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![Location, bathymetry and landscape of Gonghai Lake. (a) Location of Gonghai Lake (red star), and other sites mentioned in the text (Dali lake, Daihai lake, site LJC in the Chinese Loess Plateau, Mugeco Lake, and core ECMA from the East China Sea [yellow triangle]). (b) Bathymetry of Gonghai Lake and the location of core GH19A used in this study, and of cores GH09B and GH09C (Chen et al., 2020; F. Chen, Xu, et al., 2015). (c) Panoramic image of the modern landscape of Gonghai Lake. Dashed line means Asian summer monsoon limit (Chen et al., 2008). Maps were generated using ArcMap 10.2.](profile/Panpan-Ji/publication/353663420/figure/fig1/AS:11431281174411294@1689229384227/Location-bathymetry-and-landscape-of-Gonghai-Lake-a-Location-of-Gonghai-Lake-red.png)
Location, bathymetry and landscape of Gonghai Lake. (a) Location of Gonghai Lake (red star), and other sites mentioned in the text (Dali lake, Daihai lake, site LJC in the Chinese Loess Plateau, Mugeco Lake, and core ECMA from the East China Sea [yellow triangle]). (b) Bathymetry of Gonghai Lake and the location of core GH19A used in this study, and of cores GH09B and GH09C (Chen et al., 2020; F. Chen, Xu, et al., 2015). (c) Panoramic image of the modern landscape of Gonghai Lake. Dashed line means Asian summer monsoon limit (Chen et al., 2008). Maps were generated using ArcMap 10.2.
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Wildfire activity is an important activity in evolution of vegetation and carbon cycling. Whether wet weather will suppress wildfire or promote them by increasing fuel reserves during the Holocene is not clear. We obtained a record of black carbon from a sediment core spanning the last 14.8 kyr from Gonghai Lake, in North China. There is a close re...
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Forest fires are a significant factor that affects the boreal forest carbon distribution which emits carbon into the atmosphere and leads to carbon redistribution among carbon pools. However, knowledge about how much carbon was transferred among pools and the immediate changes in soil nutrient contents in areas that were burned by fires of various...
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... All the pollen records indicate severe forest degradation during the two intense phases of intense fire, although there are differences in the timing of this forest degradation due to the zonal asynchrony of regional paleofire. In contrast, comparison of the modelled woodland proportions and zscores of paleofire resulted in a positive correlation (r = 0.29, p < 0.5), although the strength of this correlation for the lower Yangtze is much weaker than that observed for other regions in monsoonal China, such as the Dali Lake watershed (r = 0.45, p = unknown), Yangtze River basin (r = 0.47, p < 0.01), and Gonghai Lake (r = 0.72, p < 0.01) (Ji et al., 2021;Pei et al., 2020;Zhang et al., 2022). From the foregoing we conclude that the fire intensity in the lower Yangtze during the Holocene was not related to biofuel accumulation. ...
The lower Yangtze is one of the regions of origin of rice agriculture but it is unclear if environmental change drove the transition from hunting-gathering to agriculture. Long-term and continuous lacustrine records of anthropogenic fire are a more effective means of addressing this problem than the fragmentary terrestrial records available for the lower Yangtze region. We constructed a Holocene fire history revealed by records of black carbon content (BCC) and grain size of the sediments of Lake Nanyi in the lower Yangtze. Our results show the following: 1) Peaks in fire activity occurred during ∼8400–6500 (fire peak P1) and ∼ 1100–0 cal BP (fire peak P2), while weaker fire activity occurred during ∼6500–1100 cal BP (S2). 2) This temporal pattern of fire activity, with a double peak (P1-S2-P2), was asynchronous from east to west across the lower Yangtze. The warm and humid climate would not have caused intense fires and the reduction of forest during ∼8400–6500 and ∼ 1100–0 cal BP. Therefore, we suggest that anthropogenic ignitions, corresponding to pronounced population fluctuations after 8400 cal BP, dominated the regional fire activity. Combined with archaeological evidence, the inverse relationship between the agricultural and population levels and fire intensity during the mid-Holocene suggests that fire intensity at this time was the result of the diversity of landscape types associated with prehistoric subsistence patterns, rather than the magnitude of anthropogenic activity. Combined with sea level, rainfall and archaeological evidence, we propose a mechanism whereby asynchronous water-level rise during ∼8400–6500 cal BP forced the migration of humans to the foothills where they often used fire to modify the landscape as part of a broad-spectrum subsistence pattern. Whereas, water-level fall after 6500 cal BP expanded the area of open ground for human settlement, and in this less diverse landscape, less use was made of fire in agricultural subsistence. Overall, our study reveals how regional water-level, driven by sea-level rise and extreme rainfall, delayed the transition from hunting-gathering to agriculture in the lower Yangtze region.
