Late Holocene Wetland Environmental Changes and Their Climatic Drivers in the Marginal Regions of the Tibetan Plateau

Abstract. This study investigates the dynamics and driving mechanisms of wetland environment changes in the northeastern Tibetan Plateau, focusing on the expansion and contraction of wetlands in Maqin County, on the northeastern edge of the Tibetan Plateau during the late Holocene. By analyzing sediment samples from three borehole profiles through spore-pollen extraction and identification, OSL dating, and other methods, we reconstructed the spatiotemporal dynamics of wetland expansion and contraction. The results of pollen analysis show that changes in the proportion of Cyperaceae and Asteraceae pollen reflect the dynamic transition between wetland and grassland ecosystems. In the early period (approximately 7000–4000 BP), Cyperaceae dominated, indicating a more humid wetland environment; however, in the middle and late periods (from about 4000 BP onwards), the proportion of Cyperaceae gradually decreased, and Asteraceae increased significantly, reflecting a trend of increasing aridification and grassland expansion. Further analysis suggests that the primary drivers of wetland degradation may be related to the weakening of the Asian monsoon, rising temperatures, and regional aridification. A comparison with global climate models (CMIP6) reveals that wetland changes in the northeastern Tibetan Plateau are somewhat synchronized with global climate patterns during both wet and dry periods. This study reveals the spatiotemporal characteristics of the dynamic transition between wetland and grassland ecosystems in the northeastern Tibetan Plateau and explores the influence of climate change, monsoon fluctuations, and other factors on wetland evolution, providing new perspectives and theoretical foundations for understanding the response of plateau ecosystems to global climate change and for wetland conservation.