The Behavior of Various Elements in Tropical Swamp Forest and Sago Plantation

Abstract

The annual nutrient fluxes in the tropical swamp and sago palm plantation ecosystems and their changes after harvesting were estimated. Open bulk precipitation, throughfall, and litterfall were monitored as inputs to the soil system, and drainage water, randomly selected trees and sago palms were collected to assess the nutrient output from this ecosystem. No significant differences were observed in the cation concentrations between the open bulk precipitation and in the secondary swamp forest throughfall in this study. The concentrations of elements (Na, K, Mg and Ca) in drainage water near the sago plantation were slightly higher than those in small streams near swamp forests, suggesting that nutrients are gradually leached from sago plantation ecosystems. The swamp forests have low phosphorus and high calcium concentrations in their total litterfall compared to most temperate forests. Substantial amounts of nutrients are returned via dead sago fronds to the ground of sago plantations. Annual input-output budgets indicated that swamp forest recycled the accumulated nutrients efficiently, whereas larger amounts of nutrients were lost from sago forests through streamflow. Sago cultivation accelerates total P, Na, K and Mg loss from this ecosystem via the withdrawal of vegetation. The net gain of swamp forests equals the net loss from sago palm plantations. For continuous sago palm production, swamp forests should be retained in the same watershed which act as the nutrient reservoir for sago plantation. Repeated harvests of sago palm would have detrimental effects on site productivity and soil fertility due to the depletion of nutrients. Nutrient management is essential.