生态保护工程和气候变化对长江源区植被变化的影响量化
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摘要
分析长江源区生态保护工程和气候变化对植被变化的影响程度,对于长江源区生态工程的生态效益评估,以及区域植被适应性生态管理政策的制定具有重要意义。因此,本文基于1982-2015年的归一化植被指数数据(Normalized Difference Vegetation Index, NDVI)和气象数据,分析长江源区植被NDVI的时空变化规律,构建预测植被NDVI对气候因子响应的人工神经网络模型,在此基础上,在年和季节尺度上量化气候变化和生态保护工程对长江源区植被变化的影响程度。结果表明:①在长江源区气候条件变化和生态保护工程影响下,长江源区植被退化得到遏制,植被生长呈好转趋势;②海拔相对较低的通天河附近植被NDVI增加幅度较大,高海拔的沱沱河和当曲流域的植被NDVI增加幅度相对较小;③长江源区植被NDVI对气候因子响应存在1～2月的滞后性。构建的人工神经网络模型的拟合优度参数人工神经网模型具有较高的预测精度,可以用来模拟植被NDVI对气候因子的响应;④年尺度的植被NDVI增加受到生态保护工程的影响程度(58.5%)大于气候变化的影响程度(41.5%)。生长季生态保护工程对NDVI的影响程度(63.3%)大于气候变化对NDVI的影响程度(36.7%),而非生长季气候变化是影响长江源区植被生长的关键要素(52.8%)。研究结果有助于为长江源区植被生态系统恢复、管理和利用战略的科学制定提供决策依据。
Quantitative research on the effects of ecological conservation projects and climate variations on vegetation changes is vital to the ecological benefit evaluation of ecological conservation projects, and has important implications for sustainable ecological rehabilitation management strategies in the source region of the Yangtze River. Based on the normalized difference vegetation index(NDVI) data and meteorological data during 1982-2015, this paper examines the temporal and spatial variations of NDVI; constructs back propagation artificial neural network(BPANN) model to simulate the responses of NDVI to climate factors; and quantifies the effects of ecological conservation projects and climate variations on vegetation changes at the annual and seasonal scales in the source region of the Yangtze River. The results indicate that:(1) Because of the effects of ecological conservation projects and climate variations, vegetation degradation curbed in the source region of the Yangtze River.(2) NDVI increased greatly near the Tongtian River located at relatively low altitudes. Minor increases in NDVI were observed near the Tuotuo and Dangqu rivers located at relatively high altitudes.(3)A time lag(about 1-2 months) existed between NDVI and major climate factors in the source region of the Yangtze River. The goodness of fit of the BPANN model shows that the simulation accuracy is relatively high. The model can be used to simulate the responses of NDVI to climate variations.(4) Ecological conservation projects exerted a slightly greater impact on NDVI changes than they did on climate variations at the yearly time scale(58.5%and 41.5%, respectively). During growing season, ecological conservation projects also exerted a slightly greater impact on NDVI changes than they did on climate variations(63.3% and36.7%, respectively). During non-growth season, climate variations are the key factor affecting vegetation growth in the source region of the Yangtze River(52.8%). The research results provide a basis for scientific decision-making about the vegetation ecosystem rehabilitation,management and utilization strategies in the source region of the Yangtze River.
