| Water replenishment from the South-North Water Transfer Central Project has an important role in ecosystem restoration and environmental improvement in the receiving area,and to a certain extent,leads to changes in land use/cover.Based on the In VEST model,the paper assesses the habitat quality and water yield of the regional ecosystem service function over a long time series to reveal the evolutionary characteristics of the regional ecosystem service function,taking Hebi city as an example.The project research is important for the sustainable performance of regional ecosystem services,maintaining ecological security and promoting sustainable economic and social development.The thesis aims to evaluate and dynamically analyse the regional habitat quality and water yield,based on the remote sensing image data of five representative years,namely 2000,2005,2010,2015 and 2020,and uses the object-oriented classification method to obtain the spatial distribution data of land cover.The spatial and temporal patterns of land cover in the study area over the past 20 years were analysed using Markov transfer matrix and landscape pattern index models and methods;an In VEST-based regional habitat quality and water yield assessment model was constructed,and its parameters were optimised and validated with relevant literature and monitoring data to assess the dynamic changes of habitat quality and water yield in the study area;a comprehensive zoning of the study area was carried out by overlaying various ecosystem service functions;and the influence of relevant environmental context factors on the regional habitat quality state The study also explored the influence of environmental contextual factors on the evolution of regional habitat quality.The main findings are as follows.(1)Through the study of the spatial and temporal changes in land cover in the study area,the proportion of urban land in the study area increased from 12.47%in2000 to 27.65%in 2020,with an increase of 15.18%over the 20-year period,which is the largest increase;the proportion of arable land decreased from 42.24%in 2000 to25.84%in 2020,with a decrease of 16.4%during the study period The area share of forest land,grassland and water area showed an overall increasing trend during the study period,with 21.26%,18.43%and 5.12%respectively by the end of the study period.(2)The land cover situation in the study area changed continuously between 2000and 2020,with the most drastic change being the conversion between arable land and construction land,and the highest retention rate of forest land,while with the opening of the South-North Water Diversion Central Project,the conversion of various types of land to watershed increased significantly in the last cycle.The overall landscape in the study area shows a stronger trend towards fragmentation and heterogeneity,with the maximum patch number index decreasing to 63.27;the edge density index increasing to 66.93;the sprawl index decreasing to 59.53;and the Shannon diversity index increasing to 0.96.(3)From the results of the habitat degradation assessment of the study area from2000 to 2020,it can be seen that the degree of habitat degradation in the study area has shown a trend of first increasing and then fluctuating down since 2000,and the overall habitat quality degradation index is relatively small.In addition,the spatial distribution of the medium and high values of habitat degradation is mainly around the areas around artificial surfaces such as residential,transportation and industrial land,where human activities are more frequent.The Habitat Quality Index in the study area from 2000 to2020 shows a trend of rapid decline followed by a slow rebound,and the study area is currently in a critical period of stopping the decline and rebounding in habitat quality.The overall structure of the Habitat Quality Index is characterised by a fluctuating decline in the proportion of high-grade habitat quality and a slow increase in the proportion of low-grade habitat quality.(4)The water yield in the study area from 2000 to 2020 first declined and then increased,with the highest value of 702.30 mm in the northwestern mountainous region in 2000 and the lowest value of 465.73 mm in 2015 near the Panshui Reservoir.The land use types in the areas where water yield rose against the trend during this time period were mostly artificial land surfaces,while water yield showed an overall upward trend during the period 2010-2020.This suggests that water yield is closely related to natural conditions such as precipitation and evaporation of vegetation in the area,with areas with high precipitation and low evaporation of vegetation usually yielding the highest water,which is consistent with the principles of water yield calculation.(5)A comprehensive zoning of ecosystem service functions in the study area was conducted,and the study area was classified into three classes:excellent,good and average.The results show that the area covered by the excellent grade has been expanding since 2005,and by 2020 the area covered by the excellent grade of ecosystem service function in the study area will reach 1251.57km~2,while the area covered by the general grade has been increasing year by year with the influence of various factors such as urbanisation and strong human activities.By 2020,the general grade area will cover an area of 187.29km~2.(6)The correlation analysis by SPSS software showed that climate change and landscape pattern index were the correlated factors causing changes in habitat quality and water production in the study area.The correlation between habitat quality and landscape pattern index was greater than that between habitat quality and climate change,and the strongest correlation with the landscape pattern index was edge density;the correlation between water production and climate change was greater than that between water production and landscape pattern index,and the strongest correlation with the meteorological factor was precipitation. |
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