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−1at 3025 m to 11.48 Mg C ha−1at 2720 m. WD respiration was significantly correlated with moisture content (P< 0.001;R2= 0.25), temperature (P< 0.001;R2= 0.12) and wood density (P< 0.001;R2= 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, orQ10, 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. [ABSTRACT FROM PUBLISHER]