Quantitative research on the effects of ecological conservation projects and climate variations on vegetation changes is vital to the ecological benefit evaluation of ecological conservation projects, and has important implications for sustainable ecological rehabilitation management strategies in the source region of the Yangtze River. Based on the normalized difference vegetation index(NDVI) data and meteorological data during 1982-2015, this paper examines the temporal and spatial variations of NDVI; constructs back propagation artificial neural network(BPANN) model to simulate the responses of NDVI to climate factors; and quantifies the effects of ecological conservation projects and climate variations on vegetation changes at the annual and seasonal scales in the source region of the Yangtze River. The results indicate that:(1) Because of the effects of ecological conservation projects and climate variations, vegetation degradation curbed in the source region of the Yangtze River.(2) NDVI increased greatly near the Tongtian River located at relatively low altitudes. Minor increases in NDVI were observed near the Tuotuo and Dangqu rivers located at relatively high altitudes.(3)A time lag(about 1-2 months) existed between NDVI and major climate factors in the source region of the Yangtze River. The goodness of fit of the BPANN model shows that the simulation accuracy is relatively high. The model can be used to simulate the responses of NDVI to climate variations.(4) Ecological conservation projects exerted a slightly greater impact on NDVI changes than they did on climate variations at the yearly time scale(58.5%and 41.5%, respectively). During growing season, ecological conservation projects also exerted a slightly greater impact on NDVI changes than they did on climate variations(63.3% and36.7%, respectively). During non-growth season, climate variations are the key factor affecting vegetation growth in the source region of the Yangtze River(52.8%). The research results provide a basis for scientific decision-making about the vegetation ecosystem rehabilitation,management and utilization strategies in the source region of the Yangtze River.
引文
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[7]Du Jizeng,Wang Genxu,Li Yuanshou.Rate and causes of degradation of alpine grassland in the source region of the Yangtze and Yellow rivers during the last 45 years.Acta Prataculturae Sinica,2015,24(6):5-15.[杜际增,王根绪,李元寿.近45年长江黄河源区高寒草地退化特征及成因分析.草业学报,2015,24(6):5-15.]
[8]Yang Guishan,Xu Xibao,Li Pingxing.Research on the construction of green ecological corridors in the Yangtze River Economic Belt.Progress in Geography,2015,34(11):1356-1367.[杨桂山,徐昔保,李平星.长江经济带绿色生态廊道建设研究.地理科学进展,2015,34(11):1356-1367.]
[9]Shao Quanqin,Fan Jiangwen,Liu Jiyuan,et al.Target-based assessment on effects of first-stage ecological conservation and restoration project in Three-river source region,China and policy recommendations.Bulletin of Chinese Academy of Sciences,2017,32(1):35-44.[邵全琴,樊江文,刘纪远,等.基于目标的三江源生态保护和建设一期工程生态成效评估及政策建议.中国科学院院刊,2017,32(1):35-44.]
[10]Chen Ting,Liang Sihai,Qian Kaizhu,et al.Regularity and cause of vegetation coverage changes in the headwaters of the Changjiang River over the last 22 years.Earth Science Frontiers,2008,15(6):323-331.[陈婷,梁四海,钱开铸,等.近22年长江源区植被覆盖变化规律与成因.地学前缘,2008,15(6):323-331.]
[11]Yao Yubi,Yang Jinhu,Wang Runyuan,et al.Responses of net primary productivity of natural vegetation to climatic change over source regions of Yangtze River in 1959-2008.Journal of Glaciology and Geocryology,2011,33(6):1286-1293.[姚玉璧,杨金虎,王润元,等.1959-2008长江源被净初级生产力对气候变化的响应.冰川冻土,2011,33(6):1286-1293.]
[12]Liu Lulu,Cao Wei,Shao Quanqin.Change of ecological condition in the headwater of the Yangtze River before and after the implementation of the ecological conservation and construction project.Journal of Geo-information Science,18(8):1069-1076.[刘璐璐,曹巍,邵全琴.三江源生态工程实施前后长江源区宏观生态状况变化分析.地球信息科学学报,2016,18(8):1069-1076.]
[13]Li Huixia,Liu Guohua,Fu Bojie.Response of vegetation to climate change and human activity based on NDVI in the Three-River Headwaters region.Acta Ecologica Sinica,2011,31(19):5495-5504.[李辉霞,刘国华,傅伯杰.基于NDVI的三江源地区植被生长对气候变化和人类活动的响应研究.生态学报,2011,31(19):5495-5504.]
[14]Liu Guangsheng,Wang Genxu,Sun Xiangyang,et al.The response of soil moisture in swamp meadow in the source regions of the Yangtze River to artificially warming.Journal of Glaciology and Geocryology,2015,37(3):668-675.[刘光生,王根绪,孙向阳,等.长江源区沼泽草甸多年冻土活动层土壤水分对模拟增温的响应.冰川冻土,2015,37(3):668-675.]
