Research On Regeneration Characteristics And Influencing Factors Of Quercus Forest In Hunan Province

Quercus natural forest is a typical forest type in Hunan Province.Natural secondary forest is the main type.Understanding the regeneration and succession mechanism of Quercus secondary forest is an important prerequisite for promoting the restoration of this forest.Based on the investigation data of 51 sample plots and used K-means cluster analysis to classify forest types and the species composition of different secondary oak forests in Hunan Province was analyzed.The regeneration characteristics of different Quercus secondary forests in Hunan Province were studied from four aspects:the status quo of saplings regeneration,diameter class structure,species diversity and spatial distribution pattern.We examined the correlation of the sapling regeneration index(density,average ground diameter,average height,and average crown width of saplings)with environmental and stand factors in different Quercu.s natural secondary forests in Hunan.This study aimed to provide a theoretical basis for the restoration and management of natural secondary forests of different Quercus species in Hunan Province.The main results are as follows:(1)Cluster analysis can be used to classify the natural secondary forests of Quercus species into five types,including Castanopsis eyrie-Castanea henryi mixed forest(CC),Fagus lucida-Cyclobalanopsis multinervis mixed forest'(FC),Lithocarpus glaber-Cinnamomum bodinieri mixed forest(LC),Quercus serrata-Castanopsis eyrie mixed forest(QC),and Cyclobalanopsis glauca 1mixed forest(CG).The species composition of tree layer and regeneration layer in natural secondary forest of different oak species was significantly different.There are 30 species belonging to 25 genera and 16 families in the tree layer in CC,and 14 species belonging to 11 genera and 6 families in the regeneration layer.The dominant tree species in the tree layer and regeneration layer are Castanopsis eyrei and Cinnamomum porrectum.There are 36 species belonging to 27 genera and 18 families in the tree layer and 22 species belonging to 15 genera and 12 families in the regeneration layer in FC.The dominant tree species in the tree layer and regeneration layer are Fagus lucida and Cyclobalanopsis multinervis.There are 6 families,8 genera and 10 species in the arbor layer,3 families,4 genera and 6 species in the regeneration layer in LC,and the dominant tree species in the arbor layer and regeneration layer are all Lithocarpus glaber(Thunb.)Nakai.There are 28 species belonging to 21 genera and 17 families in the arbor layer,18 species belonging to 16 genera and 10 families in the regeneration layer in QC,and the dominant species in the arbor layer and regeneration layer are Quercus serrata Thunb.and Symplocos caudata.There are 12 species belonging to 10 genera and 8 families in the tree layer and 6 species belonging to 5 genera and 5 families in the regeneration layer in CG.The dominant tree species in the tree layer and regeneration layer are Cyclobalanopsis glauca.(2)The dominant species and species richness of the regeneration forests of different types of Quercus secondary forests were significantly different.The sapling density in five different secondary forests of Quercus was<500 trees/hm2,and sapling regeneration was poor.The number of saplings of different Quercus secondary forests was significantly different,in the order of FC>LC>CG>QC>CC.The sapling growth status in different forests was significantly different,and in the sequence of CG>FC>QC>CC>LC.(3)There were significant differences in diameter class structure among different forest types and dominant Quercus species.The distribution types of diameter class structure of five dominant species of Quercus secondary forest are mainly close to inverted"J" distribution and close to normal distribution.Among them,the dominant species of Quercus which are close to the inverted "J" type distribution are:Castanopsis eyrei(CC),Cyclobalanopsis multinervis and Cyclobalanopsis glauca,which have great regeneration potential;the dominant species of Quercus which tend to normal distribution are:Castanea henryi,Cyclobalanopsis gracilis,Fagus lucida,Lithocarpus glaber(Thunb.)Nakaia,Quercus serrata Thunb.,Castanopsis eyrei(QC),among which,except Castanea henryi with small-diameter class and small-diameter class individuals,the regeneration potential is insufficient.The dominant tree species are close to the right-skewed normal distribution,which has a certain renewal potential.(4)There are differences in species diversity among different secondary forests of Quercus species,and there are differences in species diversity among different levels of secondary forests of Quercus species of the same forest type.The species richness of the tree layer was highest in FC,followed by CC,and the smallest in LC.The variation trend of Shannon-Wierner diversity index was consistent with Pielou evenness index.The mixed forest of FC was the largest,CC was the second,and CG was the smallest.The trend of Simpson dominance index is contrary to Shannon-Wierner diversity index and Pielou evenness index.The change trend of abundance and evenness of regeneration layer was the same,and FC was the largest,followed by QC,and CG was the smallest.The trend of Simpson dominance index is opposite to Margalef richness index and Shannon-Wierner diversity index.Pielou evenness index showed that QC was the largest,followed by FC and CC,and CG was the smallest.In the same forest classification type,the species diversity index among different levels showed the following rules:the richness and diversity of tree layer were generally higher than that of regeneration layer,while the evenness and dominance of regeneration layer were generally higher than that of tree layer.(5)The distribution patterns of tree layer and regeneration layer of different forest types are different.Distribution patterns of dominant species of Quercus in the arbor layer of five Quercus secondary forests were aggregated,and the difference mean ratio(C)was significantly tested by t test.However,the aggregation index(m*/m)of dominant species of Quercus in LC and CG was close to 1(1.074,1.062),while the negative binomial distribution index(K)was larger(13.434,16.079),and aggregation index(m*/m)was close to 1(1.074,1.062).The degree of set is low,which is close to random distribution.The distribution pattern of dominant Quercus species in regeneration layer of five Quercus secondary forests was as follows:Castanea henryi,Castanopsis eyrei(CC),Cyclobalanopsis multinervis,Castanopsis eyrei(QC)and Cyclobalanopsis glauca were clustered distribution,while Cyclobalanopsis gracilis,Fagus lucida,Lithocarpus glaber(Thunb.)and Quercus serrata Thunb.were random distribution.(6)The results of correlation analysis showed that the main influencing factors of saplings regeneration of different Quercus secondary forests were different,and the stand age had no significant effect on saplings regeneration of five Quercus secondary forests.The main factors affecting the regeneration of young trees in CC are the thickness of humus layer,shrub coverage and herbaceous coverage.The regeneration of young trees in FC was mainly affected by altitude,slope position,humus thickness,litter thickness,herbaceous coverage and canopy density.The regeneration of young trees was significantly correlated with slope position and soil thickness in the mixed forest of LC.The regeneration of young trees in QC is mainly affected by topographic factors(slope,slope position)and density factors(canopy density,tree density).Soil thickness,tree density and shrub coverage are the main factors affecting the regeneration of young trees in CG.