Pub Date : 2024-11-17DOI: 10.1016/j.gloplacha.2024.104634
Yixuan Zhu, Zhoutao Zheng, Guang Zhao, Juntao Zhu, Bo Zhao, Yihan Sun, Jie Gao, Yangjian Zhang
Evapotranspiration (ET) is a crucial component of both the water cycle and energy balance, with vegetation being a key factor influencing ET. Vegetation impacts ET primarily through two modes: vegetation growth change (VGC) and vegetation type conversion (VTC). Despite the different mechanisms by which VGC and VTC influence ET, previous studies have rarely differentiated their individual effects. This has left the relative contributions of VGC and VTC to ET changes unclear. To address this gap, this study focuses on the arid and semi-arid regions of China (ASAC), where substantial vegetation changes have been observed. The spatiotemporal patterns of ET in ASAC were analyzed using remote sensing ET data from 2001 to 2018. The leaf area index (LAI) and land use/land cover (LULC) data were incorporated to perform pairwise comparison and contribution analysis to investigate the specific effects of VGC and VTC on ET. The results revealed a significant increase in mean annual ET across ASAC, with a rate of 4.5 mm/yr (p < 0.05). This increase was more pronounced in forest land and cropland compared to grasslands. ET increased across all seasons, with the largest increase occurring in summer, accounting for approximately 50 % of the annual ET increment. The pairwise comparison and contribution analysis indicated that ET in ASAC is more sensitive to vegetation greening than to VTC. VTC played a moderating role in ET changes, with relative contribution ranging from 1.3 % to 57.8 % across different LULC change types. These findings enhance our understanding of how vegetation changes influence ET. They can also provide valuable insights for land management strategies in ASAC, aiming to optimize vegetation construction and promote ecosystems sustainability.
{"title":"Evapotranspiration increase is more sensitive to vegetation greening than to vegetation type conversion in arid and semi-arid regions of China","authors":"Yixuan Zhu, Zhoutao Zheng, Guang Zhao, Juntao Zhu, Bo Zhao, Yihan Sun, Jie Gao, Yangjian Zhang","doi":"10.1016/j.gloplacha.2024.104634","DOIUrl":"https://doi.org/10.1016/j.gloplacha.2024.104634","url":null,"abstract":"Evapotranspiration (ET) is a crucial component of both the water cycle and energy balance, with vegetation being a key factor influencing ET. Vegetation impacts ET primarily through two modes: vegetation growth change (VGC) and vegetation type conversion (VTC). Despite the different mechanisms by which VGC and VTC influence ET, previous studies have rarely differentiated their individual effects. This has left the relative contributions of VGC and VTC to ET changes unclear. To address this gap, this study focuses on the arid and semi-arid regions of China (ASAC), where substantial vegetation changes have been observed. The spatiotemporal patterns of ET in ASAC were analyzed using remote sensing ET data from 2001 to 2018. The leaf area index (LAI) and land use/land cover (LULC) data were incorporated to perform pairwise comparison and contribution analysis to investigate the specific effects of VGC and VTC on ET. The results revealed a significant increase in mean annual ET across ASAC, with a rate of 4.5 mm/yr (<ce:italic>p</ce:italic> < 0.05). This increase was more pronounced in forest land and cropland compared to grasslands. ET increased across all seasons, with the largest increase occurring in summer, accounting for approximately 50 % of the annual ET increment. The pairwise comparison and contribution analysis indicated that ET in ASAC is more sensitive to vegetation greening than to VTC. VTC played a moderating role in ET changes, with relative contribution ranging from 1.3 % to 57.8 % across different LULC change types. These findings enhance our understanding of how vegetation changes influence ET. They can also provide valuable insights for land management strategies in ASAC, aiming to optimize vegetation construction and promote ecosystems sustainability.","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"250 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142672809","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Central Asia is a substantial source of long-range-transported dust, yet the historical and geological variability of dust activity in this region remains poorly understood. This study presents a Holocene record of dust activity from a 6.2-m loess section located near Tashkent in the westerlies-dominated region of eastern Uzbekistan, Central Asia. Utilizing the quartz optically stimulated luminescence dating protocol, we employed grain-size analysis and trace-element geochemistry to reconstruct Holocene dust activity. Dating indicated that this section was deposited over the last 9.6 ka. Four grain-size end-member (EM) components were identified, each representing different atmospheric circulation patterns and sedimentary environments. End-member 2, with a modal size of 11.2 μm, likely represents particles transported by upper-level westerlies, while EM 3, with a modal size of 28.3 μm, is associated with near-surface winds linked to dust storms. Zirconium is concentrated in coarse particles, whereas Rb is enriched in finer particles during dust deposition. Therefore, higher Zr/Rb ratios indicate stronger or more distant dust transport; hence, the Zr/Rb ratio is a reliable indicator of dust activity. Holocene dust activity was reconstructed using the EM 3 component and Zr/Rb ratio, revealing several extreme dust-storm events. During the early–middle Holocene (9.6–5 ka), dust activity was stronger but less frequent compared with the subsequent shift to lower intensity but higher frequency dust events. The long-term orbital-scale decline in Holocene dust activity can be attributed to reduced solar insolation and weakening of the Siberian High since the early Holocene. On a centennial to millennial scale, extreme dust-storm events are teleconnected with cold ice-rafted debris events in the North Atlantic. Projections for the coming century suggest that dust activity in eastern Uzbekistan may further decline, accompanied by an increase in precipitation. This study provides new insights into understanding and predicting dust storms in Central Asia.