[15]Cai H Y,Yang X H,Xu X L.Human-induced grassland degradation/restoration in the Central Tibetan Plateau:The effects of ecological protection and restoration projects.Ecological Engineering,2015,83:112-119.
[16]Julien Y,Sobrino J A.The Yearly Land Cover Dynamics(YLCD)method:An analysis of global vegetation from NDVIand LST parameters.Remote Sensing of Environment,2009,113(2):329-334.
[17]Zhang G L,Zhang Y J,Dong J W,et al.Green-up dates in the Tibetan Plateau have continuously advanced from 1982 to2011.Proceedings of the National Academy of Sciences of the United States of America,2013,110(11):4309-4314.
[18]Wang K C;Liang S L.An improved method for estimating global evapotranspiration based on satellite determination of surface net radiation,vegetation index,temperature,and soil moisture.Journal of Hydrometeorology,2008,9:712-727.
[19]Qi Wei,Zhang Yili,Gao Jungang,et al.Climate change on southern slope of Mt.Qomolangma region in Nepal from1971 to 2009.Acta Geographica Sinica,2013,68(1):82-94.[祁威,张镱锂,高俊刚,等.1971-2009年珠穆朗玛峰地区尼泊尔境内气候变化.地理学报,2013,68(1):82-94.]
[20]Gao Ge,Xu Chongyu.Characteristics of water surplus and deficit change in 10 major river basins in China during 1961-2010.Acta Geographica Sinica,2015,70(3):380-391.[高歌,许崇育.1961-2010年中国十大流域水分盈亏量时空变化特征.地理学报,2015,70(3):380-391.]
[21]Bai Jianjun,Bai Jiangtao,Wang Lei.Spatio-temporal change of vegetation NDVI and its relations with regional climate in Northern Shaanxi Province in 2000-2010.Scientia Geographica Sinica,2013,34(7):882-888.[白建军,白江涛,王磊.2000-2010年陕北地区植被NDVI时空变化及其与区域气候的关系.地理科学,2013,34(7):882-888.]
[22]van Hoek M,Jia L,Zhou J,et al.Early drought detection by spectral analysis of satellite time series of precipitation and normalized difference vegetation index(NDVI).Remote Sensing,2016,8(5):422.
[23]Stepchenko A,Chizhov J.NDVI short-term forecasting using recurrent neural networks.Proceedings of the 10th International Scientific and Practical Conference:Volume III,2015,180:185.
[24]Huang S Z,Ming B,Huang Q,et al.A case study on a combination NDVI forecasting model based on the entropy weight method.Water Resources Management,2017:1-15.
[25]Wang X Y,Yi S H,Wu Q B,et al.The role of permafrost and soil water in distribution of alpine grassland and its NDVIdynamics on the Qinghai-Tibetan Plateau.Global and Planetary Change,2016,147:40-53.
[26]Chen Jin.Water cycle mechanism in the source region of Yangtze River.Journal of Yangtze River Scientific Research Institute,2013,30(4):1-5.[陈进.长江源区水循环机理探讨.长江科学院院报,2013,30(4):1-5.]
[27]Moriasi D N,Arnold J G,Van Liew M W,et al.Model evaluation guidelines for systematic quantification of accuracy in watershed simulations.Transactions of the ASABE,2007,50(3):885-900.
[28]Bao Z X,Zhang J Y,Wang G Q,et al.Attribution for decreasing streamflow of the Haihe River Basin,northern China:climate variability or human activities?Journal of Hydrology,2012,460/461:117-129.
[29]Wang W G,Shao Q X,Yang T,et al.Quantitative assessment of the impact of climate variability and human activities on runoff changes:A case study in four catchments of the Haihe River Basin,China.Hydrological Processces,2013,27(8):1158-1174.
[2]Tietjen B,Schlaepfer D R,Bradford J B,et al.Climate change-induced vegetation shifts lead to more ecological droughts despite projected rainfall increases in many global temperate drylands.Global Change Biology,2017,23(7):2743-2754.
