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

Abstract

This study aims to improve our understanding of temporal variations and controlling factors of soil respiration (Rs) and its components (microbial respiration or Rm and root respiration or Rb) in an Asian tropical seasonal forest at diurnal, seasonal and annual timescales in relation to biotic and abiotic controls. Rs 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 Rs during 2008–2011. Analysis of Rs in relation to both biotic and abiotic factors was carried out to understand its temporal variations at different timescales. Rm was the main contributor to overall magnitude and variability of Rs. 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 Rs 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 Rs during 2008–2011 were 3.20, 3.89, 3.52, 4.14 kgCO2 m−2 years−1, respectively. The 4-year average ratio of Rm (trenched) to Rs (untrenched) was 66 ± 4 %. Rm plays a crucial role in determining the magnitude (large ratio between Rm and Rs) and temporal variations of Rs. In this forest ecosystem, high seasonal variations in Rs were observed and were mainly attributed to the response of Rm to moisture.