中亚是远距离传播沙尘的一个重要来源，但人们对这一地区沙尘活动的历史和地质变化仍然知之甚少。本研究展示了中亚乌兹别克斯坦东部西风主导地区塔什干附近一个 6.2 米黄土断面的全新世沙尘活动记录。利用石英光学激发发光测年协议，我们采用粒度分析和痕量元素地球化学方法重建了全新世的尘埃活动。测年结果表明，该剖面沉积于过去的 9.6 ka。我们确定了四种颗粒大小的末端分子（EM）成分，它们分别代表了不同的大气环流模式和沉积环境。末端成分 2 的模态尺寸为 11.2 μm，可能代表了由高层西风输送的颗粒；而 EM 3 的模态尺寸为 28.3 μm，与沙尘暴相关的近地表风有关。锆富集在粗颗粒中，而铷富集在尘埃沉积过程中的细颗粒中。因此，Zr/Rb比率越高，表明尘埃迁移越强或越远；因此，Zr/Rb比率是尘埃活动的可靠指标。利用 EM 3 分量和 Zr/Rb 比率重建了全新世的沙尘活动，揭示了几个极端沙尘暴事件。在全新世早中期（9.6-5 ka），沙尘活动强度较大，但频率较低，而随后的沙尘事件强度较低，但频率较高。全新世沙尘活动在轨道尺度上的长期下降可归因于自全新世早期以来太阳日照减少和西伯利亚高纬度的减弱。在百年到千年尺度上，极端沙尘暴事件与北大西洋的寒冷冰雪碎片事件存在着千丝万缕的联系。对下个世纪的预测表明，乌兹别克斯坦东部的沙尘活动可能会进一步减少，同时降水量也会增加。这项研究为了解和预测中亚沙尘暴提供了新的视角。
{"title":"New insights into Holocene dust activity in eastern Uzbekistan","authors":"Yougui Song, Haoru Wei, Mengping Xie, Shugang Kang, Xiulan Zong, Nosir Shukurov, Shukhrat Shukurov, Yun Li, Yue Li, Mingyu Zhang","doi":"10.1016/j.gloplacha.2024.104633","DOIUrl":"https://doi.org/10.1016/j.gloplacha.2024.104633","url":null,"abstract":"Central Asia is a substantial source of long-range-transported dust, yet the historical and geological variability of dust activity in this region remains poorly understood. This study presents a Holocene record of dust activity from a 6.2-m loess section located near Tashkent in the westerlies-dominated region of eastern Uzbekistan, Central Asia. Utilizing the quartz optically stimulated luminescence dating protocol, we employed grain-size analysis and trace-element geochemistry to reconstruct Holocene dust activity. Dating indicated that this section was deposited over the last 9.6 ka. Four grain-size end-member (EM) components were identified, each representing different atmospheric circulation patterns and sedimentary environments. End-member 2, with a modal size of 11.2 μm, likely represents particles transported by upper-level westerlies, while EM 3, with a modal size of 28.3 μm, is associated with near-surface winds linked to dust storms. Zirconium is concentrated in coarse particles, whereas Rb is enriched in finer particles during dust deposition. Therefore, higher Zr/Rb ratios indicate stronger or more distant dust transport; hence, the Zr/Rb ratio is a reliable indicator of dust activity. Holocene dust activity was reconstructed using the EM 3 component and Zr/Rb ratio, revealing several extreme dust-storm events. During the early–middle Holocene (9.6–5 ka), dust activity was stronger but less frequent compared with the subsequent shift to lower intensity but higher frequency dust events. The long-term orbital-scale decline in Holocene dust activity can be attributed to reduced solar insolation and weakening of the Siberian High since the early Holocene. On a centennial to millennial scale, extreme dust-storm events are teleconnected with cold ice-rafted debris events in the North Atlantic. Projections for the coming century suggest that dust activity in eastern Uzbekistan may further decline, accompanied by an increase in precipitation. This study provides new insights into understanding and predicting dust storms in Central Asia.","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"22 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142672810","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-12DOI: 10.1016/j.gloplacha.2024.104632
Yongheng Yang , Yunfa Miao , Xuelian Wang , Tao Zhang , Liwu Li
The accurate paleoelevation reconstruction of the Qilian Mountains is critical to advancing our understanding the integrity of the Tibetan Plateau (TP) uplift model, its deep structural mechanisms, and corresponding connections with climatic, environmental, and biodiversity changes. Recently, the first quantitative reconstruction of the paleomidrange (i.e., average elevation of the basin and mountains) of the northern Tibetan Plateau (NTP) was completed, using innovative palynological paleoaltimetry-TP/TPAP [(Tsuga% + Podocarpus%) / (Tsuga% + Podocarpus% + Abies% + Picea%)] ratios, which revealed a rapid uplift of the NTP from low to high elevations during the late Middle Miocene. Here, we analyzed the Ebotu Fauna pollen record (13–12 Ma) from the Hongyazi Basin, situated within the Qilian Mountains, to directly infer the paleoelevation of this region. The pollen assemblages were predominantly composed of conifers (average of 64.0 %), including Picea, Cedrus, and Pinus of the Pinaceae, as well as Cupressaceae, with broadleaves and steppes taxa each accounting for <15 %. This pollen composition evidently reflects a vegetation type dominated by high-mountain conifers forest, consistent with Middle Miocene pollen assemblages from the Qaidam Basin. Application TP/TPAP ratios yielded a paleomidrange of 3492 ± 87 m at 13–12 Ma. Combined with the known elevation of the Qaidam Basin during this period (1885 ± 566 m), the elevation of the Qilian Mountains was calculated to be 4338 ± 653 m. In turn, an elevation of 2646 ± 740 m was obtained for the Hongyazi Basin. This high-elevation terrain provides evidence to support the multi-stage convective removal model of the TP caused by crustal shortening and thickening. It also led to the formation of a humid ecosystem dominated by conifers forest in the Qilian Mountains, supporting the diversification of mammalian taxa.
