为明确旱地耕层土壤全氮(TN)和pH含量的时空变异特征。研究基于云南墨江县1985年第二次土壤普查数据及2006年测土配方施肥农业项目调查数据,通过spss17.0和Arc GIS10.1等软件,采用数理统计和地统计相结合的方法,探讨了近20年土壤TN和pH的时空变异特征。结果表明:近20年来土壤pH和TN均有不同程度的变化,土壤TN有一定程度的增加,增幅达3.45%,而土壤pH整体呈下降趋势,降幅达7.56%;1985年和2006年土壤TN含量分别为1.16±0.46 g kg-1和1.20±0.62 g kg-1,变异系数分别为40.07%和51.35%,两个时期TN变异函数均符合Exponential模型,块金系数分别为61.36%和79.48%,TN含量具有中等程度的空间相关性;2006年墨江县坡耕地耕层pH为5.01,较1985年有了一定程度的降低,降幅达7.56%,且土壤pH变异系数较小,分别为10.78%(1985年)和12.20%(2006年)。土壤pH变异函数理论模型分别符合Gaussian(1985年)和Exponential(2006年)模型,2006年土壤块金系数68.75%较1985年的53.33%有了明显提高,土壤pH空间自相关程度降低。近年来,由于人为耕作活动、施肥结构变化及工业污染物排放等随机因素和气候变化的影响,旱地耕层土壤TN有所增加,土壤酸化比较明显。

This study aimed to explorethe spatiotemporal variation characteristics of total nitrogen (TN) and pH in cultivated soil layer of dry land in Mojiang Country, Yunnan Province of China from 1985 to 2006. Thedata were obtained from the second national soil survey (SNSS) in 1985 and the formula fertilization by soil testingcarriedby Mojiang Agriculture Bureau in 2006. Mathematical statistics and geo-statistics methods were used to analyze the data and the ordinary kriging method was applied to map the spatial patterns of TN and pH. The content of TN and pH value showed the different degrees of variation in the cultivated soil layer during the past 20 years. TN increased averagely by 3.45%, while pH decreased averagely by 7.56%. The mean of TN content increased from 1.16±0.46 g kg~(-1) in 1985 to 1.20±0.62 g kg~(-1) in 2006, and the variation of coefficient increased from 40.07 % in 1985 to 51.35%in 2006. The Exponential model for semivariogram fitted these variation both in 1985 and 2006, which indicated that TN content had a moderate spatial dependence in the two sampling periods with the nugget-to-sill rationof 61.36% in 1985 and 79.48% in 2006. The average pH values were decreased from 5.42 in 1985 to 5.01 in 2006, while its variation coefficient increased from 10.78% in 1985 to 12.20% in 2006. The variograms of pH fitted the Gaussian model (in 1985) and Exponential model (in 2006). And since the SNSS, the nugget-to-sill ration increased from 53.33% in 1985 to 68.75% in 2006, which showed that spatial auto correlation of soil pH became weaker. The decrease of TN content and pHshould be attributed to the effects of fertilization, cultivation, the discharge of industrial pollutant, together with climate and other random factors during the recent decades.