Microbial functioning in response to a simulated drought in Malaysian rain forest and oil palm soils.

Abstract

Abstract In this study, soils were collected from a primary forest and an adjacent oil palm plantation and subjected to a brief simulated drought and subsequent rewetting to assess the short-term resistance and resilience of the microbial community from the different land-use types. Soil (Ultisols) samples (n=10) were collected from Pasoh Forest Reserve in south-central Malaysia and an adjacent oil palm plantation (approximately 8 years since planting) in February 2011. Result showed that microbial activity was significantly greater in the primary forest soil than the oil palm soil (P<0.001). Drought reduced fluorescein diacetate hydrolysis to a similar magnitude in both soil types to around 25-30% of initial (pre-drought) conditions (P<0.001). Microbial activity recovered to around two-thirds of pre-drought activity after rewetting. Primary forest soil microbial communities showed a better recovery after rewetting than the oil palm plantation communities (73% of initial value compared to 58% of initial value) as they were significantly different from the activity during the drought, whereas the oil palm plantation communities were not. This study has shown that conversion of South East Asian primary forest to oil palm plantation leads to changes in soil chemical and biological properties with general reductions in soil C and microbial activity in common with many other studies of tropical land-use change. It has also shown that disturbance to the soil system (in this case drying and rewetting) led to differential responses from the microbial communities in soils under the two land-use types. These results have implications for C, N and nutrient cycling and losses from the ecosystem. More broadly, changes in tropical land use and soil management have implications for biogeochemical cycling that will depend upon an improved understanding of both how microbial populations and their functioning are impacted by land-use changes and how this is differentially modulated by additional stresses and disturbances.