Understanding the distribution,dispersal,and correlation of modern pollen with vegetation in mountainous regions is essential for establishing accurate modern analogs for fossil pollen records.This study,conducted in ...Understanding the distribution,dispersal,and correlation of modern pollen with vegetation in mountainous regions is essential for establishing accurate modern analogs for fossil pollen records.This study,conducted in Leigong Mountain on the YunnanGuizhou Plateau of southwestern China,involved the collection of 35 surface soil samples from diverse vegetation communities along an elevational gradient ranging from 1210 to 1875 meters.The results reveal a close correspondence between modern pollen assemblages and vegetation zones.Principal Component Analysis(PCA)results indicate that pollen assemblages can effectively distinguish between subtropical montane evergreen broad-leaved forest(SEBF)and subtropical montane deciduous broadleaved forest(SDBF).However,both SEBF and SDBF show significant overlap with subtropical montane evergreen-deciduous broad-leaved mixed forest(SEMF).Detrended Correspondence Analysis(DCA)results clearly distinguish the three vegetation zones,and the first axis of DCA shows a significant positive correlation with elevation(p<0.01,R=0.48).Discriminant Analysis(DA)successfully assigns 94.4%of the modern pollen samples to their respective vegetation zones.Pollen taxa such as Impatiens,Astertype,and Rosaceae exhibit significant indicative capabilities for the SEBF zone,effectively distinguishing this vegetation zone from others.Pinus and Alnus display overrepresentation in the Leigong Mountain region,while Quercus(D,deciduous-type)and Poaceae exhibit high representation in the SEBF zone.In the SEBF zone,both pollen diversity and richness are the lowest.Our study reveals the complex relationship between the richness and diversity of pollen and vegetation.The diversity and richness of tree and shrub pollen are found to be lower than those of the corresponding plants.The pollen-vegetation relationship elucidated in this study serves as a critical reference for reconstructing ancient environments from fossil pollen retrieved in this region.展开更多
准确理解地质历史时期气候变化的现象和机制,对预测未来气候变化有重要的启示意义。末次间冰期早期是研究未来气候变化可参考的典型暖期。目前,基于气候模式模拟的末次间冰期早期温度低于气候记录重建的结果。这一现状的一个潜在原因在...准确理解地质历史时期气候变化的现象和机制,对预测未来气候变化有重要的启示意义。末次间冰期早期是研究未来气候变化可参考的典型暖期。目前,基于气候模式模拟的末次间冰期早期温度低于气候记录重建的结果。这一现状的一个潜在原因在于,这些气候模拟研究中采用的植被数据为工业革命前水平,忽略了植被动态对气候的反馈作用。本研究利用iLOVECLIM气候模式耦合植被模块VECODE和LPJ-GUESS开展末次间冰期早期(125 ka B. P.)植被动态对气候反馈作用的模拟分析。模拟结果显示,相比基于工业革命前植被条件模拟得到的温度水平,耦合动态植被模拟的全球气候更温暖,但仍略低于记录重建的温度。在大陆/亚大陆尺度,高纬和北非地区模拟的125 ka B. P.植被覆盖度明显高于工业革命前水平,增温幅度也显著高于其他地区;此外,末次间冰期早期北非植被覆盖对区域气温的正反馈通过增强的大气环流使低纬地区输送到高纬地区热量增加,从而表现出对全球气温的正反馈作用。展开更多
The spatial shift of the North Atlantic Oscillation (NAO) is analyzed by using the Twentieth Century Reanalysis version 2 dataset and identifying NAO action centers directly on winter mean sealevel pressure (SLP) anom...The spatial shift of the North Atlantic Oscillation (NAO) is analyzed by using the Twentieth Century Reanalysis version 2 dataset and identifying NAO action centers directly on winter mean sealevel pressure (SLP) anomaly maps. The spatial shift of the NAO is characterized by four NAO spatial shift indices: the zonal and meridional shifts of the NAO southern and northern action centers. It is found that the zonal and meridional shift trends of the NAO action centers move along a path of southwest-northwest direction. Spectral analysis shows that the four NAO spatial shift indices have periodicity of 2-6 years and the NAO index has periodicity of 2-3 years in terms of high-frequency variations. On a decadal time scale, the NAO spatial shift indices are closely (positively) related to the NAO index, which is in agreement with previous studies of the relationship between the NAO index and the spatial shift of the NAO pattern. However, there is no relationship between the NAO index and the meridional shift of the northern action center on an interannual time scale. The significant relationship between the NAO index and the interannual variability of NAO spatial shift indices is very likely to be associated with synopticscale Rossby wave breaking, which generates surface pressure anomalies and thus affects the phase and pattern of the NAO. The correlations of winter westerly winds over 90°W-0° and the NAO index and the NAO spatial shift indices have a '+ - + -' structure from the Equator to the North Pole. Although there is close correlation between the NAO spatial shift indices and the strength of the zonal winds in the North Atlantic region, the effect of the zonal winds on the NAO spatial shift differs at different latitudes. Hence, the role of the zonal winds is probably a result of the NAO spatial shifts.展开更多
