| Broad-leaved Korean pine forest,an important forest type in Northeast China,plays a crucial role in carbonsequestration,timber supply,biodiversity and soil and water conservation(Zang Runguo,1995).Due to historical reasons,broad-leaved Korean pine forest suffered from the interference of several high-intensity logging,resulting in large area of over cutting forest and secondary forest community(An Huijun,2003).Ecosystem problems includingpoor stability,decline in growth and degraded health have appeared in the broad-leaved Korean pine forest.Therefore it is necessary to carry out scientific and effective forest management research(Kang Xingang et al.,2008).With the help of six hectares of sample plots set by the research team of structural management in Jiaohe,Jilin Province,this study comparatively analyzed the survey data of 3 different periods,i.e.the initial period of sample plot setting,September2012(Time 1)and May 2018(Time2),and elaborated the impact of structural forest management on the status of broad-leaved Korean pine forest in Jiaohe,Jilin Province from the aspects of stand growth,competition,key structural characteristics,state evaluation and differences.The analysisprovides a theoretical basis for forest management in the future.The results are as follows:(1)Structured-Based Forest Management can effectively promote Korean pine forest stand growth.The results show that the stand growth was improved by removing the unhealthy competitive trees with no silvicultural value.The management measures reduced the natural loss,improved the growth of basal area,and the growth volume and rate of basal area was much closer to the near target stand.Although some trees were removed and the basal area decreased,the annual growth volume of the basal area in the first period was 0.2m~2higher than that of the control stand,with 0.49%increase of annual growth rate;in second period,the annual growth of the basal area was 0.12m~2higher than that of the control stand,and the annual growth rate increased by 0.45%.In the first period,the annual average stock volume of near target stand increased most significantly,and that of the management stands were lower,but significantly higher than that of the control stand.The annual growth rate of the management stand was 1.1m~3higher than that of the control stand,and the annual growth rate was higher by 0.53%.The annual stock volume of the control stand was smaller and the growth rate was slower.In the second period,the annual growth of the management stand was 0.5m~3more than that of the control stand,and growth rate was higher by 0.22%.The growth trend of the management stand has approached the target stand,and the gap is gradually narrowing.It can be seen that structure-based management can improve the Korean pine forest growth rate of stand area and stock volume thus can promote the growth of stand.(2)Structured-Based Forest Management can effectively improve the Korean pine forest competition.Through the analysis of BAL index and SCI competition index based on spatial structure parameters,it is found that:after management,BAL competition index decreases rapidly and remains at a low level,maintaining the same development trend as the near target forest stand;structured forest management releases forest competition pressure and controls the competition relationship among trees;SCI competition index also decreases significantly after management.The change of index value in each period of managed forest is small,and the development trend is stable.After a week of structured forest management measures,the competition among trees began to ease,and the stand was still in a good state of natural succession and stable growth.Structured forest management can quickly and effectively alleviate the competition among trees(3)Structured-Based Forest Management is conducive to maintaining the Korean pine forest climax community of natural forest and the basic feature that"random wood is the core of natural forest structure".The total yield of random trees was much higher than that of uniform trees and aggregated trees in different periods,accounting for more than 50%of the total yield in all sample plots,and the maximum yield was about 63%.The yield of uniform distribution and aggregated distribution accounted for 10-30%of the total yield respectively.The distribution of basal area proportion of neighbor types in different periods was relatively consistent,which was approximately normal distribution,and the variation of basal area proportion in different periods was not significant.It was found that the dominance of main tree species was enhanced by structur-based forest management to a certain extent and maintained at a high level.At the same time,the reasonable structure of diameter distribution curve of natural forest with inverted J shape was maintained.These analysis explains that structure-based forest management has a significant positive impact on the non-spatial structure of the stands.(4)Structured-Based Forest Management can effectively maintain the best proportion of structure in Korean pine forest.The bivariate distribution of the uniform angle index(W)-mingling degree(M)of structural parameters shows that structure-based forest management helps to maintaining the best structure in the stand in different periods,and the micro environment of the main cultivated objects and the overall spatial structure of the stand are optimized.Structure-based forest management can improve the micro environment of the individual tree and maintain the stability of the whole stand.Through the method of marked second-order characteristic,it can be seen that:the size differentiation of each stand is intensified,the diversity of the size of the trees is higher,the function of second-order characteristic indicating mingling degree of each stand changes little,and the state of the mixed tree species was good and remained in a stable state.The aggregation of trees was reduced,which is closer to the random development process.Through the coupling analysis of the diameter order and spatial structure parameters,it can be seen that the proportion of random distribution pattern was the largest,while the proportion of the small and medium-sized trees in the same distribution pattern is larger;with the increase of the tree diameter scale,the proportion of the size ratio of the trees decreases gradually;the proportion of the mixed good trees in different diameter grades is larger,while the same mixed grade forest is larger The majority of the trees are small and medium diameter trees,especially those with good mixed ones are the most obvious;the trees of different diameter grades overlap with the 3-4 neighbor trees,while trees of the same density are mostly medium and small-diameter trees.The coupling characteristics and trends of different periods are similar,mainly reflected in the increase of the proportion of the management stand with the body proportion,especially the small-diameter wood;the proportion of the trees with moderate density increases,especially the small-diameter wood;the mingling degree and the size ratio of different size trees do not change significantly.(5)Structure-Based Forest Management can make the status of managed stand closer to the target stand in Korean pine forest.The comprehensive evaluation method based on unit circle and the analysis of stand state difference showed that the broad-leaved Korean pine forest in different periods was a multi-layer forest with good growth and abundant different ages,and the diameter distribution was inverted J type,and the competition potential of top species in broad-leaved Korean pine forest in different periods was obviously thinning to be good.The overall difference between each stand and the near target stand was maintained at a low level,and the difference in comprehensive status was small.The difference value of the control stand increased slightly in the first period,but increased greatly in the second period,and the difference with the near target stand gradually increased.After the implementation of structur-based forest management,the differences of all managed stands decreased significantly except Stand C.The management stand maintained a small and stable upward trend in the first and second periods.Although the change trend of the control stand was consistent with that of the near target stand,the difference between the two was increasingly bigger;the state of management stand became closer to that of the near target stand rapidly,but the growth rate of slowed down in the last period.The forest should be managed periodically.In short,Structure-Based Forest Management can solve many problems in forest management,and quickly adjust and optimize the stand structure and maintain relative stability,which can effectively improve the stand state in Korean pine forest.It has been proven that Structure-Based Forest Management is a sicentific and reliable forest management method.However,due to the low intensity mangment at the initial stage,the four stands were only slightly managed.Therefore,in order to consolidate the management effects,it is better to formulate a reasonable management cycle and apply Structure-Based Forest Management measures.Ultimately the research aims to provide scientific theories and methods for secondary forest cultivation and management in northern China. |
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