IPM Construction And Population Dynamic Analysis Of Pinus Massoniana Based On Competitive Relationship

As the main part of the terrestrial ecosystem,the forest plays an indispensable role in maintaining ecological balance and promoting sustainable development of resources,providing abundant natural resources for the development of human society and economy.However,due to the excessive anthropogenic activities of the forest,the original ecosystem of the eroded and degraded areas in southern China has been destroyed,and the forest vegetation has disappeared on a large scale.Revegetation has become the key task of the degraded ecosystem reconstruction.In the process of ecological restoration of degraded ecosystems,pioneer species play an important role in the pioneer stage of ecological restoration.Its population dynamics are controlled by individual birth rate,mortality rate,and influence of the external environment,which determine the process of ecological restoration.Intraspecific competition is an important ecological relationship that affects the dynamics of pioneer species.It exists for a long time in the process of ecological restoration and regulates the development direction of Pinus massoniana population under different restoration levels.To evaluate the influence of intraspecific competition on the life history strategy and driving mechanism of P.massoniana population dynamics during different ecological restoration stages,we used the general linear mixed model to quantify the relationship between the intraspecific competition intensity and vital rates of the P.massoniana,and the Integral Projection Model was constructed based on four-year population life history research data.The result showed that:(1)Intraspecies competition intensity and size structure composition of P.massoniana had significant differences in different stages of ecological restoration.The intraspecific competition showed different intensity level under different ecological restoration levels,the sequence is the highest restoration level plots,serious erosion plot and medium restoration level plots,meanwhile,the variation of competition intensity among P.massoniana individuals was the highest in the serious erosion plot(1136.6%,935.0%,1127.0%).The competitive pressure of the individual decreased with the increase of the individual size among the plots with different restoration levels.With the improvement of habitat restoration,the average individual size of P.massoniana in the plots increased,but the distribution of the individual size of P.massoniana in the highest restoration level plot showed obvious polarization.The number and size structure of the P.massoniana population is closely related to the level of ecological restoration.The availability of resources within the population and the time of ecological development determines the population structure and composition of the P.massoniana population,so the difference of individual diameter class structure caused by the different level of ecological restoration is the reason of the variability for intraspecific competition.(2)Under different ecological restoration levels,the response of vital rates of the P.massoniana to the change of competition intensity was various.Meanwhile,the change of competition intensity affected the adjustment of life history strategy of the P.massoniana population.The large P.massoniana individuals suffered lower mortality risk,and the survival rates of small individuals were 84%,68%,and 42% in medium restoration level plots,serious erosion plots,and the highest restoration level plots,respectively.The intraspecies competition intensity showed a significant effect on the survival rate of the P.massoniana individuals in the serious erosion plot and medium restoration level plots.The increase of intraspecies competition intensity would reduce the possibility of survival of small individuals.The population was showing a positive growth state under different levels of ecological restoration,the average growth of the P.massoniana population was(2.91±0.29)mm in the serious erosion plot,(6.90±0.32)mm in the medium restoration level plots,and(2.52±0.34)mm in the highest restoration level plot.Meanwhile,at the medium recovery level,intraspecies competition affected the individual growth rate of P.massoniana.With the increase of intraspecific competition intensity,the individual diameter growth rate slowed down.Moreover,the intraspecies competition had significant effects on the individual reproductive rate of the P.massoniana at different levels of ecological restoration.With the increase of intraspecies competition intensity,the possibility of individual reproductive rate decreased.The result indicated that the increase of intraspecies competition intensity would promote the resource allocation of P.massoniana life history strategy to vegetative growth,the reproductive strategy would be changed from early reproduction to delayed reproduction,and individuals would reduce reproduction to ensure their competitive advantage.(3)The results indicated that the intraspecific competition of P.massoniana population affected the future development trend of the population by adjusting the life history strategies of the population,and the variation trend of P.massoniana population dynamics was various with the increase of competitive intensity during the different ecological restoration levels.P.massoniana population are showed recession trend under different level of ecological restoration,the population growth rate of P.massoniana in the medium restoration level plots is lowest(λ= 0.740,0.878),and the population structure was most instability.The elasticity analysis confirmed that the individual survival dominated the population growth rate changes.The increase of intraspecific competition intensity increased the population growth rate by improving the survival rate of large individuals in the serious erosion plot.The increase of intraspecific competition intensity by 50% increased the population growth rate by 0.5% and 2.8%,respectively.Furthermore,in the medium restoration level plots,the increase of intraspecific competition intensity accelerated the decline of population growth rate by decreasing the survival rate of small-size individuals,reducing the individual growth rate and reproductive rate.The population growth rate decreased by9.6% and 5.5%,respectively,when the intensity of intraspecies competition increased by 50%.However,the effect of intraspecific competition intensity on the population dynamics of P.massoniana was negligible in the highest restoration level plots.