{"title":"High-elevation Qilian Mountains and its inspiration for tectonics and biodiversity during the late Middle Miocene","authors":"Yongheng Yang , Yunfa Miao , Xuelian Wang , Tao Zhang , Liwu Li","doi":"10.1016/j.gloplacha.2024.104632","DOIUrl":"10.1016/j.gloplacha.2024.104632","url":null,"abstract":"<div><div>The accurate paleoelevation reconstruction of the Qilian Mountains is critical to advancing our understanding the integrity of the Tibetan Plateau (TP) uplift model, its deep structural mechanisms, and corresponding connections with climatic, environmental, and biodiversity changes. Recently, the first quantitative reconstruction of the paleomidrange (i.e., average elevation of the basin and mountains) of the northern Tibetan Plateau (NTP) was completed, using innovative palynological paleoaltimetry-TP/TPAP [(<em>Tsuga</em>% + <em>Podocarpus</em>%) / (<em>Tsuga</em>% + <em>Podocarpus</em>% + <em>Abies</em>% + <em>Picea</em>%)] ratios, which revealed a rapid uplift of the NTP from low to high elevations during the late Middle Miocene. Here, we analyzed the Ebotu Fauna pollen record (13–12 Ma) from the Hongyazi Basin, situated within the Qilian Mountains, to directly infer the paleoelevation of this region. The pollen assemblages were predominantly composed of conifers (average of 64.0 %), including <em>Picea</em>, <em>Cedrus</em>, and <em>Pinus</em> of the Pinaceae, as well as Cupressaceae, with broadleaves and steppes taxa each accounting for <15 %. This pollen composition evidently reflects a vegetation type dominated by high-mountain conifers forest, consistent with Middle Miocene pollen assemblages from the Qaidam Basin. Application TP/TPAP ratios yielded a paleomidrange of 3492 ± 87 m at 13–12 Ma. Combined with the known elevation of the Qaidam Basin during this period (1885 ± 566 m), the elevation of the Qilian Mountains was calculated to be 4338 ± 653 m. In turn, an elevation of 2646 ± 740 m was obtained for the Hongyazi Basin. This high-elevation terrain provides evidence to support the multi-stage convective removal model of the TP caused by crustal shortening and thickening. It also led to the formation of a humid ecosystem dominated by conifers forest in the Qilian Mountains, supporting the diversification of mammalian taxa.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"243 ","pages":"Article 104632"},"PeriodicalIF":4.0,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661948","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-10DOI: 10.1016/j.gloplacha.2024.104631
Wenhan Chen , David B. Kemp , Hugh C. Jenkyns , Stuart A. Robinson , Shouyi Jiang , Chengrong Pan , Chao Li
The early Toarcian (∼183 Ma) was characterized by pronounced climate warming associated with massive release of 13C-depleted carbon to the exogenic system, as evidenced by globally recognized negative carbon-isotope excursions (N-CIE) in biospheric carbon reservoirs. Global warming during this interval triggered a variety of environmental perturbations, of which large-scale marine deoxygenation (as indicated by the presence of widespread organic carbon-rich deposits) is arguably diagnostic and led to the naming of the interval in question as the Toarcian Oceanic Anoxic Event (T-OAE). Nevertheless, the spatial variability of water-column redox during the T-OAE is unclear because most sedimentological and geochemical methods used to infer marine redox are likely reflective of bottom-water and/or pore-water conditions. Here we report new I/(Ca + Mg) and Cerium (Ce)-anomaly data from two carbonate successions from northern Italy that encompass the T-OAE interval. Both successions were deposited in the Alpine-Mediterranean Tethys; one in a shallow-water platform setting and the other within a pelagic environment. Both successions record an abrupt drop in I/(Ca + Mg) values, coupled with positive excursions in Ce-anomaly records at the onset of the T-OAE N-CIE. The synchronized changes in marine iodate depletion and Ce enrichment suggest widespread and significant upper-ocean deoxygenation in the Alpine-Mediterranean Tethys. This redox pattern is attributed to an expanded oxygen minimum zone (OMZ) formed as a result of sluggish oceanic circulation under climate warming, augmented by enhanced dissolved oxygen consumption due to increased nutrient availability and the consequent eutrophication in both proximal and distal settings. Because reduced seawater dissolved oxygen [O2] would increase the ecological stress and constrict any potentially hospitable habitats, the broad synchroneity between biotic turnovers and upper-ocean deoxygenation in the Alpine-Mediterranean Tethys is compatible with a potential causal link.
