ROLE OF SOIL TEMPERATURE AND MOISTURE ON SOIL RESPIRATION IN A TEAK PLANTATION AND MIXED DECIDUOUS FOREST IN THAILAND

This study aimed to estimate and compare diurnal and seasonal variations of soil respiration in a teak (Tectona grandis) plantation and a mixed deciduous forest in Thailand, and to investigate the role of soil temperature and soil moisture in affecting soil respiration. Soil respiration was determined by closed-chamber technique with three replicates in each experimental plot and was measured twice in a month from April 2010 till March 2011. This study showed that land cover change had no effect on soil diurnal and seasonal respiration behaviour. Diurnal variation in soil respiration was largely fluctuated in teak plantation compared with mixed deciduous forest. Seasonally, soil respiration values were 326.8 and 313.2 g C m(-2) year(-1) (136.7 and 131.0 mg CO2 m(-2) hour(-1)) in the teak plantation and mixed deciduous forest respectively. There were seasonal variations in soil respiration at both sites; soil respiration in the wet season was significantly higher than that in the dry season (p = 0.011 and 0.005 in teak plantation and mixed deciduous forest respectively). On the other hand, differences in soil respiration between teak plantation and mixed deciduous forest were not significant in the wet and dry seasons. Soil moisture was a major factor influencing seasonal variation of soil respiration while soil temperature played a key role in controlling diurnal variation. Soil respiration in mixed deciduous forest was more sensitive to change in soil temperature (Q(10) = 2.02) than that in teak plantation (Q(10) = 1.63) due to large soil respiration variation in mixed deciduous forest observed during the early wet season.