Phytoliths and the Late Quaternary vegetation history of West Africa

植硅体和西非晚第四纪植被历史

• 批准号: 267710502
• 负责人: Professorin Dr. Katharina Neumann
• 金额: --
• 依托单位: Department of Geography and Environmental Sciences
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/267710502?language=en
• 关键词: Phytoliths; Late; Quaternary; vegetation; history

Phytoliths (= plant silica bodies) are a valuable palaeoecological tool and complementary to pollen and plant macro-fossils. Phytolith studies on sediments for which other botanical proxies are available allow for combining and calibrating the different signals. While grass pollen is only identifiable to family level, with the highly diverse grass short cell phytoliths (GSCP) modern and ancient grasslands can be differentiated. This is especially important in Africa where savannas and grasslands cover the largest part of the continent. The major objective of the proposed project is an innovative contribution to the vegetation history of West Africa through the study of phytolith assemblages in modern plants and soils, and in Late Quaternary lake and fluvial sequences for which other botanical proxies (pollen, wood charcoal) have already been published. In West Africa, three major issues in palaeo-phytolith research merit attention and will be considered by the project: 1) distinguishing grassland communities, 2) assessment of the woody plant cover (forest-savanna question), 3) detecting human impact. The research is organized into three complementary work packages: WP 1) We will study modern soil phytolith assemblages along a precipitation gradient of 400-1300 mm from the Sahel to the Guinean zone. In Burkina Faso, the major objective is the separation of climatic, edaphic and anthropogenic signals in the phytolith spectra of different savanna vegetation communities. In Benin, we will study the soil phytoliths of gallery and semi-deciduous forests for a better discrimination of forest types. For characterizing the grassland, savanna and forest communities, we will use a recently developed GSCP classification system and detailed morphotypes characteristic for woody plants (see WP3). Commelinaceae phytoliths, first described by our working group, will help to detect and quantify human impact. Based on the statistical evaluation of the modern assemblages, we will test new phytolith indices to apply them, in a second step, to the fossil samples. WP 2) We will reconstruct the development of Holocene and Late Pleistocene grasslands and their correlation with climatic fluctuations for three well-dated palaeoecological sequences of the Sahelian and the Sudanian zone (Lake Tilla and Manga Grasslands / Nigeria; Ounjougou / Mali). We will also test if human impact, mainly agriculture, is detectable in the Late Holocene Sahelian and Sudanian assemblages, as suggested by archaeological evidence. For the sequence of Lac Sélé / Benin the major question is how the distinct shift from forest to savanna around 4500 cal BP, as visible in the pollen diagram, is represented in the phytolith record. WP 3) For a better interpretation of the signal for woody plants in the modern and ancient sediments, we will study herbarium material from modern trees and shrubs to identify potentially diagnostic morphotypes

植硅体（=植物硅体）是一种有价值的古生态工具，是花粉和植物宏观化石的补充。对沉积物的植硅体研究可以使用其他植物替代物来组合和校准不同的信号。虽然草花粉只能在科水平上识别，但通过高度多样化的草短细胞植硅体（GSCP），可以区分现代和古代草原。这在非洲尤为重要，因为稀树草原和草原覆盖了非洲大陆的最大部分。该项目的主要目标是通过研究现代植物和土壤以及晚第四纪湖泊和河流序列中的植硅体组合，对西非的植被历史做出创新贡献，其他植物学代表（花粉、木炭）已经发表。在西非，古植物硅体研究中的三个主要问题值得关注，并将由该项目考虑：1）区分草原群落，2）评估木本植物覆盖（森林-稀树草原问题），3）检测人类影响。该研究分为三个互补的工作包： WP 1) 我们将研究从萨赫勒到几内亚地区沿 400-1300 毫米降水梯度的现代土壤植硅体组合。在布基纳法索，主要目标是分离不同稀树草原植被群落植硅体光谱中的气候、土壤和人为信号。在贝宁，我们将研究廊道和半落叶林的土壤植硅体，以便更好地区分森林类型。为了描述草原、稀树草原和森林群落的特征，我们将使用最近开发的 GSCP 分类系统和木本植物特征的详细形态类型（参见 WP3）。我们的工作组首先描述了鸭跖草科植物硅体，它将有助于检测和量化人类影响。基于对现代组合的统计评估，我们将测试新的植硅体指数，以便在第二步中将它们应用于化石样本。 WP 2) 我们将重建萨赫勒和苏丹地区三个年代久远的古生态序列（尼日利亚蒂拉湖和曼加草原；马里 Ounjougou）全新世和晚更新世草原的发展及其与气候波动的相关性。我们还将测试，正如考古证据所表明的那样，在全新世晚期的萨赫勒和苏丹组合中是否可以检测到人类影响（主要是农业）。对于贝宁塞莱湖的序列，主要问题是在距今 4500 年左右从森林到稀树草原的明显转变（如花粉图中所示）如何在植硅体记录中体现出来。 WP 3) 为了更好地解释现代和古代沉积物中木本植物的信号，我们将研究现代树木和灌木的植物标本，以确定潜在的诊断形态类型