喀斯特山顶区域濒危裸子植物群落特征及其地形关联

喀斯特濒危裸子植物往往局限分布于生境恶劣的山顶区域，受保护的急迫性和必要性较强，但目前针对该区植物群落的研究较少，保护技术措施缺乏理论支持。对木论喀斯特山顶区域典型的濒危裸子植物群落进行了调查，分析了该群落特征的空间变异及其地形关联。结果表明：该群落共有植物73种，隶属于39科58属；裸子植物、双子叶植物、单子叶植物分别有3、67、3种；壳斗科、蔷薇科和樟科物种相对较多；64.1%的科和81.0%的属只含有1个物种。双子叶植物净关系指数（NRI）和最近关系指数（NTI）表现出随机格局。个体数、总基面积、NTI分别在5.66、4.75、6.51 m尺度内具有强烈的空间相关性，空间连续性相对较差；Shannon多样性指数、Simpson多样性指数、Pielou均匀度指数分别在71.01、71.01、42.44 m尺度内具有强烈的空间相关性，空间连续性相对较好。总基面积与凹凸度呈显著正相关关系；濒危裸子植物相对基面积与坡度呈显著正相关关系；NTI与相对海拔呈极显著正相关关系，与坡度和坡向均呈显著负相关关系。上述结果对于喀斯特濒危裸子植物的保护和恢复工作具有一定的指导意义。

Community characteristics of endangered Gymnosperms and their topographic relationships in a karst mountaintop region

Most rare and endangered Gymnosperms in karst regions are restricted to mountaintop habitats with inferior conditions and require urgent protection. However, in the literature there is a lack of information about the plant community structure of biotic communities in these ecosystems, which could be used to inform conservation efforts. Here a plant community typical of endangered Gymnosperms in the Mulun karst forest was selected for investigating plant community structure and microtopography. Spatial variability of plant community characteristics was studied using geo-statistical techniques, and the correlations between community characteristics and topographic factors were analysed. The results indicated a complex community structure of 73 species belonging to 39 families and 58 genera, with 3, 67, and 3 species representing Gymnosperms, Dicotyledons, and Monocotyledons, respectively. Dominant families were Fagaceae, Rosaceae and Lauraceae, containing more than five species each. About 64.1% of all families and 81.0% of all genera were represented by only one species. Focussing on Dicotyledoneae, the net relatedness index (NRI) and nearest taxon index (NTI) of this class indicated a random phylogenetic community structure. The individual number, total basal area of all species (BA) and the NTI had strong spatial correlations, at 5.66 m, 4.75 m, and 6.51 m, respectively, showing relatively small ranges of spatial continuity. Shannon''s diversity index, Simpson''s diversity index, and Pielou''s evenness index had strong spatial correlations, at 71.01 m, 71.01 m, and 42.44 m, respectively, showing relatively large ranges of spatial continuity. There were significantly positive correlations between BA and convexity, and between relative basal area of endangered Gymnosperms and slope degree. NTI showed a extremely significant positive correlation with relative elevation, and significantly negative correlations with both slope aspect and slope degree. These results provide useful information for conservation and restoration efforts for endangered Gymnosperm species in karst regions.