{"title":"Widespread upper-ocean deoxygenation in the Alpine-Mediterranean Tethys during the Toarcian Oceanic Anoxic Event","authors":"Wenhan Chen , David B. Kemp , Hugh C. Jenkyns , Stuart A. Robinson , Shouyi Jiang , Chengrong Pan , Chao Li","doi":"10.1016/j.gloplacha.2024.104631","DOIUrl":"10.1016/j.gloplacha.2024.104631","url":null,"abstract":"<div><div>The early Toarcian (∼183 Ma) was characterized by pronounced climate warming associated with massive release of <sup>13</sup>C-depleted carbon to the exogenic system, as evidenced by globally recognized negative carbon-isotope excursions (N-CIE) in biospheric carbon reservoirs. Global warming during this interval triggered a variety of environmental perturbations, of which large-scale marine deoxygenation (as indicated by the presence of widespread organic carbon-rich deposits) is arguably diagnostic and led to the naming of the interval in question as the Toarcian Oceanic Anoxic Event (T-OAE). Nevertheless, the spatial variability of water-column redox during the T-OAE is unclear because most sedimentological and geochemical methods used to infer marine redox are likely reflective of bottom-water and/or pore-water conditions. Here we report new I/(Ca + Mg) and Cerium (Ce)-anomaly data from two carbonate successions from northern Italy that encompass the T-OAE interval. Both successions were deposited in the Alpine-Mediterranean Tethys; one in a shallow-water platform setting and the other within a pelagic environment. Both successions record an abrupt drop in I/(Ca + Mg) values, coupled with positive excursions in Ce-anomaly records at the onset of the T-OAE N-CIE. The synchronized changes in marine iodate depletion and Ce enrichment suggest widespread and significant upper-ocean deoxygenation in the Alpine-Mediterranean Tethys. This redox pattern is attributed to an expanded oxygen minimum zone (OMZ) formed as a result of sluggish oceanic circulation under climate warming, augmented by enhanced dissolved oxygen consumption due to increased nutrient availability and the consequent eutrophication in both proximal and distal settings. Because reduced seawater dissolved oxygen [O<sub>2</sub>] would increase the ecological stress and constrict any potentially hospitable habitats, the broad synchroneity between biotic turnovers and upper-ocean deoxygenation in the Alpine-Mediterranean Tethys is compatible with a potential causal link.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"243 ","pages":"Article 104631"},"PeriodicalIF":4.0,"publicationDate":"2024-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661946","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study aims to elucidate the environmental changes signified by biogenic components, assess fluctuations in upwelling over the past century, and evaluate the potential risks associated with variations in coastal upwelling intensity on the degradation of fisheries within the Zhoushan Fishing Ground. High-resolution sediment records were established to reveal long-term variations in Zhoushan coastal upwelling. Results showed a significant reduction in nutrient components between 1900s and 1950s, suggesting a decline in upwelling strength. Since the 1960s, lightened δ15N and the incline of nutrients suggests an increase in anthropogenic nutrients influx, and increased OP and CUISST (SST-based coastal upwelling index) indicates strengthening of upwelling during the 1950s to 1980s. A positive correlation between organic phosphorus (OP) and δ13C has been observed since the 1960s, implying that P is a limiting nutrient due to increasing anthropogenic N influx, and the change in CUISST coincides well with our OP records. OP is a potential indicator of upwelling strength because upwelling contributes to over 90 % of the P on the East China Sea shelf. A prominent decline in the nutrient composition occurred from the 1980s to 2010s, despite substantially increased anthropogenic nutrients influx and eutrophication in adjoining Changjiang delta regions in the past decades. Weakening upwelling and the consequent decreasing nutrients influx has presumably hindered recovery and thus contributed to the degradation of fishery resources in recent decades.
