科尔沁沙地退化植被恢复过程中土壤有机碳和全氮的空间异质性

Spatial Heterogeneity of Soil Organic Carbon and Total Nitrogen of Sandy Grassland in the Restoration of Degraded Vegetation in Horqin Sandy Land,Northern China

采用地统计学分析方法研究了沙地退化植被恢复过程中（封育0 a的流动沙丘、封育11 a的流动沙丘和封育20 a的流动沙丘）土壤有机碳和全氮的空间异质性,探讨了它们与植被恢复演替和地形特征变化的关系.结果表明,随着流动沙丘的固定和封育年限的增加,植被盖度、丰富度、物种多样性、土壤有机碳和全氮含量（0-20 cm）逐渐增加.在流动沙丘植被恢复过程中,土壤有机碳和全氮的结构方差与基台值的比值C/（C0＋C）均大于65%,反映出它们具有明显的空间自相关性;土壤有机碳和全氮含量的空间自相关范围分别为58.39 m和91.00 m（封育0 a）、28.59 m和23.61 m（封育11 a）和63.31 m和61.05 m（封育20 a）.由半方差函数及其参数和空间分布格局图分析表明,其空间异质性在所研究的尺度上表现出先增大（封育0-11 a）后减小（封育11-20 a）的变化特点.沙丘植被恢复过程中植被盖度、丰富度、物种多样性与土壤有机碳和全氮均有极显著的正相关关系（p〈0.01）.分析表明沙丘植被变化和地形特征影响着土壤有机碳和全氮在沙丘上的空间分布,沙丘植被恢复演替过程极大地影响了土壤有机碳和全氮的积累及其空间异质性变化.

Based on the field investigation and lab analysis, we used geostatistics method to examine the spatial heterogeneity of soil organic carbon and total nitrogen in a 0-year fenced mobile dune （MD11 ）, an 11-year fenced mobile dune （MD11 ） and a 20-year fenced mobile dune （MD20） in Horqin Sandy Land. The results showed that the average values of vegetation cover, species number and diversity, soil organic carbon and total nitrogen （0-20 cm） contents increased with the increase in fenced age of mobile dunes. Geostatistical analysis showed that the proportions of relative structural variance C/（ Co ＋C） of soil organic carbon and total nitrogen in each dune were over 65%, which suggested that they had obvious spatial autocorrelation. Calculated ranges of spatial autocorrelation for soil organic carbon and total nitrogen were 58.39 m and 91.00 m （MD0）, 28.59 m and 23.61 m （MDll） and 63.31 m and 61.05 m （MD20）, respectively. The analysis from semivariance calculated parameters and spatial distributed maps showed that the spatial heterogeneity of soil organic carbon and total nitrogen firstly increased from MD0 to MD11 then decreased from MD11 to MD20. Correlation analysis indicated that there were significantly positive correlations among vegetation cover, species richness and diversity index, soil organic carbon and total nitrogen （p 〈 0.01 ）. The analyzed results indicate that the spatial distributions of soil organic carbon and total nitrogen are most strongly related the topography features and vegetation changes in sand dune ecosystems prone to wind erosion. The accumulation and spatial haterogeniety of soil organic carbon and total nitrogen in the restoration of dune degraded vegetation are greatly affected by vegetation restoration succession.