Table1_Climatic and Ecological Changes in the Subtropical High Andes During the Last 4,500 Years.DOCX

The effects of climate change may be more evident in mountainous areas. In these areas, an increase in temperature and a decrease in precipitation can reduce the amount of snow, which represents a source of water for human consumption and vegetation. To analyze the effects of climate change on vegetation, it is possible to examine the climate–vegetation relationship in the past and observe the influence of variation in temperature and precipitation on the dynamics of plant communities. The aim of the present work was to describe the climate–vegetation dynamics of the last 4,500 years in the high subtropical Andes of Chile (30°S). The paleoclimatic reconstruction was carried out through the analysis of fossil pollen and macroscopic carbon obtained from sediment cores from two high Andean lakes. The dynamics of the vegetation was analyzed taking into account the alpha and beta diversity. The pollen and carbon records showed three contrasting periods during the last 4,500 years. From the beginning of the sequences until ∼1900 cal. yr BP, relatively dry climatic conditions are suggested, with a slight trend toward more humid conditions after 2,700 cal. yr BP. Pollen records from ∼1900 to ∼600 cal. yr BP suggest wetter conditions than today. Finally, relatively arid conditions have reappeared in the last ∼600 years. The diversity analysis showed that the climate mainly influences the composition of taxa in the communities (beta diversity) and not the richness (alpha diversity). In periods of dry/wet transition and vice versa, beta diversity changes. On the other hand, richness remains relatively constant throughout the record.

气候变化的影响在山地地区往往更为显著。在此类区域中，气温升高与降水减少会导致积雪储量下降，而积雪是人类用水与植被生长的重要水源。为探究气候变化对植被的影响，可通过回溯过去的气候-植被关系（climate–vegetation relationship），考察气温与降水变化对植物群落动态的调控作用。本研究旨在阐明智利南纬30°亚热带安第斯（Andes）高海拔区域过去4500年的气候-植被动态变化过程。本研究通过分析采自两座安第斯高海拔湖泊的沉积岩芯中的化石花粉与宏观炭屑，完成了古气候重建工作。本研究结合α多样性（alpha diversity）与β多样性（beta diversity）指标，对植被动态展开分析。花粉与炭屑记录显示，过去4500年中存在三个截然不同的气候阶段：从沉积序列起始至约1900个校准年距今年代（cal. yr BP）时，区域气候整体偏干旱，且在约2700 cal. yr BP后呈现向湿润方向缓慢转变的趋势；约1900 cal. yr BP至约600 cal. yr BP期间，区域气候较现今更为湿润；最后，在过去约600年中，区域再度回归相对干旱的气候状态。多样性分析结果显示，气候主要影响植物群落的类群组成（即β多样性），而非物种丰富度（即α多样性）。在干湿转换阶段及其反向过程中，β多样性会发生显著变化；而物种丰富度在整个沉积记录中始终保持相对稳定。