西南喀斯特木本植物区系成分的纬度变异格局

本研究选取3个极具代表性的喀斯特原生植被区域,即北热带的广西弄岗自然保护区、南亚热带的广西龙虎山自然保护区和中亚热带的贵州茂兰自然保护区为研究对象,通过野外实地调查及查阅文献,整理出3个区域的木本植物名录,比较分析木本植物种类组成和区系成分的纬度变异格局。结果显示,弄岗、龙虎山和茂兰3个不同气候区域内的木本植物分别有104科425属936种、99科363属636种和100科352属995种。木本植物区系均以热带亚热带成分为主,其优势科热带性质随纬度升高逐步降低。热带区系成分与温带区系成分的比值(R/T)反映出,弄岗和龙虎山自然保护区的木本植物区系属的热带性质明显,而茂兰自然保护区植物属的热带性质较弱,温带性质属的比重随纬度升高而增加。科、属、种相似性系数表明,弄岗和龙虎山间的木本植物亲缘关系较密切,弄岗和茂兰间次之,而龙虎山和茂兰间亲缘关系较远。

Latitudinal patterns in geographical elements of woody plants in a karst area of southwestern China

Three representative distribution areas of native karst vegetation were surveyed, including Nonggang and Longhushan Nature Reserves respectively located in the northern tropics and southern subtropics of Guangxi Province and Maolan Nature Reserve situated in the central subtropics of Guizhou Province. Woody plant species in the three regions were determined according to field surveys and literature review, with their latitudinal variation and floristic composition then analyzed. The categories of woody plants in the three climatic zones were as follows:104 families, 425 genera, and 936 species in Nonggang; 99 families, 363 genera, and 636 species in Longhushan; and 100 families, 352 genera, and 995 species in Maolan. The woody flora was dominated by tropical and subtropical components, and the tropical nature of the dominant families gradually decreased with increasing latitude. The ratio of tropical floristic components to temperate floristic components (R/T) reflected the tropical nature of the woody flora of Nonggang and Longhushan Nature Reserves, whereas the ratio value was much lower in Maolan Nature Reserve, indicating that the proportion of genera with temperate characteristics increased with latitude. The similarity coefficients at the family, genus, and species level indicated that the woody plants of Nonggang and Longhushan were closely related, followed by those of Nonggang and Maolan, and finally those of Longhushan and Maolan, which were relatively distantly related.