Distributions of soil phosphorus in China’s densely populated village landscapes
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Village landscapes, which integrate small-scale agriculture with housing, forestry and a host of other land use practices, cover more than 2 × 106 km2 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 were divided into five environmentally distinct regions across China. Within each region, a single 100 km2 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 × 106 km2 area of our five village regions was approximately 0.14 Pg (1 Pg = 1015 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 surprisingly large portion of village STP stock was associated with built structures and disturbed lands surrounding them (15.0% in North China Plain, 19.3% in Yangtze Plain, 5.9% in Sichuan Hilly Region, 7.8% in Subtropical Hilly Region, 2.7% in Tropical Hilly Region), which had a significant relationship with population density.
Our results demonstrated that local patterns of land management and human residence were associated with substantial differences in STP both within and across China’s village landscapes which have increased their potential contribution to P pollution. With the rapid change in land use/land cover in China’s densely populated landscapes, such information is essential for rational planning of future management to reach agricultural sustainability.
KeywordsChina Land cover Land form Land use Pollution Soil phosphorus Village landscapes
Funding support came from the US National Science Foundation (DEB-0075617) awarded to Erle C. Ellis in 2000. Work in China was conducted in collaboration with Prof. Lin Zhang Yang of the Institute of Soil Science, Chinese Academy of Sciences (CAS), Nanjing, China, Prof. Hua Ouyang of the Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing, China and Prof. Xu Cheng of China Agricultural University, Beijing, China. We are grateful to our local collaborators for field assistance and anonymous reviewers for helpful comments on the manuscript. Any opinions, findings, conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.
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