关键词: 天然次生灌丛, 树种多样性, 封禁管理, 群落结构, 树种组成, 目标树抚育

Abstract: Under different light intensities \[55.4%, 18.9%, 5.5%, 2.2%, 0.5% of natural sunlight (NS)\] created by shading, we examined the effects of light intensity on the seed germination and seedling growth of Caragana korshinskii. The results showed that the maximums of germination percentage, germination rate, germination index and germination value of C. korshinskii seeds were all observed under the treatment of 18.9% NS and all these four parameters decreased with the decrease of light intensity. The reduction of light intensity resulted in the gradual increase of vigor index. Basal stem diameter, paripinnate number, taproot length and total dry mass of C. korshinskii seedlings all declined continuously or with fluctuation, while shoot height increased when the light density decreased gradually, indicating that lower light intensity not only affect the growth of basal stem diameter and the increase of paripinnate number but also restrict the elongation of taproot and the accumulation of dry matter of seedlings. Increase in specific leaf area of seedlings was detected with the weakness of light intensity. Root/shoot ratio, however, decreased with the decline of irradiance. In summary, our results suggested that seed germination of C. korshinskii was in part dependent on the light intensity, and shortterm water stress resulted from high light intensity could contribute to the inhibition of seed germination. The facilitation of high light intensity to the growth of seedlings suggested the adaptation of C. korshinskii to sufficient light resource of its natural distribution regions, and seedlings had great morphological plasticity across different light regimes.

Key words: community structure, target tree tending, species composition, natural secondary shrubs, species diversity, closed forest management