Characteristics and mechanism of organic and inorganic carbon burial and the climate response of Late Holocene alpine lakes in Yunnan, SW China

As a sensitive indicator of carbon cycle in alpine ecosystems, the carbon burial process in alpine lakes is of great significance for understanding the regional and global carbon cycle and revealing the key coupling mechanism between climate and lake ecosystems. The dynamics and driving mechanism of organic carbon (OC) and inorganic carbon (IC) burial in alpine lakes in Yunnan Province (SW China) driven by climate since the late Holocene were revealed by comprehensive analysis on multi-environmental proxies from lake sediments since 3500 cal.aBP in the Dinggong Co Lake, NW Yunnan, combined with high-precision AMS¹⁴C dating and principal component analysis. Results show that between 3500~1100 cal.aBP, the erosion intensity of the basin was relatively low as indicated by Rb/Sr and Zr/Sr, which corresponded to the continuous decrease of OC. Since 700 cal.aBP, temperature rose in the alpine region, which weakened the freeze-thaw effect, promoted the erosion and nutrient input into the lake basin, and drove the OC recovery and IC fluctuation. Meanwhile, the significant negative correlation between organic carbon and inorganic carbon burial in Dinggong Co Lake sediments (R=−0.321, P<0.001) reflects the burial mechanism of “double carbon balance” in the alpine lakes under climate regulation. The burial of organic carbon was mainly driven by the accumulation of total nitrogen (R=0.644, P<0.001) and C/N (R=0.385, P<0.001), reflecting the transport of terrestrial organic carbon. Inorganic carbon burial was significantly positively correlated with the median particle size (R=0.490, P<0.001), and was inhibited by precipitation dilution (R=−0.355, P<0.001), indicating that the burial process was dominated by watershed erosion and exogenous input. This study clarified the driving mechanism of climate-erosion-nutrient coupling in the vertical zonation framework, and provided a scientific basis for the adaptive management of alpine ecologically fragile areas in response to climate warming and the assessment of carbon sinks in alpine areas.