资源环境科技发展态势分析平台

This study analyzes the structure and regeneration dynamics of a Mediterranean high-altitude natural pine forest (Pinus nigra subsp. salzmannii) located in Sierra de Cazorla (Jaen, Spain). Spatial relationships among the adult tree overstory and understory strata are investigated in order to clarify the spatial dynamics of this unique forest stand. As regards the understory strata, we examine shrubs and pine recruitment separately. Both understory strata are better described by the area they occupy than by their constituent individuals. This approach invalidates using traditional spatial point pattern analysis with indicators such as the K-function, which only deal with vector data of the same dimension (points, lines or polygons). We use a recently developed approach in spatial association analysis to investigate spatial association between adult tree overstory (points) and understory strata (polygons) from both global and local spatial insights. Tree-stand overstory has been investigated regarding size and spatial tree-stand structure considering adult trees as points. The results show that the pine stand presents an irregular and uneven-aged structure of trees due to the effective and gradual recruitment of new trees over time, even if the forest cover is quite low. Spatial analysis of the overstory and understory relationship has shown a mainly attractive spatial relationship between the pine overstory and the pine regeneration understory, with seedling patches more likely to appear in the neighborhood of adult trees than away from them. In contrast, shrub patches presented a repelling location in relation with adult trees, and were less abundant near the pines than far from them. Shade intolerance of shrub species could account for this finding. The spatial relationship among shrubs and pine recruitment turned out to be clearly mutually exclusive in our study. Global and local spatial analysis using indices of point-polygon spatial assessment has proven to be a good tool to elucidate relationships among different forest stand strata.