东北样带上的克隆植物及其重要性与环境的关系

Clonal plants along NECT and relation of their importance to environmental conditions

1 997年野外调查资料 ,对中国东北样带克隆植物沿样带的分布、克隆植物在群落中的重要性以及其与环境因子之间的关系进行了研究。结果表明 :克隆植物相对种数 ( C/ Pt)和克隆植物相对重要值 ( IV)随样带上环境梯度变化呈增加的趋势。群落中克隆植物相对种数与土壤全氮含量负相关 ,与海拔高度正相关 ,与年平均温度和年降水相关不显著 ;克隆植物相对重要值与土壤全氮含量负相关 ,与海拔高度正相关 ,与年平均温度和年降水相关不显著。研究还发现 ,群落中克隆植物种数与非克隆植物种数随样带上海拔高度、年平均温度、年降水梯度变化相关性较差 ,而克隆植物种数与土壤全氮含量负相关不显著 ,非克隆植物物种数与土壤全氮含量正相关不显著。根茎型、分蘖型及鳞茎球茎型克隆植物在土壤湿度较差的生境中出现频率较高 ,而匍匐茎型。

Northeast China Transect (NECT) is a transect designated for Global Change and Terrestrial Ecosystem Program (GCTE) and recognized by the International Geographical and Biological Plan (IGBP) as one of the four major global transects (GCTE core project office 1994). It extends from the northern Changbai Mountains of Jilin Province through the Songliao plain to the plateau of Inner Mongolia, at approximately 112～130°30′ E and 43°30′～44°30′ N. The altitudes range from 120 to 1700m along the NECT. Along the transect from east to west, there are decreasing gradients of precipitation and temperature as well as variations in plant communities and the soil nitrogen content. Quadrats along the NECT were set up and the number, coverage and frequency of each species were investigated from 14 July to 1 August 1997. Based on the data, the richness and importance of each species were calculated. The distribution and the role of clonal plants in the communities along the NECT were investigated. Regression analysis was used to discover the relationship between importance of clonal plants and environmental factors.Our result show that the positions of clonal plants in phylogenetic tree were different significantly. They occurred in most of the families. Out of 315 plant species occurred in the NECT, 155 were clonal plant species. They belong to 38 families and 88 genus respectively. The result supports the multi originated hypotheses of plant clonality. It was evident that there were more abundant clonal plants in monocots than that of in dicotyledon species, indicating a strong phylogenetic factor in evolution of clonality although this does not preclude ecological interpretations. 155 clonal plants belong to 15 geographic elements respectively. Clonal plants were abundant in Dahurica Mongolia and Pan Arctic pole component and scarce in North China, Ancient Mediterranean, Europe Sibiricum and World component. Clonal plants commonly were perennial grasses and shrubs, but less were annual and woody species. Plant species with different clonal growth from were unevenly and non randomly distributed among 155 clonal plants and plant families. Rhizomatous clonal plants were abundant. However, tuberous, bulbous and stoloniferous clonal plants were scarce, and were restricted to Rosaceae and Liliaceae respectively.Clonality was unevenly distributed over the six vegetation types along the NECT. Species relative frequency of clonal plants ( C/P t ) and relative importance value of clonal plants ( IV ) along the environmental gradient in NECT show a ascending trend from the east to the west. Clonal plants were abundant in the typical steppe and the desert steppe. Clonal plants played a more important role in the typical steppe and the desert steppe than that in other vegetation types. Species relative frequency as well as importance of clonal plants was negatively correlated to total nitrogenous content in the soil (N) respectively, and positively correlated to elevation respectively, but not significantly correlated to mean annual temperature or annual precipitation respectively. The correlations between the number of clonal plants, non clonal plants and elevation, mean annual temperature or annual precipitation were not significant,and the same pattern to non clonal plants. While the number of clonal plants tended to negatively correlate to N, but the correlation was not significantly at p =0.05, which is contrary to non clonal plants. These indicates that the occurrence of clonal plants and non clonal plants varied markedly different among the plant communities of NECT. Clonal plants were adaptive under stressed conditions such as in lower soil nitrogen content and drier habitats, whereas non clonal plants were favored under more optimal conditions, which imply that clonality may have great significance in the evolutionary processes.There was marked difference in the distribution of clonal growth forms along NECT. Rhizomatous, tillering, bulbous and tuberous types occurred in the most of communities.