基于MODIS影像估算中国大陆区域草地火污染物时空格局

草地火是草地生态系统重要干扰因子,对草地生态系统结构和功能有重要影响.草地火释放的大量烟气和颗粒物对大气环境、生态系统和人类健康有重要影响.本研究基于2001—2017年中国大陆区域MODIS-MCD64A1数据,结合生物质密度,估算各区域草地火燃烧生物量.并运用排放因子法,估算17年间中国大陆区域草地火排放污染物总量.研究结果表明,中国大陆地区草地生物质密度存在差异,由东向西逐渐递减.草地火时空分布不均衡且存在明显季节性差异,主要集中在3月和9月.中国大陆地区2001—2017年草地火次数、火面积和燃烧总量分别是1.63×10~5次、6.12×10~6 hm~2和23.86 Mt,排放CO_2、CO、CH_4、SO_2、NMVOC、NO_x、PM_(2.5)、BC、OC和TC总量分别为37.27 Mt、1.31 Mt、43.30 kt、11.05 kt、287.74 kt、79.60 kt、155.82 kt、9.25 kt、64.95 kt和75.54 kt.此外,各污染物在时间和空间上不均衡,在东北、华北、华中和西南区域呈增加趋势,华东和西北区域呈降低趋势,华南区域呈显著降低趋势.本研究揭示了中国大陆地区草地火释放污染物的时空变化,为深入揭示草地火对区域环境影响提供数据支持.     

Fires in tropical forests – what is really the problem? lessons from Indonesia

Fires have attracted interest and generated alarm since the early 1980s. This concern has been particularly evident in tropical forests of Southeast Asia and the Amazon, but disastrous fires in recent summers in Australia, Europe, and the United States have drawn worldwide attention. Concern about forest fires, and related air pollution and biodiversity impacts, led international organisations and northern countries – such as the Asian Development Bank, the European Union, the Food and Agriculture Organisation, the United Nations Environment Programme, the World Bank, and the government of Germany – to undertake fire assessments and provide technical assistance. Nongovernmental organisations, such as the International Union for Conservation of Nature and Natural Resources and World Wide Fund for Nature, have also devoted increased attention to fires. Aiming at prevention of future fires, 40 fire projects and missions costing well over US$30 million have worked in Indonesia over the last 20 years. Despite the money and effort spent on them, fires continue to burn every year. It may appear to some that efforts to address the ‘fire problem’ have not been effective as fires still occur. There remains a lack of clarity about ‘fire problems’, which has, at times, led to the adoption of policies that may have negative impacts on livelihoods, the environment, and the economy. Two ‘simple’ changes in the way fires are considered would significantly improve fire-related policies and initiatives.

Vulnerability of land systems to fire: Interactions among humans,climate, the atmosphere,and ecosystems

Fires are critical elements in the Earth System, linking climate, humans, and vegetation. With 200–500 Mha burnt annually, fire disturbs a greater area over a wider variety of biomes than any other natural disturbance. Fire ignition, propagation, and impacts depend on the interactions among climate, vegetation structure, and land use on local to regional scales. Therefore, fires and their effects on terrestrial ecosystems are highly sensitive to global change. Fires can cause dramatic changes in the structure and functioning of ecosystems. They have significant impacts on the atmosphere and biogeochemical cycles. By contributing significantly to greenhouse gas (e.g., with the release of 1.7–4.1 Pg of carbon per year) and aerosol emissions, and modifying surface properties, they affect not only vegetation but also climate. Fires also modify the provision of a variety of ecosystem services such as carbon sequestration, soil fertility, grazing value, biodiversity, and tourism, and can hence trigger land use change. Fires must therefore be included in global and regional assessments of vulnerability to global change. Fundamental understanding of vulnerability of land systems to fire is required to advise management and policy. Assessing regional vulnerabilities resulting from biophysical and human consequences of changed fire regimes under global change scenarios requires an integrated approach. Here we present a generic conceptual framework for such integrated, multidisciplinary studies. The framework is structured around three interacting (partially nested) subsystems whose contribute to vulnerability. The first subsystem describes the controls on fire regimes (exposure). A first feedback subsystem links fire regimes to atmospheric and climate dynamics within the Earth System (sensitivity), while the second feedback subsystem links changes in fire regimes to changes in the provision of ecological services and to their consequences for human systems (adaptability). We then briefly illustrate how the framework can be applied to two regional cases with contrasting ecological and human context: boreal forests of northern America and African savannahs.     

