COLLABORATIVE RESEARCH: A combined phytolith-isotope geochemistry approach to paleo-vegetation reconstruction in Montana

合作研究：植物岩-同位素地球化学联合方法在蒙大拿州新生代古植被重建中的应用密歇根大学的athan Shelton和Selena Smith和华盛顿大学的carolyn Stroemberg草原占地球陆地植被的40%左右，为人类提供主食（如玉米、水稻、小麦）。持续的人为气候变化将如何影响草地生态系统和农业作物生产力是一个关键问题，要解决这个问题，首先需要了解这些重要的生物群落是如何形成的。根据植物大化石、共同进化的哺乳动物、稳定同位素、土壤化石和植物岩（植物硅）数据，科学界认为，在中新生代的某个时期，草原生态系统在洲际地理尺度上分散。然而，由于不同的代用物在总空间和时间格局方面显示了草地出现的不同情景（例如，北美与非洲），这种深刻的生态转变的细节不太确定。在大多数地区，只应用了一种古植被代理，因此对不同记录中可能影响植被解释的潜在采样和地貌学偏差知之甚少。此外，潜在重要的环境异质性仍未得到证实。为了解决这些问题，pi将使用跨学科，多代理方法重建蒙大拿州过去~40 Ma的草原演变，可以直接与基于古土壤的古气候重建进行比较。具体来说，pi将利用植物岩、成土碳酸盐和从古土壤中收集的有机质（即C同位素来评估光合作用途径）构建一个长期的、高分辨率的古植被记录。他们将专注于三个关键的气候转变，即始新世-渐新世转变（EOT），渐新世-中新世转变（OMT）和中新世中晚期转变（MLMT），这些气候转变被广泛认为对北美草的存在和丰富度产生了重大影响。

Collaborative Research: A combined phytolith-isotope geochemistry approach to Cenozoic paleo-vegetation reconstruction in MontanaNathan Shelton and Selena Smith, University of MichiganCarolyn Stroemberg, University of WashingtonGrasslands make up ~40% of Earth's terrestrial vegetation and provide humans with our staple foods (e.g., corn, rice, wheat). Exactly how ongoing anthropogenic climate change will impact grassland ecosystems and agricultural crop productivity is a crucial question, and addressing it requires knowledge of how these important biomes were assembled in the first place. Based on plant macrofossils, co-evolved mammals, stable isotopic data, fossil soils, and phytolith (plant silica) data, the scientific community knows that grassland ecosystems dispersed at an intercontinental geographic scale sometime during the mid-Cenozoic. However, because different proxies suggest different scenarios for the emergence of grasslands both in terms of gross spatial and temporal patterns (e.g., North America vs. Africa), the details of this profound ecological transition are less certain. In most areas, only one paleo-vegetation proxy has been applied, so very little is understood about potential sampling and taphonomic biases in different records that could affect vegetation interpretation. In addition, potentially important environmental heterogeneity remains undocumented. To resolve these issues, the PIs will use an interdisciplinary, multi-proxy approach to reconstructing the evolution of grasslands in Montana over the past ~40 Ma that can be compared directly with a paleoclimatic reconstruction based on paleosols. Specifically, the PIs will construct a long-term, high-resolution record of paleovegetation using phytoliths, pedogenic carbonates, and organic matter collected from paleosols (i.e., C isotopes to assess photosynthetic pathways). They will focus on three critical climatic transitions that are broadly believed to have significantly impacted the presence and abundance of grasses in North America, namely the Eocene-Oligocene transition (EOT), the Oligocene-Miocene transition (OMT), and the Middle-Late Miocene transition (MLMT).