澜沧江自然保护区半湿性常绿阔叶林的群落学及植物区系特性研究

对澜沧江自然保护区分布于海拔高度2 300~2 540 m较原始的半湿性常绿阔叶林的群落学及植物区系特性进行了调查研究。其2 500 m2的样地调查统计资料表明,组成本区半湿性常绿阔叶林的种子植物有44科、93属、149种,蕨类植物有7科、9属、13种。其群落的5个层次组成显明。群落中,泛热带分布的属最多,有24属;其次为热带亚洲及其变型的属,有15属。热带性质的属(51属)多于温带性质的属(32属),无中国特有属,显示该保护区的半湿性常绿阔叶林在属的水平上具有较强的热带性质。群落中,中国特有种多达76种,包括保护区特有的2个种,与云南共有的28种,与中国其他地区共有的46种,其中与西南片共有27种,表明本保护区半湿性常绿阔叶林的构成种类主要起源于云南和我国西南地区。其群落中也有一定数量的中国—喜马拉雅成分(32种)和热带亚洲成分(30种),显示与喜马拉雅地区和热带亚洲地区的区系渊源。群落中温带性质的种(113种)比热带性质的种(35种)多,说明在本区山地条件下,在该群落中形成和迁入了大量温带的种类。以此认为,相对干燥的山地气候,是本区的半湿性常绿阔叶林能够分布到海拔高度2 540 m,明显高于高黎贡山和无量山的原因。此外,构成本区半湿性常绿阔叶林种子植物的种类明显少于无量山的相同林分(177种),这或许也与两地区降雨量的差异有关。同样的由硬斗石栎、木果石栎等优势物种组成的林分,在高黎贡山和无量山属于中山湿性常绿阔叶林,而在本保护区则属于半湿性常绿阔叶林。说明具有类似优势成分的森林群落,可以划分到不同的高等级植被类型(如植被亚型)中,这主要取决于它们的生态特征,而不完全取决于它们的区系组成。

A Study on the Flora of Semi-humid Evergreen Broad-leaved Forest in Lancangjiang Nature Reserve

The flora and community characteristics of semi-humid evergreen broad-leaved forest in Lancangjiang Nature Reserve at the altitude of 2 300~2 540m was investigated and studied.The results showed that the plant community of Lancangjiang Nature Reserve had five obvious layers,there were 44 families,93 genera,149 species of seed plants and 7 families,9 genera,13 species of fern plants recorded from 5 plots totaled 2 500 m~(2).As for generic distribution,the Pantropic areal type was the majority,with 24 genera,followed the tropical Asia distribution with 15 genera.There were 51 tropical genera,which was higher than that of temperate genera(32 genera).There was no genus of Chinese endemic.On the genus level,the semi-humid evergreen broad-leaved forest in Lancangjiang Nature Reserve had significant tropical characteristics.There were 76 species endemic to China,among which,2 species were endemic to Lancangjiang Nature Reserve,28 species were endemic to Yunnan,46 species were endemic to other regions of China with 27 endemic species of southwest China.The result indicated that the origins of the components of semi-humid evergreen broad-leaved forest in Lancangjiang Nature Reserve were mainly Yunnan and southwest areas of China.There were also Sino-Himalayan flora and tropical Asia flora,with the number of 32 species and 30 species respectively,which showed the origin of Himalayan region and tropical Asia.In this community,there were 113 temperate species,which was higher than that of tropical species(35),which indicated that under the upland condition of this nature reserve,a lot of temperate species formed and entered.The relatively dry climate of this region might be the reason that the semi-humid evergreen broad-leaved forest could distributed in the areas with the altitude up to 2 540 m,which was higher than both Mt.Gaoligongshan and Mt.Wuliangshan.It perhaps related to the rainfall that the region's seed plant were fewer than Mt.Wuliangshan.Constituted of same dominant species,such as Lithocarpus xylocarpus, and L.hancei,formed mid-montane humid evergreen broad-leaved forest in Mt.Gaoligongshan and Mt.Wuliangshan whereas semi-humid evergreen broad-leaved forest in Lancangjiang Nature Reserve.These results indicated that the communities with same dominant elements could be separated into different high grade vegetation types such as vegetation subtypes and this was mainly decided by the ecological characteristics of the community instead of totally decided by the flora.