Enhanced Mid-Holocene Vegetation Growth and Its Biophysical Feedbacks in China

Proxy-based reconstructions show that the climate during the mid-Holocene (MH) was warmer and wetter than the present day in most regions of China, characterized by a northwestward extension of the East Asian summer monsoon and an increase in woody cover. However, climate simulations that neglect vegetation shifts yield cooler climates than proxy-based reconstructions for the MH. Here, we simulate MH vegetation cover, productivity, and terrestrial parameters in China using a state-of-the-art land surface model forced with realistic proxy-based climate data. Our simulations corroborate MH vegetation cover inferred from 246 pollen sites, and indicate a higher vegetation productivity in China, despite the lower CO2 concentration during the MH compared to the present day. Enhanced vegetation growth during the MH could have affected land surface energy and hydrological budgets through biophysical feedbacks. Our findings highlight the impact of vegetation dynamics on the terrestrial carbon cycle and regional climate in China. Multiple paleoclimate archives illustrate warmer and wetter climate during the mid-Holocene (MH; similar to 6,000 years ago) than at present in most regions of China. However, current model results and proxy-based reconstructions have some key discrepancies in climate reconstructions, possibly because these climate simulations have overlooked vegetation changes. Therefore, it is essential to develop a vegetation cover map for China to examine the vegetation-climate feedback during the MH. Here, we present reconstructions of mid-Holocene vegetation cover, productivity and terrestrial parameters in China at a very high resolution using a land surface model. Simulation results can reproduce MH vegetation cover indicated by paleo-records and suggest increased tree cover and vegetation productivity in China. Vegetation changes during the MH likely had an important impact on regional climate in China through altering terrestrial parameters. In contrast, multiple-model ensembles in the latest Paleoclimate Modeling Intercomparison Project significantly underestimated MH vegetation growth primarily because of inherent bias in prescribed vegetation maps. This work reveals the critical impact of MH vegetation cover on terrestrial carbon, energy and hydrological budgets in China, and underlines the need to incorporate vegetation dynamics in terrestrial or climate simulations for the past and future. Our work provides a reliable and spatially continuous mid-Holocene vegetation map for China at a resolution of 0.5 degrees Calculated mid-Holocene vegetation gross primary productivity of similar to 7.5 PgC/yr in China is higher than the present dayVegetation dynamics should be considered in simulating mid-Holocene terrestrial carbon cycle and climate change for China

Automated summary

Proxy-based reconstructions suggest that the climate in most regions of China during the mid-Holocene (MH) was warmer and wetter than present day, with an extension of the East Asian summer monsoon and an increase in woody cover. However, climate simulations that neglect vegetation changes yield cooler climates for the MH. In this study, a state-of-the-art land surface model is used to simulate MH vegetation cover, productivity, and terrestrial parameters in China. The results agree with paleo-records and indicate higher vegetation productivity in China during the MH. The findings emphasize the importance of vegetation dynamics on the carbon cycle and regional climate in China.