Coarse woody decay rates vary by physical position in tropical seasonal rainforests of SW China

Abstract

Decomposition of woody detritus is an important but often ignored process in forest ecosystems. Moisture and temperature regimes are dominant controls over woody decay, contributing to significant variability at local, regional, and global scales. Our focus was on local variability in woody decay rates depending on their physical position. Woody detritus may decay on the forest floor, aboveground, or combination of both, depending on the mortality agent. In this study, we measured decay rates of logs, large branches on the forest floor, and snags over a three-year period. We also collected monthly respiration estimates, and analyzed woody detritus N and P content throughout the study. Logs exhibited the greatest mass loss with a decay-rate constant of k = 0.606 ± 0.020), followed by large branches (k = 0.316 ± 0.012) and snags (k = 0.268 ± 0.008). Heterotrophic respiration was greatest prior to the peak of rainy season, and was greatest for snag material during the first two years of sampling, probably a result of water saturation in ground material. Both N and P were released in all materials, but the rate of P release was much slower in snags. There were large differences of P concentration and C:P among the materials, but their value became similar after three years, indicating P limitation on microbial activities. Our results presented robust evidence for the physical-position-dependence of coarse woody detritus decomposition in the forests.

When a tree falls: Controls on wood decay predict standing dead tree fall and new risks in changing forests

“…Whether forest dieback tips forests from net C sinks to sources reflects, among other factors, how snag formation and fall influences deadwood decay [ 4 ]. While deadwood is suspended off the ground, desiccation and nutrient limitation slow both decomposer activity and the rate of decomposition-derived greenhouse gas emissions to the atmosphere [ 5 , 6 ]. In this state, snags can delay the C efflux following disturbance for many years.…”

Decomposition of coarse woody debris in a long‐term litter manipulation experiment: A focus on nutrient availability

“…Finally, there was a greater proportion of standing dead trees ( snags ) in the litter removal plots than in controls or litter addition plots (Table S2), suggesting that decreased decomposition rates increased snag residence time. This potentially explains the interaction between litter treatment and bole age – snags decompose more slowly than downed boles (Harmon et al., ; Song et al., ) and the accumulation of snags should have a positive feedback effect that further reduces long‐term CWD decomposition rates. Cumulatively, these results suggest that reduced nutrient availability decreased wood decomposition rates, and thus soil nutrient availability is important to long‐term CWD decomposition.…”

Sampling system for estimating woody debris in an urban mixed tropical forest

“…Quantifying woody debris is required for forest fire research (van Wagner 1968, Donato et al 2016, making it an important resource for evaluation and control of the deadwood in the forest (Montes and Cañellas 2006). In addition, the woody debris inventory enables to estimate its potential use for fuel purpose (Waddell 2002), as well as ecological aspects (Clark et al 2002), wildlife habitat assessment (Haughian and Frego 2017), carbon stock (Eaton and Lawrence 2006), and nutrient dynamics (Song et al 2017).…”