... Pollen-based reconstruction results demonstrate that the average precipitation was only 370 mm between 1500 and 1900 CE, which is significantly lower than the modern average of 445 mm (Fig. 7c) (Chen et al., 2015a). Additionally, the low frequency of wildfires in the region during the Little Ice Age has been attributed to insufficient biofuels under drought conditions (Ji et al., 2021). ...
In recent decades, lakes in arid and semi-arid regions of northern China have been rapidly shrinking, threatening the area's ecological security. However, the impacts of climate change and human activities on lake shrinkage remains unclear due to short instrumental records and a lack of long-term lake-level change records. To address this issue, we reconstructed the water depth changes of Daihai Lake, a typical lake experiencing rapid shrinkage in northern China, over the last 500 years using lake-level-sensitive chironomid assemblages. We established a regional quantitative transfer function of chironomid water-depth using 54 surface sediments from Daihai Lake and Bosten Lake in northern China. The partial least squares (PLS) model yielded a coefficient of determination (R 2 jack) of 0.85, a maximum bias of 1.75 m, and a root mean square error prediction (RMSEP) of 1.58 m demonstrating the reliability of inferred water depth. Several diagnostic methods were used to verify the results, and they were compared with a 60-years instrumental record. The reconstructed data revealed that the lake level was low during 1500-1780 CE, gradually increasing to its peak in the 1960s and then rapidly decreasing by approximately 10 m in the last few decades. By comparing the results with regional historical documents, palynology and stalagmite records, and meteorological data, we concluded that climate change was the main driver of lake level dynamics before the 1960s, while human activities dominated the rapid shrinkage of the lake in recent decades. Our results provide a valuable limnological dataset for the water management in Daihai Lake and a reliable method for reconstruct the lake-level changes.
... Biological and chemical indicators include diatoms, TOC, TN and TP, which are generally used to reflect the evolution of lake trophic status [11,[53][54][55][56]64], and biosilica (Bio-Si) in particular can be used as a proxy of diatom productivity [35]. Black carbon (BC) is a stable product of fossil and biomass fuel combustion and can be used to reconstruct regional wildfire history [30], and to reflect the regional intensity of anthropogenic BC emission [21,26]. The element composition of lake sediments can be used reconstruct the history of climate change [61], and of regional metal aerosol pollution [67]. ...
... We used the stratigraphic records of TN, TP, TOC and Bio-Si to reconstruct the history of changing nutrient levels, diatom productivity, and sedimentary organic carbon accumulation in Gonghai and Yueliang lakes. BC was used to indirectly reflect changes in anthropogenic fossil fuel consumption [26] and the natural background of regional wildfire as well [30]. ...
... The sedimentary BC content of Yueliang lake is low and close to the background level of ~2 mg/g at Gonghai lake. And, the BC content of Yueliang reflects the natural level of regional wildfire, which controlled by the regional temperature variation (Fig. 2b, S3) [30]. It fails to express the signal of N emission from fossil energy consumption, or the response is weak. ...
Anthropogenic emissions have resulted in increases in the atmospheric fluxes of both nutrient and toxic elements. However, the long-term geochemical impacts on lake sediments of deposition activities have not been clearly clarified. We selected two small enclosed lakes in northern China—Gonghai, strongly influenced by anthropogenic activities, and Yueliang lake, relatively weakly influenced by anthropogenic activities—to reconstruct historical trends of atmospheric deposition on the geochemistry of the recent sediments. The results showed an abrupt rise in the nutrient levels in Gonghai and the enrichment of toxic metal elements from 1950 (the Anthropocene) onwards. While, at Yueliang lake, the rise on TN was from 1990 onwards. These consequences are attributable to the aggravation of anthropogenic atmospheric deposition in N, P and toxic metals, from fertilizer consumption, mining and coal combustion. The intensity of anthropogenic deposition is considerable, which leave a significant stratigraphic signal of the Anthropocene in lake sediments.
... The increasing number of high-resolution BC records from different sedimentary archives provide evidence for understanding the characteristics and variations of past fire regimes in different regions during the Holocene (e.g., Bird and Cali, 1998;Ji et al., 2021;Kang et al., 2020). Previous globally distributed sedimentary charcoal records suggest that biomass burning generally occurred under relatively dry climatic conditions (Marlon et al., 2013); however, recent BC records from the Yangtze River basin in China and from northwestern Montana in the USA indicate that increased biofuel availability as a result of wet conditions can also increase the incidence of fires (Alt et al., 2018;Pei et al., 2020). ...
Global warming and human activities have significantly increased the wildfire risk in highly populated subtropical East Asia over recent decades; however, the factors driving fire occurrence on multiple timescales remain unclear. We present and analyze an observational dataset of fire for the Yunnan Plateau in southwestern China for the past 20 years, together with a Holocene fire history documented by four sedimentary black carbon records from four lakes on the Yunnan Plateau: lakes Dian, Xingyun, Qilu, and Yilong. Our aims were to explore the linkage between wildfires and natural and anthropogenic variables driving wildfire occurrence on multiple timescales. The results show that on a short timescale, more wildfires occurred in drier seasons, and on a longer timescale, more wildfires occurred during 6–2.8 cal kyr BP, when humidity decreased. In contrast, there was a moderate wildfire incidence during the relatively humid interval from 11.7 to 6 cal kyr BP. These observations indicate that fire activity is controlled by the humidity, against the background of the abundance of biofuel. The lowest degree of biomass burning occurred after ∼2.8 cal kyr BP and was linked to an anthropogenic reduction of biomass availability, despite an increase in drought. This suggests the importance of active fire management and prescribed clearance measures, especially given projections of continued drought and increased vegetation cover.
