Effects Of Submerged Irrigation On Plant Communities And Soil Environment Of Desert Riparian Forest

In recent years,the economic and social disturbance of the Tarim River Basin has strengthened the natural ecosystem.Eco-water resources drop sharply.Due to the long-term lack of ecological water in desert river bank forests,Populus euphratica forests in some areas have deteriorated seriously and under forests.In order to repair the degraded desert riparian forest and prevent the further destruction of the desert riparian forest ecosystem,in 2016,the autonomous region decided to carry out a project to protect the water in the ecologically degraded area.This article mainly explores its water replenishment effect and selects the research area in the key P.euphratica irrigated areas in the lower reaches of the Yarkant River and the middle and upper reaches of the Tarim River.Through field investigation of vegetation and soil data,the effects of submerged irrigation on plant communities and soil environment are analyzed,and the plant communities and environmental factors Redundancy analysis was conducted to discuss the relationship between flooding irrigation,plant communities and their environment;the study provided basic data and theoretical basis for the development of monitoring of the ecological water replenishment effect in the key protected areas of desert riparian forests in river basins.The main conclusions are as follows:(1)The soil moisture content of the lower reaches of the Yarkant River and the upper and middle reaches of the Tarim River increased by 341% and 233.5%,respectively.As the distance from the river increased,the surface soil moisture content showed a decreasing trend.The internal groundwater level was reduced from 4-6m before irrigation to 1.7-2.7m after irrigation,and the groundwater depth in the upper and middle reaches of the Tarim River decreased from 4-4.5m to 1-4.5m;the soil salt content in the area after flooding in the lower reaches of the Yarkant River It increased by 37.5%,and with the increase of distance from the ecological gate,the salinity of the surface soil increased.After the flood in the upper and middle reaches of the Tarim River,the salt content of the surface soil decreased by 14.2%;and as the distance from the ecological gate increased,The salinity of surface soil has an increasing trend.The soil organic matter in the lower reaches of the Yarkant River and the upper and middle reaches of the Tarim River decreases slightly after flooding.As the distance from the ecological gate increases,the organic matter content in the surface soil increases.(2)The P.euphratica growth rate is highest after 3 years of flooding in the lower reaches of the Yarkant River,and the highest rate of P.euphratica growth after 2 years of flooding in the upper and middle reaches of the Tarim River.The height of P.euphratica branches decreased year by year.Among them,the height of P.euphratica branches in the lower reaches of the Yarkant River decreased by 78.5cm,which was 20.1% lower than that before flooding.It has dropped by 31.6%;the overall growth of P.euphratica is that the situation in the upper reaches of the Tarim River is better than in the middle reaches of the Tarim River and the lower reaches of the Yarkant River.The age structure of the population before flooding in the study area is similar to the spindle type and belongs to the "declining population".After 3 years of water replenishment,P.euphratica forests have an increasing trend at all age levels.The population structure of P.euphratica forests is relatively healthy,and the degree of poplar populations has increased.(3)Through flood irrigation,12 and 11 new plants were added to the lower reaches of the Yarkant River and the upper and middle reaches of the Tarim River,mainly plant seedlings,wet plants and annual herbs.The dominant species are P.euphratica,Tamarix and drought-tolerant perennial herbs after 450 m in the lower reaches of the Yarkant River.The dominant species are annual herbs or wet plants within 300 m of submerged irrigation.Herbs,within 300 m,are mainly P.euphratica,Tamarix spp.Seedlings,and one-year or perennial herbs that prefer wetness.Especially,P.euphratica seedlings and annual herbs disappear after 450 m.(4)From the perspective of environmental factors,the degree of flooding,river direction in the study area are the main factors affecting the distribution of plant communities.With the increase of groundwater depth,Margalef richness index,surface soil organic matter and surface soil total salt content have a significant increase trend;with the increase of latitude and longitude,Simpson diversity index,Shannon diversity index,Pielou uniformity index was a significant increase in the length of new branches;soil water content was negatively correlated with soil organic matter and soil total salt content,respectively.Plant community?,community ?,community ?,and community ? are mainly affected by the surface soil moisture content of 0-60m;plant community ?,plant community ?,plant community ?,plant community?,plant community X are affected by the depth of groundwater and total salt content of 0-60 cm And organic matter.