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Spatial relevance between natural regeneration of Picea and heterogeneity of soil available nitrogen in Guandi Mountain

关帝山云杉天然更新与土壤有效氮素异质性的空间关联性


在山西关帝山华北次生林分布区选择云杉针叶林和云杉、杨、桦混交林为研究样地,应用地统计学理论和格局分析方法,分析了该地区云杉天然更新的空间格局及结构特征;运用地统计分析中的变异函数分析方法定量分析了样地土壤氮素的空间异质性特征.采用GIS叠加分析和统计分析方法,定量评价云杉更新苗分布格局和土壤有效氮素空间异质性之间的空间关联程度,以了解森林土壤氮营养生境的异质性对云杉幼苗更新的影响.结果表明:1)在云杉针叶林中,云杉更新苗分布呈空间斑块状格局,且表现出自相关空间变异特征;在云杉、杨、桦混交林中,云杉更新苗空间分布格局呈集聚分布特征,但表现为随机性的空间变异.2)云杉针叶林土壤氮素含量相对低,有效氮含量空间异质性特征明显,空间结构性变异所占比例较大;混交林土壤氮素含量相对高,有效氮呈随机性变异特征.3)在土壤氮素含量相对低的云杉针叶林中,云杉更新苗分布格局与土壤有效氮异质性之间存在较明显的空间关联性,在土壤NH4+-N含量相对高的斑块中,云杉更新苗发生数量多.在土壤氮素含量相对高的混交林,云杉更新苗空间分布与土壤有效氮异质性之间的空间关联性不明显.

By using geostatistic and pattern analysis methods, this paper studied the spatial pattern of Picea seedlings in naturally regenerated conifer (Picea) and mixed (Picea-Populus-Betula) forests in Guandi Mountain of Shanxi Province, China. The spatial distribution of soil nitrogen was also quantified by semivariogram analysis. To understand the effects of spatial heterogeneity of soil nitrogen on the regeneration of Picea seedlings, the relationships between the regeneration pattern of the seedlings and the spatial distribution of soil nitrogen were investigated by using GIS superposition and statistical analysis. In conifer stands, the distribution of Picea seedlings appeared as a patch pattern and was auto-correlated; while in mixed stands, the distribution was of gathering distribution pattern controlled by random factors. In the Picea stands with relatively low soil nitrogen content, the spatial distribution of soil available nitrogen was significantly heterogeneous and auto-correlated; whereas in the mixed stands with high nitrogen content, the distribution of soil available nitrogen showed random heterogeneity. In the conifer stands, the spatial correlation between Picea seedlings regeneration pattern and soil available nitrogen distribution was significant, regenerating more seedlings in the patches with higher NH4+-N concentration; while in the mixed stands, the correlation was not significant.