Studies On Management Diagnosis And Effectiveness Of Thinning Based On Crop Tree Management For Over-logged Spruce-fir Forest

Over-logged spruce-fir forest derive from virgin spruce-fir forest underwent several heavy harvest cutting which is distinguished both from virgin forest and natural secondary forest.It has more special formation mechanism and growth process.There is a large area of over-logged forests in the northeast region of China,which is facing a situation of low forest quality and weak ecological service functions.What are the urgent problems for the protect and restore of over-logged spruce-fir forest and the improvement of quality and function of spruce-fir forest are studying the status quo of forest stand structure features and exploring a reasonable scientific forest management on over-logged spruce-fir.The study area is located at the Jingoulin forest fram of Wangqing forestry bureau,Jilin province,and the study object is over-logged spruce-fir forest.Based on 12 fixed sample plots(100m*100m),using the forest management of related theory and technology and combining the forest ecology principle,on the basis of ground sample plot survey and statistics,using the combination of quantitative and qualitative method,the forest stand structure comprehensive feature of over-logged spruce-fir forest were studied which include the stand spatial structure and non-spatial structure,distribution pattern and spatial association of trees,spatial heterogeneity of attribute variable of tree.In addition,four types of processing including traditional management(TM),crop tree releasing1(CTR1),crop tree releasing2(CTR2),and control treatment(CT)were implemented to compare and analyze the dynamic changes of over-logged forests before and after the thinning.The study has a certain theoretical and practical significance for for guiding vegetation restoration,optimizing forest structure,accelerating the forest's forward succession,and promoting forest ecological environment construction.The main results were as follows:(1)The species distribution of number and volume in group of sapling is extraordinary uneven,and the Abies nephrolepis occupy an absolute position.The diameter distribution of forest stands is divided into three parts: the middle DBH class from 14 cm to 34 cm shows inverted J-shape distribution and the small DBH class under 14 cm mainly show the left side mountain-liking curve,and the big DBH class above 34 cm show sharp discontinuous decline.Weibull function,Negative exponential function and Gamma function can better reflect the diameter distribution.According to the diameter distribution curve for tree species,Abies nephrolepis and Picea jezoensis show a growing trend;Pinus koraiensis and Tilia amurensis show a stable state;Larix olgensis,Betula costata,Betula platyphylla and Populus davidiana show a declining state.Abies nephrolepis,Lonicera japonica,Carex siderosticta is the dominant species in arbor layer,shrub layer and herb layer respectively.In contrast,the species diversity of the shrub and grass layers is richer than that of the arbor layer.The status of natural regeneration is badness,and tree species composition is not reasonable.(2)The spatial isolation degree is reasonable at different DBH class.With the increase of DBH class,the spatial isolation degree rise gradually or discontinuously.The spatial isolation degree of Abies nephrolepis is the lowest and of Taxus chinensis is the highest.With the increase of DBH class,the average mixing degree of Betula platyphylla,Larix olgensis and Acer mono increases gradually,and of Tilia amurensis,Pinus koraiensis and Populus davidiana ramains stable relatively,while the average mixing degree of other species is complex.With the increase of DBH class,the competitive pressure of forest trees decrease gradually,but the difference of variation trend is complex in different tree species.The performances of Abies nephrolepis,Picea jezoensis,Populus davidiana,Acer mono,Tilia amurensis and Betula costata in sapling group and large DBH class group are the oppssite,but fraxinus mandshurica and Ulmus propinqua remain stable.Generally,The distribution of forest stand is aggregative.The frequency of uniform angle index of each tree species showed a normal distribution curve that was approximately left-handed.The frequency of random distribution was more than 50%.Among them,Betula platyphylla was the highest and Tilia amurensis was the lowest.(3)The over-logged spruce-fir forest has the characteristics of multiple layers,uneven-aged,and mixed characteristics of the original spruce-fir forest.Therefore,the potential problems hidden in over-logged spruce-fir forest are easily overlooked.However,the over-logged forests of spruce fir still have a huge gap compared with the original forests of spruce fir in terms of tree species composition,stand volume,and other aspects.According to the urgency analysis of forest management,it can be further known that over-logged spruce-fir forest deviates from a healthy and steady state in terms of natural regeneration,tree distribution,dominance of purpose trees,proportion of healthy trees,degree of trees crowdedness and intensity of purpose trees.The urgency index of forest stand management in the study area exceeds 0.5 and it indicates that the forest stand management is very urgent.