近20年城乡交错带土壤养分时间空间变异特征分析——以北京市大兴区为例

SPATIAL AND TEMPORAL VARIATION OF SOIL NUTRIENTS IN PERIURBAN REGION──A CASE STUDY OF DAXING DISTRICT IN BEIJING CITY

以北京市大兴区为城乡交错带的分析样区,通过对1982年、2000年2期土壤养分变化情况进行时间空间变异特征分析,结果发现:1982～2000年近20年间大兴土壤养分除土壤速效K含量略有下降外,其他土壤养分含量均呈上升趋势,尤以速效P含量增长最多。各项养分增加值分别为有机质31.02%、全N 50 %、碱解N 37.89%、速效P 177%,而速效K则减少6.97%。1982年的5种土壤养分中,速效P的变异系数最高,为0.50;全N次之,为0.4;有机质、速效K、碱解N的变异系数较小,在0.28～0.32之间。2000年的5种土壤养分中,变异系数最高的仍是速效P,为0.57;速效K次之,为0.36;有机质、全N和碱解N含量的变异系数较小,在0.19～0.23之间。1982年有机质的块金值与基台值之比为45.32%,2000年的为26.54%,说明其在小尺度上的空间相关性增强。1982年速效K的块金值与基台值之比为36.96%,2000年的为29.82%。2000年全N、碱解N和速效P的块金值与基台值的比值大于1982年的比值。2000年各项土壤养分的空间相关距离均比1982年增大,基本上趋向于以大块状变异为主,具有较强的渐变性分布规律。

Geostatistics has proven to be useful for characterizing and mapping spatial variability of soil properties, however, most of the previous geostatistical studies focused on data at small scales. With the development of GIS and GPS, geostatistcs and GIS are becoming indispensable in characterizing and summarizing spatial information of large regions and providing quantitative support to decision and policy making for management of the soil, agricultural and natural resources. In this paper, geostatistics combined with GIS was used to analyze spatial-temporal variation of available potassium, available phosphorus and organic matter in the surface soil (0~20cm) in Daxing District of Beijing City, in the past 20 years or so from 1982 to2000 as a case study. The results show that in term of variation coefficient of soil nutrients, a decreasing order of available phosphorus (0.50) > total nitrogen (0.40) > organic matter > available potassium > available nitrogen was observed in 1982, and one of available phosphorus > available potassium > organic matter > total nitrogen >available nitrogen in 2000. The ratio of nugget to sill of organic matter is 45.32% in 1982,and that is 26.54% in 2000.it shows that the spatial relationship variation decrease at small scale, that leads to the increase of soil organic matter on he whole, due to the adoption of the technique of straw returning to the field. The ratio of nugget to sill of available potassium was 36.96% in 1982, and 29.82% in 2000, which shows the variation of spatial relationship decreases at small scale. This is maybe the result of ignorance of application of potassium fertilizer. The ratio of nugget to sill of all the other nutrients become higher from 1982 to 2000, which leads to the increase in variation of spatial relationship at small scale. The spatial-temporal variation may be the result of the general management on the whole and different variation of application of nitrogen fertilizer and phosphatic fertilizer in soils under different types of land use over the past 20 years.