Climate change as the dominant driver of recent ecological changes in a semi-arid alpine lake from the Chinese Loess Plateau

Semi-arid areas of northern China are under increasing pressures from anthropogenic activities and climate change. Although wetland areas in these drylands have experienced dramatic, unidirectional shifts in their ecological status in recent centuries, fundamental driving forces are poorly quantifie...

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Bibliographic Details
Published in:Journal of paleolimnology 2022-06, Vol.68 (1), p.39-57
Main Authors: Yan, Xinwei, Liu, Jianbao, Rühland, Kathleen M., Smol, John P., Chen, Fahu
Format: Article
Language:English
Subjects:
Achnanthidium minutissimum
Algae
Anthropogenic factors
Arid lands
Arid zones
Benthos
Catchment area
Chlorophyll
Chlorophyll a
Climate Change
Deforestation
Diatoms
Dominance
Earth and Environmental Science
Earth Sciences
Ecology
Environmental changes
Fluctuations
Freshwater & Marine Ecology
Freshwater lakes
Geology
Grain size
Human impact
Human influences
Ice cover
Isotopes
Lakes
Lindavia comensis
Marine microorganisms
Mountain lakes
Original Paper
Paleontology
Physical Geography
Precipitation
Primary production
Sedimentology
Semi arid areas
Silica
Silicon dioxide
Soil erosion
Stable isotopes
Staurosirella pinnata
Thermal stability
Wind speed
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Summary:Semi-arid areas of northern China are under increasing pressures from anthropogenic activities and climate change. Although wetland areas in these drylands have experienced dramatic, unidirectional shifts in their ecological status in recent centuries, fundamental driving forces are poorly quantified. Here, we examine changes in sedimentary proxies (diatoms, spectrally-inferred chlorophyll-a, stable isotopes) preserved in a radiometrically-dated core from Tianchi Lake, an alpine lake within the margin of the East Asian Summer Monsoon (EASM) limit in China’s southwestern Loess Plateau. Our algal trends were compared with regional instrumental records, changes in EASM intensity, and with previously published paleolimnological data from this same lake to determine the principal drivers of regional ecological changes. We found no clear evidence that geochemical and biological proxies were strongly affected by deforestation and other human activities. Major environmental changes during the past ~ 200 years were found to be predominantly driven by climatic fluctuations, extreme precipitation events, and changes in EASM intensity. Prior to ~ 1965 CE, diatom assemblages indicate an oligotrophic, clear water state. Shifts in dominance between benthic Staurosirella pinnata and planktonic Lindavia comensis were likely controlled by ice-cover dynamics. Between ~ 1965 and 1980 CE an abrupt shift to a turbid water state during a period of extreme precipitation events was caused by excessive nutrient-laden soil erosion in the already susceptible deforested catchment. This turbid period was evidenced by a rapid increase to dominance of Achnanthidium minutissimum , a sharp decline in oligotrophic Lindavia comensis , increased primary production, and peaks in sediment grain size and SiO 2 content. Post- ~ 1980 CE, we provide evidence that a shift towards planktonic diatom dominance can best be explained by changes in climate and EASM intensity, despite substantial nitrogen deposition in the region during the past few decades. Specifically, a drier and warmer climate together with weakened EASM wind strength resulted in decreased erosion and a return to a clear water state, coupled with enhanced thermal stability. Collectively, these observations expand our understanding of how changes in climate, extreme precipitation events, and fluctuations in EASM intensity influence semi-arid alpine lakes in northern China, as well as climate’s leading role in driving ecological change
ISSN:0921-2728
1573-0417
DOI:10.1007/s10933-020-00167-5