Ecological Function Zoning Based On Ecosystem Health Assessment

A healthy ecosystem is an important guarantee for the sustainable development of society,economy and nature,and is considered to be the ideal goal of environmental management.However,rapid economic development and unreasonable human activities have greatly changed the structure and function of ecosystems,causing great negative impacts on ecosystem health(EH)and seriously threatening the survival and development of human beings.Therefore,the accurate assessment of EH is important for understanding the state of ecosystems as well as regional ecosystem management.Ecological function zoning(EFZ)brings new guidelines and ideas for coordinating ecosystem protection with economic and social development.EFZ based on EH assessment not only takes into consideration more ecological information and ecosystem background characteristics,but also focuses more on ecosystem integrity,which makes the zoning assessment framework more complete and helps to comprehensively grasp the regional ecological status and provides theoretical basis for comprehensive spatial management of highland ecosystems.In this paper,we quantitatively assessed the multi-scale EH of the Qinghai Tibet Plateau(QTP)from 2000 to 2018 at the raster,township,county and basin scales based on multi-source data and the Vigor-Organization-Resilience-Service(VORS)model,and then analyzed the spatial clustering characteristics of EH using spatial autocorrelation.We identified the direct and indirect effects of influencing factors on EH by using path analysis.Finally,a dual evaluation index system was constructed based on the EH evaluation index and the ecosystem sensitivity index,and the self-organizing feature mapping network(SOFM)was used for spatial clustering.The optimal number of clusters was determined and the ecological function zones on the QTP were delineated by combining small patches and fine-tuning smoothing.The main conclusions are as follows:(1)From 2000 to 2018,the mean values of ecosystem vigor,ecosystem organization,ecosystem resilience and ecosystem services at different scales were low,medium,high and medium,respectively.Spatially,ecosystem vigor showed a spatial distribution pattern of“high in the southeast and low in the northwest”.The high values of ecosystem organization were mainly located in eastern Qinghai Province and central and eastern Tibet,and low values were mainly distributed in the northwestern part of the QTP.The high values of ecosystem resilience were mainly in the eastern part of Qinghai Province and most parts of the Tibet,and the low values were in the northwestern part of Qinghai Province.The high values of ecosystem services were mainly located in southern Tibet,while the low values were mainly in central and western Qinghai Province,and parts of western Tibet.(2)From 2000 to 2018,the mean value of EH on the QTP at different scales was mostly at “relatively healthy” and “ordinary” levels,and showed an increasing trend at the raster,township,county and basin scales.At the same time,the mean value of EH at the township,county and basin scales was higher than that at the raster scale.In terms of the proportion of EH at four scale,the EH in most areas of the QTP was mostly at the “unhealthy”,“relatively unhealthy”,and “ordinary” levels during the 19 years.In terms of spatial distribution,the EH on the QTP varied among the four scales during the 19 years,but in general,the areas with poor EH were mainly in the northwestern part of Qinghai Province and most of the central and western parts of Tibet,while the areas with good EH were mainly in the eastern part of Qinghai Province and the southeastern part of Tibet,especially in the southern Tibetan region,where EH was the best.(3)From 2000 to 2018,the global Moran index of EH on the QTP at four scales was positive,indicating that there was a significant positive global spatial autocorrelation of EH at four scales,and there was a decreasing trend in the global Moran index,indicating a decrease in the spatial clustering of EH at four scales.The univariate local spatial autocorrelation results indicated that “low-low spatial match” and “high-high spatial match” were the main types of spatial match for EH at the four scales during the 19-year period.In terms of spatial distribution patterns,the spatial clustering characteristics of EH on the QTP were similar at all four scales during the 19-year period,with the “low-low spatial match” mainly in the northwestern part of Qinghai Province and Tibet,while the “high-high spatial match” was mainly in the eastern part of Qinghai Province and the eastern and southeastern parts of Tibet.(4)Among the influencing factors,the proportion of grassland area(Grass)and NDVI had the strongest and direct positive influence on EH on the QTP,followed by proportion of forestland area(Forest)and precipitation,while the distance from resident point(Resident)had a weak and direct negative influence on EH.Precipitation,temperature,and Forest had positive effects on EH mainly by promoting the increase of NDVI,and Resident showed the strongest negative and indirect effects,which were generated by suppressing the increase of NDVI.In terms of decision coefficients,NDVI,precipitation and Forest were the main decision variables for EH.(5)When the number of categories is 8,it corresponds to the optimal clustering results.The QTP was finally divided into five ecological function zones by merging small patches,which were: North-Alpine desert-Sand fixation zone(zone Ⅰ),West-Alpine desert steppe-Ecological fragile zone(zone Ⅱ),Southwest-Alpine steppe and meadow – Water sensitive zone(zone Ⅲ),East-Alpine meadow – Water yield zone(zone Ⅳ),and Southeast-Tropical seasonal rainforest-Ecosystem services provisioning zone(zone Ⅴ).The zoning results could reflect the ecological function characteristics of each zoning area,and were basically consistent with the ecological background condition of each zoning area.The results had certain practical significance for guiding the regional ecological management of the QTP.