作 者 ：武俊喜,程序*,焦加国,肖红生,杨林章,王洪庆,张福锁,Ellis, Erle C
期 刊 ：生态学报 2010年 30卷 23期 页码：6309~6322
Keywords:Yangtze Plain, village landscapes, croplands, upscaling, soil total nitrogen density, soil total nitrogen storage, soil total phosphorus density, soil total phosphorus storage, land use and land cover change,
摘 要 ：过去60a间，长江中下游平原乡村景观区域中土地利用覆被类型，特别是耕地类型发生了显著地转变，并对其土壤全氮和全磷产生了明显地影响。通过选取区域代表性样方、研究耕地类型的小尺度转化、土壤取样和收集1965年前土壤全氮、全磷历史数据，采用尺度推绎和蒙特卡洛不确定性分析方法，评价了1940—2002年长江中下游平原人口密集的乡村景观区域中耕地类型及其土壤全氮、全磷储量的变化。结果表明: 近60a来，在86×103 km2的区域中有47%的面积发生了变化，其中33%的面积是耕地类型转化。耕地面积减少18.6%（-16.0×103 km2），其中稻田面积减少21.5%（-18.5×103 km2），种植木本作物的旱地面积减少1.7%（-1.5×103 km2）；而种植木本作物和种植1年生作物的水浇地的面积分别增加了3.5%（3.0×103 km2）和2.0%（1.7×103 km2）。尽管稻田面积大幅减少，但其仍是区域中面积最大的土地利用覆被类型。 1940—2002年，有98%的可能性区域耕地0—30 cm土壤全氮储量净减少，而其0—30 cm土壤全磷储量则无明显变化。区域耕地土壤全氮储量明显减少（-7.2 Tg N），主要受稻田土壤全氮储量显著减少（-8.0 Tg N）的影响，而稻田面积大幅减少是导致稻田土壤全氮储量减少的主要原因。与此同时，种植木本作物的旱地的土壤全氮储量减少了0.7 Tg N；而种植木本作物和种植1年生作物的水浇地分别增加1.3和0.7 Tg N。区域耕地土壤全磷储量变化不明显，主要受稻田土壤全磷储量无明显变化的影响。尽管稻田面积大幅减少，但由于稻田土壤全磷密度增加了29%（其净增加的可能性为76%）；加之稻田土壤全磷密度变异较大，所以稻田土壤全磷储量并没有明显减少，其净减少的可能性仅为64%。与此同时，有75%的可能性种植木本作物的旱地的土壤全磷储量净减少，但仅减少了0.3 Tg P；而种植木本作物的水浇地和种植1年生作物的水浇地土壤全磷都有少量增加，分别为0.7 和0.4 Tg P。 通过选取区域代表性样方、研究耕地类型的小尺度转化、土壤取样和收集土壤历史数据、结合尺度推绎和蒙特卡洛不确定性分析方法，能够揭示1940—2002年长江中下游平原人口密集的乡村景观区域中耕地类型及其土壤全氮和全磷储量的变化。
Abstract:Over the past 60 years, land use and land cover (LULC) have changed dramatically within the village landscapes of China’s Yangtze Plain, especially in croplands, causing significant changes in their soil total nitrogen (TN) and total phosphorus (TP). Estimates of long-term changes in the region′s cropland LULC areas and TN and TP in the top 30 cm of soils from the 1940s to 2002 were made using a regional landscape sampling and upscaling approach. Fine-scale LULC area estimates were obtained by field-validated high-resolution ecological mapping of 12 regionally-stratified landscape sample cells based on historical aerial photographs (1942) and IKONOS imagery (2002). Current soil TN and TP was measured at points selected at random within ecologically-distinct landscape features chosen within landscape sample cells using a regional-area-weighted stratified sampling design. 1940s-era soil TN and TP data were obtained from regional historical sources published before 1965. Long-term changes in cropland LULC areas and in soil TN and TP across the village landscapes of the Yangtze Plain were then estimated by integrating these data using a multivariate regional optimization and resampling procedure combined with Monte Carlo uncertainty analysis. From the 1940s to 2002, 47% of village landscape area (86×103 km2) in China′s Yangtze Plain underwent a substantial change in LULC class, of which 33% was cropland transformation. Cropland areas declined by 18.6% (-16.0×103 km2) overall, caused by a 21.5% (-18.5×103 km2) decrease in paddy and a 1.7% (-1.5×103 km2) decrease in rainfed perennial cropland, coupled with net increases in irrigated perennial (3.5%, 3.0×103 km2) and annual (20%, 1.7×103 km2) croplands. However, even with this substantial decline, paddy remains the most extensive land use in the village landscapes of China′s Yangtze Plain. This study demonstrates with 98% probability that soil TN storage in the top 30 cm of croplands across the village landscapes of the Yangtze Plain decreased from the 1940s to 2002, while soil TP storage did not change significantly. Cropland soil TN storage declined by a total of 7.2 Tg N, caused mainly by an 8.0 Tg N decrease in paddy soil TN attributed to the 22% decline in paddy area. Over the same period, soil TN storage in rainfed perennial croplands also decreased by 0.7 Tg, while soil TN storage increased by 1.3 Tg in irrigated perennial and by 0.7 Tg N in irrigated annual croplands. Soil TP storage in croplands did not change significantly across village landscapes, partly because paddy soil TP density variation was very large, and because TP density increased at the same time that paddy area decreased, such that the net 29% median increase observed in soil TP density yielded only a 76% probability of a net increase. Similarly, soil TP storage in rainfed perennial croplands changed very little, decreasing by 0.3 Tg P with a 75% probability of a net decrease. In contrast, soil TP storage increased significantly in irrigated perennial and annual croplands, by 0.7 and 0.4 Tg P, respectively. By combining a regionally-stratified sample of fine-scale landscape features with current and historical soil data in a regionally-weighted upscaling analysis, long-term changes in cropland areas and soil TN and TP storage were revealed across the agricultural areas of China′s densely populated Yangtze Plain.
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