Study On The Structure,Interspecific Association And Niche Of Plant Community On The Ridges Of The Loess Plateau

The Loess Plateau is one of the regions with serious soil erosion in China,and its gravity erosion is also an important source of soil erosion,especially in the loess hilly and gully regions and plateau areas,where ridges and steep slopes are dense,gravity erosion is serious,and erosion intensity is large.At present,prevention and control of ridges and collapse of steep slopes has become an important measure to control soil erosion.The thesis takes the ridge plant community in the Loess Area of Yongshou County,Changwu County and Xifeng District as the research object.Through systematic field surveys,the composition structure,community type,species diversity,dominant interspecies relationship and niche characteristics of ridge vegetation communities were analyzed.Clarified the differences of species diversity in different community types and resistance to gravity erosion environment,evaluated the adaptability of dominant species to the environment,and provided theoretical support and technical basis for gravity erosion control and gulley fixation and tablelandand protection.The main results are as follows:(1)A total of 115 plants appeared in the survey area,belonging to 36 genera and 95 genera,of which the Asteraceae,Leguminosae,Gramineae and Rosaceae accounted for 57.39% of the plant species;the flora is mainly temperate,and it is also related to tropical flora;the plant growth type in this area can be divided into 5 categories,mainly perennial herbs and annual herbs;the life type is divided into 5 categories,mainly ground bud plants and annual herbs;according to the ability of plants to adapt to water,they can be divided into four types.The number of xerophytes is relatively large,accounting for 37.39% of the total number of plants;nine shrub dominant species and 25 herbaceous dominant species were screened by species importance value,which can be used as the first-selected plant material for the measures of gravity erosion and gully protection.(2)Plant communities in the area can be divided into 16 associations,including 5 grass clusters and 11 shrub grass clusters,among which the Ass.Artemisia giraldii +Carex lanceolata are the most widely distributed,followed by the Ass.Ziziphus jujuba var.spinosa-Artemisia giraldii and Ass.Ziziphus jujuba var.spinosa-Agropyron cristatum+Artemisia capillaris,the dominant species in the association are mostly xerophytes,with well-developed root systems and strong soil-fixing capabilities,which play an important role in stabilizing the ridge and preventing gravity erosion.(3)The species diversity varies in different regions.The maximum value of the species diversity index,evenness index and richness index of the shrub layer appears in Yongshou County,and the minimum value appears in Changwu County;the maximum value of the species diversity index,evenness index and richness index of the herb layer is in the Xifeng District,and the minimum value The value is in Changwu County.The species diversity of different community types is quite different.The maximum values of Simpson index,Shannon-Wiener index and Margalef index are Ass.Ziziphus jujuba var.spinosa-Poa sphondylodes +Artemisia giraldii(the association XV)and Ass.Artemisia giraldii +Carex lanceolata(the association I).The maximum value of Pielou index is Ass.Ziziphus jujuba var.spinosa+Rubus corchorifolius-Artemisia giraldii+Stipa capillata(the association XVI).The species diversity of these community types is relatively high.(4)Through the analysis of the interspecific associations of the dominant in shrub and grass,it can be seen that the overall connectivity between dominant shrub species and between dominant herb species shows a significant positive correlation.The dominant species pairs of shrubs and the dominant species pairs of herbs are more positively correlated than negatively correlated,which shows the competition between species is not strong.The number of species with significant correlations is relatively small,and most species pairs are relatively low correlated.The relationship between species is relatively loose.(5)According to the analysis of the niche of the dominant shrub and grass species,among the dominant shrub species,the Ziziphus jujuba var.spinosa and Lespedeza daurica have large niche breadth,wide distribution,strong adaptability,relatively consistent utilization of resources and environment,and relatively larger niche overlap;among the dominant herbaceous species,the larger niche breadths are Artemisia giraldii,Heteropappus altaicus,Artemisia capillaris,and Carex lanceolata et al.However,most shrub dominant species and herbaceous dominant species have small niche overlap values.