The assessment of the impact of oil palm and rubber plantations on the biotic and abiotic properties of tropical peat swamp soil in Indonesia

Current intensification of agricultural activities in Indonesia has led to increased use of tropical peat swamp forests for agriculture. Ideally, peat swamp ecosystems should not be disturbed as they provide essential services such as soil erosion control, ecosystem stabilization and moderation of climate and energy fluxes as well as reducing carbon emission and conserving biodiversity. In this study, agricultural land from Giam Siak Kecil-Bukit Batu Biosphere Reserve in Indonesia was evaluated to assess the impact of oil palm (burning and without burning) and rubber (5-10 and >40 years old) plantations on soil properties through comparisons with soils from a natural forest (NF). Substantial changes in the physico-chemical properties of soils from both plantations were observed including significant reductions in soil organic matter (4-18%) and water holding capacity (22-53%), but an increase in bulk density (rho b) (0.08-0.17 g cm(-3)). A significant increase in bacterial biomass was also observed following conversion of the NF to plantation (p<0.05). However, the oil palm plantation (OPP) (without burning) showed reduced microbial activities and the lowest Shannon diversity values (2.90) compared to other samples. Community-level physiological profiling showed impaired community function only in soils from the OPP but higher CO2 exchange rates in most plantation soils. Soils from the rubber plantation (RP) were less impaired in terms of their natural function and therefore RPs appeared to be more suitable for sustainable agricultural use than OPP.