Factors controlling soil organic matter decomposition in small home gardens in different regions of Indonesia
To understand soil organic matter (SOM) dynamics in agricultural land in Indonesia, soil respiration rate was determined by both field measurement and laboratory incubation in small home gardens (pekarangan) in different regions of Java and East Kalimantan and extensive survey on the general distribution patterns of SOM-related properties was also conducted. The primary factor controlling field soil respiration rate was often the moisture factor under savanna climate or cropland-like plots, though its contribution was poor under rainforest climate. Annual field soil respiration was typically very high, often exceeding 20 Mg C ha<sup>-1</sup> y<sup>1</sup>, indicating a high contribution of plant root respiration. Comparison of the field data with laboratory incubation data revealed that: 1) surface 15-cm layers of soils are the likely source of microbial respiration and 2) annual soil respiration derived from both plant root and microbial respiration (determined by field measurement) was primarily controlled by the temperature factor, while that from microbial decomposition of SOM (determined by laboratory incubation) was strongly affected by SOM pool size. Application of the parameters determining soil respiration, which were obtained at the intensive monitoring plots, to the dataset collected in the extensive survey revealed that: 1) annual soil respiration in fields shows a clear regional trend, that is, it is highest in East Kalimantan, followed by low-elevation areas of Java and then high-elevation areas of Java, and 2) both SOM stock and annual soil respiration with microbial origin are higher under more forest-like land use, with exceptionally high accumulation of SOM relative to its decomposition (soil respiration) in plots derived from volcanic tephra. Generally pekarangan land management in Java is advantageous because a high population density can provide continuous input of organic materials, such as domestic waste or crop residues, into the soils and there are tephra-derived soils, which are more resistant to rapid decreases in SOM because of the high potential of these soils for retaining SOM.
Tropics 17(1), 59-72, 2007-11-30
JAPAN SOCIETY OF TROPICAL ECOLOGY