我国中西部表层沉积物中微炭屑记录的火活动信息

微炭屑作为植物体不完全燃烧的产物, 是良好的火活动代用指标。目前, 国内外更多地关注微炭屑对不同时间尺度上火的重建, 对现代微炭屑的分布特征及其与火的关系缺少系统分析。本研究采集了35个跨越我国中西部约2950 km的表层沉积样品, 利用孢粉流程法获取微炭屑, 结合采样点周边50 km、100 km及200 km范围内卫星火点数量以及植被、降水、湿度及温度等指标, 分析不同空间范围微炭屑的粒径、形态及浓度特征, 探讨其与火活动频率的关系。结果表明: 陆表(表土、湖泊与其他水体表层沉积物)微炭屑浓度可有效地反映区域火活动特征, 其浓度高值往往与区域内火点高值相对应; 现代火活动频繁区域主要分布在植被、降水与温度条件偏好的半湿润-半干旱区(也是人类农业活动密集区); 据二者对比结果推测, 微炭屑的来源范围可能主要为50~100 km以内; 同时, 长条形与近圆形微炭屑的比值与50 km范围内草地火活动有较好的对应关系(r=0.61, p＜0.05), 对燃烧的草本与木本植物比例具有较好的指示意义。考虑到区域环境条件差异, 未来拟将更大空间范围内微炭屑记录与火点数量和燃烧面积相结合, 进一步揭示微炭屑与现代火活动的关系, 为地层古火重建提供现代过程基础。

     

新疆艾里克湖炭屑记录的中亚干旱区MIS 3中期以来的古火灾演化

大规模火灾能够对当地植被和生产经济造成不可逆的损害, 严重影响着人们的生产生活。中亚干旱区生态系统脆弱, 火灾频发, 使得该地区成为研究古火灾的理想地区之一。MIS 3时期是距离现今最近的间冰阶, 气候上与现在有许多相似之处, 是进行古气候研究的重要时段。通过对长时间尺度上的火灾演化及其影响因素的了解, 即有助于我们理解火灾对植被和气候变化的响应机制, 又能够为现代预测和治理火灾提供一定的科学依据。本研究以新疆艾里克湖Ailike-2019孔(岩芯长4.49 m)沉积岩芯为研究对象, 通过AMS ¹⁴C测年、花粉通量和炭屑分析, 重建艾里克湖约40 ka以来的古火灾演化序列。结果表明, MIS 3中、晚期(40.2~26.7 cal.ka B.P.), 植被覆盖度较差, 火灾较少; MIS 2时期(26.7~11.7 cal.ka B.P.), 植被覆盖度差, 火灾少; 全新世(11.7 cal.ka B.P. 至今), 植被覆盖度显著上升, 火灾频发。研究区自MIS 3中期以来的火灾活动与植被覆盖度的变化具有相似的趋势, 说明火灾的发生可能与植被覆盖度的变化有关。这与中亚干旱区的其他炭屑记录相似, 表明中亚干旱区轨道尺度上的火灾可能主要受可燃生物量控制。暖湿/冷干的气候条件导致植被覆盖度扩张/缩小, 从而提供了更多/更少的可燃生物量, 使得火灾能够产生大量/少量炭屑。

     

中国北方煤火与遥感探测技术

本文以宁夏汝箕沟煤矿区为例,在系统研究和分析矿区地质、煤层自燃机理的基础上,探讨了应用遥感技术实现快速、精确探测煤田火区分布,构建煤火预警与监测体系的可行性。     

新疆SCZ17剖面黑碳记录的16~12 ka火灾历史及其驱动因素探究

基于新疆深390 cm的SCZ17黄土剖面的黑碳（BC）记录以及总有机碳含量（TOC）和磁化率结果,并与巴里坤湖孢粉记录的温度数据对比,重建了该区末次冰消期（16~12 ka,对应剖面深度202~274 cm）的火灾历史并探讨了其控制因素。结果表明：1）在末次冰消期期间黑碳通量与TOC变化具有较好的一致性,均呈上升趋势,说明随着植被量的增加,生物质燃烧活动增加;2）BC通量与湿度和温度数据的EEMD结果显示：①在13~16 ka期间,剖面的黑碳通量指示的区域生物质燃烧变化与温度变化存在着近乎同步的关系,而在12~13 ka期间可能由于湿度的影响二者的同步关系不太明确;②χ_fd%所指示的湿度变化和黑碳通量的对比结果显示,湿度峰值/谷值分别对应着黑碳通量的谷值/峰值,即当气候湿润时,火灾活动频率低;气候干旱时,火灾活动频率高。因此,认为研究区火灾活动倾向于发生在暖干的气候条件下,且可燃生物量可能控制着区域火灾变化的长期趋势,而由温度和湿度变化所造成的火灾活动的次一级波动叠加在这一长期趋势上。

     

