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

Abstract

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 In this study, we thoroughly collected the relevant data from the literature and unpublished data from Huanjiang Observation and Research Station of Karst Ecosystem, Chinese Academy of Sciences.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.