Multiscale analysis of the relationship between topography and aboveground biomass in the tropical rainforests of Sulawesi, Indonesia

This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, redistribution , reselling , loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material. This article aims to explore spatial and altitudinal non-stationarity in the relationship between aboveground biomass (AGB) of tropical rainforest in Sulawesi (Indonesia) and topography. An autoregressive model through a geographically weighted regression (GWR) framework was used to study the relationship between ground-measured values of AGB and altitude above sea level at 85 sampling plots. The relationships between AGB and altitude were found to be significantly spatially variable and scale-dependent. The results also suggested high altitudinal variability in the examined relationship. Both the strength of the AGB–altitude relationship (r) and the altitudinal gradient (a) showed a high changeability in the horizontal and vertical dimensions. The complex spatio-altitudinal patterns in the GWR-based local estimates of the r and a parameters gave rise to both spatial and altitudinal variations in the scale effects. The approach presented in this study enables finding the most appropriate scale for data analysis within different altitudinal bands. The study found that the changes of the gradient a along altitudinal transects relate to prevalent environmental conditions observed at different altitudes, whereas the optimal bandwidth was related to the terrain surface heterogeneity. 1. Introduction Terrain and its topography are paramount in ecological studies for their influence on numerous physical processes associated with the distribution of soil properties, plant growth, vegetation structure, decomposition rates and biomass accumulation (Austin et al. 1994, Coops et al. 1998). Altitude above sea level is the major factor predicting vegetation patterns in landscapes with diverse terrain conditions. Reduction in air temperature with increasing altitude reduces the energy available for plant growth and strictly affects forest vegetation (Tanner 1980, Richards 1996, Reich et al. 1997). Many studies have examined the changes in forest vegetation associated with changing altitude in a variety of …