<div style="text-align:justify;"> With global warming and increased human activity, more and more ground surface areas have been affected, which leads to the creation of many problems. To understand th...<div style="text-align:justify;"> With global warming and increased human activity, more and more ground surface areas have been affected, which leads to the creation of many problems. To understand the ecological environment changes in a typical alpine region, information on landcovers changes in the study area from 2000 to 2020 was obtained by combining remote sensing, geographic information system, and traditional statistical analysis for the Sanjiangyuan National Nature Reserve on the Qinghai-Tibet Plateau, China. The results show that the changes of surface cover in Sanjiangyuan National Nature Reserve are relatively concentrated, mainly distributed in the sections of south, northwest, central, and northeast, with the area of the changed regions and the unchanged regions being 31,127.45 km<sup>2</sup> and 271,941.37 km<sup>2</sup>, respectively. The transformation between the various types of ground landcover is mainly characterized by a shift from other types to grassland and from grassland to bare land. And the regions of change are mostly concentrated between 3500 - 4600 m in elevation. </div>展开更多
Aims Vegetation dynamics are simultaneously regulated by climate change and anthropogenic activities.Since the 1980s,climate has been warming on the Tibetan Plateau(TP)at a rate higher than North Hemisphere average.An...Aims Vegetation dynamics are simultaneously regulated by climate change and anthropogenic activities.Since the 1980s,climate has been warming on the Tibetan Plateau(TP)at a rate higher than North Hemisphere average.Anthropogenic activities,including grazing,farming,and urbanization,are also influencing the alpine ecosystem on the TP.Especially,an ensemble of large engineering projects,such as power transported from west to east by State Grid,has been in operation on the TP.While studies disentangling effects of climate and anthropogenic activities interference are still lacking for the forest ecosystems on the TP.The overarching objectives of this study were to separate effects of natural climates and human interferences on forest ecosystem dynamics on the TP.Methods We compared vegetation activities of two typical natural reserves(Gongbu natural reserve,GNR,and Yarlung zangbo river grand canyon natural reserve,YNR)and their surroundings in southeastern Tibet(outside of the natural reserves,ONR)using long-term satel-lite normalized difference vegetation index(NDVI)dataset.Linear regression and partial correlation analyses were constructed for the relationship between vegetation activity and climates to evaluate the distinct climate effects on the two natural reserves.Important Findings The two natural reserves were established at different time,which were related to anthropogenic activities impact durations.The results showed that the annual mean NDVI fluctuated between 0.5 and 0.6 in the relatively longer reserved YNR,which was re-markably higher than those in other regions(with NDVI lower than 0.45).The vegetation vigor in the YNR showed neither a sig-nificant temporal trend nor significant relationship with climate.Nevertheless,vegetation vigor exhibited a significant increasing trend during the last three decades(0.012/decade)at the GNR.The inter-decadal analysis turned out positive relationships between vegetation vigor and annual temperature since late 1990s until early 2000s when the GNR was officially established.This study underlined the importance of considering human interference duration when assessing the relationships between vegetation dy-namics and climates.展开更多
文摘<div style="text-align:justify;"> With global warming and increased human activity, more and more ground surface areas have been affected, which leads to the creation of many problems. To understand the ecological environment changes in a typical alpine region, information on landcovers changes in the study area from 2000 to 2020 was obtained by combining remote sensing, geographic information system, and traditional statistical analysis for the Sanjiangyuan National Nature Reserve on the Qinghai-Tibet Plateau, China. The results show that the changes of surface cover in Sanjiangyuan National Nature Reserve are relatively concentrated, mainly distributed in the sections of south, northwest, central, and northeast, with the area of the changed regions and the unchanged regions being 31,127.45 km<sup>2</sup> and 271,941.37 km<sup>2</sup>, respectively. The transformation between the various types of ground landcover is mainly characterized by a shift from other types to grassland and from grassland to bare land. And the regions of change are mostly concentrated between 3500 - 4600 m in elevation. </div>
基金Science and Technology Project of State Grid Corporation of China(SGxzzzlwzhbGCJS1700095)National Key Research&Development Program of China(2018YFA0606101,2017YFA0604802)National Natural Science Foundation of China(41501103).
文摘Aims Vegetation dynamics are simultaneously regulated by climate change and anthropogenic activities.Since the 1980s,climate has been warming on the Tibetan Plateau(TP)at a rate higher than North Hemisphere average.Anthropogenic activities,including grazing,farming,and urbanization,are also influencing the alpine ecosystem on the TP.Especially,an ensemble of large engineering projects,such as power transported from west to east by State Grid,has been in operation on the TP.While studies disentangling effects of climate and anthropogenic activities interference are still lacking for the forest ecosystems on the TP.The overarching objectives of this study were to separate effects of natural climates and human interferences on forest ecosystem dynamics on the TP.Methods We compared vegetation activities of two typical natural reserves(Gongbu natural reserve,GNR,and Yarlung zangbo river grand canyon natural reserve,YNR)and their surroundings in southeastern Tibet(outside of the natural reserves,ONR)using long-term satel-lite normalized difference vegetation index(NDVI)dataset.Linear regression and partial correlation analyses were constructed for the relationship between vegetation activity and climates to evaluate the distinct climate effects on the two natural reserves.Important Findings The two natural reserves were established at different time,which were related to anthropogenic activities impact durations.The results showed that the annual mean NDVI fluctuated between 0.5 and 0.6 in the relatively longer reserved YNR,which was re-markably higher than those in other regions(with NDVI lower than 0.45).The vegetation vigor in the YNR showed neither a sig-nificant temporal trend nor significant relationship with climate.Nevertheless,vegetation vigor exhibited a significant increasing trend during the last three decades(0.012/decade)at the GNR.The inter-decadal analysis turned out positive relationships between vegetation vigor and annual temperature since late 1990s until early 2000s when the GNR was officially established.This study underlined the importance of considering human interference duration when assessing the relationships between vegetation dy-namics and climates.