基金supported by the National Natural Science Foundation of China(grant numbers 42171157,42107475 and 41907379)College Students'Innovation and Entrepreneurship Program of Nantong University,and Foundation of Hunan Province(2023JJ40099 and 23B0678)。
文摘Understanding the distribution,dispersal,and correlation of modern pollen with vegetation in mountainous regions is essential for establishing accurate modern analogs for fossil pollen records.This study,conducted in Leigong Mountain on the YunnanGuizhou Plateau of southwestern China,involved the collection of 35 surface soil samples from diverse vegetation communities along an elevational gradient ranging from 1210 to 1875 meters.The results reveal a close correspondence between modern pollen assemblages and vegetation zones.Principal Component Analysis(PCA)results indicate that pollen assemblages can effectively distinguish between subtropical montane evergreen broad-leaved forest(SEBF)and subtropical montane deciduous broadleaved forest(SDBF).However,both SEBF and SDBF show significant overlap with subtropical montane evergreen-deciduous broad-leaved mixed forest(SEMF).Detrended Correspondence Analysis(DCA)results clearly distinguish the three vegetation zones,and the first axis of DCA shows a significant positive correlation with elevation(p<0.01,R=0.48).Discriminant Analysis(DA)successfully assigns 94.4%of the modern pollen samples to their respective vegetation zones.Pollen taxa such as Impatiens,Astertype,and Rosaceae exhibit significant indicative capabilities for the SEBF zone,effectively distinguishing this vegetation zone from others.Pinus and Alnus display overrepresentation in the Leigong Mountain region,while Quercus(D,deciduous-type)and Poaceae exhibit high representation in the SEBF zone.In the SEBF zone,both pollen diversity and richness are the lowest.Our study reveals the complex relationship between the richness and diversity of pollen and vegetation.The diversity and richness of tree and shrub pollen are found to be lower than those of the corresponding plants.The pollen-vegetation relationship elucidated in this study serves as a critical reference for reconstructing ancient environments from fossil pollen retrieved in this region.
文摘准确理解地质历史时期气候变化的现象和机制,对预测未来气候变化有重要的启示意义。末次间冰期早期是研究未来气候变化可参考的典型暖期。目前,基于气候模式模拟的末次间冰期早期温度低于气候记录重建的结果。这一现状的一个潜在原因在于,这些气候模拟研究中采用的植被数据为工业革命前水平,忽略了植被动态对气候的反馈作用。本研究利用iLOVECLIM气候模式耦合植被模块VECODE和LPJ-GUESS开展末次间冰期早期(125 ka B. P.)植被动态对气候反馈作用的模拟分析。模拟结果显示,相比基于工业革命前植被条件模拟得到的温度水平,耦合动态植被模拟的全球气候更温暖,但仍略低于记录重建的温度。在大陆/亚大陆尺度,高纬和北非地区模拟的125 ka B. P.植被覆盖度明显高于工业革命前水平,增温幅度也显著高于其他地区;此外,末次间冰期早期北非植被覆盖对区域气温的正反馈通过增强的大气环流使低纬地区输送到高纬地区热量增加,从而表现出对全球气温的正反馈作用。
基金supported by the National Basic Research Program of Chi-na (2010CB950204)the Innovation Team Project of the National Natural Science Foundation of China (40721061)the 111 Project (B06026)
文摘The spatial shift of the North Atlantic Oscillation (NAO) is analyzed by using the Twentieth Century Reanalysis version 2 dataset and identifying NAO action centers directly on winter mean sealevel pressure (SLP) anomaly maps. The spatial shift of the NAO is characterized by four NAO spatial shift indices: the zonal and meridional shifts of the NAO southern and northern action centers. It is found that the zonal and meridional shift trends of the NAO action centers move along a path of southwest-northwest direction. Spectral analysis shows that the four NAO spatial shift indices have periodicity of 2-6 years and the NAO index has periodicity of 2-3 years in terms of high-frequency variations. On a decadal time scale, the NAO spatial shift indices are closely (positively) related to the NAO index, which is in agreement with previous studies of the relationship between the NAO index and the spatial shift of the NAO pattern. However, there is no relationship between the NAO index and the meridional shift of the northern action center on an interannual time scale. The significant relationship between the NAO index and the interannual variability of NAO spatial shift indices is very likely to be associated with synopticscale Rossby wave breaking, which generates surface pressure anomalies and thus affects the phase and pattern of the NAO. The correlations of winter westerly winds over 90°W-0° and the NAO index and the NAO spatial shift indices have a '+ - + -' structure from the Equator to the North Pole. Although there is close correlation between the NAO spatial shift indices and the strength of the zonal winds in the North Atlantic region, the effect of the zonal winds on the NAO spatial shift differs at different latitudes. Hence, the role of the zonal winds is probably a result of the NAO spatial shifts.
