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燃烧形成的黑碳粒子进入大气中可影响辐射平衡,导致全球气候变暖,其沉降在河流、湖泊、海洋、土壤等环境中对全球生物地球化学循环起到重要的作用,成为当前国际地球科学研究的热点问题。综述了黑碳的定义及排放、沉降、降解过程,并总结了其在现在及过去环境和气候系统中的重要作用与研究意义。黑碳是全球惰性有机碳库的重要组成部分,在全球慢速碳循环中发挥潜在作用。因其具有很强的吸光特性,它在区域气候变暖过程中扮演重要角色。沉降在不同地质载体中的黑碳难以降解,可以保存几百万年,为地质历史时期古气候和古环境重建研究提供重要信息。海洋沉积物过去数百万年的黑碳记录指示了天然火的演化信息,晚第四纪黄土剖面黑碳也指示了天然火的变化信息,最近千年的湖泊和冰芯黑碳记录既反映了天然火的信息,也指示人类活动的信号。未来黑碳研究应进一步关注标准测量方法,以真正理解黑碳在全球气候与环境系统中的作用。 相似文献
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火对气候、生物地球化学循环和人类健康产生广泛影响,为了避开人类活动的干扰,在整体上把握古火灾、古植被和古气候之间的相互作用关系,并为进一步的深入研究古火灾提供框架,本文聚焦冰期—间冰期时间尺度,整理了深海沉积、湖泊沉积、黄土等沉积物中的古火灾信息,并与对应的古气候、古植被情况结合讨论,总结归纳在冰期—间冰期尺度上不同地区的火灾机制情况,并分析其异同及原因。全球不同海域的深海沉积物中黑碳记录所指示的古火灾没有统一的规律和解释,自然火灾发生机制存在区域性差异。长时间尺度的湖泊记录反映的冰期—间冰期火灾活动情况较一致,今后更多长时间尺度的湖泊沉积物研究可以为火灾活动的轨道驱动研究增添有力证据。黄土中的冰期—间冰期的火灾演化规律存在不同观点,这可能是选用火灾代用指标不同导致,黄土中的黑碳沉积通量可能更准确的揭示古火灾历史。 相似文献
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自然火是地球系统的重要组成部分,与气候、植被关系紧密。全球增温情景下,自然火的演化规律和控制因素已经成为学术界的研究热点,通过整理分析自然火实际监测记录、模型模拟结果以及古记录反映的自然火历史,发现还存在一些亟待解决的问题:全球不同增温情景下自然火增多还是减少?其控制因素如何改变?本文选取距今最近的地质历史时期新生代中的典型增温期"中中新世气候适宜期"和"全新世大暖期",对其自然火研究进行分析总结,归纳得出温度是增温情景下自然火的重要控制因素,但是不同地区自然火控制因素有所不同,雨热条件的季节分配、植被类型的演替、雷电和火山活动等因素也对自然火有重要影响。季风区气候变幅大、植被类型丰富,其自然火演化及控制因素具有复杂性,是自然火研究的重要区域,建议在今后研究中,在东亚季风区选择涵盖未来百年可能增温幅度的理想沉积记录,对其记录的自然火历史、增温幅度、植被演替进行系统研究,进而探讨未来增温情景下自然火的演化规律和控制因素。 相似文献
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干旱气候因子与森林火灾 总被引：5，自引：0，他引：5
森林火灾作为一种自然灾害, 气候变化直接或间接影响森林燃烧的火环境, 进而对火发生和火行为产生影响. 干旱气候条件与森林火灾的发生有密切的关系, 气象条件通过气温、 日照、 蒸发量、 风力、 空气湿度等影响着森林火灾的发生和发展. 一般情况下, 气温高、 降水少、 湿度小、 风力大易发生森林火灾. 在山区, 山谷风和地形影响森林火灾蔓延, 森林火灾的蔓延主要受山谷风所控制, 具有间歇性, 另外地形的变化在很大程度上制约着火势的蔓延. 所以, 要利用不同时段的气象条件、 山风出现的时间及有利地形, 及时组织灭火和控制火势蔓延. 森林火灾的发生有各种类型, 通过对森林火灾中一些特殊火行为及相关元素对火灾发展蔓延影响分析, 找出森林火灾扑救与逃生的方法及注意事项. 相似文献
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中国陆地生态系统近 2 0年碳空间动态的初步研究(英文) 总被引：4，自引：0，他引：4
陆地生态系统的净生产力 (NEP)是生态系统净初级生产力 (NPP)和异氧呼吸 (Rh)之差。在全球尺度上 ,反映NPP和Rh之差的NEP直接揭示陆地生态系统与大气系统之间的二氧化碳交换 ,即碳平衡 ,因此 ,意义重大。文章简短回顾了关于中国陆地生态系统碳平衡的研究状况。由于植物根部呼吸很难从土壤表面总二氧化碳 (CO2 )通量中分开 ,因此直接从野外测量土壤异氧呼吸几乎是不可能的。虽然由于像诸如火灾、森林砍伐、土地利用变化及气候和大气变化等干扰因素 ,全球陆地生态系统很大程度上处于非平衡态 ,利用生态系统在平衡态时NPP等于Rh这一事实 ,我们估算了全球和中国森林生态系统的土壤异氧呼吸。利用遥感和地面的NPP观测数据 ,我们也估算了中国森林生态系统逐月的净生产力 (1982— 1998)。NPP的估算主要采用NOAA卫星AVHRR 8km的NDVI数据 ,结合地面气候数据完成。土壤呼吸是通过地面观测数据与温度和降水的关系得到的。在此基础上我们得到了中国陆地生态系统在过去近 2 0年中碳的动态变化 ,并给出了初步结果。 相似文献
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土壤甲烷吸收汇研究进展 总被引：12，自引：0，他引：12
人类活动导致大气中温室气体浓度增加,是全球气候变暖的主要原因之一。由于陆地生态系统中通气状况良好的土壤是甲烷最大的吸收汇,研究吸收汇强度及其影响因素对估算大气中甲烷储存增量、采取措施增强土壤吸收汇的强度是很有意义的。综述了全球透气土壤吸收甲烷总量及土地利用变化、农业措施对甲烷吸收汇的影响。 相似文献
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浅层滑坡型火后泥石流起动机理研究进展与案例分析 总被引：1，自引：0，他引：1
火后泥石流由起动条件的不同可以分为表面径流型火后泥石流和浅层滑坡型火后泥石流。由于表面径流型火后泥石流多发生于火灾后的前两年,水土流失严重,灾害效应明显,因此,大多数研究集中在表面径流型火后泥石流。然而,对于火灾较长时间后发生的浅层滑坡型火后泥石流,现有研究相对较少,这制约了人们对于浅层滑坡型火后泥石流起动条件和起动机理的认知。与表面径流型火后泥石流相比,浅层滑坡型火后泥石流的形成主要是由于根-土强度的退化导致。因此,定量测定火灾后根和土强度的衰减,是了解浅层滑坡型火后泥石流机理的必要条件。本文以四川省凉山州木里县的火后浅层滑坡为研究对象,针对未火烧、火烧后3年及火烧后9年的马尾松进行根系数量统计、根系极限抗拉力测试、根土复合体抗剪强度测试及对不同火烧后时间的坡体进行稳定性分析。结果表明,火后根系数量、极限抗拉力随火后时间而递减。由于火灾造成植被死亡根系腐烂,土中产生大孔隙,使得根土复合体抗剪强度下降,进而造成降雨条件下的浅层滑坡的起动。研究成果解释了火灾后数年内浅层滑坡-泥石流的起动机理,为滑坡型火后泥石流防灾减灾提供了数据支撑。 相似文献
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土壤溶解性有机质的研究进展 总被引：7，自引：0，他引：7