{"title":"Nutrient changes from Zhoushan coastal upwelling fluctuations since 1900 and its implications for fisheries","authors":"Meiqun Xiao , Bing Deng , Guosen Zhang , Hui Wu , Yuanyuan Chen , Lijun Hou","doi":"10.1016/j.gloplacha.2024.104630","DOIUrl":"10.1016/j.gloplacha.2024.104630","url":null,"abstract":"<div><div>This study aims to elucidate the environmental changes signified by biogenic components, assess fluctuations in upwelling over the past century, and evaluate the potential risks associated with variations in coastal upwelling intensity on the degradation of fisheries within the Zhoushan Fishing Ground. High-resolution sediment records were established to reveal long-term variations in Zhoushan coastal upwelling. Results showed a significant reduction in nutrient components between 1900s and 1950s, suggesting a decline in upwelling strength. Since the 1960s, lightened δ<sup>15</sup>N and the incline of nutrients suggests an increase in anthropogenic nutrients influx, and increased OP and CUI<sub>SST</sub> (SST-based coastal upwelling index) indicates strengthening of upwelling during the 1950s to 1980s. A positive correlation between organic phosphorus (OP) and δ<sup>13</sup>C has been observed since the 1960s, implying that P is a limiting nutrient due to increasing anthropogenic N influx, and the change in CUI<sub>SST</sub> coincides well with our OP records. OP is a potential indicator of upwelling strength because upwelling contributes to over 90 % of the P on the East China Sea shelf. A prominent decline in the nutrient composition occurred from the 1980s to 2010s, despite substantially increased anthropogenic nutrients influx and eutrophication in adjoining Changjiang delta regions in the past decades. Weakening upwelling and the consequent decreasing nutrients influx has presumably hindered recovery and thus contributed to the degradation of fishery resources in recent decades.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"243 ","pages":"Article 104630"},"PeriodicalIF":4.0,"publicationDate":"2024-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661943","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-08DOI: 10.1016/j.gloplacha.2024.104629
Canh Tien Trinh Nguyen , Mengli Chen , Chris Gouramanis , Gonzalo Carrasco , Robert J. Wasson , Alan D. Ziegler
We investigate the contributions of natural (geogenic) and anthropogenic sources of lead (Pb) to the Nee Soon Swamp Forest, a relatively undisturbed catchment in Singapore. Using a Bayesian statistical source tracking approach with Pb isotopes preserved in sediment sections, our findings reveal a predominance of geogenic Pb in contemporary sediments, despite the significant presence of anthropogenic Pb in aerosols from local and distant sources. However, the geogenic Pb isotope signatures of the two main soil types in the catchment overlap with those of anthropogenic sources, introducing considerable uncertainty in using Pb isotopes as tracers within this catchment and potentially across larger areas. This uncertainty raises concerns about past interpretations of Pb contamination in both terrestrial and aquatic environments in Singapore and the broader region. To address these challenges, we emphasize the importance of accurately determining the signatures of all natural sources before using Pb isotopes as tracers in future studies. We also suggest that incorporating additional Pb isotope ratios or other stable isotope ratios (e.g., Ba, Cu, Sr, Zn) could enhance our ability to distinguish between natural and anthropogenic Pb sources. Ultimately, our study highlights the complexity of Pb sources in the environment and underscores the need for more comprehensive approaches to assessing their impacts.
Synopsis
This paper highlights insights and challenges in lead (Pb) source tracing studies conducted in urban catchments. These challenges primarily stem from the inadequate identification of all Pb isotope sources. We address these challenges by employing a Bayesian statistical approach to effectively identify, discriminate, and quantify Pb sources within a wetland ecosystem in Singapore.
{"title":"Unraveling lead sources in a tropical urban Swamp Forest: Insights and challenges","authors":"Canh Tien Trinh Nguyen , Mengli Chen , Chris Gouramanis , Gonzalo Carrasco , Robert J. Wasson , Alan D. Ziegler","doi":"10.1016/j.gloplacha.2024.104629","DOIUrl":"10.1016/j.gloplacha.2024.104629","url":null,"abstract":"<div><div>We investigate the contributions of natural (geogenic) and anthropogenic sources of lead (Pb) to the Nee Soon Swamp Forest, a relatively undisturbed catchment in Singapore. Using a Bayesian statistical source tracking approach with Pb isotopes preserved in sediment sections, our findings reveal a predominance of geogenic Pb in contemporary sediments, despite the significant presence of anthropogenic Pb in aerosols from local and distant sources. However, the geogenic Pb isotope signatures of the two main soil types in the catchment overlap with those of anthropogenic sources, introducing considerable uncertainty in using Pb isotopes as tracers within this catchment and potentially across larger areas. This uncertainty raises concerns about past interpretations of Pb contamination in both terrestrial and aquatic environments in Singapore and the broader region. To address these challenges, we emphasize the importance of accurately determining the signatures of all natural sources before using Pb isotopes as tracers in future studies. We also suggest that incorporating additional Pb isotope ratios or other stable isotope ratios (e.g., Ba, Cu, Sr, Zn) could enhance our ability to distinguish between natural and anthropogenic Pb sources. Ultimately, our study highlights the complexity of Pb sources in the environment and underscores the need for more comprehensive approaches to assessing their impacts.</div></div><div><h3>Synopsis</h3><div>This paper highlights insights and challenges in lead (Pb) source tracing studies conducted in urban catchments. These challenges primarily stem from the inadequate identification of all Pb isotope sources. We address these challenges by employing a Bayesian statistical approach to effectively identify, discriminate, and quantify Pb sources within a wetland ecosystem in Singapore.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"243 ","pages":"Article 104629"},"PeriodicalIF":4.0,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142662455","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-07DOI: 10.1016/j.gloplacha.2024.104621
Bing Liu , Yongtao Zhao , Aimin Liang , Aijun Sun , Zhengcai Zhang , Jianhui Ge , Hui Zhao , Fahu Chen
The aeolian deserts of northwestern China are major landscape types in the arid regions of the Northern Hemisphere, and collectively they are one of the largest dust source regions on Earth. However, owing to occurrence of sedimentary hiatuses within aeolian deposits in the deserts, we lack clear knowledge of the history of Holocene aeolian activity and the interaction between aeolian processes and their potential drivers. In this study, we extracted an environmentally sensitive grain-size component from the sediments of a closed interdune lake in the hinterland of the Tengger Desert. Our methodology included the application of End Member Analysis (EMA) of different modern sediment types from catchment to regional scales. We reconstructed aeolian activity over the past 13 cal ka BP and quantified the contributions of environmental factors. The results indicated that the EM 2 fraction of the interdune lake sediments is mainly transported by local winds and reflects changes in the intensity of aeolian activity. Based on EM 2 the strongest aeolian activity occurred during 13.0–7.0 cal ka BP, especially during 8.0–7.0 cal ka BP, and the weakest activity occurred during 7.0–3.5 cal ka BP. Aeolian activity increased after 3.5 cal ka BP, but with a gradually weakening trend. The occurrence of the weakest aeolian activity in the Tengger Desert during the Middle Holocene differs from that on the Asian Summer Monsoonal Boundary and in the area influenced by the Westerlies-dominated climate regime. Thus, there was a clearly defined spatio-temporal differentiation of Holocene aeolian activity across the deserts and dune fields of northern China. Quantitative analysis of the contributions of the potential drivers indicated that wind activity forced by different atmospheric circulation systems, rather than changes in vegetation cover, were the most important driver of regional aeolian activity, although their relative effects varied during the Holocene.
