Collaborative Research: Assessing climate-biosphere linkages using Late Holocene records of climate variability and vegetation dynamics from the Brazilian Amazon and Savanna

该合作项目旨在调查南美夏季风（SASM）强度变化在全新世晚期森林-稀树草原生物群落变化中的作用。从季风区核心内部和附近的古气候记录的发展，可以评估整个地区的古季风信号的强度。研究人员希望在巴西亚马逊河流域和塞拉多（热带稀树草原）产生独立的、但同时存在的关于过去气候（洞穴主题）和植被（土壤剖面）动态的记录，这些记录是现有记录缺失的。古气候和生态解释将通过洞穴监测和代理系统建模进行验证。研究人员拟对以下问题进行评估：i)洞穴δ 18-氧值是否反映了SASM强度的变化？ ii) SASM强度的变化是否驱动了相应的局部湿度条件的变化？ iii)晚全新世SASM强度和局部湿度条件变化的性质和驱动因素是什么？ iv)植被过渡带生物群落对SASM强度和局部湿度条件的变化有多敏感？该项目包括对现代洞穴环境的监测，以评估洞穴中δ 18-氧值（代表SASM强度）和洞穴中微量元素浓度和锶同位素组成（代表当地湿度条件）。本研究将把亚马逊河和塞拉多地区过去一千年的洞穴三角洲18-氧记录进一步追溯，并发展相应的洞穴微量元素、87-锶/86-锶和土壤有机质三角洲13-碳记录，以评估区域季风强度、当地水分条件和生物群落变化之间的共变性。该项目有助于增进对SASM的了解，并促进与巴西科学家的密切合作。SASM是该地区最重要的降雨来源，具有重大的社会经济和环境意义，包括确定当前的生态系统分布和稳定性、水电生产和农业。

This collaborative project aims to investigate the role of changes in the South American Summer Monsoon (SASM) intensity on forest-savanna biome shifts that occurred during the Late Holocene. Development of paleoclimate records from in and near the core of the monsoon region enables an assessment of the strength of the paleo-monsoon signal across the region.The researchers look to generate independent, yet co-located, records of past climate (speleothems) and vegetation (soil profiles) dynamics from the Brazilian Amazon and Cerrado (savanna), for which existing records are absent. Paleoclimate and ecological interpretations will be validated using cave monitoring and proxy system modeling.The researchers intend to evaluate the following questions: i) Do speleothem delta 18-Oxygen values reflect variations in SASM intensity, ii) Do variations in SASM intensity drive corresponding variation in local moisture conditions, iii) What was the nature and driver of Late Holocene variability in SASM intensity and local moisture conditions, and iv) how sensitive were biomes in vegetative transition zones to variability in SASM intensity and local moisture conditions. The project involves the monitoring of modern cave environments to evaluate speleothem delta 18-Oxygen values as a proxy of SASM intensity and speleothem trace element concentrations and Strontium isotope compositions as a proxy of local moisture conditions. The research will extend existing speleothem delta 18-Oxygen records of the last millennium from the Amazon and Cerrado further back in time and develop corresponding records of speleothem trace element and 87- Strontium /86-Strontium and soil organic matter delta 13-Carbon to assess the co-variability between regional monsoon intensity, local moisture conditions, and biome shifts.The project helps promote greater understanding of the SASM and strong collaboration with Brazilian scientists. The SASM is the most important source of rainfall to the region with great socio-economic and environmental relevance, including defining current ecosystem distribution and stability, hydroelectric production, and agriculture.