黔中喀斯特次生林优势物种空间分布格局及关联性

Spatial distribution and correlation of dominant species of karst secondary forest in central Guizhou,China

以黔中天龙山2 hm^(2)喀斯特次生林为对象,采用成对相关函数g(r)结合完全随机模型(CSR)研究重要值前4位优势树种的空间分布格局及其关联性。结果表明:样地树种的径级结构呈倒“J”型分布,在优势树种窄叶石栎和圆果化香的影响下,第Ⅴ径级(≥10 cm)的数量较多。窄叶石栎呈现倒“J”型分布,种群更新良好,处于生长发育初级阶段;而圆果化香和云南鼠刺随着径级的增大数量逐渐递增,成年树、大树数量远多于幼树、小树,表明该种群更新不足,处于生长发育的中后期并逐渐衰退。除窄叶石栎外,其余优势树种整体呈现出在较大尺度上聚集分布,聚集程度随着尺度的增大逐渐下降并趋于随机分布,此规律在幼树径级中表现得尤为突出;而受各种因素的影响,各个树种不同径级呈现出不同的空间分布格局。在种间关联上,4个优势树种之间大多呈现负关联或者无关联关系,树种重要值越高与其他优势树种关联程度越低,呈现负关联的2个树种在小尺度上关联程度最低,随着尺度的增大负关联程度逐渐降低并趋向于无显著关联。

We analyzed the spatial distribution pattern and correlation of the top four dominant tree species in a 2 hm^(2) karst secondary forest plot of Tianlong Mountain in central Guizhou,using pairwise correlation function g(r)combined with a completely random model(CSR).The results showed that the diameter structure of trees followed an inverted J-shape,and that more trees belonged to diameter classⅤ(≥10 cm)driven by the dominant trees of Lithocarpus confinis and Platycarya longipes.L.confinis presented an inverted J-shaped distribution,and the population could renew very well and was in the primary growth stage.The abundance of P.longipes and Itea yunnanensis increased gradually with increasing diameter class.The density of grown and large trees was far more than the young and small individuals,which indicated poor population regeneration,and the population was in the middle and late growth stages.The top dominant tree species,except L.confinis,showed clustering distribution at large scale,which was decreased gradually with scale and trended to distribute randomly.The pattern was particularly prominent in the diameter class for young trees.Different diameter classes of different tree species presented diffe-rent spatial distribution patterns which influenced by many factors.In terms of interspecific associations,the four dominant tree species showed negative or no associations.The higher importance value of tree species,the lower the degree of association with other dominant species.The two negative correlation tree species had the lowest degree of correlation at small scale.With the increase of spatial scale,the degree of negative correlation decreased gradually,and tended to be no correlation.