(4)With the increase of scale,the pattern change from aggregation to random distribution.The large and middle DBH class trees present random distribution on all scale,and saplings and small DBH class trees present aggregation distribution on medium and small scale.In contrast,the range and intensity of aggregation distribution in saplings is the largest.The distribution pattern of pioneer tree is the most complex,but the associated and climax tree species have obvious pattern.Both Pinus koraiensis and Picea jezoensis have similar spatial pattern,and Abies nephrolepis presents larger aggregation range and intensity.The spatial association change from a condition mainly with positive and unrelated relation to another condition mainly with unrelated and negative relation when the saplings were tied to small,middle and large DBH class respectively.There is a positive correlation between small DBH class and middle DBH class on a very small scale within 2m,but the spatial association between large DBH class and small or middle DBH class is unrelated and negatively correlated.The negative spatial association between climax species and pioneer or associated species is significant,but it is not significant between associated species and pioneer species.The spatial association between Abies nephrolepis and Pinus koraiensis is similar to the spatial association between Abies nephrolepis and Picea jezoensis,but the latter have more significant negative relation on large and middle scale.The spatial association between Pinus koraiensis and Picea jezoensis present unrelated and negative relation mainly.(5)Index model,spherical model and Gaussian model can effectively reflect the variation characteristics of tree property variables.Each tree property variable has strong spatial autocorrelation.Among them,tree height has the highest degree of spatial autocorrelation and east-west crown has the largest range of spatial autocorrelation.The range and degree of spatial heterogeneity and spatial autocorrelation of each property variable tree in east-west,south-north,northeast-southwest and northwest-southeast direction have obvious differences.The tree property,by contrast,has stronger spatial dependence at east-west direction,while there is a complex variation in the northwest-southeast or northeast-southwest direction in the small-scale range.Spatial correlations of tree attribute variables are all moderate,but the variation ranges of spatial correlation of that are different.There are not necessarily correlations about tree attribute variables in spatial structure which have correlations in quantity.(6)The forests in the plots treated with CTR1 and CTR2 exhibited a large amount of growth and a relatively high growth rate,especially in terms of the growth promotion effect on the crop tree.CTR1 has a significant effect on promoting the growth of the whole crop tree and the crop tree of Picea jezoensis.The effect of CTR2 on the growth of the crop tree of Abies nephrolepis and the crop tree of Pinus koraiensis is significant.The dominant effect of TM is mainly reflected in the growth of DBH,growth rate and volume growth rate of non-target trees of stand level and Picea jezoensis,as well as the volume growth rate of non-target trees of Abies nephrolepis and the DBH growth rate of non-target trees of Pinus koraiensis.In CT,the efficiency of trees grow is the lowest except the volume growth rate of Abies nephrolepis and Pinus koraiensis.(7)TM has obvious effect to promoting growth rate of stand basal area at stand level and growth rate of stand basal area and volume at small DBH class group.CTR2 has obvious effect to promoting growth rate of volume at sapling group.CTR1 and CTR2 has obvious effect to promoting growth increment of pioneer species and associated species in basal area and stand volume,and TM has obvious effect to promoting growth rate of pioneer species in basal area and stand volume.CTR1 and CTR2 significantly increased the proportion of volume of large DBH class.CTR1 further increase the species diversity of shrub layer and herb layer,and CT is the most unfavorable to the maintenance of biodiversity by contrast.TM and CTR1 increased the proportion of tree at high-strength mixed dominant tree and high-strength mixed random tree,and decreased the proportion of tree at random dominant tree.CTR2 increased the proportion of tree at high-strength mixed dominant tree also,but it decreased the proportion of tree at high-strength mixed random tree and random dominant tree.CT is the unique treatment which decreased the proportion of three kinds of optimal combination.CTR1 and CTR2 caused a great disparity in the number between dead wood and inside boundary timber.Diameter distribution of dead wood in CT is more dispersed.Under the various treatments,the forests tend to concentrate towards a few dominant tree species.The change rate of Abies nephrolepis under all treatments is positive,and the value under CTR1 treatment is the largest.