Lake Sediment Records on Climate Change and Human Activities in the Xingyun Lake Catchment, SW China

Abstract

Sediments from Xinyun Lake in central Yunnan, southwest China, provide a record of environmental history since the Holocene. With the application of multi-proxy indicators (total organic carbon (TOC), total nitrogen (TN), δ13C and δ15N isotopes, C/N ratio, grain size, magnetic susceptibility (MS) and CaCO3 content), as well as accelerator mass spectrometry (AMS) 14C datings, four major climatic stages during the Holocene have been identified in Xingyun′s catchment. A marked increase in lacustrine palaeoproductivity occurred from 11.06 to 9.98 cal. ka BP, which likely resulted from an enhanced Asian southwest monsoon and warm-humid climate. Between 9.98 and 5.93 cal. ka BP, a gradually increased lake level might have reached the optimum water depth, causing a marked decline in coverage by aquatic plants and lake productivity of the lake. This was caused by strong Asian southwest monsoon, and coincided with the global Holocene Optimum. During the period of 5.60–1.35 cal. ka BP, it resulted in a warm and dry climate at this stage, which is comparable to the aridification of India during the mid- and late Holocene. The intensifying human activity and land-use in the lake catchment since the early Tang Dynasty (∼1.35 cal. ka BP) were associated with the ancient Dian culture within Xingyun’s catchment. The extensive deforestation and development of agriculture in the lake catchment caused heavy soil loss. Our study clearly shows that long-term human activities and land-use change have strongly impacted the evolution of the lake environment and therefore modulated the sediment records of the regional climate in central Yunnan for more than one thousand years.

Lake geochemistry reveals marked environmental change in Southwest China during the Mid Miocene Climatic Optimum

“…Therefore, the C/N ratios reflect the proportion of autochthonous (within the lake) and allochtonous (outside the lake) organic matter preserved in the sediments. In Wenshan, the C/N ratios in the whole sedimentary succession may seem unusually high, but similar high values have been found in Xingyun Lake (Yunnan) between 12 and 1.2 ka [23]. The C/N ratios in Zone 1 (average 22.5) indicate higher relative contributions of terrestrial organic matter, while the lower values in Zone 2 (average 14.7) imply that the relative algal contribution increased.…”

“…Lakes are environmentally sensitive and so are ideal to study past climatic fluctuations [18]. For example, lake sediment geochemistry has been widely used to explore environmental changes on the Tibetan Plateau during the Miocene [19,20] and in Yunnan during the Quaternary [21][22][23]. However, there is very limited research using terrestrial geochemistry to investigate environmental changes in Yunnan during the Miocene, and the MMCO in particular.…”

Climate Change and Drought Events in the Geochemical Records of the Lacustrine Deposits in the Southeastern Tibetan Plateau

“…The sedimentation rate in the section is approximately and 0.385 and 0.461 mm/a. The estimated sedimentation rate corresponds with other geochronology in Yunnan Province [24, 25]. The characterties of chemical weathering and climate change in the layer (1.75–0 m) of XB section were not included in the following analyses because it has the only 14 C data around the Holocene.…”

Tropical Rainforest Dynamics and Palaeoclimate Implications since the late Pleistocene, Nilgiris, India

“…This interval demonstrates a general shift towards a wet–dry tropical climate comprising episodes of intense, excessive summer monsoon years interrupted by infrequent monsoon failures, which led to repetitive episodes of desiccation and refilling of the lake. The low rates of sediment accumulation imply sediment hiatuses of erosive origin consistent with periods of stronger monsoons (Sadler, 1999; Servant-Vildary et al, 2001) or discontinuous sedimentation associated with intervals of dry conditions and reduced sediment supply (Zhang et al, 2014). The sediment texture, characterized by clayey silt, displays a yellowish-brown colour (10 YR 5/6), indicating oxidized conditions—a consequence of historically fluctuating lake levels.…”