溶解性有机质(DOM)是土壤的重要组成部分,虽然含量占土壤有机质成分的比例不高,却是非常活跃的化学物质,可影响土壤的形成及肥力,通过水循环进入水生生态系统参与水体内的各个过程、经微生物作用进入大气圈对全球气候产生巨大影响,在土壤乃至全球系统中都发挥着极其重要的作用,已渐成为土壤学家、环境学家和生态学家研究的焦点。本文综述了众多学者的研究成果,讨论了土壤DOM的来源、含量、组成和分类,以及影响其含量变化的因素及其环境效应,指出了研究中存在的问题和未来发展趋势。 相似文献
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冻土是全球中高纬地区和高山地带普遍存在的自然现象,它对全球以及区域性气候、水循环、水平衡等都有着巨大的影响,土壤冻融条件下的陆面过程正是这种影响的重要环节,介绍了土壤冻融条件下陆面过程的研究现状,特别是在大气环流模型(GCM)中引入水文陆面模型以来陆面过程研究的迅猛发展,对现在国际上正在进行的考虑冻土的陆面过程研究项目,如陆面过程参数化比较计划的第二阶段第五期PILPS(2E)以及美国NASA的寒区陆面过程实地试验计划也进行了介绍,并在此基础上对土壤冻融条件下陆面过程的发展趋势进行了分析. 相似文献
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Adam A. Ali Philip E. Higuera Yves Bergeron Christopher Carcaillet 《Quaternary Research》2009,72(3):462-468
Sedimentary charcoal particles from lakes are commonly used to investigate fire history. Fire-history reconstructions are based on measuring the surface area or counting the number of charcoal fragments in adjacent samples. Recently, the volume of charcoal particles was advised as a more accurate method for quantifying past charcoal production. Large charcoal datasets, used to synthesize global fire history, include these different types of charcoal measurements and implicitly assume that they provide comparable fire-history information. However, no study has demonstrated that this assumption is valid. Here we compare fire-frequency reconstructions based on measurements of charcoal area and number, and estimates of charcoal volume from two lake sediment records from the eastern Canadian boreal forest. Results indicate that the three proxies provide comparable fire-history interpretations when using a locally defined threshold to identify fire events. 相似文献
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轨道尺度亚洲气候演化是古气候热点问题之一,其变化过程和机理对理解当前全球变暖下亚洲气候变化具有重要参考意义。最近几十年,基于黄土、石笋、湖泊等载体的轨道尺度亚洲气候重建研究获得显著进展,气候演化历史的基本框架已被构建,不同区域和指标记录之间的差异暗示了气候演化机理的复杂性。数值模拟作为研究气候动力学的重要工具之一,在轨道尺度亚洲气候变化中也得到广泛应用和快速发展。基于此,本文尝试对最近十数年轨道尺度亚洲气候演化机理的数值模拟研究做一简单总结和梳理。目前的数值模拟尚未对地质记录给出的各种变化特征、区域差异等现象,尤其是东亚夏季风的黄土和石笋差异、季风和干旱气候的耦合关系等,给出合理解释。因此,在未来工作中亟须涵盖多轨道旋回的高分辨率瞬变试验,结合良好定年的重建记录,以期对轨道尺度亚洲气候变化机理获得更深入完整的认识。 相似文献
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We show how sedimentary charcoal records from multiple sites within a single landscape can be used to compare fire histories and reveal small scale patterns in fire regimes. Our objective is to develop strategies for classifying and comparing late-Holocene charcoal records in Midwestern oak- and pine-dominated sand plain ecosystems where fire regimes include a mix of surface and crown fires. Using standard techniques for the analysis of charcoal from lake sediments, we compiled 1000- to 4000-yr-long records of charcoal accumulation and charcoal peak frequencies from 10 small lakes across a sand plain in northwestern Wisconsin. We used cluster analysis to identify six types of charcoal signatures that differ in their charcoal influx rates, amount of grass charcoal, and frequency and magnitude of charcoal peaks. The charcoal records demonstrate that while fire histories vary among sites, there are regional patterns in the occurrence of charcoal signature types that are consistent with expected differences in fire regimes based on regional climate and vegetation reconstructions. The fire histories also show periods of regional change in charcoal signatures occurring during times of regional climate changes at ~ 700, 1000, and 3500 cal yr BP. 相似文献
