Spodosols of East Kalimantan: Land Cover Disturbances Induced Degradation of Soil Properties

Abstract

Spodosols are mineral soils derived from sandy to loamy sand parent materials developed under humid or wetter climate condition. Soils are coarse in texture, the acid in reaction and low in water and nutrient retention. In addition, these soils are characterized by a spodic horizon associated with the presence of fragipan or duripan layers at varying depth, limiting not only the growth of plant roots but also water and air availability and movement. The fertility of these soils relies on the SOM of the A layer of the soils. Any disturbance to these soils’ land cover may lead to irreversible degradation of soil properties and productivity. Vegetation found on the disturbed lands is mostly pioneer species, Imperata cylindrica and fern (Pteridophyta sp). Two land cover types, namely natural secondary forest and plantation forest in Semboja District, East Kalimantan, were selected for this study. This study aims to determine Spodosols’ properties – morphological, physical and chemical properties – induced by land cover change. For each land cover type, three soil profiles were established for the soil morphological property determination, and eight soil samples were drawn for the soil physical and chemical property analysis. The results show that compared to the soil in natural secondary forest, spodosols soil of plantation forest underwent loss of A horizon, bleaching of E horizon, soil compaction and fine particle leaching enhancement, especially in E layers. Furthermore, land cover disturbances intensify soil acidification and C- and N-organic decomposition.