青海三江源地区退化草地土壤全氮的时空分异特征

在第二次土壤普查和2009、2010年实地采样的基础上,运用地统计学和GIS技术研究了青海三江源地区1980～2010年退化草地0～10 cm、10～30 cm、30～50 cm全氮的时空分异特征.结果表明,进行特异值处理后,两期的土壤全氮的均值都表现出从表层到底层下降的趋势.从同一土层对比来看:2010年的土壤全氮的含量平均值及变异系数比1980年低.经对数转换后两期数据符合正态分布,经过半方差函数模型的拟合得出,两期同一层次上的块金效应2010年都比1980年小,表示三江源地区各分层上全氮的空间分布的自相关性在加强,结构性因素对土壤全氮的空间分布起着越来越重要的作用.普通克里格插值结果表明,30年来三江源地区土壤全氮的含量变化存在地区差异,南部、中部、东部以递减为主,西部的部分地区以增加为主.

Temporal-spatial Variations of Total Nitrogen in the Degraded Grassland of Three-River Headwaters Region in Qinghai Province

Based on the data of the second soil survey and field sampling in 2009 and 2010, temporal-spatial variations of total nitrogen (TN) in the degraded grassland 0-10 cm, 10-20 cm and 30-50 cm beneath the surface soil at the Three-River Headwaters region in Qinghai Province for a 30-year period (1980-2010) were evaluated using geostatistics and geographic information system (GIS). After exclusion of the outliers, the results showed a downward trend from the surface to the bottom in the mean TN values measured in the samples collected during the two periods. For the same soil layers, the average TN contents and the coefficient of variation in 1980 were higher than those in 2010. The TN contents of the two periods showed a log-normal distribution. Semivariograms analysis of the experiments indicated that the nugget effect in the same soil layer was lower in 2010 than in 1980; suggesting that the spatial distribution autocorrelation of TN in the Three-River Headwaters region in Qinghai Province was strengthened and structural factors played a more and more important role on the spatial distribution of TN. The results of ordinary kriging showed that there were regional differences in variations of the total nitrogen content. There were significant decreases in the southern, central and eastern regions, while the increase mainly occurred in the western areas.