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Holocene fire-climate-vegetation linkages are mostly understood at individual sites by comparing charcoal and pollen records with other paleoenvironmental proxy and model simulations. This scale of reconstruction often obscures detection of large-scale patterns in past fire activity that are related to changes in regional climate and vegetation. A network of 31 charcoal records from southern South America was examined to assess fire history along a transect from subtropic to subantarctic biomes. The charcoal data indicate that fire activity was greater than present at ca. 12,000 cal yr BP and increased further and was widespread at 9500 cal yr BP. Fire activity decreased and became more spatially variable by 6000 cal yr BP, and this trend continued to present. Atmospheric circulation anomalies during recent high-fire years show a southward shift in westerlies, and paleoclimate model simulations and data syntheses suggest that such conditions may have prevailed for millennia in the early Holocene when the pole-to-equator temperature gradients were weaker and annual temperatures were higher than present, in response to orbital-time-scale insolation changes. 相似文献
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Late Holocene high resolution palaeoclimatic reconstruction inferred from Sebkha Mhabeul, southeast Tunisia 总被引：1，自引：0，他引：1
Relations between climate change and landscape evolution during the last two millennia in southeastern coastal Tunisia have been documented using high-resolution reconstruction of flood history and fire activity in the Sebkha Mhabeul core. The age model, based on tephrochronology, indicates that the core extends from Roman to modern times and encompasses the well-defined climatic periods of the last two millennia. This record provides a first palaeoecological/palaeoclimatic high resolution reconstruction in North Africa using a cross-disciplinary approach with both physical (grey-scale intensity, quartz particles) and biological (charcoal and pollen) indicators. The flood history shows four wet/dry cycles (ca. AD 550-950, 950-1300, 1300-1570 and 1570-1870) of different duration. Major hydrological instabilities are concentrated during the Medieval Climate Anomalies and the early Little Ice Age, between AD 1000 and 1550. Direct correlation between climate and fire cannot be established suggesting that the fire history of the Sebkha environment is mainly influenced by human activity. This study demonstrates the great value of sebkhas as palaeoenvironmental archives. 相似文献
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Ccile C. Remy Dominic Senici Han Y. H. Chen Yves Bergeron Martin Lavoie Laure Paradis Adam A. Ali 《第四纪科学杂志》2019,34(7):509-518
