白龙江干旱河谷木本植物多样性及其区系地理特征

基于历年植物区系调查和补点采集,对白龙江流域干旱河谷地带木本植物区系进行了物种多样性统计和区系分析.结果表明:白龙江流域干旱河谷地带木本植物计有59科、138属、269种、1亚种、26变种、2变型.组成群落的建群种或优势种约有50余种.世界分布属、热带分布属和温带分布属分别占本区木本植物总属数的5.1%、31.3%和66.4%,植物区系整体具有明显的温带属性,在起源上也与热带、亚热带植物区系有一定的渊源关系.木本植物的个体和营养器官对干暖河谷生境具有多样化的适应形式,以落叶、植株矮化、减少叶面积、阻滞蒸散、枝叶刺化为主要适应途径.主要生长型为落叶阔叶小乔木和低矮落叶阔叶灌木,落叶树种占总种数的90.33%.叶级以小型叶为主,占总种数的57.99%,其次是微型叶和中型叶,分别占26.77%和10.78%.叶片质地多半为中生形态草质叶和以坚纸质叶和薄革质为主的旱生形态硬叶.很多种以叶片被毛或鳞片和枝叶刺化适应干旱生境.依据优势种原则将干旱河谷木本植物群落大致划分为38个群系,其中落叶阔叶灌丛有28个群系,是构成干旱河谷植被的主体,其次为常绿针叶林、落叶阔叶林和半灌木灌丛.

Species diversity and floristic characteristics of woody plants in the dry valley of the Bailong River,China

On the basis of the data and specimens obtained from floristic survey in the past years and additional collection in recent years,the characteristics on species diversity and floristic geography of woody plants in the dry valley of the Bailong River(in Gansu Province of China) were analyzed and discussed in this paper.The results showed that there were 59 families,138 genera,269 species,1 subspecies.26 varieties and 2 forms of woody plants in the dry valley located in the whole reaches of the Bailong River.Of which over 50 species were established constructive or dominant species that composed specific communities.The numbers of the cosmopolitan,tropical and temperate genera occupied 5.1 %,31.3 % and 66.4 % of the whole genera number of woody plants in the dry valley,thus the flora in general displayed significant temperate distribution property,but also related to the tropical and subtropical flora in historical origin of certain degree.The ecological adaptive ways at two levels of the individuals and nutritive organs of woody plants to the habitat in dry and warm valley diversed,mainly including defoliation,individuals dwar fing,leaf area reducing,evapotranspiration obstructing and thorny shoots and leaves.The growth forms was dominanted by the deciduous and broadleafed low arbor and dwarf shrub.The deciduous tree species ocuppied by 90.33 % of total species number.In aspect of leaf size,the tree species with microphyll ocuppied by 57.99 % of total species number,followed by nanophyll and mesophyll species ocuppied by 57.99 % 26.77 % and 10.78 % respectively.The principal types of leaf texture were mesomophic orthophyll and scleromophic sclerophyll.Many species had tomentum and lepidoste usually covering leaves,and some species had devoloped thorny shoots or leaves,so as to adapted to dry habitat.According to the species dominance priciple,the woody plant communities in the dry valley were divided into 38 formations,of which 28 formations belonged to deciduous broadleaved thicket and could be regarded as the main part of the dry valley vegetation,followed by evergreen coniferous forest,deciduous broadleaved forest and subshrub thicket.