Demographic Strategies And Population Dynamic Of Pinus Massoniana In Response Of Logging In Changting Erosion Region

As the main part of the terrestrial ecosystem,forest,which maintains the natural environment and human society,plays a key role in ecological balance maintenance and biological diversity protection.Meanwhile,as the main way of exploitation and utilization of the forest resource,logging is one of the important measures to regulate the community structure and promote the growth of forest.Subtropical evergreen broad-leaved forests are the most extensive type in China,especially in the southeast.To address the environmental problem posed by it,the reforestation program led by the Chinese government has been adopted widely over recent decades.Although forest cover has elevated greatly after reforestation programs have been implemented,most of secondary forests are monoculture plantations,in which a small set of commercial species were selected,such as Pinus and Cunninghamia.Frequent small-scale logging is still prevalent due to mankind's and society's demand for energy and economic well-being with increased human population.To evaluate the response of P.massoniana to logging at individual's level(survival,growth and reproduction)and the demographic level(population growth rate,stable size distribution and elasticity analysis),we constructed Integral Projection Models(IPMs)combined with field survey and traditional analysis method based on the seven years life history research data.And we discuss the implications of our findings for degraded subtropical forests management.The result showed that the survival probability reduced greatly after logging and the interannual fluctuation of seedlings survival rate was significant than that of adults.The number of dead individuals increased substantially after logging.Mortality was observed during all life stages,mainly in seedlings and small individuals.Diameter growth increased with individual's size with adult individuals showing faster growth than those at other life stages.The number of pinecones and new recruitments declined greatly after logging and the size stage of reproduction was delayed.Logging negatively affected population growth rate:from slight expansion(?=1.070)before logging to constantly declining((?=0.964-0.730)after logging,and the period of logging is a rapid decline(?=0.625).The instability of population was enhanced by logging.Elasticity analysis revealed that the survival of all individuals,especially seedlings,was the key to population growth.The growth of individuals is also important to population development,while the contribution of shrinkage is limited.The importance of fecundity was increased gradually to population growth rate after logging.As a pioneer tree species,population growth of P.massoniana is strongly dependent on the survival rate,rather than the fecundity,which is the characteristic of its successful establishment in degradation erosion region.At the same time,management recommendation can be based on vital rates that are mostly affected by logging(the number of seedling recruitments)and those that are most important for population growth(survival rate).Nursery treatments that improve the survival and growth of small individuals,as well as the establishment of seedling recruitments,are beneficial to pioneer species regeneration with similar demography to P.massoniana after logging.