Holocene C3/C4 vegetation variations in arid Central Asia: Implications for paleoclimate

Abstract

Understanding past climate and environmental evolutions is of great significance for predicting the future in the context of global warming in arid Central Asia. Here, we report new Holocene paleovegetation records based on the concentrations and distributions of leaf wax long chain (C28-C32) n-acids and stable carbon isotopes of leaf wax C28 n-acid from Lake Balikun, arid Central Asia. The long chain (C28-C32) n-acid concentrations show two distinct terrestrial vegetation degradation and desertification events during periods of 12.0–7.8 ka (1 ka = 1000 cal. yr BP) and 5.8–3.6 ka, indicating dry climate conditions. We reconstructed Holocene C4 plant relative abundance variations (ranging from 0 to 49%) based on stable carbon isotope records of leaf wax C28 n-acid. The C4 plants show large fluctuations in the early Holocene, high abundance in the mid-Holocene and a decrease of 40% after 3.6 ka, which is likely driven by precipitation seasonality. In Lake Balikun, the C4 grass expansion during 7.8–5.8 ka indicates significantly increased summer precipitation, resulting in a wet climate during the warm mid-Holocene. In contrast, C3 plant expansion indicates the increased contribution of precipitation in winter and spring seasons during the late Holocene. According to our results, we propose that the regional and temporal differences in the Holocene optimum moisture and moisture-temperature relationships are likely attributed to asynchronous precipitation in the winter-spring and summer seasons, linked to the interaction of westerlies and the Asian summer monsoon.