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

植硅体是一种有价值的古生态工具，是花粉和植物宏体化石的补充。对沉积物的植硅体研究允许结合和校准不同的信号，而其他植物学代用品是可用的。禾本科植物花粉只能在科的水平上识别，而高度多样的禾本科植物短细胞植硅体（GSCP）可以区分现代和古代草原。这在非洲尤其重要，因为非洲大草原和草原覆盖了非洲大陆的大部分。拟议项目的主要目标是通过研究现代植物和土壤中的植硅体组合以及晚第四纪湖泊和河流序列，对西非的植被历史做出创新性贡献，其他植物学代用品（花粉、木炭）已经发表。在西非，古植硅体研究中的三个主要问题值得注意，并将在项目中加以考虑：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。研究分为三个互补的工作包：WP 1）我们将研究现代土壤植硅体组合沿着400-1300毫米的降水梯度从萨赫勒到几内亚区。在布基纳法索，主要目标是在不同稀树草原植被群落的植硅体光谱中分离气候、土壤和人为信号。在贝宁，我们将研究廊道林和半落叶林的土壤植硅体，以便更好地区分森林类型。为了表征草原、稀树草原和森林群落，我们将使用最近开发的GSCP分类系统和木本植物的详细形态特征（见WP 3）。我们的工作组首次描述的鸭跖草科植硅体将有助于检测和量化人类的影响。基于现代组合的统计评估，我们将测试新的植硅体指数，将其应用于第二步，化石样品。WP 2）我们将重建全新世和晚更新世草原的发展及其与萨赫勒和苏丹地区（蒂拉湖和曼加草原/尼日利亚; Ounjougou /马里）的三个良好的古生态序列的气候波动的相关性。我们还将测试，如果人类的影响，主要是农业，是检测在全新世晚期萨赫勒和苏丹的组合，考古证据表明。对于Sélé湖/贝宁湖层序，主要的问题是，在花粉图中可见的大约4500 cal BP从森林到稀树草原的明显转变如何在植硅石记录中表现出来。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材料，以确定潜在的诊断形态型