Nutrient dynamics in different sub-types of peat swamp forest in central Kalimantan, Indonesia

Nutrient dynamics of two sub-types of peat swamp forest, mixed swamp forest and low pole forest, in the upper catchment of the Sebangau River in Central Kalimantan, Indonesia were studied. Three permanent study plots, 50 x 50 m, were established in each forest sub-type to facilitate collection of throughfall, stemflow, litterfall, decomposition, above ground and below ground biomass, peat and water samples. Graphical presentation, Wilm's method, and analysis of variance were carried out for both sub-types of forest in order to analyse data to detect any significant differences. Rainfall is slightly acid (pH 5.96+0.35) with a predominance of NH4-N, Ca and K. Throughfall and stemflow are enriched in most elements analysed compared to rainfall and the pH values are lower. Throughfall pH is 4.76±0.33 in mixed swamp forest and 4.37±0.33 in low pole forest. Stemflow pH is 4.03±0.19 in mixed swamp forest and 3.57±0.11 in low pole forest. Greater litter production was obtained in mixed swamp forest (8,411 kg ha-1 yr-1) than in low pole forest (6,534 kg ha-1 yr-1). Dry weight of the different fractions of litterfall (leaves, branches, reproductive parts and other debris) for MSF and LPF were 6216,1246, 460 and 489 kg ha-1 and 4864,1251,169 and 251 kg ha-1, respectively. Decomposition rates (k) in the MSF and LPF are 0.396 yr-1and 0.285 yr-1 respectively. Above ground biomass in MSF and LPF are 313,899 and 252,547 kg ha-1 respectively, while below ground (root biomass) is 26,533 and 14,382 kg ha respectively. Nitrogen is the predominant nutrient in peat soil at 50 cm depth in both MSF and LPF, while manganese is the lowest. Calcium is the element in greatest amount in water run off in MSF and LPF at 8,15 and 7.15 kg ha-1 yr-1 respectively, while manganese was the lowest at 0.01 and 0.02 kg ha-1 yr-1, respectively. Nutrient inputs were higher than nutrient losses during the 1-year study period with the greatest nutrient gain for calcium while manganese was the lowest in both sub-types of forest. Moreover, the results of this study highlight that nutrient concentrations in peat soils are low and the substrates are acidic. These factors are likely to be strongly limiting to agricultural development, including plantations of estate crops and trees. Under such conditions the maintenance of intact forest for natural ecosystem services (e. g. carbon storage, watershed, biodiversity maintenance, timber production in certain time period) is likely to be a far wiser land use from a long-term perspective.