[3]Chen B X,Zhang X Z,Tao J,et al.The impact of climate change and anthropogenic activities on alpine grassland over the Qinghai-Tibet Plateau.Agricultural and Forest Meteorology,2014,189:11-18.
[4]Sun Qingling,Li Baolin,Li Fei,et al.Review on the estimation of net primary productivity of vegetation in the ThreeRiver Headwater Region,China.Acta Geographica Sinica,2016,71(9):1596-1612.[孙庆龄,李宝林,李飞,等.三江源植被净初级生产力估算研究进展.地理学报,2016,71(9):1596-1612.]
[5]Jiang LL,Jiapaer G,Bao A,et al.Vegetation dynamics and responses to climate change and human activities in Central Asia.Science of the Total Environment,2017,599:967-980.
[6]Zhang Yili,Li Lanhui,Ding Mingjun,et al.Greening of the Tibetan Plateau and its drivers since 2000.Chinese Journal of Nature,2017,39(3):173-178.[张镱锂,李兰晖,丁明军,等.新世纪以来青藏高原绿度变化及动因.自然杂志,2017,39(3):173-178.]
[7]Du Jizeng,Wang Genxu,Li Yuanshou.Rate and causes of degradation of alpine grassland in the source region of the Yangtze and Yellow rivers during the last 45 years.Acta Prataculturae Sinica,2015,24(6):5-15.[杜际增,王根绪,李元寿.近45年长江黄河源区高寒草地退化特征及成因分析.草业学报,2015,24(6):5-15.]
[8]Yang Guishan,Xu Xibao,Li Pingxing.Research on the construction of green ecological corridors in the Yangtze River Economic Belt.Progress in Geography,2015,34(11):1356-1367.[杨桂山,徐昔保,李平星.长江经济带绿色生态廊道建设研究.地理科学进展,2015,34(11):1356-1367.]
[9]Shao Quanqin,Fan Jiangwen,Liu Jiyuan,et al.Target-based assessment on effects of first-stage ecological conservation and restoration project in Three-river source region,China and policy recommendations.Bulletin of Chinese Academy of Sciences,2017,32(1):35-44.[邵全琴,樊江文,刘纪远,等.基于目标的三江源生态保护和建设一期工程生态成效评估及政策建议.中国科学院院刊,2017,32(1):35-44.]
[10]Chen Ting,Liang Sihai,Qian Kaizhu,et al.Regularity and cause of vegetation coverage changes in the headwaters of the Changjiang River over the last 22 years.Earth Science Frontiers,2008,15(6):323-331.[陈婷,梁四海,钱开铸,等.近22年长江源区植被覆盖变化规律与成因.地学前缘,2008,15(6):323-331.]
[11]Yao Yubi,Yang Jinhu,Wang Runyuan,et al.Responses of net primary productivity of natural vegetation to climatic change over source regions of Yangtze River in 1959-2008.Journal of Glaciology and Geocryology,2011,33(6):1286-1293.[姚玉璧,杨金虎,王润元,等.1959-2008长江源被净初级生产力对气候变化的响应.冰川冻土,2011,33(6):1286-1293.]
[12]Liu Lulu,Cao Wei,Shao Quanqin.Change of ecological condition in the headwater of the Yangtze River before and after the implementation of the ecological conservation and construction project.Journal of Geo-information Science,18(8):1069-1076.[刘璐璐,曹巍,邵全琴.三江源生态工程实施前后长江源区宏观生态状况变化分析.地球信息科学学报,2016,18(8):1069-1076.]
[13]Li Huixia,Liu Guohua,Fu Bojie.Response of vegetation to climate change and human activity based on NDVI in the Three-River Headwaters region.Acta Ecologica Sinica,2011,31(19):5495-5504.[李辉霞,刘国华,傅伯杰.基于NDVI的三江源地区植被生长对气候变化和人类活动的响应研究.生态学报,2011,31(19):5495-5504.]
