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）强度的变化对全新世晚期发生的森林-稀树草原生物群落变化的作用。 从季风区域核心内部和附近开发古气候记录，可以评估整个区域的古季风信号强度。研究人员希望生成独立但位于同一地点的巴西亚马逊和塞拉多（稀树草原）过去气候（洞穴）和植被（土壤剖面）动态的记录，而这些记录是缺乏的。古气候和生态解释将使用洞穴监测和代理系统建模进行验证。研究人员打算评估以下问题：i）洞穴δ 18-氧值是否反映了 SASM 强度的变化，ii）SASM 强度的变化是否会驱动当地湿度条件的相应变化，iii）全新世晚期 SASM 强度和当地湿度条件变化的性质和驱动因素是什么，以及 iv）植被过渡区的生物群落对 SASM 强度和当地湿度变化的敏感度如何？当地的湿度条件。该项目涉及对现代洞穴环境的监测，以评估作为 SASM 强度代表的洞穴沉积物 delta 18-氧值，以及作为当地湿度条件代表的洞穴沉积物微量元素浓度和锶同位素组成。 该研究将把亚马逊和塞拉多上个千年现有的洞穴沉积物 Delta 18-氧记录延伸到更早的时间，并开发相应的洞穴沉积物微量元素和 87- 锶/86-锶和土壤有机质 Delta 13-碳记录，以评估区域季风强度、当地湿度条件和生物群落变化之间的共同变异性。该项目有助于促进对 SASM 的更深入了解以及与巴西科学家。 SASM 是该地区最重要的降雨源，具有重大的社会经济和环境相关性，包括确定当前的生态系统分布和稳定性、水力发电和农业。

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.