Guangdong nongye kexue (Mar 2023)
Dynamic Change Characteristics of Population Structure and Quantity of Kandelia obovata in Dongzhai Harnor of Hainan
Abstract
【Objective】As a common mangrove tree species in Hainan, Kandelia obovata is also a tree species widely used in mangrove ecological restoration. In recent years, global climate change and the increase of human disturbance have brought serious threats to mangrove ecosystem. Therefore, establishing fixed plots to monitor the dynamic changes of mangrove communities and populations has important research value for the protection and restoration of mangroves.【Method】The population structure characteristics and the dynamic change of the population in a fixed 1 hm2 plot in the national mangrove reserve of Dongzhai Harbor, Hainan Province were analyzed and studied.【Result】(1) The diameter class structure of the K. obovata population in the area showed an irregular pyramid shape, and the total number of individuals in the Ⅰ-Ⅳ age class accounted for 75.4% of the total number of individuals in the population, and the number of individuals in the Ⅳ age class decreased obviously. (2) The dynamic changes in the number of individuals in various age groups showed a trend of "recession-recession-recession-growth-growth growth-growth". The dynamic indices Vpi and V'pi of the whole population were both greater than 0 and tend to be 0, indicating that the K. obovata population in this area was a growth population with high sensitivity to external interference, and the growth trend was not obvious when subjected to external interference. (3) In the static life table of the K. obovata population, the life expectation of the population showed a trend of decreasing gradually. (4) The survival curve fitting equation was y=2406e-0.505x, R2 = 0.962, F= 194.036, P< 0.001, indicating that the survival curve of the K. obovata population was consistent with the Deevey-Ⅲ curve. (5) Both the mortality rate and disappearance rate showed a trend of increasing first, decreasing then increasing again. The peaks of appeared in Ⅴ and Ⅸ age classes were 52%, 73% and 77%, 92%, respectively. (6) Survival analysis showed that the survival rate (Si) decreased gradually, while the cumulative death rate (Fi) increased gradually. There was a crossover point between the Ⅱ and Ⅲ age classes. The death density (fti) and the risk rate (λti) of the population showed a decreasing trend, and the death density decreased sharply between the I and Ⅱ age classes, and the minimum value of death density was 0.3% in the Ⅷ age class. (7) Time series analysis also reflected that although there were a large number of individuals at the lower age level, relatively few individuals would develop to the older age level in the future several age levels, and the majority of the future population would be individuals at the middle and older age levels.【Conclusion】The results reflect that the K. obovata population of the research area is a growing population, which is more sensitive to external interference. The dynamic change of the numberof the senior population is more stable than that of the younger population, and the population in the future will be dominated by the senior individuals.
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