Significance of stump-sprouting for the population size structure and spatial distribution patterns of endangered species, Magnolia cylindrica

摘要

Magnolia cylindrica Wils. is one of the third most-protected wild plants in China. To describe the size structure and dynamics of its population, field data were obtained from eight newly established sites, using a contiguous grid quadrate method in jiulong Mountain of East China. The population size structure and spatial distribution pattern were discussed based on a theoretical distribution model and assembling intensity index. The population size structure showed a declining trend because of the lack of seedlings. The number of stump-sprouting, size class III (sapling trees) individuals was large enough to make up for the shortage of small seedlings and the complete regeneration of populations through sprouting. The distributions of M. cylindrica, both seedling populations (Group A) and overall populations (Group B), were mostly clumped. The spatial pattern intensities of the populations at different stages (mainly small trees, middle trees, and big trees) were higher for Group A than those for Group B. The two groups have the same tendency in that the pattern intensity declined from small trees to the larger ones. Group A and Group B differed in spatial pattern: small and middle trees were randomly distributed in seedling populations, but aggregated in overall populations. The populations of M. cylindrica (both group A and B) were characterized by the pattern scale between 16 to 32 m(2), measured by Greig-Smith and Kershaw methods. These results suggest that sprouting should be seriously considered in population rehabilitation and forest tending management and the area of forest tending management should be close to the maximum intensity.