Effects Of Structural Characteristics Of Typical Artificial Forest Stands On The Diversity Of Understory Plants In Qinghai

The protection and restoration of natural forests is a large and complex social project implemented in China.Therefore,the rational development and research of natural forest resources has gradually become a hot spot of social concern.As the undergrowth vegetation layer with the most species diversity in forest communities,it has a negligible effect on the stability of forest ecosystems.In this paper,the two forest types of Qinghai spruce pure forest and mixed forest were studied.Through the analysis of the structural factors of forest stands,the research on plant diversity and biomass status under the forest,aiming to find out the stand structure and the understory plants.On the basis of this analysis,based on the analysis,based on the structural factors of forests that significantly affect the diversity and biomass of understory plants,the rationalization of forest stands to improve the diversity and biomass of understory plants was proposed.Structural adjustment measures.The main contents and conclusions of the study are:(1)Analysis of structural characteristics of standDiameter structure::The growth rate of young trees in pure forest is slow,the growth space is insufficient,and it faces the problem of forest stand degradation.In the mixed forest,the number of trees of the same species will decrease with the increase of the diameter of the breast,and the distribution of trees will be more uniform,which is conducive to the growth and development of the community and is beneficial to the health of the stand.Tree height structure:pure forest is mainly mature forest,mixed forest is mainly sapling and different types of trees show a certain balance in height.Compared with pure forests,the number of trees in high-order(especially small and medium-order high-order)mixed forests increased significantly,and the distribution of trees was more uniform,which was beneficial to the development of communities.Leaf area index:The average leaf area index of pure forest plots was significantly larger than that of mixed forest plots.The difference in structure between pure forest and mixed forest had no significant effect on leaf area index,but the size of leaf area index of different forest types.Have a certain impact.Stand volume and canopy density:pure forest volume is greater than mixed forest,and the difference in structure between pure forest and mixed forest has significant impact on stock volume,and the effect on canopy density is not significant,but mixed forest is different.The stand structure has a significant impact on the canopy closureOpenness:Mixed forests are much larger than pure forests.Within the unit area,more than 80%of the forests in the pure forest are seriously lacking in growth space.The mixed forests provide more adequate growth space for trees,and their needs for space and resources are basically metSize differentiation degree:The size differentiation degree of forest trees in mixed forests is generally closer to the moderate state than pure forests,and the performance in stand structure stability is better than pure forest.(2)Analysis of plant diversity and biomass under forestImportant values of the species:the number of plant species in pure forests is less,and there are more mixed forests.The dominant species of pure forests are wild strawberry Fragaria vesca,and the dominant species of mixed forests are Poa annua L.or wild strawberry Fragaria.Vesca,from the whole experimental area,Poa annua L.and wild strawberry Fragaria vesca have an absolute advantage in the understory herb layer.The sum of the important values is between 40 and 70,and the structure of the undergrowth herb community.The formation has a great impact.Plant diversity and biomass:The plant diversity index and evenness index of pure forests are slightly larger than that of mixed forests,and different types of mixed forests correspond to different diversity indices,and the range varies greatly.The biomass of plant under pure forest is less than that of mixed forest,and the growth space of undergrowth herb is insufficient and the growth condition is poor.(3)Relationship between stand structure and plant diversity and biomass under forestAmong the structural factors of the stand,the degree of mixedness and the average DBH,average tree height,and forest separation openness were significantly correlated,and the correlation coefficients were-0.949,-0.927 and 0.812.The correlation coefficient between the size ratio and the density of the stand was-0.85,which reached a significant correlation level;the correlation coefficient between the canopy density and the stand density was 0.961,and the correlation coefficient between the average height of the stand and the average chest was 0.877.Significant level.Biomass is closely related to the species richness index,with a correlation coefficient of 0.899,which is a significant correlation level.The diversity index is also significantly correlated with the uniformity index based on it.The significant factors affecting the species diversity of the understory herb layer are the size ratio,the average height and the canopy density.The correlation coefficient between size ratio and species richness S was 0.872,which reached a significant correlation level.The correlation coefficient between average tree height and richness was 0.804,and the correlation coefficient between canopy density and diversity H was 0.812,which all reached significant correlation level.(4)Forest structure adjustment measuresBy targeting YB2,the YB1 stand was adjusted.After selective cutting and replanting,the average tree height,mixed proportion and size differentiation of the stand structure were improved,and the stand structure was ideal.