中国西北部的风化沙漠是北半球干旱地区的主要地貌类型，也是地球上最大的尘源区之一。然而，由于沙漠中的风化沉积出现了沉积间断，我们对全新世风化活动的历史以及风化过程与其潜在驱动因素之间的相互作用缺乏清晰的认识。在这项研究中，我们从腾格里沙漠腹地一个封闭沙丘间湖泊的沉积物中提取了对环境敏感的粒度成分。我们的研究方法包括从流域到区域尺度对不同的现代沉积物类型进行末端成分分析（EMA）。我们重建了过去 13 cal ka BP 的风化活动，并量化了环境因素的贡献。结果表明，沙丘间湖泊沉积物中的EM 2部分主要由当地风力搬运，反映了风化活动强度的变化。根据 EM 2，最强的风化活动发生在 13.0-7.0 cal ka BP，尤其是 8.0-7.0 cal ka BP，最弱的活动发生在 7.0-3.5 cal ka BP。风化活动在 3.5 cal ka BP 之后有所增加，但有逐渐减弱的趋势。中全新世时期腾格里沙漠的风化作用最弱，这与亚洲夏季季风边界和受西风带气候影响地区的情况不同。因此，全新世风化活动在华北沙漠和沙丘地带存在明显的时空分异。对潜在驱动因素贡献的定量分析表明，不同大气环流系统驱动的风活动，而不是植被变化，是区域风化活动的最重要驱动因素，尽管它们在全新世期间的相对影响各不相同。
{"title":"Quantitative contributions of different atmospheric circulation systems to Holocene aeolian activity in northwestern China: Evidence from a closed interdune lake in the Tengger Desert hinterland","authors":"Bing Liu , Yongtao Zhao , Aimin Liang , Aijun Sun , Zhengcai Zhang , Jianhui Ge , Hui Zhao , Fahu Chen","doi":"10.1016/j.gloplacha.2024.104621","DOIUrl":"10.1016/j.gloplacha.2024.104621","url":null,"abstract":"<div><div>The aeolian deserts of northwestern China are major landscape types in the arid regions of the Northern Hemisphere, and collectively they are one of the largest dust source regions on Earth. However, owing to occurrence of sedimentary hiatuses within aeolian deposits in the deserts, we lack clear knowledge of the history of Holocene aeolian activity and the interaction between aeolian processes and their potential drivers. In this study, we extracted an environmentally sensitive grain-size component from the sediments of a closed interdune lake in the hinterland of the Tengger Desert. Our methodology included the application of End Member Analysis (EMA) of different modern sediment types from catchment to regional scales. We reconstructed aeolian activity over the past 13 cal ka BP and quantified the contributions of environmental factors. The results indicated that the EM 2 fraction of the interdune lake sediments is mainly transported by local winds and reflects changes in the intensity of aeolian activity. Based on EM 2 the strongest aeolian activity occurred during 13.0–7.0 cal ka BP, especially during 8.0–7.0 cal ka BP, and the weakest activity occurred during 7.0–3.5 cal ka BP. Aeolian activity increased after 3.5 cal ka BP, but with a gradually weakening trend. The occurrence of the weakest aeolian activity in the Tengger Desert during the Middle Holocene differs from that on the Asian Summer Monsoonal Boundary and in the area influenced by the Westerlies-dominated climate regime. Thus, there was a clearly defined spatio-temporal differentiation of Holocene aeolian activity across the deserts and dune fields of northern China. Quantitative analysis of the contributions of the potential drivers indicated that wind activity forced by different atmospheric circulation systems, rather than changes in vegetation cover, were the most important driver of regional aeolian activity, although their relative effects varied during the Holocene.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"243 ","pages":"Article 104621"},"PeriodicalIF":4.0,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142662454","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-07DOI: 10.1016/j.gloplacha.2024.104626
Mengyu Wang , Chao Yue , Junhao He , Pengyi Zhang , Mengyang Xu , Yu Li , Jiaming Wang , Lele Wang , Can Xu
Forest management policies play a crucial role in enhancing the carbon sequestration capacities of forests. China's current harvest-prohibitive policies may result in the development of old-growth forests and the eventual saturation of their carbon stocks. This study combines empirically derived forest biomass growth models, spatially explicit information on forest age and live biomass carbon stock, and life cycle analysis to explore whether wood harvesting followed by forest regrowth can enhance carbon sequestration in the forest sector for 2021–2060 in China, by accounting for carbon stock changes in both live biomass and harvested wood products (HWP). The results showed that the net effect of wood harvesting on carbon sequestration, compared to that without any harvesting, is crucially dependent on the half-life of HWP and, secondarily, on harvest intensity. The ‘no-harvest’ scenario will enable 9.58 Pg more carbon to be