Comparison of soil depths between evergreen and deciduous forests as a determinant of their distribution, Northeast Thailand

Abstract

In several areas in Northeast Thailand, evergreen and deciduous forests coexist under uniform terrain and climatic conditions. We compared depth and physical properties of soils between evergreen and deciduous forests in the Sakaerat Environmental Research Station to clarify what factor determines their distribution. The averaged soil depths were 79 ± 27 cm and 135 ± 58 cm in the deciduous and evergreen forests, respectively. The soils in the deciduous forests were relatively coarser in soil texture than those in the evergreen forests, particularly in the surface layers. The average available water capacity of the solum was lower in the deciduous forest soils (78 mm) than in the evergreen forest soils (123 mm). Compared with the evapotranspiration from the evergreen forest in the study area, the available water capacity of the evergreen forest soil was almost the same as the water deficit during the dry season (November–February), while that of the deciduous forest soil was lower and insufficient to maintain the evapotranspiration. These results suggest that the distribution of deciduous and evergreen forests in the study area was associated with soil water availability, which mainly depends on soil depth.