Multiple timescale variations and controls of soil respiration in a tropical dry dipterocarp forest, western Thailand

This study aims to improve our understanding of temporal variations and controlling factors of soil respiration (R-s) and its components (microbial respiration or R-m and root respiration or R-b) in an Asian tropical seasonal forest at diurnal, seasonal and annual timescales in relation to biotic and abiotic controls. R-s was studied by the trenching method in a seasonal dry diptercarp forest, western Thailand. An automated soil chamber system was used to produce hourly data of R-s during 2008-2011. Analysis of R-s in relation to both biotic and abiotic factors was carried out to understand its temporal variations at different timescales. R-m was the main contributor to overall magnitude and variability of R-s. Soil temperature alone was the main driver of diurnal variation, while the combination of soil moisture and soil temperature determined the seasonal variations. The amount of R-s was also related to the fine root (< 2 mm) and microbial biomass at seasonal timescales. Due to the small inter-annual variations in soil temperature and moisture, total soil respiration among the 4 years was not significantly different (p < 0.05). The annual totals for R-s during 2008-2011 were 3.20, 3.89, 3.52, 4.14 kgCO(2) m(-2) years(-1), respectively. The 4-year average ratio of R-m (trenched) to R-s (untrenched) was 66 +/- 4 %. R-m plays a crucial role in determining the magnitude (large ratio between R-m and R-s) and temporal variations of R-s. In this forest ecosystem, high seasonal variations in R-s were observed and were mainly attributed to the response of R-m to moisture