An Experimental Burn to Restore a Moth-Killed Boreal Conifer Forest, Krasnoyarsk Region, Russia

Mechanical treatment and prescribed fire were used to restore a mixed conifer stand (Picea-Abies-Pinus) following mortality from an outbreak of Siberian moth (Dendrolimus superans sibiricus). Moth-killed stands often become dominated by Calamagrostis, a sod-forming grass. The large amount of woody debris and the sod hinder coniferous seedling establishment and development as well as creating conditions favorable to the establishment and propagation of wildfires. Fire has been demonstrated to be an effective method of reducing woody debris and eliminating sod, but the random nature and timing of wildfires often do not create conditions favorable for conifer regeneration. Our study was conducted in a mature fir dominated stand that died during an outbreak 6–8 years previously with most of the dead trees still standing. A bulldozer drove through the stand downing standing snags in late summer with 15–20 m between passes. Snags knocked down by the bulldozer and additional snag fall throughout the following winter increased downed dead wood 50–60% and large downed dead wood 80% compared to an adjacent untreated area. In June, a prescribed fire was set and fuel load consumption averaged 70%. Average soil temperatures during the burn ranged from 47 ^∘C at a depth of 2 cm to 10 ^∘C at 10 cm; hot enough to kill the grass. Following treatment, the potential for wildfire was reduced and the area was suitable for either natural conifer regeneration or planting without further mechanical site preparation.     

Effects of environmental factors on the production and release of matrix-bound phosphine from lake sediments

Effects of pH, temperature, and oxygen on the production and release of phosphine in eutrophic lake sediments were investigated under laboratory tests. Results indicated that the elimination of matrix-bound phosphine was accelerated under initial pH 1 or 12. Phosphine levels could reach maximum under initial pH 10. The contents of phosphine increased with the addition of alkali under pH 4–12. The rates of phosphine production and release from lake sediments varied with temperature. 20°C was the most favorable temperature for the production of matrix-bound phosphine. Oxygen showed little effect on matrix-bound phosphine. Matrix-bound phosphine concentrations in lake sediments were concluded to be dependent on a balance of natural generation and depletion processes. Translated from Acta Scientise Circumstantiae, 2005, 25(5): 681–685 [译自: 环境科学学报]     

近30年来高邮湖(含邵伯湖)自然水域面积变化及其影响因素

湖泊水域面积变化特征反映气候与人类活动对湖泊生态系统结构与功能的影响,对湖泊健康评价与水生态修复有重要指导价值.以1988-2015年8期Landsat TM/ETM+遥感影像为数据源,综合运用目视解译法与比值阈值法提取了研究区高邮湖（含邵伯湖）及其围网养殖区的边界信息,分析了研究区水域面积变化特征及其影响因素.结果表明:①1988-2015年研究区自然水域面积呈现前期持续缩小、近期部分恢复的阶段性变化趋势.其中,1988-2000年自然水域面积缓慢缩减,平均减小速率为4.08 km2/a;2000-2011年迅速缩减,平均减小速率为12 km2/a;2011-2015年迅速增长,自然水域面积增加108 km2;1988年自然水域面积最大（716 km2）,2011年最小（535 km2）,2015年部分恢复（643 km2）.②1988-2015年流域内年均降水量先减后增,年均气温逐渐升高.年均气温升高与自然水域面积变化具有相关性（R2=0.472）;年均降水量则与自然水域面积变化无明显关联（R2=0.118）.③1988年和1992年研究区内未见明显的围网养殖,2000年围网养殖区面积仅为45 km2,2011年最大,达199 km2.2000-2009年和2009-2015年围网养殖区面积平均增长速率分别为15.56和9.00 km2/a;北部湖区围网养殖集中,自然水域面积变化最为显著,东西湖区次之.研究显示,1988年以来,年均气温和围网养殖对高邮湖自然水域产生了显著影响,湖区北部湿地侵占严重,湿地生态屏障功能下降.      

