以2011年盐源县实地采样数据和1980年代第二次土壤普查资料为基础,采用地统计学、方差分析及相关分析等研究方法,分析了该区域近30年来耕层土壤有机碳时空变化特征,并探讨不同影响因素的显著性变化特征。结果表明,研究区土壤有机碳含量平均值从23.02 g kg~(-1)下降到16.69 g kg~(-1),整体呈下降趋势。土壤有机碳初始含量较高的土类、海拔段和地貌区下降幅度明显较大,导致研究区土壤有机碳空间分布格局发生明显变化,高值区由西北部中高山地区变为东部区域。半方差分析表明,近30年间研究区耕层土壤有机碳空间变化的变程由67.5 km缩短至55.8 km,块金值和基台值之比从42.8%增加至50.0%,表明人类施肥耕作等随机因素使得结构性因素的作用减弱,空间自相关程度和范围降低。影响因素的显著性变化分析表明,土类和海拔的作用由极显著(p < 0.01)变为显著(p < 0.05);土壤有机碳与主要养分因子中全氮的相关程度减弱,与全磷和pH的相关关系不再显著,这进一步说明施肥耕作等随机性因素对研究区土壤有机碳时空变异的影响在增强。
英文摘要:
Soil organic carbon (SOC) played an important role in soil fertility and climate change. Based on the data of the Second National Soil Survey of Yanyuan County in 1980s and data measured in 2011, spatio-temporal variation of SOC was analyzed at the depth of 0 ~20 cm cultivated land and significant changes in its impact factors were discussed using geostatistics, variance analysis and correlation analysis. Results showed that the mean value of SOC content in the study area dropped from 23.02 g kg~(-1) to 16.69 g kg~(-1) during 1982 to 2011, showing a descending trend. The spatial distribution pattern of SOC changed significantly in area with high value varying from the mountain area of the northwest to the eastern area, arising from the obvious reduction of SOC content on the effect of soil type, altitude gradient and geomorphologic zoning with high initial content. Semivariogram analysis showed the range of SOC reduced from 67.5 km to 55.8 km while the value of the nugget to sill ratio increased from 42.8% to 50.0%, which indicated that the effect of structural factors was weakened due to the effect of random factors such as tillage and fertilization. As a result, the spatial autocorrelation extent and scope of SOC in the study area were reduced. Significant analysis of impact factors indicated that the significant level on the effect of soil type and altitude gradient decreased with the P value increasing from 0.002 to 0.046 and from 0.003 to 0.022, respectively. The correlation between SOC and total nitrogen (TN) decreased while the correlations between SOC and total phosphorus (TP) and soil pH were not significant, which further confirmed that the random factors such as fertilization and tillage played a more important role on the spatio-temporal variation of SOC in the study area.