Search Results (2)

The driving force of climate change in the monsoon margin is complex, making it a key area for regional and global climate change research. Palaeohydrological studies in the monsoon margin have increased the resolution of research in the long term, transitioning from qualitative to quantitative studies to comprehend climate change processes, patterns, and mechanisms. Testate amoebae (TA) in peat sediments are used as a proxy indicator organism for quantitative reconstruction of palaeohydrology. Thus, their community changes are directly related to precipitation, and widely used to reconstruct the patterns of summer precipitation globally. We investigated TA species and reconstructed palaeohydrological changes in the Greater Khingan Mountains’ Hongtu (HT) peatland, located in the East Asian Summer Monsoon (EASM) margin. The result showed that the most abundant TA species were Assulina muscorum (12.4 ± 5.0%) and Nebela tincta (8.9 ± 4.9%) in the HT peat core. The increase in dry indicator species (e.g., A. muscorum and Alabasta militaris) indicated a drying pattern in the HT peatland since 150 cal yr BP. Principal component analysis (PCA) explained 47.6% of the variation in the selected TA assemblages. During 400 to 250 cal yr BP, PCA axis 1 scores ranged from 0.2 to −1.3 (reflecting a drier climate), associating with the Little Ice Age. The paleohydrology of the northern part of the Greater Khingan Mountains was mainly controlled by the EASM, which was associated with changes in North Atlantic Sea surface temperature and solar radiative forcing. The apparent drying pattern may be the result of the gradual intensification of anthropogenic activities and the increase in EASM intensity. Full article

A better understanding of past East Asian summer monsoonal (EASM) variations, which play a key role in the development of the largely rain-watered agriculture in China, could contribute to better appraising potential impacts on EASM with regard to global climate change. However, our knowledge of the relationship between mid-Holocene hydrological recession and the development of Neolithic culture is limited due to a lack of joint studies and a compilation of spatiotemporal data, especially on the episode of ~6–5 ka from the mid-Holocene Optimum (HO) along the peripheral realm of the EASM. Here, we suggest that the hydrological recession between ~6–5 ka, on the basis of lithology and geochemical element analysis, occurred not only in the Horqin sandy land, but also in other fluvial-lacustrine, stalagmitic, loess, and aeolian records across the whole monsoon-influenced boundary belt. These records indicated varied, more or less synchronous, and coherent moisture changes, yet with not entirely consistent onsets, durations, and degrees. We attributed this spatiotemporal complexity to the orbit-induced weakening of summer solar insolation, and the interactions of the Asian monsoon (AM) and westerlies, as well as topography and regional vegetation factors. Furthermore, the mid-Holocene initial hydroclimatic recession during ~6–5 ka within the thresholds of an eco-environment bearing a capacity system, might have facilitated the development of mid–late Neolithic culture and stimulated the north and northwest expansion and integration of region-specific Neolithic culture. Full article