贵州习水国家级自然保护区习水杜鹃种群空间分布格局和生态位特征分析

Spatial distribution pattern and niche characteristics of Rhododendron xishuiense population in Xishui National Nature Reserve,Guizhou

为探索习水杜鹃在贵州习水国家自然保护区的种群空间格局及生态位特征,对现存习水杜鹃群落开展详细的调查,采用Ripley点格局法、Levins和Shannon-Wiener生态位宽度指数和Pianka生态位重叠指数进行分析。结果表明:(1)乔木层中优势种习水杜鹃、光枝杜鹃表现为随机分布,桂南木莲、岭南石栎、小果润楠在尺度范围表现为更多的聚集分布,灌木层优势种杜鹃表现为聚集分布;(2)乔木层中习水杜鹃生态位宽度值最大,对资源的利用和环境的适应能力更强,但生态位重叠值也较高,且重叠物种数占比100%,遭受较强的竞争。灌木层中习水杜鹃生态位宽度值仅次于杜鹃,遭受的竞争相对较小,但受资源限制,总体优势程度并不明显;(3)乔木层中的桂南木莲、厚皮香和草本层中的蕙兰、矛叶荩草重叠值为1,它们在生态学或生物学的特性极为相似,可能会出现某一种在竞争中衰退,或出现生态位的分化以达到共存。生态位重叠值为0的物种有26对,其中灌木层硬壳柯、草本层稀羽鳞毛蕨与多对物种间重叠值为0,占据着相对独立的资源,相较于其他的物种更具较强的发展潜力。综上,习水杜鹃分布格局反映了其种子具有一定扩散能力,但因为种子萌发障碍导致幼苗幼树稀少,且习水杜鹃乔木遭受程度较强的竞争,建议开展一些促进习水杜鹃种子萌发的研究,并进行培育,以应对种群遭受的衰退威胁。

In order to understand the spatial distribution pattern and niche characteristics of Rhododendron xishuiense population in Xishui National Nature Reserve,Guizhou,the existing Rhododendron comnunity in Xishui was investigated in sample plots.Ripley point pattern,Levins and Shannon-Wiener niche breadth index and Pianka niche overlap index were used for the analysis.The results show that:(1)in the tree layer,the dominant species(Rhododendron xishuiense and Rhododendron haofui)distribute randomly,while Lithocarpus brevicaudatu,Manglietia chingii,and Machilus microcarpa show more aggregated distribution;in the shrub layer,the dominant species(Rhododendron)presents aggregated distribution.(2)In the tree layer,Rhododendron xishuiense has the largest niche breadth,better resource utilization capacity and stronger adaptability to environment,but the niche overlap value is high,and the number of overlapping species accounts for 100%,which indicates strong competition;in the shrub layer,the niche width of Rhododendron xishuiense is second only to Rhododendron,suffering relatively little competition,but the advantage is not obvious.(3)The overlap value of Ternstroemia gymnanthera and Manglietia chingii in the tree layer,and Cymbidium faberi and Arthraxon lanceolatus in the herb layer is 1.They are very similar in ecological or biological characteristics,and may decline in competition or differentiate in niche to coexist.There are 26 pairs of species with niche overlap value of 0,including Lithocarpus hancei in the shrub layer and Dryopteris sparsa in the herb layer.In conclusion,the distribution pattern of Rhododendron xishuiense reflects that its seeds have a certain diffusion ability,but there are few seedlings and young trees due to the difficulty in seed germination.Meanwhile,Rhododendron xishuiense trees suffer from strong competition.It is suggested that researches be carried out on promoting seed germination and cultivation of Rhododendron xishuiense to deal with the threat of decline of the population.