Analysis of ecosystem degradation and recovery using precipitation use efficiency and NDVI in the headwater catchment of the Yellow River basin

Autor: 舒俭民 Shu Jianmin, 杜加强 Du Jiaqiang, 张林波 Zhang Linbo
Rok vydání: 2012
Předmět:
Zdroj: Acta Ecologica Sinica. 32:3404-3413
ISSN: 1000-0933
Popis: The accurate identification of areas of ecosystem degradation and an objective evaluation of the effects of ecological restoration projects is necessary for ecological management and planning at the landscape scale.Ecological degradation and ecological restoration are dynamic equilibrium processes,while degradation must be considered relative to the pristine state of the ecosystem,and need to be analyzed from a time series perspective.Satellite remote sensing is widely used in ecological monitoring and assessment,as it provides extensive coverage,good spatial and temporal continuity and a long time-series dataset.This paper proposes a method for the identification of areas of ecosystem degradation and ecosystem recovery using long time-series satellite remote sensing and precipitation data,which are integrated into trend analyses of the precipitation use efficiency(PUE) and a normalized difference vegetation index(NDVI).The PUE is calculated as the ratio of cumulative NDVI to precipitation.Significantly reduced PUE and NDVI values indicate that ecological degradation is occurring,while increasing PUE and NDVI values indicate ecological recovery.This method was applied to the headwater catchment of the Yellow River basin in China using Advanced Very High Resolution Radiometer NDVI data from 1982 to 2006 and meteorological data from the same time period.The annual PUE value was calculated using the cumulative NDVI and precipitation in the growing season for each pixel.A comparative analysis of the trends in PUE and NDVI was undertaken to detect areas of ecosystem degradation and restoration.The results show that:(i) The average PUE and NDVI values across the region increased slightly,and the area undergoing ecosystem rehabilitation during 1982—2006 comprised more than 80% of the study area.(ii) The degraded area,with significantly negative trends in the PUE and NDVI values,mainly occurred in the region surrounding Maduo County,Zaling and Eling lakes and Longyangxia Reservoir.Significant ecosystem recovery was found in southeast part of the study area,where strong positive trends were identified in the PUE and NDVI values.(iii) The areas with ecosystem degradation and restoration detected in this study were consistent with the current grassland degradation situation in the headwater catchment of the Yellow River basin,indicating that this method is reliable and could be applied to the evaluation of the regional ecosystem.(iv) The PUE value is partially dependent on changes in the precipitation,so false ecosystem degradation or ecosystem recovery trends may be identified caused by rapid increases and decreases,respectively,in the precipitation rate.For example,a decrease PUE in Xining City was partly caused by increased precipitation.Evaluating the trends in both PUE and NDVI may avoid the errors caused by using PUE as the only factor when evaluating ecosystem degradation and recovery.This method is simple,feasible,usable and practical,and the required data are easily accessible.This method allows ecosystem changes to be studied at the landscape scale,and can be used for a preliminary investigation prior to a large scale survey of ecological degradation or restoration.The results of this study suggest that evaluating the temporal change in PUE and NDVI may provide a useful large-scale indicator of landscape degradation or recovery at decadal time intervals.We recommend the broad-scale application of this method,using temporal trends in the PUE and NDVI.This study provides a scientific basis for the planning and regulation of ecological reconstruction in the headwater catchment of the Yellow River basin,China.
Databáze: OpenAIRE
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