Variability of Fire Behavior, Fire Effects, and Emissions in Scotch Pine Forests of Central Siberia

As part of the Russian FIRE BEAR (Fire Effects in the Boreal Eurasia Region) Project, replicated 4-ha experimental fires were conducted on a dry Scotch pine (Pinus sylvestris)/lichen (Cladonia sp.)/feathermoss (Pleurozeum schreberi) forest site in central Siberia. Observations from the initial seven surface fires (2000-2001) ignited under a range of burning conditions quantified the different fuel consumption and fire behavior characteristics (e.g., rate of spread, fireline intensity, etc.) possible in this particular forest fuel type. Experimental results and dendrochronological study of local fire history both support the dominance of local fire regimes by low to moderate-intensity surface fires. Carbon released by the experimental fires ranged from 4.8 to 15.4 t C ha^{− 1} depending on fuel conditions and fire severity. Preliminary emission data show a strong correlation between carbon dioxide (CO₂) and carbon monoxide (CO) emissions, which should facilitate accurate estimates of fire impacts on atmospheric chemistry. Carbon concentration in smoke samples was related to fire severity. The short landscape-scale fire-return interval (50 years), combined with typically low fire severity, in pine ecosystems of central Siberia is often associated with low tree mortality and relatively rapid buildup of litter and understory fuels after a fire.     

Application of ecosystem health cost-effect analysis in eco-planning in Guangzhou City,China

Ecosystem health has been a focal point and research frontier of applied ecology in recent years, increasingly used in urban ecological studies. To quantify the effect of ecological improvement from eco-planning, an ecosystem health assessment method is used in eco-planning evaluation and decision support in the urban eco-planning research of Guangzhou City of China. Based on features of an urban ecosystem, five factors such as vigor, organizational structure, resilience, ability to maintain ecosystem service, and influence on people’s health were selected to develop the assessment indicator system. Then, to evaluate the validity of planning measures, a cost-effect analysis of the different scenarios on eco-planning was made, taking investment of the planned projects as the cost and ecosystem health state after implementing the scenarios as the effect. To establish priority of all the proposed planning schemes or countermeasures, variation of the ecosystem health state was evaluated when the investment of eco-environmental construction projects changes by ±10%, ±20% and ±50%, respectively. Thus, the order of importance of eco-environment construction projects to the urban ecosystem health state can be worked out, providing a reference for prioritizing the implementation of such urban eco-environmental projects. The study proved the trial value of an ecosystem health evaluation method in urban eco-planning research. Translated from China Population, Resources and Environment, 2005, 15(5): 126–130 [译自: 中国人口资源与环境]     

History of equatorial vegetation fires and fire research in Southeast Asia before the 1997–98 episode: A reconstruction of creeping environmental changes

Charcoal fragments in forest soils give evidence of prehistoric and historic natural and anthropogenic wildfires in the equatorial rainforests and in seasonal monsoon forests of continental and insular South Asia. Conditions favourable for the occurrence of historic and contemporary rainforest fires are associated with droughts, especially during dry spells caused by the El Niño–Southern Oscillation (ENSO) event. Historic land-use fires and wildfires can be reconstructed from a number of narrative reports, including documents that reveal drought and famine. In the eastern part of Borneo prehistoric and historic records of coal fires reveal a unique natural source of wildfires. Starting with modern transmigration programs and systematic conversion of primary and secondary vegetation, including peat-swamp ecosystems, into farmland and industrial plantations, the use of fire as a land-clearing tool escalated in the 1990s. During droughts land-clearing fires additionally contribute to wildfires. A detailed study of the ecological consequences of the episode of land-use fires and wildfires of 1982–1983 was conducted on an area of 2.7 million ha of dipterocarp rainforest in East Kalimantan. The results show that dipterocarps are highly susceptible to fire and are replaced by pioneers and fire-tolerant species that occupy the disturbed sites or survive the immediate fire effects. Smoke from forest conversion burning caused considerable environmental problems, reducing visibility and affecting human health and security. Emissions from vegetation burning influence chemistry and functioning of the global atmosphere. The situation is different in those parts of mainland and insular Southeast Asia that are characterized by seasonal climate. Through long-term influence of climate variability, fire influence, and anthropogenic pressure the vegetation is better adapted to extrinsic stresses. During the 15 years between the extreme ENSO events and fire episodes of 1982–1983 and 1997–1998 the national and international communities have been alerted and prepared to respond to the escalating fire situation in Indonesia. The response to the onset of the 1997–1998 fire and smoke episode, however, was absolutely inadequate and erratic. Meanwhile a whole continent – the maritime continent of Southeast Asia – has been degraded by excessive fire application for more than 20 years.     

