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We have investigated the pools and distributions of soil phosphorus (P) in the top 50 cm of soil in China by using a combination of total and available P information from more than 2400 soil profiles and a map of soil types at a resolution of 1:1,000,000. Our estimates indicate that the average total P density and available P density in China are about 8.3 × 10² g/m³ and 5.4 g/m³, respectively. The total national soil P pool in the surface half meter is 3.5 Pg (1015 g). The available P density ranges from 0.7 g/m³ in the Lithosols to 16.7 g/m³ in the Irrigated Silting Soils. The total P density ranges from 1.2 × 10² g/m³ in the Lithosols to 19 × 10² g/m³ in the Frigid Desert Soils. The ratio of available P to total P density ranges from 0.6 × 10-3 in Aeolian Soils to 21.6 × 10-3 in Coastal Solonchaks. The available P content and its vertical distribution show a complex pattern among soil orders of different development stages, possibly indicating the important role of biota's control over soil available P content. There are large variations of P content in different climatic regions. The tropical and subtropical region has the lowest available P density (4.8 g/m³) and the second lowest total P density (8.2 × 10² g/m³) among all climatic regions. The large variation in the soil P content suggests that further study is needed to investigate climatic and land-use controls over the soil P content. [ABSTRACT FROM AUTHOR]

Southern China has abundant natural resources and is a major region of agricultural production. However, soil erosion is increasingly threatening the agricultural productivity of this region. Increases in soil erosion are caused by improper land use practices with soils of high rainfall erosivity. Much of the area prone to accelerated erosion was previously forested and subsequently logged four times since the 1920s. This paper discusses the effects of biological control practices on soil erosion according to erosion types, soil properties, and terrain. [ABSTRACT FROM PUBLISHER]