Title: Estimation of net primary productivity of young teak plantations under the intensive Tumpangsari system in Madiun, East Java
Abstract: Teak plantations (2 to 7-year-old) under an agroforestry system (tumpangsari) in a humid tropical region in the Madiun Forest District, East Java, were analyzed for aboveground biomass and net primary productivity through the stratified clip techniques. Tumpangsari is an agroforestry system adopted in Indonesia to establish teak plantations. Tumpangsari means co-occupation for a limited period, and the co-occupants are agricultural crops in the forest area. The research was carried out from October, 1996 to September, 2000, and allometric relationships were determined relating diameter at breast height and total height to weights of stem, branches and leaves. Root weight was estimated from the weight of non-photosynthetic components (stem and branch). The total biomass ranged from 2.76 for 2-year stands to 55.39 t ha-1 for 7-year stands. The annual amount of leaf litter fall in the 7-year-old stands was 5.58 t ha-1. The annual consumption of leaves by herbivores varied considerably by stand age, ranging between 0.18 - 0.41 t ha-1; equivalent to 12% of leaf biomass. The net primary productivity (NPP) increased with age, and was greater in trees living in open spaces previously covered by cash crops under tumpangsari. The mean productivity was 36.05 t ha-1 yr-1 in 7-year-old stands. The estimated NPP was higher than those of teak plantations in a dry tropical region in Chakia, India, whose largest productivity was 25.60 t ha-1 yr-1. The large productivity of teak trees at the young stage in the Madiun Forest District is considered to be partly because of the high humidity and temperatures in East Java. However, the high productivity also seems to be influenced by the teak plantation management of tumpangsari, which includes applying intensive cultural practices such as soil work (tillage in land preparation and weeding), fertilization with both chemicals and manure, and thinning.