[14]Liu Guangsheng,Wang Genxu,Sun Xiangyang,et al.The response of soil moisture in swamp meadow in the source regions of the Yangtze River to artificially warming.Journal of Glaciology and Geocryology,2015,37(3):668-675.[刘光生,王根绪,孙向阳,等.长江源区沼泽草甸多年冻土活动层土壤水分对模拟增温的响应.冰川冻土,2015,37(3):668-675.]
[15]Cai H Y,Yang X H,Xu X L.Human-induced grassland degradation/restoration in the Central Tibetan Plateau:The effects of ecological protection and restoration projects.Ecological Engineering,2015,83:112-119.
[16]Julien Y,Sobrino J A.The Yearly Land Cover Dynamics(YLCD)method:An analysis of global vegetation from NDVIand LST parameters.Remote Sensing of Environment,2009,113(2):329-334.
[17]Zhang G L,Zhang Y J,Dong J W,et al.Green-up dates in the Tibetan Plateau have continuously advanced from 1982 to2011.Proceedings of the National Academy of Sciences of the United States of America,2013,110(11):4309-4314.
[18]Wang K C;Liang S L.An improved method for estimating global evapotranspiration based on satellite determination of surface net radiation,vegetation index,temperature,and soil moisture.Journal of Hydrometeorology,2008,9:712-727.
[19]Qi Wei,Zhang Yili,Gao Jungang,et al.Climate change on southern slope of Mt.Qomolangma region in Nepal from1971 to 2009.Acta Geographica Sinica,2013,68(1):82-94.[祁威,张镱锂,高俊刚,等.1971-2009年珠穆朗玛峰地区尼泊尔境内气候变化.地理学报,2013,68(1):82-94.]
[20]Gao Ge,Xu Chongyu.Characteristics of water surplus and deficit change in 10 major river basins in China during 1961-2010.Acta Geographica Sinica,2015,70(3):380-391.[高歌,许崇育.1961-2010年中国十大流域水分盈亏量时空变化特征.地理学报,2015,70(3):380-391.]
[21]Bai Jianjun,Bai Jiangtao,Wang Lei.Spatio-temporal change of vegetation NDVI and its relations with regional climate in Northern Shaanxi Province in 2000-2010.Scientia Geographica Sinica,2013,34(7):882-888.[白建军,白江涛,王磊.2000-2010年陕北地区植被NDVI时空变化及其与区域气候的关系.地理科学,2013,34(7):882-888.]
[22]van Hoek M,Jia L,Zhou J,et al.Early drought detection by spectral analysis of satellite time series of precipitation and normalized difference vegetation index(NDVI).Remote Sensing,2016,8(5):422.
[23]Stepchenko A,Chizhov J.NDVI short-term forecasting using recurrent neural networks.Proceedings of the 10th International Scientific and Practical Conference:Volume III,2015,180:185.
[24]Huang S Z,Ming B,Huang Q,et al.A case study on a combination NDVI forecasting model based on the entropy weight method.Water Resources Management,2017:1-15.
[25]Wang X Y,Yi S H,Wu Q B,et al.The role of permafrost and soil water in distribution of alpine grassland and its NDVIdynamics on the Qinghai-Tibetan Plateau.Global and Planetary Change,2016,147:40-53.
[26]Chen Jin.Water cycle mechanism in the source region of Yangtze River.Journal of Yangtze River Scientific Research Institute,2013,30(4):1-5.[陈进.长江源区水循环机理探讨.长江科学院院报,2013,30(4):1-5.]
[27]Moriasi D N,Arnold J G,Van Liew M W,et al.Model evaluation guidelines for systematic quantification of accuracy in watershed simulations.Transactions of the ASABE,2007,50(3):885-900.
[28]Bao Z X,Zhang J Y,Wang G Q,et al.Attribution for decreasing streamflow of the Haihe River Basin,northern China:climate variability or human activities?Journal of Hydrology,2012,460/461:117-129.
[29]Wang W G,Shao Q X,Yang T,et al.Quantitative assessment of the impact of climate variability and human activities on runoff changes:A case study in four catchments of the Haihe River Basin,China.Hydrological Processces,2013,27(8):1158-1174.
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