Early human impact in a 15,000-year high-resolution hyperspectral imaging record of paleoproduction and anoxia from a varved lake in Switzerland
| Autor: | Stamatina Makri, Adrian Gilli, Martin Grosjean, Willy Tinner, Erika Gobet, Fabian Rey |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
010506 paleontology
Archeology Global and Planetary Change geography Biogeochemical cycle geography.geographical_feature_category Varve 010504 meteorology & atmospheric sciences Drainage basin Geology 910 Geography & travel 580 Plants (Botany) 01 natural sciences Paleolimnology Freshwater ecosystem Deforestation 550 Earth sciences & geology Environmental science Physical geography Eutrophication Ecology Evolution Behavior and Systematics Holocene 0105 earth and related environmental sciences |
| Zdroj: | Quaternary Science Reviews. 239:106335 |
| ISSN: | 0277-3791 |
| DOI: | 10.1016/j.quascirev.2020.106335 |
| Popis: | 20th century eutrophication and global spread of anoxia is a threat for freshwater ecosystems. Little is known about Holocene anoxia and meromixis events when anthropogenic impacts were weaker and natural ecosystem variability played the dominant role. In this study, we examine the relationship between lake mixing and lake production, climate variability, vegetation cover, catchment erosion and (pre)historic anthropogenic impacts in Moossee (Switzerland), over the last 15,000 years. We use sub-annually resolved calibrated hyperspectral imaging data (total chlorophyll for paleoproduction, bacteriopheophytin for anoxia and meromixis) combined with X-ray fluorescence and pollen data. Production shows a first increase at 14,500 cal yr BP, a further increase after 7500 cal BP, relative maxima in the late Bronze, Iron and Middle Ages, and the unprecedented peak in the 20th Century. Until 7500 cal BP, the lake was well mixed with only scarce phases of seasonal to multiannual anoxia. Repeated meromixis events occurred between 7500 and 2500 cal BP when temperatures were high, forests closed, and lake production was already enhanced. After the forests were cleared (2500 cal BP) the lake remained mostly holomictic. Holocene meromixis events were systematically terminated by local deforestation related to Neolithic and Bronze Age lakeshore settlements: charcoal peaked, tree pollen dropped below a threshold of 80%, soil erosion and lake production increased and bacteriopheophytin disappeared. Meromixis re-established after the termination of lakeshore settlements and the onset of afforestation with tree pollen exceeding 80%. These repeated cycles unambiguously document how even early human societies affected the mixing regime and biogeochemical cycling in this lake. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Full Text from ScienceDirect