Holocene vegetation and environmental changes with a focus on peat ecosystems in southwestern and northeastern Amazonia

by Bowen Wang
Doctoral thesis
Date of Examination:2024-02-06
Date of issue:2024-03-27
Advisor:Prof. Dr. Hermann Behling
Referee:Prof. Dr. Hermann Behling
Referee:Prof. Dr. Holger Kreft
Persistent Address: http://dx.doi.org/10.53846/goediss-10417

 

 

Files in this item

Name:Bowen Wang_PhD thesis.pdf
Size:91.7Mb
Format:PDF

The following license files are associated with this item:

Abstract

English

Amazon rainforests are well-known for playing a significant role in the climate, hydrological cycle, and biodiversity on earth. Recent investigations found that Amazonia may contain the largest peat carbon (C) stock in the tropics. Easily to be degraded, Amazonia peat ecosystems are potentially to be a large C source which impacts the global climate. Thus, it is important to understand what drives the development of Amazonia peat ecosystems, and if the drivers are local or regional. In this study, we used the multiproxy method to investigate peat ecosystems in southwestern Amazonia (southern Peru) and northeastern Amazonia (northern Brazil) where the knowledge of peat ecosystems is little known. In the Madre de Dios region in southern Peru, we investigated a Mauritia palm swamp (aguajal) using an aguajal core and an oxbow lake core. Indicated by the aguajal record, the studied aguajal developed from open water since ca. 1380 cal yr BP, then became a marsh since ca. 820 cal yr BP, and then formed a dense aguajal since ca. 640 cal yr BP and more open aguajal since ca. 300 cal yr BP. Peat and C stayed at high accumulation rates since their start in ca. 820 cal yr BP, but the rates became lower since ca. 520 cal yr BP. The oxbow lake record revealed that the initial open water may develop from a cutting off from the Madre de Dios River at ca. 1760 cal yr BP, and the lower peat and C accumulation rates since ca. 520 cal yr BP were probably caused by regional less wet climate. In the Caxiana region in northern Brazil, a peat record named Lagoa da Fazenda, from a net of former small river valleys was studied. The results show that since ca. 7000 cal yr BP, the local inundated forest started to form with the onset of peat and C accumulation, caused by Atlantic sea level rise blocking the rivers. The study site was influenced by flooding since ca. 2600 cal yr BP and by strong local human activities since ca. 260 cal yr BP. Through the investigations and comparison with other available studies, we found that the processes of peat ecosystems are diverse whether in vegetation successions or peat and C accumulation rates. The diversity is caused by various conditions in different regions. For example, we found that the peat ecosystem closer to the sea is more influenced by Atlantic sea level, but it is driven by river dynamics in more inland areas. Regional human activities may play an important role in peat ecosystem development by changing regional climate or causing flooding (by causing soil erosion). This study helps to further understand the mechanism of tropical peat ecosystems and make conversation plans.
Keywords: holocene; peat ecosystems; vegetation dynamics; environmental changes; climate changes; human activities; sea level changes
 
Statistik