Study On Vegetation At Different Development Stages Of Erosion Ditch In Yuanmou Dry-Hot Valley

Located in the Jinsha River basin,the Yuanmou dry-hot valley is a unique ecological region in southwestern China.Unlike the northeast black soil region,the Loess Plateau region and the southern red soil region,the Yuanmou dry-hot valley has been the main research object of scientific research workers.The erosion gully is widely developed,the ecological environment is fragile,and the soil erosion problem is serious,because the evaporation is much larger than the rainfall,the vegetation is sparse,and the special climatic conditions.In this paper,the developmental stage of erosion gully is taken as the starting point and the foothold of the study.By comparing the stability of the development of the erosion gully and analyzing the species composition,vegetation coverage,dominant species and diversity of the plant communities in the Yuanmou dry-hot valley.The characteristics of the plant community at the development stage were analyzed in depth to reveal the relationship between the development stage of the erosion gully and the plant community.The main findings are as follows:(1)By analyzing and comparing the research methods of predecessors in other regions,drawing on the research experience,based on the cluster analysis of the results of erosion gully length,combined with the investigation of vegetation coverage in the field,the development stage of the erosion gully of Yuanmou dry-hot valley is proposed.The unique division method divides the erosion gully into development gully,semi-stable gully and stable gully.In this study,a total of 135 erosion gullyes were investigated,mainly semi-stable gully,followed by stable gully and development gully.From the long point of view of the gully gully,the eroded gully is dominated by medium-sized eroded gully,the small eroded gully is the second,the large eroded gully is the least,and the sum of the small eroded gully and the medium-sized eroded gully(the gully length <40m)accounts for 85.92% of the total number of eroded gully.In terms of the width-to-length ratio and the width-to-depth ratio of the eroded gully,the width-to-length ratio and the width-to-depth ratio of the stable gully are larger than those of the development gully and the semi-stable gully.(2)A total of 71 species of plants were recorded through the investigation of plant communities in Yuanmou Dry-hot Valley.The plant community structure has obvious stage characteristics,mainly based on shrub community and herb community.The distribution range and number of arbors are limited.Most of single family,multi-genera and multi-species are dominant in the plant community structure,accounting for 68.66% of the overall situation.In terms of plant dominant species,the current plant community structure is roughly defined as the structure of the arbor-shrub-grass community of the eucalyptus urophylla,dodonaea viscosa,heteropogon contortus.In terms of plant species diversity,Shannon-Weiner index,Simpson index and Gleason index are all arbor layer <shrub layer <herb layer,Margalef index is shrub layer <herb layer < arbor layer,and Pielou index is herb layer < shrub layer < arbor layer.(3)By analyzing the characteristics of plant communities at different developmental stages of eroded gully,in terms of plant community composition,with the increase of stability of eroded gully,the coverage of shrub layer vegetation continued to increase,and the coverage of herb layer vegetation continued to increase first and then decrease,the average number of individuals in the plant community showed an increasing trend,while the average number of species generally showed a trend of increasing first and then stabilizing.In the dominant species of plant species,the dominant species in each stage of the arbor layer are the same,which is eucalyptus urophylla and mainly distributed in semi-stable gully,with less stable gully and development gully.The dominant species in each stage of shrub layer are dodonaea viscosa and leucaena glauca,and the important value of the dodonaea viscosa is greater than that of leucaena glauca;the dominant species in the herbaceous layer is heteropogon contortus,and the development stages of different eroded gullies are different common species.In terms of species diversity of plant communities,with the increase of development stability of erosion gully,the Ma index showed an increasing trend.The H' index,D index and Gl index showed a trend of increasing first and then decreasing,and the E index showed a decrease,but the law of change is not obvious.(4)Through correlation analysis,regression analysis,principal component analysis and cluster analysis on the development stage of eroded gully and the plant community parameters.The plant community parameters include number of plants,number of species,diversity index,etc.And calculate the multivariate linearity regression equation of the development stage of eroded gully and plant community parameters.By comparing several analytical methods,although the obtained plant community parameters are slightly different,the effects of plants on the stability of the erosion gully are determined.The results of the analysis are usually significantly or significantly positively correlated with the number of plants N and H' index.With the increase of the number of individual plant communities,the development stage of erosion gully has become more and more stable.With the increase of shrub H' index,the stability of the development stage of erosion gully will also increase.