沉积物中黑碳在古环境古气候研究中的应用

黑碳是指生物质或化石燃料不完全燃烧以及岩石风化所产生的一系列含碳物质连续体的统称。其特殊的物理化学性质可对全球气候环境造成显著影响,如加剧温室效应、影响水文循环和碳封存;由于其具有较为稳定的化学性质以及燃烧前后碳同位素分馏小的特征,又使黑碳作为一种载体被应用到地质时间尺度火历史与植被演化重建工作中。通过对黑碳的特征、来源、循环、在沉积物中的提取方法及其在不同时间尺度古环境重建中的应用进行评述,提出了目前黑碳记录在古环境重建中存在的一些问题,如黑碳的降解转化过程对黑碳沉积的影响,以及黑碳年龄具有滞后性,沉积物中黑碳来源及沉积过程的复杂性,地质时间尺度黑碳参与碳循环的角色仍不明确等。另外对未来研究进行了展望：相对于陆地土壤、湖泊、河流、冰川等载体,海洋沉积物中黑碳的研究工作还非常缺乏。自1966年以来,深海钻探计划、国际大洋钻探计划、综合大洋钻探/发现计划航次及我国自主航次在全球海洋获取了大量高质量沉积岩芯,为未来利用黑碳研究新生代以来构造、气候、植被、火乃至人类活动之间的相互作用提供了可能性。     

高分辨地电阻率探测与互联网络远程监测煤田火烧区

为发现、治理、监控煤田火烧区,将互联网的创新成果深度融合于传统地勘技术领域之中,开发了具有探测火烧区范围和中心温度、连续采集、高温传感、远程遥控等主要功能的永久性的无线传感器网络远程监测系统.研发出新型传感器节点,能够与单极-偶极装置互联储存并发送探测数据,同时将高温探头直接放置于地下火烧区巷道进行监测;通过带保护电路的太阳能供电装置,为现场数据采集网络提供了持续充足的能源;由移动通信网和互联网将信号传送到监测中心,实现远程控制监测;在新疆地区的12个火烧区同时部署了所研发的监测系统,至今已工作45个月,表明采取的技术措施可以保障监测系统的免维护长期稳定运行.乌鲁木齐监测中心收到110多万条现场信息,授权后可任意查询、永久保存,为新疆大面积煤田自燃火区的治理和保卫治理成果,提供基础数据.研究结果表明,充分发挥互联网在地球物理探测监测中的优化和集成作用,对提升煤田地质基勘查的创新和生产能力,具有重要的意义.

     

中国东南海域活跃火强度时空动态与发生类型

自然和人为因素引发的植被火是全球生态系统的重要干扰因子,而基于卫星获取的活跃火（active fires）是探究人-火关系与活跃火发生机理、扩展机制的基础。相对于陆域活跃火,海上活跃火发生的时空动态及其强度、类型等研究较为薄弱。基于VIIRS活跃火和海洋地形等数据,通过分析中国东南海域活跃火发生的时间规律、强度特征、地形属性和距海岸线距离等特性,初步确定了海上活跃火类型界定体系。结果表明：(1)本区相同位置活跃火发生具有时序性。2015年前后两年内相同位置活跃火逐渐减少,且低纬地区更突出;而2015年前后三年内低纬地区活跃火发生强度稳定、高纬地区逐渐减少。(2)中国东南海域活跃火呈现明显的空间集-疏特征,即沿岸海域“条带状”聚集区、以曾母暗沙为中心的“团状”聚集区、南海诸岛周围的分散区。(3) 2012—2013年、2015年、2020年活跃火总强度与其月均强度变化一致,即其发生强度增强归因于活跃火的面状、分散发生;2014年、2016—2019年活跃火总强度与月均强度峰值不同步,即其强度增强归因于活跃火的点状、集中发生。(4)基于时空、强度和集聚特征,结合人类活动频繁区布局,将发生时...     

