Soil Phosphorus Dynamics as Influenced by Land Use Changes in Humid Tropical, Southwest China

摘要

Land use changes can greatly influence soil phosphorus (P) dynamics, especially when converting native forests to agricultural land. Soils in Xishuangbanna, which is one of southwest China's tropical areas that maintain fragments of primary forests, were studied to a) evaluate the effect of two common land use changes, conversion of forests to agricultural land or rubber tree plantation, on the dynamics of available P and total P in bulk soils as well as total P in particle size fractions; b) assess the relationship between soil P dynamics and soil organic carbon (SOC); and c)elucidate the relationship between soil P content and soil properties such as pH and texture. Clearing secondary forests with subsequent shifting cultivation and establishment of rubber tree plantation caused significant decreases (P ＜ 0.05)in available P at 0-20 cm soil depths, whereas for total P there was a significant decrease (P ＜ 0.05) when converting to shifting cultivation, rubber tree plantation, or fallow field at both 0-20 and 20-40 cm depths. Abandonment of fields used for shifting cultivation led to significant increases (P ＜ 0.05) in available P at 20-40 cm depth. In addition, there was a significant positive relationship between soil organic carbon and soil P content. Compared to secondary forests, the ratio of organic carbon to total P in surface soils (0-20 cm) of shifting cultivation and rubber tree plantation was significantly lower (P ＜ 0.05).