2015年厄尔尼诺年东南亚主要国家活跃火发生类型与影响分析

2015年强厄尔尼诺引起东南亚干旱少雨与活跃火加剧,但目前有关活跃火时空特征、发生类型与强度及其对人口—社会经济影响仍分析不足。利用美国国家航空航天局火灾信息资源管理系统（FIRMS）VIIRS V1活跃火位置矢量产品,通过月际、地形、土地覆被类型等GIS分析确定东南亚主要国家活跃火主要类型,并评价各国活跃火对人口分布的影响范围与国别差异。结果表明：（1）东南亚2015年活跃火发生频次达81.40×10⁵次,中南半岛与马来群岛各占69.60%与30.40%,分别集中发生在2-4月与8-10月,各国活跃火频次与发生时间差异很大。（2）中南半岛五国活跃火地形差异明显,缅甸和越南活跃火集中分布于25 m以下;老挝（85~105 m、140~200 m）、泰国（5~15 m、70~110 m）和柬埔寨（5~15 m、70~110 m）活跃火随海拔呈双峰特征;马来群岛国家（印度尼西亚、马来西亚与菲律宾）活跃火集中分布于60 m以下的平原地带;且东南亚35%以上的活跃火均集中分布5~15°的斜坡。（3）东南亚森林、农田活跃火发生率为76%,其中森林活跃火发生率由柬埔寨的52.00%到老挝的74.27%不等,农田活跃火由老挝的13.18%到泰国的42.68%不等。（4）综合活跃火发生月份、海拔、坡度与覆被特征,可从山区刀耕火种农业与平原秸秆焚烧界定东南亚主要国家活跃火发生类型。（5）东南亚活跃火随人口密度增加呈先增后减至平稳变化的趋势,且多集中于人口稀少的乡村和原始森林,其中缅甸、泰国、越南三国有10%以上的活跃火发生在人口密度为72~91人/km²的区域,而马来西亚、老挝、柬埔寨、印度尼西亚30%以上的活跃火集中发生于人口密度在20人/km²以下的区域。     

日本琵琶湖流域生态系统的修复与重建

琵琶湖流域生态系统的修复与重建着眼于全流域及中长期目标的实现. 在《琵琶湖综合保全整备规划》基础上,滋贺县政府提出了流域生物生息空间网络化构筑的长期构想,在全流域划定了16个重要生物生息空间及10条重要河流作为生态回廊;从上游的森林建设、内湖重建、河流治理到湖滨带芦苇群落的保护等开展了一系列的流域修复工作,如针对湖滨带修复,制定了芦苇群落保护条例与规划,划定了琵琶湖湖岸及周边内湖的芦苇群落保护与恢复区域,面积达138 hm2,其中芦苇带栽植面积达15 hm2,收割等维护管理每年达30 hm2等. 琵琶湖修复与重建工程的开展使生物多样性逐渐提高,生态系统功能得到恢复. 与之相比,我国湖泊流域生态修复存在的问题主要体现在生态修复缺乏流域整体的长远规划以及在湿地修复、低污染尾水的生物处理、湖滨带修复等领域存在一定的理念差异.      

