A 2500-year climate and environmental record inferred from subfossil chironomids from Lugu Lake, southwestern China

Abstract

We present a sediment record from Lugu Lake, a large and deep alpine lake in southwestern China, spanning the last c.2500 cal yr BP. This multi-proxy study focussed on subfossil chironomids but also included analyses of chemical elements using inductively coupled plasma-atomic emission spectrometry (ICP-AES), magnetic susceptibility, total organic carbon (TOC), total nitrogen (TN) and grain size. The chironomid assemblage is dominated by Procladius, Tanytarsus gracilentus-type and Polypedilum nubeculosum-type throughout the core. The record reveals that these chironomid taxa responded to two periods of catchment erosion between c.1700-1100 cal yr BP and c.1920 A.D. to the present. We provide evidence which suggests that the recent erosion episode is caused by human activities; however, the earlier event (c.1700-1100 cal yr BP) is likely related to increased regional precipitation, possibly linked to the strengthening of the Indian summer monsoon in the late Holocene. It is notable that the chironomids, through their varied ecologies, are able to detect the human-induced changes as well as natural climate changes, for instance, enhanced precipitation. Coupling palaeoecological studies using chironomids with more traditional catchment erosion indicators is thus a powerful tool for reconstructing past environmental and climate change.