Soil Enzyme Activity in Tropical Peat Swamp Forest : Insights from Sarawak, Malaysia

Tropical peat swamp forests are critical components of the global carbon (C) and nitrogen (N) cycles, with microbial decomposers playing a pivotal role in the assimilation of these elements through the activity of extracellular enzymes in the soil. This study examines the impact of C and N decomposition on microbial enzymatic activity in the Padang Alan soil of the Maludam peat swamp forest, Sarawak. To evaluate the role of extracellular enzymes in driving C and N cycling, soil samples were collected at four depths (0–10 cm, 10–50 cm, 50–100 cm, and 100–150 cm) and subjected for enzymatic assays. C-acquiring enzymatic activities were assessed using β-1,4-glucosidase and phenol oxidase, while N-assimilation activity was measured using β-1,4-N-acetylglucosaminidase. The findings revealed that both C- and N-acquiring enzyme activities peaked at the 0–10 cm depth, where organic matter decomposition is most active, and declined with increasing depth. This pattern underscores the dominance of enzymatic activities in the top soil layers, where decomposition processes are most dynamic. Additionally, N decomposition is influenced by the progression of lignin degradation during decomposition process. Although enzymatic responses varied with soil depth, edaphic factors were found to control enzymatic activity predominantly. These results deepen our understanding of microbial-mediated nutrient cycling in tropical peat soils and emphasize the relationship between soil depth, enzyme activity, and nutrient cycling. Nonetheless, enzymatic activity can be varied by forest type, and elucidating the microbial nutrient demand in peat soil provides important insights into nutrient cycling of tropical peatland ecosystems.