ROLE OF SOIL MICROARTHROPODS IN LEAF DECOMPOSITION AND N RELEASE UNDER VARIOUS LAND-USE PRACTICES IN THE HUMID TROPICS

The role of microarthropods in leaf decomposition and N release was st udied in various land-use practices: secondary forest, bush regrowth, Pueraria phaseoloides relay cropping, Leucaena leucocephala alley crop ping, and cropping without cover crop or tree hedgerows (control treat ment), using litterbags with mesh-size of 0.5 mm and 0.08 mm for 98 da ys. Litterbags with 0.5 mm mesh-size allowed access by microarthropods , whereas those with 0.08 mm mesh-size excluded microarthropods. Micro arthropod-mediated leaf decomposition and N release varied with the la nd-use practices, particularly the last named. Inclusion of microarthr opods in most cases increased leaf decomposition and N release rates, with the highest value 38 % for decomposition in control treatment and 29 % for N release in relay cropping. A decrease in leaf decompositio n rate (10 %) and N release (32 %) was observed in the secondary fores t. Microarthropod-mediated leaf decomposition and N release, which mai nly occurred in later stages of decomposition, increased as microbial decomposition decreased. The results suggest that microarthropods have a ''buffering effect'' in regulating leaf decomposition and N release , which is mediated by land-use history.