Peatland evolution and associated environmental changes in central China over the past 40,000 years

Abstract

Central China has experienced stronger summer monsoon during warm periods such as Marine Isotope Stages (MIS) 1 and 3, and weaker summer monsoon during cool periods such as MIS 2. The evolution history of Dajiuhu subalpine peatland in central China can help investigate how the expansion and shrinkage of peatland were associated with monsoonal strength over the last glacial-interglacial cycle. Here we apply bulk organic carbon and molecular biomarkers (hopane and n-alkane) to reconstruct the evolution history for the Dajiuhu peatland over the past 40,000 yr. The results indicate fluctuations between lacustrine and peat-like deposition during MIS 3, steady lacustrine deposition during MIS 2, and peatland initiation and expansion during MIS 1 in the Dajiuhu peatland. Therefore, at the glacial-interglacial scale, warmer summer and cooler winter conditions in interglacial periods are crucial to trigger peat deposition, whereas reduced evaporation in glacial period instead of decreased monsoonal-driven precipitation would have played a predominant role in the regional effective moisture balance. However, within the Holocene (MIS 1), monsoonal precipitation changes appear to be the main controller on millennial-scale variations of water-table level of the Dajiuhu peatland.

Asian Winter Monsoon Imprint on Holocene SST Changes at the Northern Coast of the South China Sea

“…Thus, the dramatically high hopane concentrations, a feature not shown in alkenone contents (Figure b), are very unlikely to originate from in situ biological production (Pearson et al, ; Peters et al, ). Rather, an enhanced influx of terrestrial‐sourced biomass plausibly acts as a reasonable explanation (He et al, ; Xie et al, ) because AWM strengthening during cool intervals promoted northeasterly winds, which would transport more terrigenous hopanes from the continent to the northern coast of the SCS (Figure a). Conversely, the co‐occurrence of increased SST and lower hopane concentrations at our study site implies a reduction in the AWM during warm intervals, for example, the MCA and HCO.…”

“…Hopane compounds in the hexane fraction were identified by the Agilent 7890 GC equipped with mass spectrometry and subsequently quantitatively determined by the 7890 GC‐flame ionization detector (He et al, , and references therein). The GC temperature protocol was set as follows: 60 (1 min) to 250 °C at a rate of 20 °C/min, 250 to 270 °C at a rate of 5 °C/min, 270 to 310 °C at a rate of 2 °C/min and ultimately maintained at 310 °C for 15 min.…”

Molecular Paleoclimate Reconstructions over the Last 9 ka from a Peat Sequence in South China

“…Chinese peat deposits from the Holocene have received more and more attention in molecular paleoclimate studies over the last decade. Researchers have investigated peat deposits in northeast China [ 15 – 18 ], southwest China [ 19 – 22 ], central China [ 23 – 26 ], and south China [ 27 , 28 ] with lipid biomarker approaches. However, studies of n -alkane δ 13 C and δD values in peat from south China are relatively few.…”

A Highly Resolved Speleothem δ13C Record from Central China and Its Manifestation on Multiple Time Scales during the Last Glacial

“…Notably, the reduction in solar irradiance may have reduced regional evaporation and thus led to a reverse hydrological evolution pattern [55,70]. Lower evaporation in the glacial period instead of decreased monsoonal-driven precipitation would have played a predominant role in regional effective moisture changes [71]. This assumption provides a plausible explanation for the humid climate conditions documented in DDH Cave and other records during the LGM period.…”