground fluxes in mature tropical forest plots along an elevational gradient (210-3025 m above sea level) in southern Peru.Methods: This work was based on inventories of fine and coarse WD (FWD and CWD, respectively), above-ground biomass, and field-based and experimental respiration measurements.Results: Total WD stocks ranged from 6.26 Mg C ha(-1) at 3025 m to 11.48 Mg C ha(-1) at 2720 m. WD respiration was significantly correlated with moisture content (P < 0.001; R-2 = 0.25), temperature (P < 0.001; R-2 = 0.12) and wood density (P < 0.001; R-2 = 0.16). Controlled experiments showed that both water content and temperature increased respiration rates of individual WD samples. The full breadth of the temperature sensitivity coefficient, or Q(10), estimates, ranging from 1.14-2.13, was low compared to other studies. In addition, temperature sensitivity of WD respiration was greater for higher elevations.Conclusions: Carbon stocks, mortality and turnover of above-ground biomass varied widely and were not significantly related with elevation or slope. This study demonstrates that some forests may be a carbon source due to legacies of disturbance and increasing temperatures, which may cause additional, short-term carbon efflux from WD. Predictions of tropical forest carbon cycles under future climate should incorporate WD dynamics and related feedback.