云南的硬叶常绿阔叶林——古地中海残余植被

Sclerophyllous evergreen broad-leaved forest in Yunnan — A remnant vegetation related to Tethys

关键词:  硬叶常绿阔叶林, 生态特征, 物种组成, 地理分布, 起源与演化

Key words:  sclerophyllous evergreen broad-leaved forest, ecological characteristics, species composition, geographical distribution, origin and evolution

摘要:

云南从干热河谷到寒温性山地广泛分布有一类常绿、阔叶、以壳斗科栎属植物为乔木优势种的森林植被,由于其独特的生态特征显示了与现代地中海地区硬叶栎林的相似性,而在群落的外貌、结构、特征种、地理分布等方面却与云南的亚热带常绿阔叶林有明显区别,因此被称为“硬叶常绿阔叶林”,它是在喜马拉雅隆升中因适应新的环境而发育的一个特殊植被类型。该植被的优势树种具有古地中海地区渊源,但在分布上大多为我国西南地区的特有种。硬叶常绿阔叶林除优势树种为硬叶栎类以外,其他种类与同域天然植被的物种组成基本一样,并没有一个独特的植物区系。硬叶常绿阔叶林群落结构简单,典型的硬叶常绿阔叶林群落有清楚的乔木、灌木和草本3个层次,而在生活型上,寒温性山地的群落以地面芽植物占绝对优势,干热河谷的群落以草本植物占优势。在中新世以前,硬叶栎类植物出现在湿润的热带-亚热带性质的古地中海常绿阔叶林里,直到上新世以后,现代的地中海式气候形成,适应干旱的地中海植物区系出现,并随喜马拉雅隆升,硬叶常绿阔叶林才从原先的热带-亚热带常绿阔叶林演化产生。

Abstract:

Widely occurred on diverse habitats from hot dry deep valleys to cold temperate mountains, the sclerophyllous evergreen broad-leaved forest dominated by Quercus species(Fagaceae), is an unique vegetation type in Yunnan. The forest is similar to sclerophyllous oak forests in the modern Mediterranean regions on physiognomy. It differs obviously from the other subtropical evergreen broad-leaved forests in Yunnan by its particular physiognomy, structure, characteristic tree species and geographical distribution, and is named as “sclerophyllous evergreen broad-leaved forest” in the vegetation classification of Yunnan. The sclerophyllous forest is a special vegetation type developed to adapt to the new environment during uplift of the Himalayas. The dominant tree species of the forest show Mediterranean floristic affinity, but they presently distribute mostly in southwestern China. Except Quercus species, its floristic composition is the same as other neighbor vegetations. The community structure of sclerophyllous evergreen broad-leaved forest is simple. The typical forest community has a profile of tree-shrub-herb layers as common forests, but hemicryptophyte plants absolutely dominate in the communities on cold temperate mountains, and herbaceous plants dominate in the communities at hot dry valleys in its life form. The sclerophyllous oak species fossils recorded in moist tropical-subtropical evergreen broad-leaf forests in Tethys region before Miocene. Until Pliocene epoch, the modern Mediterranean climate formed and drought-resistant Mediterranean flora arose, while the sclerophyllous evergreen broad-leaved forest evolved from the former tropical-subtropical evergreen broad-leaf forests with the Himalayas uplift.