Physical and chemical properties of tropical peat under stabilised land uses

Land-use change has transformed large areas of tropical peatland into globally significant carbon sources. Associated changes in the properties of peat are important for soil processes including decomposition and nutrient cycling. To characterise the changes induced by stabilised land uses, we studied the physical and chemical properties of peat from four land management conditions (undrained and drained forest, degraded land, and managed agricultural land). Peat was sampled from depths of 10-15 cm, 40-45 cm, 80-85 cm and 110-115 cm then partitioned into woody (empty set > 1.5 mm), fibric (empty set 0.15-1.5 mm) and amorphic (empty set < 0.15 mm) fractions. Bulk density and total concentrations of ash, C, N, P, K, Ca, Mg, Mn, Zn, Na, Al, Fe, S and Si were determined. There were clear differences between land uses in the characteristics of surface peat down to the 40-45 cm layer, the primary differences being between forested and open sites. Due to smaller particle sizes, the bulk density of peat was higher at the open sites, where Ca and Mg concentrations were also higher but N and P concentrations were lower. Changes in drainage and vegetation cover had resulted in differing outcomes from decomposition processes, and the properties of fire-impacted peats on the open sites had undergone extreme changes.