Soil Respiration, Litter Fall and Productivity of Tropical Rain Forest

Since undisturbed equatorial rain forest is a climax community it should have a constant biomass per unit area. This implies a steady carbon cycle with a decomposition rate of organic matter equal to the primary production. If there is no appreciable consumption by direct grazing organic substances return to the soil mainly as litter fall, timber fall and dead roots. Their complete degradation by the soil fauna and flora results in a corresponding carbon dioxide evolution. The measurement of the rate of this soil respiration (Lundegardh 1924) should thus permit an indirect estimation of net primary productivity. Reliable productivity data are very scanty for tropical rain forest (Bray & Gorham 1964; Miller & Nielsen 1965; Rodin & Bazilevich 1967). Soil respiration measurements in tropical regions have been made in Africa by Birch & Friend (1956) and by Schulze (1967) in Costa Rica. No data are available for East Asian rain forests. Some preliminary observations are reported here which were made during a visit to Bogor and Tjibodas, Indonesia and Sarawak, North Borneo. The results are compared with available data for litter fall and productivity.