中国西南喀斯特植物群落演替特征及驱动机制

植被恢复是西南喀斯特石漠化治理和生态重建的关键步骤。通过总结已有的结果和分析中国科学院环江喀斯特试验站部分试验数据,研究了西南喀斯特植被演替过程中群落的动态特征,结果发现:西南喀斯特沿北、中、南亚热带至北热带的海拔递减、气温和降雨量升高的梯度格局下,群落的高度、盖度增加,密度、科属种数量和物种多样性呈递减趋势;不同区域沿草丛、灌丛、灌乔丛、乔丛的顺向演替方向上,群落的高度、盖度增加、密度减小,科属种数量及物种多样性除北亚热带持续增加外,其他3个区域的最大值均出现在灌乔丛,乔丛反而有所下降;西南喀斯特植被演替是生物驱动因素与环境阻力相互作用的结果,不同区域不同演替阶段植被演替的建群种和关键种不同,其植物群落的稳定性受多样性和结构性的共同控制,因地质和生态环境恶劣,植被退化容易恢复难,充分理解和认识植被演替规律对西南喀斯特植被恢复和生态重建意义重大。

The succession characteristics and its driving mechanism of plant community in karst region, Southwest China

Vegetation restoration is the key step of desertification prevention and ecological rehabilitation in the karst region in Southwest China. A sound understanding of the vegetation composition, species diversity, and structural variation with succession is of great significance for vegetation protection and rehabilitation. However, until now, a systematic synthesis of information was not available for this region. In this study, we thoroughly collected the relevant data from the literature and unpublished data from Huanjiang Observation and Research Station of Karst Ecosystem, Chinese Academy of Sciences. We then systematically analyzed the data to determine the dynamics and driving mechanisms of plant community succession in the karst region of southwest China. To facilitate the analyses, the whole region was divided into northern subtropical, mid subtropical, southern subtropical, and northern tropical regions. The height of the plant community and vegetation coverage increase in the mean annual temperature and precipitation or with a decline in altitude in subtropical and northern tropical regions. Along with decreasing altitude, community structure improved, however, the community density, number of families, genera, species, and diversity decreased probably due to the increase in landscape homogeneity. Along the succession from grassland to shrubland, shrub/arbor mixed woodland, and to arborland, the height of the community and the coverage increased, but density decreased for the entire region. The number of families, genera, species, and diversity increased along the succession in the northern subtropical region, but these indices reached maximum in shrub/arbor mixed woodlands in the remaining three regions. The vegetation succession and distribution pattern were the result of multiple ecological processes including species evolution (speciation, migration, and extinction), geographical differentiation and environmental factors (e.g., geology, topography, climate, soil), and other processes. Under the impacts of natural factors (soil, climate, topography), human disturbances, and other ecological factors, long-term interactions among plant individuals resulted in spatial and temporal variation of vegetation distribution at different scales and levels. The main driving forces of vegetation succession included biological factors (microbial community, physiological ecology, and growth characteristics of species) and abiotic factors (e.g., landscape heterogeneity, topography, physical and chemical properties of the soil) and their interactions. The constructive species and key specie were variable for different successional stages and regions. With vegetation development, the climax species became richer, and the key species had a tendency to be more advanced, large in size, and long-living. The relationship between stability and diversity of plant communities was more complex. In general, along the community succession sequence, the stability was greater for the climax community than for the earlier succession stages. However, although plant species diversity helped to sustain community stability, a stable community was not only controlled by high diversity of plants, but also by reasonable community structure. In the karst region of the Southwest China, vegetation was found to degrade more easily than to recover, owing to the dual karst flow systems, high landscape heterogeneity, and fragile ecological conditions. In summary, the present study thoroughly synthesized the information in terms of dynamics of vegetation composition, diversity, and structure along with succession and the underlying mechanisms in the karst region of the Southwest China. Such information will be useful for the vegetation protection and rehabilitation in this region.