A high-resolution fossil pollen record from the sedimentary cores of Balikun Lake, northwestern China, combined with modern surface pollen data, is used to reconstruct the history of vegetation and climatic change sin...A high-resolution fossil pollen record from the sedimentary cores of Balikun Lake, northwestern China, combined with modern surface pollen data, is used to reconstruct the history of vegetation and climatic change since 16.7 cal. ka BP. Fossil pollen assem-blages and lithology indicate that the study area was dominated by desert. The desert had extremely arid climate and lower effec-tive moisture during 16.7–7.9 cal. ka BP, especially from 16.7 to 8.9 cal. ka BP when the lake maybe dried up. During 8.9–7.9 cal. ka BP, the environment gradually recovered in this area. It was then followed by the optimum period from 7.9 to 4.3 cal. Ka BP, when the effective moisture obviously increased. It was characterized by the typical desert-steppe/steppe vegetation and was ac-companied with several patch-birch woodlands around the lake. After that, a short but extremely arid climatic event occurred during 4.3–3.8 cal. ka BP, and the vegetation quickly changed from desert-steppe/steppe to desert. It was a relatively optimum period from 3.8 to 0.53 cal. ka BP showing typical desert-steppe/meadow-steppe landscape. Since 0.53 cal. ka BP, the climate has shown signs of deteriorating again. Furthermore, regional comparison shows that the characteristics of climatic and environmental evolution in this area were clearly different from East Asia monsoonal area during the last 16.7 cal. ka BP. It was characterized by the arid climate during the late-glacial and early Holocene, and relatively wet during the mid-late Holocene.展开更多
There are debates regarding whether a wet and warm climate or a dry and cold climate dominated Holocene fire activity in northern China on the millennial timescale,and when human activities overtook climate change as ...There are debates regarding whether a wet and warm climate or a dry and cold climate dominated Holocene fire activity in northern China on the millennial timescale,and when human activities overtook climate change as the dominant control on fire occurrence in the region.Here we present a high-resolution fire history for the past~15,500 years from a sediment core in Dali Lake,located in the foothills of the Greater Hinggan Mountains,one of the areas of highest fire risk in China.The results demonstrate that fire activity was rare during the last deglaciation(~15,500–11,700 yr BP),gradually increased at the beginning of the Holocene,and reached its highest level during~9000–5000 yr BP,after which there was a decreasing trend.However,after~2000 yr BP this decreasing trend ended,and the most prominent feature is a peak in fire activity during the Medieval Warm Period(MWP).Overall,fire activity corresponded well to changes in the East Asian summer monsoon(EASM)precipitation on the millennial timescale during~15,500–2000 yr BP,but this relationship changed after~2000 yr BP.We propose that fire activity in northern China on the millennial timescale during~15,500–2000 yr BP was dominated by the biofuels reserve under the control of the EASM precipitation.In contrast,with the intensification of human activities after~2000 yr BP,human activity caused a~62%–73%increase in fire activity,which altered the fire-climate relationship that had previously prevailed in northern China.Our results indicate that a wet-warm climate(increased EASM intensity),rather than a dry-cold climate,was the dominant control on fire activity in northern China during 15,500–2000 yr BP on the millennial timescale,but that human activities played an important role in fire occurrence after~2000 yr BP.展开更多
基金sup-ported by the National Natural Science Foundation of China (90502008, 40871006 and 40721061)the Program for New Century Excellent Talents in University
文摘A high-resolution fossil pollen record from the sedimentary cores of Balikun Lake, northwestern China, combined with modern surface pollen data, is used to reconstruct the history of vegetation and climatic change since 16.7 cal. ka BP. Fossil pollen assem-blages and lithology indicate that the study area was dominated by desert. The desert had extremely arid climate and lower effec-tive moisture during 16.7–7.9 cal. ka BP, especially from 16.7 to 8.9 cal. ka BP when the lake maybe dried up. During 8.9–7.9 cal. ka BP, the environment gradually recovered in this area. It was then followed by the optimum period from 7.9 to 4.3 cal. Ka BP, when the effective moisture obviously increased. It was characterized by the typical desert-steppe/steppe vegetation and was ac-companied with several patch-birch woodlands around the lake. After that, a short but extremely arid climatic event occurred during 4.3–3.8 cal. ka BP, and the vegetation quickly changed from desert-steppe/steppe to desert. It was a relatively optimum period from 3.8 to 0.53 cal. ka BP showing typical desert-steppe/meadow-steppe landscape. Since 0.53 cal. ka BP, the climate has shown signs of deteriorating again. Furthermore, regional comparison shows that the characteristics of climatic and environmental evolution in this area were clearly different from East Asia monsoonal area during the last 16.7 cal. ka BP. It was characterized by the arid climate during the late-glacial and early Holocene, and relatively wet during the mid-late Holocene.
基金National Natural Science Foundation of China,No.41790421。
文摘There are debates regarding whether a wet and warm climate or a dry and cold climate dominated Holocene fire activity in northern China on the millennial timescale,and when human activities overtook climate change as the dominant control on fire occurrence in the region.Here we present a high-resolution fire history for the past~15,500 years from a sediment core in Dali Lake,located in the foothills of the Greater Hinggan Mountains,one of the areas of highest fire risk in China.The results demonstrate that fire activity was rare during the last deglaciation(~15,500–11,700 yr BP),gradually increased at the beginning of the Holocene,and reached its highest level during~9000–5000 yr BP,after which there was a decreasing trend.However,after~2000 yr BP this decreasing trend ended,and the most prominent feature is a peak in fire activity during the Medieval Warm Period(MWP).Overall,fire activity corresponded well to changes in the East Asian summer monsoon(EASM)precipitation on the millennial timescale during~15,500–2000 yr BP,but this relationship changed after~2000 yr BP.We propose that fire activity in northern China on the millennial timescale during~15,500–2000 yr BP was dominated by the biofuels reserve under the control of the EASM precipitation.In contrast,with the intensification of human activities after~2000 yr BP,human activity caused a~62%–73%increase in fire activity,which altered the fire-climate relationship that had previously prevailed in northern China.Our results indicate that a wet-warm climate(increased EASM intensity),rather than a dry-cold climate,was the dominant control on fire activity in northern China during 15,500–2000 yr BP on the millennial timescale,but that human activities played an important role in fire occurrence after~2000 yr BP.
