The Distribution Pattern Of Dominant Shrub Species In A Typical Karst Area And The Environment Interpretation

As the spatial variability of surface micromorphology and microtopography, soil distribution of karst peak cluster depression is not uniformity and discontinuity, the microhabitat has higher heterogeneity. Shrub community is of most common vegetation types in Guangxi karst region, and is also an important part of the vegetation succession. We selected a typical karst peak cluster depression brush as the research object in northwest Guangxi, using the methods of plant community investigation and with the method of point pattern analysis, cleared the population structure characteristics, distribution pattern of the dominant species and interspecific spatial correlation among dominants species in the process of vegetation restoration of karst scrub community, understanding of karst scrub community succession tendency, discussed the main environmental factors affecting the thickets of plant distribution of degraded karst vegetation restoration process of natural vegetation succession mechanism, to assessment and the present condition of the rocky desertification area of vegetation restoration of karst further provide theoretical reference for ecological restoration and management.Each wood plants was surveyed in the 1 hm2 permanent sample plot, and we studied the distribution patterns and interspecific relationships of the main dominant species of woody plants in a typical karst peak cluster in northwest Guangxi, connected with point pattern method. The results showed that a total of 7088 moody plants (including woody vines, but excluding branch) which diameter at breast height (DBH)≥1 cm were founded in the sample plot. There were 141 species, belonging to 36 families and 91 genera. The main dominant species included Vitex negundo, Tirpitzia ovoidea, Zanthoxylum echinocarpum, Croton lachnocarpus, Ligustrum sinense, Viburnum triplinerve and Diospyros Montana. The individuals of dominant species were divided into three growth classes according to their diameter at breast height, small trees, junior trees, mature trees. The number of individual of different dominant species varied among the stages. Vitex negundo, Tirpitzia ovoidea, Zanthoxylum echinocarpum and Diospyros Montana had more small trees, Ligustrum sinense and Viburnum triplinerve had more junior trees, and Croton lachnocarpus had more mature trees.The distribution patterns of Vitex negundo, Tirpitzia ovoidea, Zanthoxylum echinocarpum and Viburnum triplinerve were aggregative, and the aggregation degree decreases gradually as the scale increased. While Croton lachnocarpus, Ligustrum sinense and Diospyros Montana presented aggregate distribution only in smaller scales, while were almost random distribution at other scales.The distribution patterns of Vitex negundo, Tirpitzia ovoidea and Zanthoxylum echinocarpum were main aggressive at different growth classes. And the distribution pattern is closely related to the scale level and age, with the scale and age level increases, the aggregation intensity is gradually weakened, tending to random distribution. The distribution patterns of sampling and juvenile trees of Viburnum triplinerve is obvious aggregated, but the mature tree tended to random. The individuals of Croton lachnocarpus, Ligustrum sinense and Diospyros Montana at different stages were distributed random.Interspecific spatial correlation is a sign of population spatial relationships, can also reflect the similarities and differences between ecological demands of different population and the interactions between species. There were 7 species pairs, such as Vitex negundo and Tirpitzia ovoidea, showed positive correlation; 4 species pairs showed no significant correlation; and 11 species pairs showed negative correlationship. Those species positively associated had similar demand habitat, they can establish a friendly relationship in the community and use space resources in harmony. And the negative correlations showed among species reflecting the result of them to meet the needs of different habitats for a long time and repellency between the different species. The spatial correlation between the individuals of the same populations at different growth stage is the result of the long-term interaction between population and environment, and is the sign of population dynamics and stability. The small trees and juvenile trees of Vitex negundo, Tirpitzia ovoidea and Zanthoxylum echinocarpum showed significant positive correlation in a certain scale, indicating that it is conducive to a better play to the group effect, improve the individual survival.In this study terrain factors significantly affected the distribution of soil nutrients in the karst peak cluster depression. And the comprehensive environmental conditions such as terrain factors and soil nutrient factors combined to form the strong heterogeneity microhabitat of the karst peak cluster depression, and thus play an important role in the composition and distribution of dominant species in the shrub community, can well explain the distribution pattern of dominant species.