... Ongoing global climatic warming and recent extensive fires are causing increasing concerns about the prospect of a 'planet on fire' (Liu et al., 2010;Pechony and Shindell, 2010;Abatzoglou and Williams, 2016;Nolan et al., 2020;Pang et al., 2021). In northern China, fire occurrence is expected to increase in the near future (Pechony and Shindell, 2010;Liu et al., 2012;Ji et al., 2021). Given the fragile ecosystems of the region (Li, 2008;Li et al., 2016), determining the underlying causes of fire occurrence by reconstructing its long-term fire history is therefore important for fire prevention and control, especially against the background of continued warming. ...
... However, in a sedimentary record from Hulun Nuur Lake in the semi-arid forest-steppe ecotone in northern China, Yin et al. (2016) observed no simple inverse relationship between fire occurrence and the EASM intensity during the Holocene and suggested that vegetation was a critical factor for fire occurrence in northern Chia, via the accumulation of biofuel. Other studies have found that the Holocene fire activity in northern China was positively correlated with the EASM intensity and with tree pollen percentages, on the millennial timescale (Wang et al., 2013;Ji et al., 2021). Additionally, Pang et al. (2021) proposed that temperature, rather than the EASM precipitation, played the primary role in driving the occurrence of forest fires in northeastern China during the Holocene. ...
... However, it remains unclear whether and when human activities overtook climate change as the dominant control of fire occurrence in the region. For example, based on the record from a sediment core from Gonghai Lake in northern China, Ji et al. (2021) proposed that the regional fire history was largely unaffected by human activity since the last deglaciation. However, Wang et al. (2013) and Mu et al. (2016) found that human activities had a significant impact on the increase in fire activity in northern China after ~2000 yr BP. ...
There are debates regarding whether a wet and warm climate or a dry and cold climate dominated Holocene fire activity in northern China on the millennial timescale, and when human activities overtook climate change as the dominant control on fire occurrence in the region. Here we present a high-resolution fire history for the past ∼15,500 years from a sediment core in Dali Lake, located in the foothills of the Greater Hinggan Mountains, one of the areas of highest fire risk in China. The results demonstrate that fire activity was rare during the last deglaciation (∼15,500–11,700 yr BP), gradually increased at the beginning of the Holocene, and reached its highest level during ∼9000–5000 yr BP, after which there was a decreasing trend. However, after ∼2000 yr BP this decreasing trend ended, and the most prominent feature is a peak in fire activity during the Medieval Warm Period (MWP). Overall, fire activity corresponded well to changes in the East Asian summer monsoon (EASM) precipitation on the millennial timescale during ∼15,500–2000 yr BP, but this relationship changed after ∼2000 yr BP. We propose that fire activity in northern China on the millennial timescale during ∼15,500–2000 yr BP was dominated by the biofuels reserve under the control of the EASM precipitation. In contrast, with the intensification of human activities after ∼2000 yr BP, human activity caused a ∼62%–73% increase in fire activity, which altered the fire-climate relationship that had previously prevailed in northern China. Our results indicate that a wet-warm climate (increased EASM intensity), rather than a dry-cold climate, was the dominant control on fire activity in northern China during 15,500–2000 yr BP on the millennial timescale, but that human activities played an important role in fire occurrence after ∼2000 yr BP.
... Gonghai lake. Therefore, we conclude that the BC content reflects the natural level 260 of regional wildfire, which resembles the regional temperature record (Ji et al., 2021). ...
Anthropogenic emissions have resulted in increases in the atmospheric fluxes of both nutrient and toxic elements; However, the long-term geochemical impacts on lake sediments of deposition activities have not been clearly clarified. We selected two small enclosed lakes in northern China—Gonghai, strongly influenced by anthropogenic activities, and Yueliang lake, relatively weakly influenced by anthropogenic activities—to reconstruct historical trends of atmospheric deposition on the geochemistry of the recent sediments. The results showed an abrupt rise in the nutrient levels in Gonghai and the enrichment of toxic metal elements from 1950(the Anthropocene) onwards. While, at Yueliang lake, the rise on TN was from 1990 onwards. These consequences are attributable to the aggravation of anthropogenic atmospheric deposition in N, P and toxic metals, from fertilizer consumption, mining and coal combustion. The intensity of anthropogenic deposition is considerable, which leave a significant stratigraphic signal of the Anthropocene in lake sediments.
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.