Mixed‐wood boreal forests are characterized by a heterogeneous landscape dominated by coniferous or deciduous species depending on stand moisture and fire activity. Our study highlights the long‐term drivers of these differences between landscapes across mixed‐wood boreal forests to improve simulated vegetation dynamics under predicted climate changes. We investigate the effects of main climate trends and wildfire activities on the vegetation dynamics of two areas characterized by different stand moisture regimes during the last 9000 years. We performed paleofire and pollen analyses in the mixed‐wood boreal forest of north‐western Ontario, derived from lacustrine sediment deposits, to reconstruct historical vegetation dynamics, which encompassed both the Holocene climatic optimum (ca. 8000–4000 a bp ) and the Neoglacial period (ca. 4000 a bp ). The past warm and dry period (Holocene climatic optimum) promoted higher fire activity that resulted in an increase in coniferous species abundance in the xeric area. The predicted warmer climate and an increase in drought events should lead to a coniferization of the xeric areas affected by high fire activity while the mesic areas may retain a higher broadleaf abundance, as these areas are not prone to an increase in fire activity. Copyright © 2019 John Wiley & Sons, Ltd. 相似文献
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Kendrick J. Brown Thomas Giesecke 《Boreas: An International Journal of Quaternary Research》2014,43(3):639-651
Holocene fire disturbance and vegetation history were reconstructed using macroscopic charcoal and pollen accumulation rates from two lake sediment records (Holtjärnen and Klotjärnen) collected in the boreal forest of central Sweden. The records were used to examine the potential drivers associated with changes in fire regime. Climate, vegetation and human activity were all identified as factors variously influencing the fire regime. In the early Holocene, near bicentennial fire return intervals were regionally widespread, suggesting that fire disturbance was largely regulated by climate at that time. In the mid‐ and late Holocene, vegetation exerted an important control on the fire regime. During the mid‐Holocene, the expansion of thermophilous broadleaf vegetation offset the influence of warmer climate by altering the local microclimate and by changing the structure and flammability of the available fuels. During the transition to the late Holocene, thermophilous vegetation decreased in abundance and Pinus increased, resulting in a more flammable forest even though the climate was cooling and moistening. Fire disturbance correspondingly increased. The modern boreal forest was established in the late Holocene as Picea expanded regionally as the climate cooled, moistened, and became increasingly continental. Although no change in the frequency of fire was apparent at this time, increased stand densities likely facilitated greater fuel consumption in subsequent fires. Within the last millennium, human action markedly modified the forested landscape, altering the fire regime. 相似文献
