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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 In this study, we thoroughly collected the relevant data from the literature and unpublished data from Huanjiang Observation and Research Station of Karst Ecosystem, Chinese Academy of Sciences.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 http: / / www.ecologica.cn 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鄄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鄄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 communit...

The karst landscape in China are mainly located in the southwest of China around Guizhou province and cover an area of 550 000 km 2 . Southwest China is most famous in the world for the continuous distribution of karst landscape, for holding the largest area of bare carbonate rocks and for experiencing the strongest karst development in the world. The karst area in southwest China is characterized by unique geological background, high landscape heterogeneity, low ecological capacity. In the meanwhile, this region is populous and in turn the exploitation of natural resources has been very high. For example, most natural vegetation has been converted to croplands. As a consequence, the region has experienced serious soil erosion or rocky desertification over the past decades due to the fragile nature of the ecosystems here, which posed great threat on the sustainable development of this region. In addition, since southwest China is located in the headwaters region of the Pearl River and Yangtze River, the ecological degradation in this region directly impacts the ecological safety the in the middle or lower reaches of the two rivers忆 watersheds. Therefore, a comprehensive control of the karst rocky desertification and an effective restoration of the degraded areas are necessary for ensuring the ecological security of the Yangtze and Pearl rivers忆 watersheds. In this paper, we systematically synthesized the information regarding rock desertification in the karst area in southwest China obtained largely from but not limited to Huanjiang Observation and http: / / www.ecologica.cn Research Station of Karst Ecosystem, Chinese Academy of Sciences. We proposed a new definition of rocky desertification and its classification criteria. Based on remote sensing data, we discussed the spatial distribution and dynamics of rock desertification in the karst area in southwest China. At different stages of rocky desertification, the ecosystems were related to different characteristics embodied by a combination of vegetation, soil physics, chemistry, and microorganism. The occurrence of karst rocky desertification was explained from natural factors ( e.g., geological factors) and human activities, especially agricultural activities. We proposed several regulation strategies according to the degree of rocky desertification to boost the harmonious and sustainable development of ecology, economy and society in the karst areas of southwest China.

Carbon storage and its controlling factors under different vegetation types in depressions between karst hills, southwest China.

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