Spatial variations in the net ecosystem productivity of a primeval tropical forest in a 50-ha plot in Pasoh, Peninsular Malaysia

Abstract

We assessed the spatial variations in net ecosystem productivity (NEP) using a biometric method based on the dynamics of coarse woody organs in a primeval lowland tropical rain forest in Pasoh, Peninsular Malaysia. The average NEP and carbon stocks in biomass and coarse woody debris over 15 years from 1990 to 2005 were -0.75 t C ha -1 y -1 , 205 t C ha -1 , and 22 t C ha -1 , respectively. However, there were large spatial variations among the five communities, which were correlated with edaphic and topographical features. A mature carbon cycling system with high biomass (where NEP ≈ 0) was observed in a subcommunity on west-facing slopes of the hill community. Over the course of 15 years, a drought and storms were the major agents causing forest disturbances. These factors affected the spatial variations of NEP through not only spatial distribution patterns in species with different sensitivities to stress but also differences in the extent of stress depending on topography. We modeled the disturbance regime as elapsing from 1907 to 1947 basing on observed values of net primary production and biomass of five communities during the 15 years. When we extrapolated high mortalities of trees under this regime, our simulation suggested that a 50-ha plot will remain a carbon-source system for the atmosphere at an average rate of NEP＝-0.95 t C ha -1 y -1 until 2060, with different biomass decreases among these five communities.

Spatiotemporal changes in biomass after selective logging in a lowland tropical rainforest in Peninsular Malaysia

“…In addition to the drought, a strong storm in 2004 with a maximum wind speed of 18.6 m s 1 knocked down many trees in plot A (Fig. 1) (Yoneda et al 2017). This storm might have resulted in the abrupt AGB reduction in the swampy area from 2004 to 2006.…”

“…High mortality after a strong storm in 1987 in plot A is the likely cause of many of the canopy gaps seen in the swampy area of this plot . Such storms (gales, specifically) occur sporadically, averaging every 5.4 years at the study site, but effects on vegetation vary in relation to the topography (Yoneda et al 2017).…”

Spatial variations in the decay coefficients of forest ecosystems in East and Southeast Asia

“…Spatial 1-NPP relations: Spatial relations differed among the four plots when we assessed these parameters based on a unit area that was nearly equivalent to the maximum autocorrelation area for 1 at each plot. We examined these relationships based on material cycling through the dynamics of coarse woody debris in a forest ecosystem (Yoneda et al 2016(Yoneda et al , 2017. The annual decomposition, DEC, is an important parameter for assessing spatial variations in productivity under dynamic equilibrium conditions.…”

Annual Tropical‐Rainforest Productivity Through Two Decades: Complex Responses to Climatic Factors, [CO2] and Storm Damage

“…Field studies to quantify this biome's C‐cycling and to identify the environmental drivers of its IAV face two major challenges. Studies of ecosystem processes in tropical forests need to be conducted at the landscape scale because of these forests' internal edaphic mosaics (e.g., Itoh et al., 2012; Valencia et al., 2009; Yoneda et al., 2017) and their characteristically localized, sporadic disturbances (Chambers et al., 2013; Marvin et al., 2014). A single small (≤1–2 ha) plot per forest, the sampling approach that has dominated tropical‐forest studies to date (e.g., Brienen et al., 2015; Hubau et al., 2020; Malhi et al., 2015; Qie et al., 2017), will not suffice for quantifying a given forest's landscape‐level processes.…”