成都平原西部土壤氮素空间变异特征及影响因素

为探究成都平原西部土壤氮素的空间异质性及其影响因素，基于134个耕层土壤采样点，运用经典统计学和地统计学方法揭示w（TN）和w（AN）（AN为碱解氮）的空间变异特征，并利用方差分析和回归分析，研究不同因素对其空间变异的影响程度.结果表明:研究区土壤w（TN）为0.81~3.50 g/kg，平均值为1.94 g/kg；w（AN）为44.42~263.99 mg/kg，平均值为138.70 mg/kg.半方差分析显示，土壤w（TN）和w（AN）的块金效应分别为52.41%和63.92%，具有中等程度的空间自相关，表明其空间分布受结构性和随机性因素共同影响.土壤氮素空间分布特征均呈现由东北向西南逐渐递增趋势.回归分析结果表明，成土母质能独立解释14.8%和9.4%的w（TN）和w（AN）空间变异；土壤类型（土类、亚类和土属）对研究区w（TN）和w（AN）空间变异的独立解释能力分别在3.6%~17.2%和5.7%~17.2%之间.各土地利用方式下，土壤w（TN）、w（AN）平均值均表现为耕地>农林用地>园地，土地利用方式对土壤w（TN）空间变异的独立解释能力仅5.8%，对w（AN）无显著影响.研究显示，成都平原西部土壤氮素含量总体处于丰富水平，其中温江-郫县一带含量相对较低，高值区在金马河以南区域.成土母质和土壤类型对土壤氮素空间变异的影响总体高于土地利用方式. 

Spatial Variability and Its Influential Factors of Soil Nitrogen in the Western Chengdu Plain

The spatial variability and its influencing factors of nitrogen in soil were investigated in the western Chengdu Plain of China. A total of 134 soil samples were collected from the plain to quantify the total nitrogen (TN) and available nitrogen (AN) in soil under various types of land use, soil, and soil parent materials using classical statistics, geostatistics and regression analysis. Results showed that the concentrations of soil TN and AN ranged from 0.81 to 3.50 g/kg and 44.42 to 263.99 mg/kg, with a mean value of 1.94 g/kg and 138.70 mg/kg, respectively. The nugget values of TN and AN were 52.41% and 63.92%, which indicated that they had moderate spatial variations and both were affected by structural and random factors. For the spatial distribution, concentrations of soil TN and AN increased gradually from the northeast to the southwest of the study area. Regression analysis results demonstrated that soil parent materials explained 14.8% and 9.4% of TN and AN concentrations variability, respectively. Meanwhile, soil types (soil group, subgroup and soil genus) explained 3.6%-17.2% and 5.7%-17.2% of TN and AN concentrations variability. The mean values of TN and AN concentrations in soil were highest in cultivated land, followed by in the agroforestry, and were lowest in the orchard/gardens. Land use type explained 5.8% of TN concentrations variability and had no significant effects on the concentrations of soil AN. We concluded that the concentrations of soil nitrogen in the western Chengdu Plain stayed a high level in the mass, and the highest values located in the southern part of Jinma River. However, the lowest distributed in the belt of Wenjiang to Pixian. Soil parent materials and soil types had more significant effects than land use types on the spatial variability of nitrogen in soil.