Characteristics Of Wetland Plant Communities And Hydrological Response In Eastern NingXia Province

Wetlands as one of the three major ecosystems of the earth have a value that cannot be ignored,but with the social development of climate change,the trend of warming and drying in northwest China has increased,and water resources are in short supply,wetland resources are experiencing unprecedented challenges.As a major factor affecting wetland ecosystems,monitoring the growth state and its response to hydrological factors is a prerequisite for mastering wetland vegetation resources and clarifying the characteristics of wetland vegetation changes.This paper takes Haba Lake National Nature Reserve in eastern Ningxia as the study area and selects typical plant communities in the study area as the research objects.Firstly,we extracted the distribution area of each plant community from 1992 to 2021 by object-oriented classification method,and calculated the normalized vegetation index data of the study area for 30 years,and analyzed the hydrological response pattern between them and hydrological elements(precipitation and surface water area).The main findings of this paper are as follows:(1)The area of each plant community showed an increasing trend between 1992and 2021,with the lemon community increasing the most,from 9.91km2 in 2000 to240.05km~2in 2021,followed by the black sagebrush community,which increased by15.50km~2in the last 22 years,and the white spurge,hyacinth,and salt claw,which are naturally growing vegetation types in the study area,increased less,with the white spurge community increasing the The area of white spurge community increased the most,with an increase of 10.19km~2in 30 years.The results indicate that the study area is subject to high anthropogenic impacts,and the artificially conducted vegetation restoration has effectively improved the fragile ecosystem in the study area.(2)During 1992-2021,the mean annual precipitation reached 307.53 mm,and the maximum value was 400.04 mm in 2018.the more obvious mutation node was in2011,and the increasing trend was significant thereafter.The spatial distribution;the cumulative precipitation from January to June increases year by year,reaching 93.63mm per year,with the maximum value of 180.50 mm in 2002,and the MK mutation(3)test shows that two periods from 2001 to 2008 and 2011 to 2021 show an increasing trend,while the rest are decreasing.The annual precipitation and its consistency,still the most in the eastern region.The surface water area in the study area is small,and the spatial distribution of surface water appears to be less in the north than in the south,and there are no significant surface water bodies in the northern area in the last decade.(4)During 1992-2021,NDVI increased at a rate of 0.038/10a,with a 30-year NDVI mean of 0.26.2009 was the main point of NDVI change,and the trend of NDVI increase since then passed the 95%significance test.For the overall NDVI ranking of the study area,83.16%of the low and medium coverage areas,13.35%of the low coverage areas,3.45%of the medium coverage areas were concentrated in the eastern region,and only 0.04%of the medium and high coverage areas.(5)The correlation between NDVI and cumulative precipitation from January to June of the same period was the highest,reaching 0.71,showing a strong correlation.The correlation with annual precipitation in the previous year and surface water area in the same period was relatively low,with the lowest correlation with annual precipitation in the previous year at 0.35,indicating that plant communities were more influenced by precipitation in the early part of the year on growth status.In the study of the correlation between different months of the year,it was found that precipitation in May had a greater correlation with NDVI in the study area,implying the importance of precipitation in May and also reflecting the lag effect of precipitation.(6)In terms of spatial series,the area of NDVI in the study area was moderately correlated with the previous year’s annual precipitation by 4.10%and weakly correlated by 15.42%,and the area of moderately correlated with the accumulated precipitation from January to June in the same period by 7.08%and weakly correlated by 12.89%,neither of which showed strong correlation,and the overall correlation was mainly positive.In the spatial correlation analysis of May precipitation and April-June cumulative precipitation,the highest spatial correlation was found with April-June cumulative precipitation,reflecting the important influence of the continuity of precipitation on the development and growth of vegetation.The results(7)show that the magnitude of spatial series correlation is consistent with the duration of accumulated precipitation,but limited by the small area of the study area,the spatial distribution of precipitation does not vary significantly resulting in low significance of spatial correlation.