Holocene rates of vegetation composition change differ between high and middle-to-low elevations in the Central Arid Zone of Asia

In this study, we calculate the Holocene rates of vegetation composition changes (RoCs) for different elevations in the Central Arid Zone of Asia based on 46 pollen records using Detrended Correspondence Analysis (DCA). In addition, we investigate the relative importance of six drivers (temperature, precipitation, CO2 concentration, fire, pasture and cropland activities) using Structural Equation Modeling (SEM). Results show that RoCs at high elevations (>2000 m a.s.l.) were generally greater in the early Holocene and then fell to their lowest values at-6000 cal. yr BP. RoCs then gradually increased between-6000 and-3000 cal. yr BP and over the past-3000 years, RoCs abruptly decreased before returning to an upward trend. We infer that the changeable characters of RoCs at high elevations are mainly modulated by fire activities. RoCs at middle-to-low elevations (<2000 m a.s. l.) experienced a steady acceleration through the Holocene, which might be attributed to climatic cooling and wetting and intensification of fire activities. Our findings shed light on the Holocene response of vegetation to climate change, CO2 concentration, fire and human activities (grazing and cropland) in the Central Arid Zone of Asia.

Automated summary

In this study, we calculated the rates of vegetation composition changes (RoCs) in the Central Arid Zone of Asia during the Holocene using 46 pollen records. We also examined the importance of six drivers (temperature, precipitation, CO2 concentration, fire, pasture, and cropland activities) using Structural Equation Modeling (SEM). The results showed that RoCs at high elevations had high values in the early Holocene, decreased to their lowest values at -6000 cal. yr BP, gradually increased between -6000 and -3000 cal. yr BP, abruptly decreased in the past 3000 years, and then resumed an upward trend. RoCs at lower elevations experienced a steady acceleration throughout the Holocene, possibly due to climate cooling and wetting, as well as intensified fire activities.