全新世
干旱化
植被(病理学)
干旱
植硅岩
自然地理学
地质学
降水
东亚季风
气候变化
生态学
季风
环境科学
气候学
海洋学
地理
古生物学
病理
生物
气象学
医学
花粉
作者
Nannan Li,Manman Xie,Dorothy Sack,Nathalie Dubois,Xuguang Yang,Guizai Gao,Dehui Li,Lidan Liu,Hongyan Liu,Chengcheng Leng,Jiangyong Wang,Baojian Liu,Dongmei Jie
摘要
Abstract Ecological responses to past climate change as determined from palaeorecords offer insights into responses that may accompany future climate change. In arid and semi‐arid lands, the interactions between regional vegetation and climate change are not yet well understood, partly due to a lack of suitable palaeovegetation proxies that can provide accurate and continuous tracers for past vegetation dynamics. To gain a better understanding of long‐term vegetation dynamics, this study employs a multiproxy approach applied to sand‐palaeosol sediments of northeastern China's Songnen grasslands. Phytolith analyses and data on the stable carbon isotope composition ( δ 13 C) of organic matter are used to reconstruct palaeovegetation composition, namely, the changing abundance of C 3 and C 4 species, whereas a geochemical weathering index (Fed/Fet ratios) tracks past East Asian summer monsoon (EASM) intensity. The phytolith assemblages and indices and δ 13 C of the soil indicate that C 4 species' abundance has been increasing in the Songnen grasslands since the mid‐Holocene, although C 3 vegetation is still dominant. Statistically significant negative correlations between the δ 13 C data and Fet/Fed ratios suggest that continuous weakening of the EASM since the mid‐Holocene may be responsible for the 13 C‐enrichment of the sediments in the Songnen grasslands. Field vegetation surveys, modern topsoil phytoliths and δ 13 C calibration data indicate that the expansion of C 4 species since the mid‐Holocene is mainly due to their ability to cope with aridity when growing season temperature is not undergoing a significant decrease. Future precipitation decreases in arid and semi‐arid lands should make C 4 species more competitive in the grasslands of northeastern China. Highlights A continuous grassland landscape history is reconstructed from a sand‐palaeosol sequence via phytolith analysis. Multiple independent approaches were used to reconstruct past EASM intensity and palaeovegetation patterns. Phytolith and δ 13 C analyses indicate an increase in C 4 species since the mid‐Holocene. Aridification drives the increase in C 4 species within the grassland ecosystem.
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