The Three-River Source Region is an important ecological security barrier in China.Revealing the spati-otemporal evolution characteristics of its landscape types and ecological risks is of great significance for promo...The Three-River Source Region is an important ecological security barrier in China.Revealing the spati-otemporal evolution characteristics of its landscape types and ecological risks is of great significance for promoting ecological restoration and landscape pattern optimization in the Three-River Source Region.Selecting the Three-River Source Region for a case study and applying the land-use data from four periods(the 1990,2000,2010,and 2020),we constructed a landscape ecological risk assessment model for the region based on the landscape pattern index.We then quantitatively assessed the ecological risks and determined the characteristics of their spa-tial-temporal evolution.The results showed that:(1)The overall landscape ecological risk in the Three-River Source Region tended to decrease from northwest to southeast,and the distribution of landscape ecological risk was closely related to the natural plateau zones and the changes in land cover.(2)From 1990 to 2020,the areas covered by grasslands,water bodies,croplands,and construction land in the Three-River Source Region increased,while the areas of woodlands and unused land decreased.The spatial-temporal changes in the ecological landscape risk were consistent with the characteristics of the changes in the landscape types.The areas categorized as highest,higher,medium,lower and lowest risk areas,while highest and higher risk areas decreased by 9.76%,medium risk areas increased by 1.03%,lower risk areas increased by 8.99%,and lowest risk areas decreased by 0.26%,respectively.(3)Overall,the Three-River Source Region was dominated by very low to medium ecological risk,the areas of which accounted for more than 70%of the entire study area.Overall ecological risks are decreasing,and there is positive spatial autocorrelation of landscape ecological risks in adjacent evaluation units.展开更多
The ＂Grain for Green Project＂ initiated by the governments since 1999 were the dominant contributors to the vegetation restoration in the agro-pastoral transitional zone of northern China. Climate change and human a...The ＂Grain for Green Project＂ initiated by the governments since 1999 were the dominant contributors to the vegetation restoration in the agro-pastoral transitional zone of northern China. Climate change and human activities are responsible for the improvement and degradation to a certain degree. In order to monitor the vegetation variations and clarify the causes of rehabilitation in the Shaanxi-Gansu-Ningxia Region, this paper, based on the MODIS-NDVI and climate data during the period of 2000-2009, analyzes the main charac- teristics, spatial-temporal distribution and reasons of vegetation restoration, using methods of linear regression, the Hurst Exponent, standard deviation and other methods. Results are shown as follows. （1） From 2000 to 2009, the NDVI of the study area was improved progres- sively, with a linear tendency being 0.032/10a, faster than the growth of the Three-North Shelter Forest Program （0.007/10a） from 1982 to 2006. （2） The vegetation restoration is characterized by two fast-growing periods, with an ＂S-shaped＂ increasing curve. （3） The largest proportion of the contribution to vegetation restoration was observed in the slightly improved area, followed by the moderate and the significantly improved area; the degraded area is distributed sporadically over southern part of Ningxia Hui Autonomous Region as well as eastern Dingbian of Shaanxi province, Huanxian and Zhengyuan of Gansu province. （4） Climate change and human activities are two driving forces in vegetation restoration; more- over anthropogenic factors such as ＂Grain for Green Project＂ were the main causes leading to an increasing trend of NDVI on local scale. However, its influencing mechanism remains to be further investigated. （5） The Hurst Exponent of NDVI time series shows that the vegetation restoration was sustainable. It is expected that improvement in vegetation cover will expand to the most parts of the region.展开更多
基金The National Natural Science Foundation of China (42171223)The National Social Science Foundation of China (19BJY205)+1 种基金The Department of Education Youth Science and Technology Talent Growth Fund of Guizhou ([2022]107)The Mountain Discipline Construction Project of Minzu Normal University of Xingyi (XKJS202332)。
文摘The Three-River Source Region is an important ecological security barrier in China.Revealing the spati-otemporal evolution characteristics of its landscape types and ecological risks is of great significance for promoting ecological restoration and landscape pattern optimization in the Three-River Source Region.Selecting the Three-River Source Region for a case study and applying the land-use data from four periods(the 1990,2000,2010,and 2020),we constructed a landscape ecological risk assessment model for the region based on the landscape pattern index.We then quantitatively assessed the ecological risks and determined the characteristics of their spa-tial-temporal evolution.The results showed that:(1)The overall landscape ecological risk in the Three-River Source Region tended to decrease from northwest to southeast,and the distribution of landscape ecological risk was closely related to the natural plateau zones and the changes in land cover.(2)From 1990 to 2020,the areas covered by grasslands,water bodies,croplands,and construction land in the Three-River Source Region increased,while the areas of woodlands and unused land decreased.The spatial-temporal changes in the ecological landscape risk were consistent with the characteristics of the changes in the landscape types.The areas categorized as highest,higher,medium,lower and lowest risk areas,while highest and higher risk areas decreased by 9.76%,medium risk areas increased by 1.03%,lower risk areas increased by 8.99%,and lowest risk areas decreased by 0.26%,respectively.(3)Overall,the Three-River Source Region was dominated by very low to medium ecological risk,the areas of which accounted for more than 70%of the entire study area.Overall ecological risks are decreasing,and there is positive spatial autocorrelation of landscape ecological risks in adjacent evaluation units.
基金National Natural Science Foundation of China, No.41171090 No.40871052
文摘The ＂Grain for Green Project＂ initiated by the governments since 1999 were the dominant contributors to the vegetation restoration in the agro-pastoral transitional zone of northern China. Climate change and human activities are responsible for the improvement and degradation to a certain degree. In order to monitor the vegetation variations and clarify the causes of rehabilitation in the Shaanxi-Gansu-Ningxia Region, this paper, based on the MODIS-NDVI and climate data during the period of 2000-2009, analyzes the main charac- teristics, spatial-temporal distribution and reasons of vegetation restoration, using methods of linear regression, the Hurst Exponent, standard deviation and other methods. Results are shown as follows. （1） From 2000 to 2009, the NDVI of the study area was improved progres- sively, with a linear tendency being 0.032/10a, faster than the growth of the Three-North Shelter Forest Program （0.007/10a） from 1982 to 2006. （2） The vegetation restoration is characterized by two fast-growing periods, with an ＂S-shaped＂ increasing curve. （3） The largest proportion of the contribution to vegetation restoration was observed in the slightly improved area, followed by the moderate and the significantly improved area; the degraded area is distributed sporadically over southern part of Ningxia Hui Autonomous Region as well as eastern Dingbian of Shaanxi province, Huanxian and Zhengyuan of Gansu province. （4） Climate change and human activities are two driving forces in vegetation restoration; more- over anthropogenic factors such as ＂Grain for Green Project＂ were the main causes leading to an increasing trend of NDVI on local scale. However, its influencing mechanism remains to be further investigated. （5） The Hurst Exponent of NDVI time series shows that the vegetation restoration was sustainable. It is expected that improvement in vegetation cover will expand to the most parts of the region.