stored in the forest live biomass by 2060 compared to that in 2020. Wood harvesting under the current average half-life of HWP in China (12.5 years) will enhance the forest sector's capability to sequester carbon with a light harvest intensity and diminish it with an intensive harvest intensity. However, the carbon sequestration capacity of the forest sector would increase, irrespective of the harvest intensity, if the HWP half-life could be doubled (25 years) or even quadrupled (50 years). Our findings highlighted the potential positive role of wood harvesting in increasing the carbon sequestration capacity of the forest sector in China and provide useful perspectives for drafting national forest management policies.
{"title":"Can wood harvest followed by forest regrowth enhance carbon sequestration of the forest sector in China?","authors":"Mengyu Wang , Chao Yue , Junhao He , Pengyi Zhang , Mengyang Xu , Yu Li , Jiaming Wang , Lele Wang , Can Xu","doi":"10.1016/j.gloplacha.2024.104626","DOIUrl":"10.1016/j.gloplacha.2024.104626","url":null,"abstract":"<div><div>Forest management policies play a crucial role in enhancing the carbon sequestration capacities of forests. China's current harvest-prohibitive policies may result in the development of old-growth forests and the eventual saturation of their carbon stocks. This study combines empirically derived forest biomass growth models, spatially explicit information on forest age and live biomass carbon stock, and life cycle analysis to explore whether wood harvesting followed by forest regrowth can enhance carbon sequestration in the forest sector for 2021–2060 in China, by accounting for carbon stock changes in both live biomass and harvested wood products (HWP). The results showed that the net effect of wood harvesting on carbon sequestration, compared to that without any harvesting, is crucially dependent on the half-life of HWP and, secondarily, on harvest intensity. The ‘no-harvest’ scenario will enable 9.58 Pg more carbon to be stored in the forest live biomass by 2060 compared to that in 2020. Wood harvesting under the current average half-life of HWP in China (12.5 years) will enhance the forest sector's capability to sequester carbon with a light harvest intensity and diminish it with an intensive harvest intensity. However, the carbon sequestration capacity of the forest sector would increase, irrespective of the harvest intensity, if the HWP half-life could be doubled (25 years) or even quadrupled (50 years). Our findings highlighted the potential positive role of wood harvesting in increasing the carbon sequestration capacity of the forest sector in China and provide useful perspectives for drafting national forest management policies.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"243 ","pages":"Article 104626"},"PeriodicalIF":4.0,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661944","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-07DOI: 10.1016/j.gloplacha.2024.104620
Liping Tian , Yingxue Yang , Li Li, Yanming Ruan, Juan He, Guodong Jia
The accuracy of paleothermometers is a prerequisite for understanding the past sea surface temperature (SST) changes in the tropical seas. Here, we analyzed the SST estimates reconstructed by four lipid proxies with common linear and newly advanced models in parallel in a sediment core collected from the southern South China Sea (SCS). After excluding the impact of terrestrial input, all of the four proxies-inferred SSTs displayed a gradually warming pattern since 18.3 ka. Our long-chain alkenones-derived annual SST at seawater depth of 0–30 m (SST 0–30 m) record closely matched the regional synthetic SST record from the entire southern SCS, corresponding to high-latitude climate events during the deglaciation. The temperatures reconstructed by long-chain diols (LCDs) showed an upper limit of 27 °C, and we thus proposed that they reflected the optimal survival temperature for organisms producing LCDs when SST was higher than 27 °C. Isoprenoid and hydroxy glycerol dialkyl glycerol tetraethers (iGDGTs and OH-GDGTs)-derived temperatures likely reflected the subsurface temperature (subT) at seawater depth of 30–125 m and SST towards the warm season in the tropical sea, respectively.