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Spores of the dung‐fungi Sporormiella provide a proxy for assessing past changes in herbivore abundance, and for temporally linking these with shifts in vegetation communities (pollen) and fire frequency (charcoal). Although the proxy is now widely used, potential influences of local environmental conditions are poorly understood. Here we assess the reliability of Sporormiella as a proxy of herbivores by presenting five new spore records from the South Island of New Zealand; a land where the herbivore extinction/introduction chronology is well established, and where extinctions occurred independently of major climate change. We show that Sporormiella spores from relatively dry soils provide a good proxy for herbivore extinctions and introductions. However, spore abundances from saturated soil sites appear to fluctuate in close correlation with changes in local hydrology (represented by wetland herb pollen, testate amoebae and moisture sensitive mosses). Our results suggest Sporormiella records derived from wetlands require cautious interpretation, and that proxies for hydrological conditions should also be considered when interpreting such records. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Walter Finsinger Daniele Colombaroli Jacques‐Louis De Beaulieu Verushka Valsecchi Boris Vannière Elisa Vescovi Emmanuel Chapron André F. Lotter Michel Magny Willy Tinner 《第四纪科学杂志》2010,25(8):1239-1247
Despite the high potential of pollen records for climate reconstruction, pollen–climate relationships may be biased due to past and present human activities on the landscape. We use (i) transfer functions based on modern pollen–climate relationships to infer seasonal temperature and summer precipitation for the period 11 500–4500 cal. a BP and (ii) lake‐level change records based on different sedimentary proxies in multiple cores that are mainly indicative for summer hydrology at Lago dell'Accesa (central Italy). Quantitative reconstructions indicate lowest summer precipitation during two phases (8500–7700 cal. a BP and after 6000 cal. a BP) and a gradual winter temperature increase from 11 500 to ca. 8000 cal. a BP. Lowest summer precipitation was reconstructed during these phases characterised by vegetation shifts from open forests dominated by summergreen oaks (Quercus) to forests dominated by evergreen oaks (Quercus ilex), which are at present most abundant where summer drought is stronger. Similarly, the lake‐level record indicates two long‐lasting low summer precipitation phases (8800–7700 and 6400–4400 cal. a BP) that were interrupted by short‐term high summer precipitation events. Based on the broad agreement between the pollen‐inferred summer precipitation and the low‐frequency lake‐level changes, we suggest that the duration of the high summer precipitation events may have been too short to maintain drought‐sensitive trees, which may have been affected by high mortality rates when summer dry conditions returned. Although past and modern pollen–climate relationships may very likely have been affected by human activities since the Neolithic (i.e. when exploitation of the landscape started), we reject the hypothesis of a significant anthropogenic bias in the pollen‐based climate reconstruction. In addition, we suggest that pollen‐based and lake‐level reconstructions may have different inherent abilities of capturing high‐ and low‐frequency precipitation signals. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献