Enhanced soil respiration, vegetation and monsoon precipitation at Lantian, East Asia during Pliocene warmth

Pliocene warmth has been used as an analogue for predicting climate response to the rapid atmospheric CO2 increase in the future. Pedogenic carbonates provide an essential archive to reconstruct terrestrial paleoenvironment in a warm world. The stable carbon isotopic compositions of pedogenic carbonate (delta(13) C-carb) are principally used to reconstruct the history of C4 plants along with coexisting organic matter delta(13) C-SOM. However, a growing body of evidence shows spatial and temporal decoupling between delta C-13(carb) and delta(13) C-SOM especially in arid regions, raising concerns when using delta(13) C-carb as a proxy for photosynthetic pathway. Here, we report paired delta(13) C-carb and delta(13) C-SOM data from Pliocene to early Pleistocene loess-paleosols in Chinese Loess Plateau (CLP), middle latitude East Asia. The model sensitivity analysis suggests the dominant control of soil respiration flux (SRF) on delta(13) C-carb values in this region. SRF is then reconstructed using the Monte Carlo simulation method. Our results show that the SRF was enhanced during Pliocene warmth, associated with increased vegetation density and East Asian Summer Monsoon (EASM) precipitation. An overall higher SRF across the CLP during the mid-Pliocene, compared with the Holocene and Last Glacial Maximum (LGM) period, suggests there was a northwestward shift of the EASM rain belt and vegetation under warmer climate. Our results suggest that global temperature has dominated the middle latitude ecosystem and soil variations through its influence on the hydrological cycle, providing insights into future ecological and environmental response to global warming in East Asia.