不同区域人口密集的乡村景观中土地利用对土壤氮磷的影响

Effects of Land Use on Soil Total Nitrogen and Phosphorus in Different Densely Populated Village Landscapes

基于IKONOS高分辨率(1 m)卫星遥感图,结合GIS研究了我国高邑、宜兴、金堂、益阳和电白5个人口密集农村地区(每个地区的研究面积为3 km2)土壤全氮、全磷密度和储量差异,以及各地区土壤全氮、全磷密度和储量在不同土地利用方式下的分布。结果表明:土壤全氮储量在5个地区间的大小顺序依次为金堂(1 022.4 t)>宜兴(995.2 t)>益阳(920.4 t)>高邑(804.0 t)>电白(632.4 t);土壤全磷大小顺序为宜兴(698.9 t)>高邑(661.3 t)>金堂(618.9 t)>益阳(360.6t)>电白(255.8 t)。从不同的土地利用方式来看,除高邑地区外(无水田),其它4个地区水田的土壤全氮密度均为当地最高,土壤全氮密度较低的有闲置地类和开采地;土壤全磷密度分布较为复杂,高邑、宜兴、金堂、益阳和电白5个地区土壤全磷密度最高的土地利用方式分别为园艺用地、旱地和建设用地、水田和旱地、水田、干扰地。在所有地区中,林地土壤全氮密度均小于农田水平,林地土壤全磷密度均为当地最低,也就是说在林地转化为人为土地利用方式后,土壤的磷水平并没有减少,反而有不同程度增加。

China＇s densely populated village landscapes play a significant role in global environmental processes because of their vast area and population. Here we investigate the influence of land use on soil nitrogen and phosphorus （top 0～30 cm） within and across these densely populated landscapes （〉150 persons km^2） based on measurements at five research sites in environmentally distinct regions across China： the North China Plain （Gaoyi County, Hebei Province）, Yangtze Plain （Yixing County, Jiangsu Province）, Sichuan Hilly Region （Jintang County, Sichuan Province）, Subtropical Hilly Region （Yiyang County, Hunan Province）, and Tropical Hilly Region （Dianbai County, Guangdong Province）. Village landscapes were first stratified into ecologically-distinct components （ecotopes） by high spatial resolution mapping （1 m） in a set of 12 regionally-representative 500 m × 500 m landscape quadrats （sample cells） in each site （total = 60） using IKONOS satellite imagery and fieldwork. Samples of eeotope features were then selected for soil sampling and analysis by a stratified sampling design based on the areas of each landscape class. Results show that soil total nitrogen stocks at the five sites decreased from a high in Jintang （1 022.4 t） to that of Yixing （995.2 t）, Yiyang （920.4 t）, Gaoyi （804. 0 t）, and Dianbai （632. 4 t）, but the sequence of soil total phosphorus stocks was different, with a high in Yixing （698. 9 t） and lower values in Gaoyi （661.3 t）, Jintang （618. 9 t）, Yiyang （360.6 t） and Dianbai （255.8 t）. Of all land use types, paddy soil had the highest total nitrogen density in all sites where it existed, and the lowest was in areas with fallow and mine ＆ fill use. Soil total phosphorus density was more complicated, with the highest densities observed under Horticulture in Gaoyi, rainfed and constructed in Yixing, paddy and rainfed in Jintang, paddy in Yiyang, and disturbed in Dianbai. Another interesting result of this study was that soil total nitrogen and phosphorus density under forestry was lower than that of rainfed and paddy in each site, indicating either that bringing forestry land into agricultural use did not cause declines in soil N and P, or that only the best soils are currently used for agriculture, and only low fertility soils are selected for forestry. Analysis of data across sites indicates that climate, soil types and tillage affected the distribution of soil total nitrogen and phosphorus at regional scales.