Abstract: 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.

Key words: Picea, natural regeneration, soil nitrogen, heterogeneity, spatial relevance, irrigation district, winter wheat, ridge and furrow rain harvesting, supplemental irrigation, photosynthetic characteristics, yield, water use efficiency.