From tree to plot: investigating stem CO2 efflux and its drivers along a logging gradient in Sabah, Malaysian Borneo

Abstract

Summary Stem respiration constitutes a substantial proportion of autotrophic respiration in forested ecosystems, but its drivers across different spatial scales and land‐use gradients remain poorly understood. This study quantifies and examines the impact of logging disturbance on stem CO2 efflux (EA) in Malaysian Borneo. EA was quantified at tree‐ and stand‐level in nine 1‐ha plots over a logging gradient from heavily logged to old‐growth using the static chamber method. Tree‐level results showed higher EA per unit stem area in logged vs old‐growth plots (37.0 ± 1.1 vs 26.92 ± 1.14 g C m−2 month−1). However, at stand‐level, there was no difference in EA between logged and old‐growth plots (6.7 ± 1.1 vs 6.0 ± 0.7 Mg C ha−1 yr−1) due to greater stem surface area in old‐growth plots. Allocation to growth respiration and carbon use efficiency was significantly higher in logged plots. Variation in EA at both tree‐ and stand‐level was driven by tree size, growth and differences in investment strategies between the forest types. These results reflect different resource allocation strategies and priorities, with a priority for growth in response to increased light availability in logged plots, while old‐growth plots prioritise maintenance and cell structure.