Response of Riparian Vegetation to the Change of Groundwater Level at Middle and Lower Reaches of the Shiyang River

Located in a zone of 36°29′-39°27′ N and 101°41′-104°16′ E,the Shiyang River Basin is one of the inland river basins where the environment is strongly disturbed by human activities,and its degeneration is resulted in.It is an important reference to study the relationship between water conditions of riverbank and riparian vegetation for revealing ecological management and regenerating entironment in the Shiyang River Basin.In September and October 2009,the vegetation,soil and water conditions were investigated in the riparian region,the study area was divided into two types,i.e.the regions with and without runoff,and then the data were analyzed.In addition,the groundwater level was observed every two months during the period of 2009-2010.The analyzed results show that there was a positive correlation between groundwater level and distance away from the river channel.The types and richness of plant communities of the riparian vegetation in the Shiyang River Basin were reduced with the increase of distance away from the river channel.In the riparian region with runoff,the change of groundwater level responded to the runoff volume at a belt of 130 m in width.The belt width of riparian vegetation,decided by distribution of the types of plant communities,vegetation coverage and groundwater level at riparian zone,was about 500 m at the middle and lower reaches of the Shiyang River.At a zone 500 m in width away from the river channel,the types and richness of plant communities of the riparian vegetation were more than that in a zone further than 500 m,soil moisture content was higher,total salt content was lower,and the vegetation coverage was higher.At the riparian region without runoff,there was a positive correlation between the depth of groundwater level and the distance away from the river channel.The riparian plant species might be found in a zone 200 m in width away from the dried-up river channel.Although stream flow was cut off at the lower reaches,the river landforms were benefit to water storage and plant growth.Vegetation at the riparian region of the study area could be classified into 12 communities and 29 sub-communities in 5 vegetation types.The riparian plant communities responded to the groundwater level.