Understory Herb Diversity Of Artificial Forest In Jinta Sandy Land Relationship With Soil Properties

The northwest region is one of the most serious areas of land desertification in China.The terrain in the region is complex and diverse,the ecological environment is seriously damaged,and the wind and sand disasters are frequent.As an important measure for vegetation restoration of degraded land in Northwest China,the change of soil in the process of forest vegetation growth and development is an important factor affecting the succession of vegetation community.Therefore,it is of great significance to explore the relationship between understory herb diversity and soil properties in artificial forest for land desertification control,soil and water conservation,plant diversity improvement and wind and sand fixation in the region.In this paper,Populus euphratica,Tamarix chinensis,Elaeagnus angustifolia,Elaeagnus angustifolia-Tamarix chinensis and Populus euphratica-Tamarix chinensis plantations with 15 years of vegetation restoration were studied,and natural restoration forest was used as control.To study the diversity of herbaceous plants and the variation characteristics of vegetation in different forest lands;at the same time,the soil particle composition,p H,electrical conductivity,soil nutrients and soil C,N,P ecological stoichiometry characteristics of different soil depths(0～20,20～40,40～60cm)were analyzed to reveal the relationship between plant diversity and soil factors.The main conclusions are as follows:(1)Compared with the control sample site,the planted forest had a stimulating effect on the growth of understory plants.18 species of plants belonging to 6 families and 16 genera were found in the forest site,and the overall drought-tolerant vegetation such as Gramineae,Staphylinidae,Leguminosae and Asteraceae were dominant.The species richness and diversity indices in the understory of planted forests were significantly higher than those in naturally restored forests(P<0.05),with increases of 109%～213% and 10%～66%,respectively,compared to the control sample sites;and the Shannon-Wiener diversity index,Margalef richness index and Pielou evenness index in the different understories were generally as follows:Tamarisk The Shannon-Wiener diversity index,Margalef richness index and Pielou evenness index of different understories were: Tamarix chinensis forest>Elaeagnus angustifolia forest> Populus euphratica-Tamarix chinensis fores >Elaeagnus angustifolia-Tamarix chinensis forest>Populus euphratica forest>control site,indicating that the artificially planted poplar forest had the least growth promoting effect on the herbaceous layer of the understory compared with other forest sites.(2)In different plantations and control plots,the soil particle composition is mainly composed of fine sand content,and the content of coarse sand is the least.Among them,the fine sand content of the soil under the Elaeagnus angustifoliaTamarix chinensis forest and Populus euphratica-Tamarix chinensis forest is the largest,indicating that the two mixed forests have the best windbreak and sand fixation effect.The total nitrogen,total phosphorus and soil water content of the soil under the artificial forest were significantly increased(P<0.05),and the soil salinization improvement effect was better.Among them,Elaeagnus angustifoliaTamarix chinensis forest and Populus euphratica-Tamarix chinensis forest increased significantly in the surface layer(0～20 cm),increasing by 67%,21%,4% and 90%,42%,5%,respectively,and the p H values decreased by 15% and 18%,respectively.(3)The mean soil C:N values(6.54～10.04)in different plantation forests were below the national average(12.03),indicating that the soil N content in the understory of the study area was high,while the soil P content was relatively high,making the soil C:P and N:P significantly lower in all soil layers,indicating that the vegetation growth in the study area was mainly influenced by the limitation of N pigments.It was found that artificial poplar stands were most severely N-limited compared to other stands,and managers are recommended to supplement N content in later stages of stand management with more tendency to poplar stands.(4)Correlation and RDA analyses showed that the diversity of understory herbaceous plants in the study area was closely related to soil water content,p H,conductivity,total potassium,total phosphorus and organic carbon;and soil water content,p H,conductivity,total nitrogen and total potassium had a greater influence on plant growth distribution.Combined with PCA analysis,we found that soil water content,p H,total nitrogen,total phosphorus and conductivity were the main determinants in both components;comprehensive analysis concluded that soil water content,p H and conductivity were the soil factors that directly affected plant diversity in different plantation forests.In conclusion,it is suggested that managers should adopt the "mixed forest +herbaceous plant" model for desertification control in Jinta County in the future,which can not only effectively improve the local ecological environment,accelerate land desertification control and increase plant diversity,but also provide data reference for ecological control in similar places in the future.