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A sediment core (YJK19-02) collected from the southern outlet of Hangzhou Bay near the Yongjiang River estuary in East China was analyzed for grain size, lignin, bulk elemental composition, stable carbon isotope, and rare earth elements (REEs) to determine the sources and diagenesis of sedimentary organic matter (OM) of the estuary and adjacent areas since the Late Pleistocene. δ13C values (−24.80‰–−23.60‰), total organic carbon/total nitrogen (TOC/TN) molar ratios (8.00–12.14), and light rare earth element/heavy rare earth element ratios (LREE/HREE=8.34–8.91) revealed the predominance of terrestrial sources of OM, mainly from the Changjiang (Yangtze) River. The lignin parameters of syringyl/vanillyl (S/V=0.20–0.73) and cinnamyl/vanillyl (C/V=0.03–0.19) ratios indicate the predominance of nonwoody angiosperms, and the vanillic acid/vanillin ratios [(Ad/Al)v=0.32–1.57] indicate medium to high degrees of lignin degradation. An increasing trend of Λ (total lignin in mg/100-mg OC) values from ca. 14 500 a BP to ca. 11 000 a BP reflected the increase in temperature during the Late Pleistocene. However, a time lag effect of temperature on vegetation abundance was also revealed. The relatively higher and stable Λ values correspond to the higher temperature during the mid-Holocene from ca. 8 500 a BP to ca. 4 500 a BP. Λ values decreased from ca. 4 000 a BP to the present, corresponding to historical temperature fluctuations during this time. Our results show that the vegetation abundance in the Yongjiang River Basin since the Late Pleistocene was related to the temperature fluctuation duo to climate change. [ABSTRACT FROM AUTHOR]

In this study, a long-term relationship amongst wildfire, vegetation, climate, and human in the central Taiwan region, spanning from 17.3 to 2.0 cal kyr BP, is explored. To investigate this relationship, multiple proxy approaches were employed, including charcoal (CHAR and fire frequency), pollen data (Liew et al., 2006), magnetic susceptibility, and the carbon isotopic composition of organic carbon, along with the elemental ratio of total organic carbon to total nitrogen in the core sediments of the Toushe Basin, central Taiwan. From 17.3 to 14.5 cal kyr BP, the Toushe Basin experienced drier climate conditions, leading to high-intensity fires and reduced area of wetland. Between 14.5 and 11.5 cal kyr BP, a wetter climate corresponded with low-intensity fires and an increase in tree prevalence. From 11.5 to 5.0 cal kyr BP, the climate remained relatively stable with peaks of extreme wet phases, with frequent low-intensity fires promoting herbaceous plant growth. During the period from 5.0 to 2.0 cal kyr BP, wetter conditions persisted, but increased human activities likely intensified high-intensity fires, resulting in reduced tree and herbaceous plant populations and an expansion of wetlands, leading to complex impacts on the region's ecological dynamics. The pollen diversity index (PDI) and pollen richness index (PRI) showed that ecological diversity in the Toushe Basin decreased with high-intensity fires and increased with low-intensity fires, highlighting the complex interactions between natural and human factors during 17.3–2.0 cal kyr BP. In addition, this study showed a strong link between El-Niño events and increased wildfire activity in the Toushe Basin. El-Niño conditions, with reduced rainfall and increased dryness, likely heightened wildfire frequencies and intensity by lowering moisture levels and ignition thresholds. Increased lightning during these periods further exacerbated wildfires. This connection highlights El-Niño 's role in driving high-intensity fires, impacting the region's vegetation and ecological dynamics. • Drier climate predominantly controls wildfires in central Taiwan. • Human-induced burning prevalent from mid to late Holocene, impacting woody forests. • El Niño caused dryness fuels Toushe Basin wildfires. [ABSTRACT FROM AUTHOR]

