Naturalness In Different Successional Stages Of Korean Pine Forests And Driven By Ecological Strategies And Environmental

The destruction of primary forests has formed degraded ecosystems and triggered an ecological crisis that has swept the world.It leads to global warming,a sharp decline in forest biodiversity,and serious ecological problems such as soil erosion and desertification,with disastrous consequences for social and economic development.In order to protect the ecological environment,curb the frequent occurrence of natural disasters,and promote sustainable social and economic development,China implemented Natural forest protection project(shortly NFPP)in 2000,which is of great significance to realize the conservation of China’s forest resources and promote sustainable resource management.As a key area of NFPP,it is imperative to restore the damaged primary Korean pine forests in the northeastern forest area.And it is also especially necessary to propose an effective restoration evaluation system.Naturalness is becoming a global priority as an evaluation of the restoration process and extent of degraded forests.However,there has been an irreconcilable contradiction between the complexity and applicability of the evaluation method,and between the accuracy and cost of the evaluation.Thus,there is an urgent need for a simple,accurate,economical,and universal method of naturalness evaluation.Primary Korean pine forests occur naturally in the Lesser Khingan and Changbai Mountains in Northeast China.Compared to forests of the southern subzone of Changbai Mountain and the northern subzone of the northern slope of Lesser Khingan Mountains,the primary Korean pine forest in the central subzone of the southern slope of Lesser Khingan Mountains is the most typical and representative of this type of forest,which is also known as typical Korean pine forest.This study is based on the southern slope of the Lesser Khingan Mountains,and the scale of study ranges from individual plants to typical sample plots,and extends to the forest landscape.C,R,and S scores for 1,344 trees,shrubs and herbaceous plants belonging to 134 species were calcultaed and applied to the evaluation of the CSR ecological strategies of vegetation(including tree layer,shrub layer and herb layer).At the stand scale,24 stands belonging to 8 forest types were selected,belonging to mesarch sere and xerosere respectively.The former successional stage encompasses Corylus mandshurica shrubland,Populus davidiana– Betula platyphylla forest with different stand ages,mixed broad leaved forest,and Tinus amurensis– Pinus koraiensis forest;the latter includes Quercus mongolica forest with different stand ages and Q.mongolica– P.koraiensis forest.At the landscape scale,Fenglin National Natural Reserve(FL),Liangshui National Natural Reserve(LS)and Lilin Forest Farm(LL)were selected,representing a gradient of forest landscape restoration,totalling 32,690 ha and 1,306 forest stands.In this study,changes in vegetation ecological strategies and processes during the restoration process of degraded forests were analyzed step by step through statistical tools such as linear mixed-effects models(LMM),redundancy analysis(RDA),principal component analysis(PCA)and structural equations models(SEM)to screen sensitive indicators.The final constructed naturalness evaluation method is simple but precise.This method is directly applicable to northeast China,it is easily extended to rest of China as well as other countries for which Forest Inventory data(FID)are accessible.The main findings of this study are as follows.(1)The increase in regional average annual temperature reduced the disturbance of low temperature stress and frost damage,which in turn led to a decrease in S and R strategies,and the increase in temperature helped to improve the competitive ability of plants,prompting an increase in C strategy.But the effect of temperature was negligible compared to the effects of regeneration type in trees and ontogenetic shifts in woody species.Resprouting trees and younger woody plants had higher R and lower S scores,probably as adaptation to disturbance.This should contribute to our understanding of plant adaptive strategy shifts caused by regional warming,and of ecological strategy shifts in tree communities(e.g.,Mongolian oak,and poplar-birch forests)during secondary succession.(2)CSR strategy,especially the CSR strategy of vegetation,has a clear trend of change during the restoration succession of degraded forest stands,and the S strategy of vegetation increases while C and R strategy decreases with the restoration of degraded forest stands,which can be used as corresponding evaluation indexes.However,plant diversity indicators and understory vegetation structure did not change significantly during the restoration succession.The CSR strategy of vegetation will have a large error in quantifying the restoration progress;it is also impossible to make a cross-sectional comparison under different stand conditions,and the S strategy of T.amurensis– P.koraiensis forest,which is also the top vegetation,is significantly lower than that of Q.mongolica– P.koraiensis forest.(3)An increase in the disturbance component(R scores)decreases naturalness while an increase in the habitat persistence component(S scores)increases naturalness.Incorporating CSR strategies for understory shrubs and herbs into the naturalness evaluation can improve accuracy.Nevertheless,the bias is still large,and this method is also costly,and thus intractable at landscape scales.Species richness is regulated by naturalness-mediated disturbance and is limited by the stress of resource environmental conditions.Soil nutrient effectiveness decreases and increases phosphorus(P)limitation with restoration of degraded forests.(4)Stand age(A),stand hectare storage(M),stand mean height(H),calculated climax index(CI,defined in this study)and succession age-group index(SAI,defined in this study)can well represent the accumulation process of natural attributes during stand restoration succession.We used PCA to obtain principal component scores to represent the naturalness of forest stands.This method is good for quantitative and accurate evaluation of near naturalness.However,a single reliance on any one of the total five indicators in this study may not be insufficient for the precisely estimatione the of forest naturalness.(5)This study constructed a measure ofn integrated naturalness through PCA to reduce dimensions and create a new variable as of naturalness based on indicators representing the processes of acquiring natural attributes.The approach is simple,precise,general,and costeffective using due to the use of FID,resolving the common contradictions between methodological complexity and methodological applicability,as well as between precision and cost in naturalness assessment.At the spatial scale,it could be achieved applied at zero cost to quantitatively assess forest restoration on the landscape and even on aat larger scales.,which While this method is basically directly applicable to northeast China,and it is easily extended to the wholerest of China as well as other countries that for which FID was are accessible.On the time scale,FID collected at different times could also be used to quantitatively assess the effects of forest management and protection.Combined This tool could be combined with Geographic Information Systems(GIS)of to map forests map,it could and visually demonstrate the progress and extent of forest restoration.Theoretically,this study refines and expands CSR theory.CSR strategy theory has not been systematically applied to sprouting in its 50-year-long history.Resprouting plant species are typically associated with disturbance.When disturbance is frequent,trade-offs in allocation to seedling vs.resprouting regeneration are predicted to shift to the latter,with resprouting species being more common in repeatedly disturbed environments.Therefore,resprouting regeneration also plays an important role in forest restoration,particularly during the initial and mid-successional stages;as succession proceeds,sprouts will gradually be replaced by seedestablished individuals.This study is the first to examine the CSR strategy values of conspecific sprouting regeneration and seedling regeneration populations within the framework of CSR theory to better understand plant adaptation strategies and ecological processes such as restoration succession,as confirmed by Pierce S.(who developed a global CSR strategy calculation formula in 2017).In addition,in the context of global warming,this difference between LS and FL in temperature is essentially the same as the climate warming seen in the region over the past 30 years.We found a small increase in mean annual temperature led to shifts in CSR strategy components for herbaceous species in this study.Practically,our method for evaluating naturalness is simple,precise,general,and costeffective.Due to the use of FID,it has a cost advantage over current methods that can be applied to large scale(landscape,regional)and accurate airborne laser scans to assess forest naturalness.It also solves the problem very well that the methods of using dead wood,tree rings,and epiphytic-epixylic cryptogams et al.for evaluating naturalness are reliable yet also involve a huge workload and high financial costs if conducting assessments at the landscape scale or greater.In the future,with the increase of detailed Sub-Compartment zoning and the application of advanced methods and tools for forest inventory work,the accuracy of this method can be further improved by appropriate screening indicators followed by PCA.