{"title":"Multi-proxy reconstructions of paleotemperature in the southern South China Sea since the last deglaciation","authors":"Liping Tian , Yingxue Yang , Li Li, Yanming Ruan, Juan He, Guodong Jia","doi":"10.1016/j.gloplacha.2024.104620","DOIUrl":"10.1016/j.gloplacha.2024.104620","url":null,"abstract":"<div><div>The accuracy of paleothermometers is a prerequisite for understanding the past sea surface temperature (SST) changes in the tropical seas. Here, we analyzed the SST estimates reconstructed by four lipid proxies with common linear and newly advanced models in parallel in a sediment core collected from the southern South China Sea (SCS). After excluding the impact of terrestrial input, all of the four proxies-inferred SSTs displayed a gradually warming pattern since 18.3 ka. Our long-chain alkenones-derived annual SST at seawater depth of 0–30 m (SST <sub>0–30 m</sub>) record closely matched the regional synthetic SST record from the entire southern SCS, corresponding to high-latitude climate events during the deglaciation. The temperatures reconstructed by long-chain diols (LCDs) showed an upper limit of 27 °C, and we thus proposed that they reflected the optimal survival temperature for organisms producing LCDs when SST was higher than 27 °C. Isoprenoid and hydroxy glycerol dialkyl glycerol tetraethers (iGDGTs and OH-GDGTs)-derived temperatures likely reflected the subsurface temperature (subT) at seawater depth of 30–125 m and SST towards the warm season in the tropical sea, respectively.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"243 ","pages":"Article 104620"},"PeriodicalIF":4.0,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661945","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-05DOI: 10.1016/j.gloplacha.2024.104627
Xiaoping Wang , Zhi Li , Fei Zhang
Sun-induced chlorophyll fluorescence (SIF) from plants offers an effective proxy for estimating gross primary productivity (GPP) by modeling SIF-GPP relationships, a widely used method to evaluate the global carbon sink. However, most SIF-GPP models ignore SIF differences between shaded and sunlit leaves, resulting in GPP underestimation, particularly in dense vegetation. This study aims to partition the contributions of sunlit and shaded leaves to canopy SIF and GPP to refine the SIF-GPP estimation model. Data from 40 eddy covariance (EC) sites representing eight major biomes and TROPOMI SIF satellite data were used for site-specific and global-scale analyses. Our results showed that the contributions of sunlit and shaded leaves to canopy SIF were 80 % and 20 %, and to canopy GPP were 55 % and 45 %, respectively. For site-specific or satellite data, the SIF-GPP relationships were the strongest for sunlit leaves (R2 > 0.51, RMSE = 4.03 μmol m−2 s−1, p < 0.001). The new SIF-GPP model, including sunlit-shaded SIF separation, can improve the accuracy of GPP estimation (R2 = 0.53, RMSE = 4.38 μmol m−2 s−1, p < 0.001). Compared with the model established with observed data, R2 was increased by 0.1, and RMSE decreased by 13.26 μmol m−2 s−1, indicating that the ‘two-leaf’ model could notably improve the SIF-GPP model. This study confirms the different contributions of sunlit and shaded leaves to canopy SIF and GPP, and ignoring this disparity would induce systematic bias in GPP estimation. Our methods and findings on sunlit-shaded SIF separation can be referenced by other studies to enhance GPP estimation accuracy.
{"title":"An improved instantaneous gross primary productivity model considering the difference in contributions of sunlit and shaded leaves to canopy sun-induced chlorophyll fluorescence","authors":"Xiaoping Wang , Zhi Li , Fei Zhang","doi":"10.1016/j.gloplacha.2024.104627","DOIUrl":"10.1016/j.gloplacha.2024.104627","url":null,"abstract":"<div><div>Sun-induced chlorophyll fluorescence (SIF) from plants offers an effective proxy for estimating gross primary productivity (GPP) by modeling SIF-GPP relationships, a widely used method to evaluate the global carbon sink. However, most SIF-GPP models ignore SIF differences between shaded and sunlit leaves, resulting in GPP underestimation, particularly in dense vegetation. This study aims to partition the contributions of sunlit and shaded leaves to canopy SIF and GPP to refine the SIF-GPP estimation model. Data from 40 eddy covariance (EC) sites representing eight major biomes and TROPOMI SIF satellite data were used for site-specific and global-scale analyses. Our results showed that the contributions of sunlit and shaded leaves to canopy SIF were 80 % and 20 %, and to canopy GPP were 55 % and 45 %, respectively. For site-specific or satellite data, the SIF-GPP relationships were the strongest for sunlit leaves (R<sup>2</sup> > 0.51, RMSE = 4.03 μmol m<sup>−2</sup> s<sup>−1</sup>, <em>p</em> < 0.001). The new SIF-GPP model, including sunlit-shaded SIF separation, can improve the accuracy of GPP estimation (R<sup>2</sup> = 0.53, RMSE = 4.38 μmol m<sup>−2</sup> s<sup>−1</sup>, <em>p</em> < 0.001). Compared with the model established with observed data, R<sup>2</sup> was increased by 0.1, and RMSE decreased by 13.26 μmol m<sup>−2</sup> s<sup>−1</sup>, indicating that the ‘two-leaf’ model could notably improve the SIF-GPP model. This study confirms the different contributions of sunlit and shaded leaves to canopy SIF and GPP, and ignoring this disparity would induce systematic bias in GPP estimation. Our methods and findings on sunlit-shaded SIF separation can be referenced by other studies to enhance GPP estimation accuracy.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"243 ","pages":"Article 104627"},"PeriodicalIF":4.0,"publicationDate":"2024-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142662453","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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