To understand the role of the East Asian summer monsoon (EASM) and the East Asian winter monsoon (EAWM) on the hydroclimate in northern Taiwan, a multiproxy study has been conducted. This study aims to achieve its goal by using micro-XRF data of Ti and sulfur (S), carbon isotopic compositions (δ13C) along with elemental concentrations of carbon (C), nitrogen (N) and S, and diatom analyses in the sediment core extracted from the Dream Lake (DL; 25°10′01.9″ N, 121°33′36.0″ E and elevation = 588 m above sea level), northern Taiwan. The radiocarbon dates revealed that the DL core covered the time interval from 4.5 to 0.4 cal kyr BP. The current records revealed wetter phases during 4.5–3.0 cal kyr BP, 2.0–1.7 cal kyr BP, and 1.0–0.4 cal kyr BP, characterized by the dominance of C3 plants in the DL catchment, increased runoff, and higher lake levels. Drier climates observed in the current study during 3.0–2.0 cal kyr BP and 1.7–1.0 cal kyr BP, marked by a reduction in C3 plants, decreased runoff, and lower lake levels. The northern Taiwan climate during the late Holocene was observed to be regulated by the interplay of EASM and EAWM. The wet climate conditions during 4.5–3.0 were due to the La Niña-like conditions, which led to a strong EASM resulting in high precipitation conditions. The dry climate conditions during 3.0–2.0 cal kyr BP have coincided with El Niño-like conditions during 3.0–2.4 cal kyr BP and a subsequently strong EAWM during 2.4–2.0 cal kyr BP. Both situations led to a reduction in precipitation in the region. Unlike the time frame from 4.5 to 3.0 cal kyr BP, wet climate conditions during 2.0–1.7 and 1.0–0.4 cal kyr BP have coincided with weak EAWM conditions, which led to an increase in precipitation in northern Taiwan. The dry climate noticed between 1.7 and 1.0 cal kyr BP appeared to be the impact of both El Niño-like conditions and strong EAWM. [ABSTRACT FROM AUTHOR]

Sediment core 'ST2' collected from southern Zhejiang-Fujian muddy coastal area (ZFMA) was analyzed for grain size, bulk elemental composition (TOC and TN), stable carbon isotopes (δ13C), and lignin-derived phenols. The C/N ratios (6.2–10.1) and δ13C values (−21.7‰ to −23.0‰) demonstrated the predominance of marine organic matter. This was supported by a three end-member mixing model generated based on N/C ratio, δ13C, and Ʌ (total lignin in mg/100 mg of TOC). The results showed that marine and soil-derived organic matter accounted for 68.0% and 29.7%, respectively, of the total organic matter. The syringyl/vanillyl (S/V; 0.32 to 1.07) and cinnamyl/vanillyl (C/V; 0.13 to 0.91) ratios, together with the estimated range of lignin phenol vegetation index (LPVI) from 22.39 to 1451.91, indicated the predominance of non-woody angiosperms. The high vanillic acid/vanillin and syringic acid/syringaldehyde ratios suggested that the sediments were degraded prior to deposition. Our results showed that the variation of soil-derived organic matter along the core was affected by the East Asian monsoons, suggesting an anti-phase relationship between East Asian Winter Monsoon and East Asian Summer Monsoon. On the other hand, the temperature variations affected the abundance and type of vegetation. In addition, the variation of soil-derived organic matter showed remarkable consistency with other climate factors, such as solar irradiance, El Niño Southern Oscillation, North Atlantic Oscillation and North Atlantic ice drift. Meanwhile, the coherency relationship between the soil-derived organic matter and paleotyphoon activity indicates a possible linkage with paleotyphoon activity. Thus, the southern ZFMA was affected by both regional and global climatic factors, as well as extreme events-typhoon activity. ● East Asian monsoons controlled the variation of the soil-derived organic matter. ● The vegetation type and abundance in southern Zhejiang-Fujian mud area can reflect temperature changes during the last 1650 yrs BP. ● Paleoclimate in southern Zhejiang-Fujian mud area was controlled by both regional and global climatic factors, as well as typhoon activities. [ABSTRACT FROM AUTHOR]