BOOK REVIEWS

Book Reviewed in this article: The Vanishing Farmland Crisis, Critical Views of the Movement to Preserve Agricultural Land . John Baden Protecting Farmlands . Frederick R. Steiner and John E. Theilacker Ecological Effects of Fire in South African Ecosystems . Peter de V. Booysen and Neil M. Tainton Geography in China . Wu Chuanjun , Wang Nailiang , Lin Chao and Zhao Songqiao Resource Inventory and Baseline Study Methods for Developing Countries . Francis Conant , Peter Rogers , Marion Baumgardner , Cyrus Mc Kell , Raymond Dasmann, and Priscilla Reining Principles of Remote Sensing . Paul J. Curran Famine As A Geographical Phenomenon . Bruce Currey and Graeme Hugo The Suburban Squeeze: Land Conversion and Regulation in the San Francisco Bay Area . David E. Dowall Senses of Place . John Eyles Uneven Development and the Geographical Transfer of Value . D. K. Forbes and P. J. Rimmer Issues in Wilderness Management . Michael Frome Land-use and Prehistory in South-east Spain , The London Research Series in Geography 8. Antonio Gilman and John B. Thornes with Stephen Wise Regions in Question, Space, Development Theory and Regional Policy . Charles Gore The Colorado River: Instability and Basin Management . William L. Graf Hazardous Waste Sites: The Credibility Gap . Michael R. Greenberg and Richard F. Anderson Peasants, Subsistence Ecology, and Development in the Highlands of Papua New Guinea . Lawrence S. Grossman Silver Cities: The Photography of American Urbanization, 1839-1915 Peter B. Hales Silicon Landscapes . Peter Hall and Ann Markusen Remaking Ibieca: Rural Life in Aragon under Franco . Susan F. Harding The European Energy Challenge: East and West . George W. Hoffman The Global Climate . John T. Houghton The Urban Jobless in Eastern Africa . Abel G. M. Ishumi . The Tourist: Travel in Twentieth-Century North America . John A. Jakle City and Society: An Outline for Urban Geography . R. J. Johnston Residential Segregation, The State and Constitutional Conflict in American Urban Areas . R. J. Johnston Accessibility and Utilization: Geographical Perspectives on Health Care Delivery . Alun E. Joseph and David R. Phillips To the Heart of Asia: The Life of Sven Hedin . George Kish North American Culture , Vol 1. Ary J. Lamme III Past and Present in the Americas: A Compendium of Recent Studies . John Lynch Ethnicity in Contemporary America: A Geographical Appraisal . Jesse O. Mc Kee The Shell Countryside Book . Richard Muir and Eric Duffey 1990 Planning Conference Series. Proceedings of the National Geographic Areas Conference . Proceedings of the Regional Geographic Areas Conferences Wood, Brick, and Stone: The North American Settlement Landscape . Vol. 2: Barns and Farm Structures . Allen G. Noble Bangladesh: Biography of a Muslim Nation . Charles Peter O'donnell     

Making the landscape “home”: Narratives of bushfire and place in Australia

This study investigated how the meaning of ‘home’ influences the social construction of bushfire in two Australian communities at high risk. An increasing number of Australians are living in proximity to areas of high bushfire risk due to climate, vegetation and demographic changes. Land and Fire Management Agencies recognise an urgent need to understand what motivates residents to take action to mitigate bushfire risk, and individual decisions whether or not to evacuate when bushfire is imminent. In bushfire policy and management, the home is considered to be synonymous with the house and associated built structures. Using a combination of visual and ethnographic research methods, we ‘mapped’ residents’ understanding of ‘home’. The findings suggest that the concept of ‘home’ embraces more than the private spaces of house and garden. Landscape practices such as gardening with indigenous plant species, ecological restoration, and habitual walking extend the home territory beyond the house and garden and into public landscapes. Physical elements of the landscape such as mountains and locally significant species of trees form part of the ‘imaginary’ of home. These findings are important to the on-going study of the meaning of home. The implications are also significant for land and bushfire managers as they suggest that community education programs that focus solely on the house may fail to connect with people’s wider sense of home in the landscape.     

Regulation of peatland evaporation following wildfire; the complex control of soil tension under dynamic evaporation demand

The capability of peatland ecosystems to regulate evapotranspiration (ET) following wildfire is a key control on the resilience of their globally important carbon stocks under future climatic conditions. Evaporation dominates post-fire ET, with canopy and sub-canopy removal restricting transpiration and increasing evaporation potential. Therefore, in order to project the hydrology and associated stability of peatlands to a diverse range of post-fire weather conditions and future climates the regulation of evaporation must be accurately parameterised in peatland ecohydrological models. To achieve this, we measure the surface resistance (r_s) to evaporation over the growing season one year post-fire within four zones of a boreal peatland that burned to differing depths, relating r_s to near surface soil tensions. We show that the magnitude and temporal variability in r_s varies with burn severity. At the peatland scale, r_s and near-surface tension correlates non-linearly. However, at the point scale no relationship was evident between temporal variations in r_s and near-surface tension across all burn severities; in part due to the limited fluctuation in near-surface tensions and the precision of r_s measurements. Where automated measurements enabled averaging of errors, the relationship between near-surface tension and r_s switched between periods of strong and weak correlation within a burned peat hummock. This relationship, when strong, deviated from that obtained under steady state laboratory conditions; increases in r_s were more sensitive to fluctuations in near-surface tension under dynamic field conditions. Calculating soil vapour densities directly from near-surface tensions is shown to require calibration between peat types and provides little if any benefit beyond the derivation of empirical relationships between r_s and measured soil tension. Thus, we demonstrate important spatiotemporal fluctuations in post-fire r_s that will be key to regulating post-fire peatland hydrology, but highlight the complex challenges in effectively parameterising this important underlying control of near-surface tensions within hydrological simulations.