石家庄市边缘带土壤养分空间分布特征研究

The Spatial Distribution of Soil Nutrients in Shijiazhuang Peri-urban Zone

在对石家庄市边缘带进行划分的基础上,利用BP神经网络模型并结合地统计学方法研究了石家庄市边缘带土壤养分的空间分布特征。结果表明:BP神经网络模型能够智能地学习各个采样点的空间位置与该点各种土壤养分含量之间的映射关系,并能稳健地对不同地理位置上的土壤养分含量进行预测。预测后的有机质、全氮、速效磷和速效钾变异函数的理论模型均符合球状模型。从养分分布图看,石家庄市边缘带有机质、全氮、速效磷和速效钾含量具有明显的斑块状分布特点,各种土壤养分高值区多分布在石家庄市西部和南部。4种养分含量均呈现从西向东、从南向北递减的趋势。通过引入土地景观格局指数和土壤养分综合得分两个指标,建立回归模型,并对土壤养分含量与土地利用格局进行了研究。结果显示:土地景观格局指数与土壤养分的主成分综合得分拟合模型为y=1.014xexp(x/1.794)+2.152,两者之间存在明显的指数增长趋势。景观格局指数越高,土地利用类型越复杂,土壤养分含量相应偏高,反之亦然。

BP neural network models combined with statistical method were applied to analyze the spatial features of soil nutrients in the areas of Shijiazhuang Peri-urban zone, which has been divided. The results of our description proved that BP modeling could not only enable us to grasp intelligently the mapping relation between spatial position and soil nutrients, but also help to predict robustly the soil nutrient contents in every spatial interpolating dot. Soil nutrient data in this study included organic matter, total N, available P and K.The results showed that the semi-variograms of soil nutrients were best described by spherical model. The conclusions were drawn from the analysis： The four soil nutrients showed the patchy distribution obviously, various high-value soil nutrient distribution in the area to the west and south of Shijiazhuang City. The content of the four soil nutrients showed the decreasing trend from west to east, from south to north. Through the establishment of regression model, the article introduced two indices, landscape patterns of land and the comprehensive scores of soil nutrients, studied the relations between the contents of soil nutrients and land use pattern. The results showed that： the fitting model between land landscape pattern index and the comprehensive scores of soil nutrients is y=1.014^＊exp（x/1.794）＋2.152, （R^2 = 0.657）. There is an obvious trend of the exponential growth. The spatial variation of soil nutrient is closely related to the landscape patterns of land use. The higher landscape pattern index, the more complex types of land use is, correspondingly, the content of soil nutrient is high.