Distributions of soil phosphorus in China’s densely populated village landscapes

Abstract

Purpose Village landscapes, which integrate small-scale agriculture with housing, forestry and a host of other land use practices, cover more than 2×10 6 km 2 across China. Village lands tend to be managed at very fine spatial scales (≤30 m), with managers altering soil fertility and even terrain by terracing, irrigation, fertilizing, and other land use practices. Under these conditions, accumulation of excess phosphorous in soils has become important contributor to eutrophication of surface waters across China’s densely populated village landscapes. The aim of this study was to investigate relationships between fine-scale patterns of agricultural management and soil total phosphorus (STP) within China’s village landscapes. Materials and methods First, China’s village landscapes weredividedinto five environmentallydistinctregions across China. Within each region, a single 100 km 2 research site was then selected, and 12 500×500 m square landscape sample cells were selected for fine-scale mapping. Soils were sampled within fine-scale landscape features using a regionally weighted landscape sampling design. Results and discussion STP stock across the 0.9×10 6 km 2 area of our five village regions was approximately 0.14 Pg (1 Pg=10 15 g), with STP densities ranging from 0.08 kg m −2 in Tropical Hilly Region to 0.22 kg m −2 in North China Plain and Yangtze Plain, with village landscape STP density varying significantly with precipitation and temperature. Outside the Tropical Hilly Region, STP densities also varied significantly with land form, use, and cover. As expected, the highest STP densities were found in agricultural lands and in areas near buildings, while the lowest were in nonproductive lands and forestry lands. As a combined result of these high STP densities and the predominance of agricultural land use, most village STP stock was found in agricultural lands. A