PRODUCTION AND NUTRIENT CIRCULATION OF DRY DIPTEROCARP FORESTS IN THAILAND II. Primary Productivity and Community Respiration

Abstract

Studies on net and gross primary productivity and community respiration of 52 stands; classified into 6 sub-community types of dry dipterocarp forest communities were carried out by an indirect estimation using the relationships between net primary productivity and leaf biomass and between net and gross primary productivity postulated by Yoda (1971) and further estimating the community respiration by simply deducting the net primary productivity from gross primary productivity and converted into CO₂ release. The estimations focusing particularly on the communities with trees over 10 cm DBH revealed that mean net primary productivity of this forest community was approximately 5.772 ± 1.162 ton/ha.yr with the highest rate in Dipterocarpus obtusifolius-Shorea obtusa-Pinus merkusii sub-community type (6.711 ton/ha.yr) and lowest in xeric sub-type of Shorea obtuse community (3.601 ton/ha.yr). Mean gross primary productivity was found to be in similar trend but approximately 1.9 times higher than mean net primary productivity in every sub- community respiration was estimated at 5.480 ± 1.424 ton/ha. yr with approximately 1/2 times of mean gross primary productivity and estimated CO₂ release was averaged by 8.925 ± 2.320 ton/ha.yr with the approximation of 1.6 times of community respiration and net primary productivity and 0.8 times of gross primary productivity.