Diatom response to climate forcing of a deep, alpine lake (Lugu Hu, Yunnan, SW China) during the Last Glacial Maximum and its implications for understanding regional monsoon variability

详细信息    查看全文

• 作者：Qian Wang ; Xiangdong Yang ; N. John Anderson ; Enlou Zhang ; Yanling Li
• 关键词：Diatom palaeoecology ; Nutrients ; Stratification ; Ice cover ; Monsoon climate ; Last Glacial Maximum (LGM)
• 刊名：Quaternary Science Reviews
• 出版年：15 February, 2014
• 年：2014
• 卷：86
• 期：Complete
• 页码：1-12
• 全文大小：2516 K

文摘

The Yunnan Plateau of southwest China is strongly influenced by the Asian monsoon and is a critical area in terms of determining its development and variability since the Last Glacial Maximum. High-resolution diatom analysis of a ¹⁴C-dated sediment core retrieved from Lugu Lake, Yunnan provides a detailed history of palaeoenvironment changes from 30,000 to 10,000聽cal. yr BP. A model of climate-diatom interactions (linking thermal stratification, ice cover and catchment-derived nutrients) is聽proposed to explain the observed changes. Prior to 24,500聽cal. yr BP the dominance of the planktonic Cyclotella rhomboideo-elliptica indicates a period of stable stratification and low nutrient levels, with a moderate change of temperature and precipitation in the southwest monsoon region. During the LGM (24,500-14,500聽cal. yr BP), the loss of the planktonic diatoms and a switch to small Fragilaria spp. suggest an altered thermal regime in the lake (i.e. weaker stratification and possibly ice cover). From 鈭?8,000聽cal. yr BP, the expansion of planktonic taxa (Stephanodiscus and the Asterionella formosa) and increased %TOC are indicative of increased nutrient availability reflecting altered vegetation and soil processes due to rising regional temperatures. After 14,500聽cal. yr BP, a rapid reversal to dominance by planktonic diatoms indicates a further increase in temperature and continued development of catchment vegetation and soils. The abrupt changes in diatom species composition around 24,500 and 14,500聽cal. yr BP suggest that the ecological status of the lake exceeded limnological thresholds. Interestingly, however, the Younger Dryas event is not clearly recognizable in either the diatom or pollen records in the Lugu Lake sediment record. In a partial redundancy analysis, 44.2% of the variability in the total diatom assemblages in the period 30,000-10,000聽cal. yr BP was accounted for by changes in summer solar radiation. The relationships between the diatom assemblages and the C/N and pollen data are further evidence of climate-catchment-vegetation interactions and their impact on lake functioning. The composition of diatom assemblages in the Lugu Lake sediment core reflects direct and indirect (i.e. via catchment processes) climate forcing and in particular, the strength of the southwest monsoon, which in turn corresponds to orbitally-induced variability in Northern Hemisphere summer solar insolation from 30,000聽cal. yr BP to 10,000聽cal. yr BP.