九寨沟世界自然遗产核心景区钙华景观的研究进展与展望

九寨沟钙华是距今约3万年(特别是1万年)以来逐渐形成的。大规模的钙华沉积是湖泊、滩流、瀑布、泉及台地景观形成的基础,覆盖核心景区2.4 km²的面积。钙华景观是九寨沟遗产地突出普遍价值——"自然美学价值"的核心,是景区的关键吸引力。为九寨沟的持续保护和为未来研究提供支持,本文从钙华沉积物、钙华景观成因、钙华景观变化及其原因、钙华景观保护恢复的角度,总结了公开和未公开发表的研究结果。针对目前钙华景观保护面临的主要问题(钙华退化、藻类生物量增加、沼泽化),本文归纳了相关的自然与人为因素,包括气候变暖、大气沉降、水化学变化、旅游活动、森林采伐、地质灾害等;归纳了地震和滑坡等地质灾害对钙华景观形成与重塑的双重作用;总结了钙华景观保护恢复的管理工作及其成效。本文提出未来可重点研究:(1)气候变化和人为活动背景下多圈层(大气、陆地生态系统、水生生态系统和基岩系统)对水体氮、磷、溶解性有机物、绿藻生物量、钙华沉积与溶蚀的影响机制及程度;(2)2017年九寨沟7.0级地震后,自然与人为干预下钙华微地貌的长期稳定性,水土流失加剧对湖泊透明度、钙华、沼泽化及美学价值的长期影响,地质灾害及其防治对钙华景观的长期效应。     

Development of the Indonesian and Malaysian Fire Danger Rating Systems

Forest and land fires in Southeast Asia have many social, economic, and environmental impacts. Tropical peatland fires affect global carbon dynamics, and haze from peat fires has serious negative impacts on the regional economy and human health. To mitigate these fire-related problems, forest and land management agencies require an early warning system to assist them in implementing fire prevention and management plans before fire problems begin. Fire Danger Rating Systems (FDRS) were developed for Indonesia and Malaysia to provide early warning of the potential for serious fire and haze events. In particular, they identify time periods when fires can readily start and spread to become uncontrolled fires and time periods when smoke from smouldering fires will cause an unacceptably high level of haze. The FDRS were developed by adapting components of the Canadian Forest Fire Danger Rating System, including the Canadian Forest Fire Weather Index (FWI) System and the Canadian Forest Fire Behavior Prediction (FBP) System, to local vegetation, climate, and fire regime conditions. A smoke potential indicator was developed using the Drought Code (DC) of the FWI System. Historical air quality analysis showed that the occurrence of severe haze events increased substantially when DC was above 400. An ignition potential indicator was developed using the Fine Fuel Moisture Code (FFMC) of the FWI System. Historical hot spot analysis, grass moisture, and grass ignition studies showed that fire occurrence and the ability for grass fires to start and spread dramatically increased when FFMC > 82. The Initial Spread Index (ISI) of the FWI System was used to develop a difficulty of control indicator for grassland fires, a fuel type that can exhibit high rates of spread and fire intensity. This ISI-based indicator was developed using the grass fuel model of the FBP System, along with a standard grass fuel load and curing level estimated from previous Indonesian studies. Very high fire intensity is expected in grasslands when ISI ≥ 6. To provide early warning, the FDRS identifies classes of increasing fire danger as the FFMC, DC, and ISI approach these key threshold values. The Indonesian FDRS is now operated nationally at the Indonesian Meteorological and Geophysical Agency. The Malaysian Meteorological Service operates the Malaysian FDRS and displays regional outputs for the Association of Southeast Asian Nations. The FDRS are being used by forestry, agriculture, environment, and fire and rescue agencies to develop and implement fire prevention, detection, and suppression plans.     

黄土高原子午岭植被自然恢复下的固碳特征

为分析黄土高原生态脆弱区植被自然恢复的碳汇效应和植被群落特征变化对生态系统碳密度的影响,采用时空互代的方法,研究了子午岭地区150 a恢复年限内8个演替阶段{坡耕地、撂荒10 a草地、20 a草地、白刺花[Sophora davidii(Franch.) Skeels.]、白桦(Betula platyphylla Suk.)、油松(Pinus tabulaeformis Carr.)、辽东栎(Quercus wutaishanic Mary)+油松(Pinus tabulaeformis Carr.)混交林和辽东栎}下植被-土壤系统的固碳特征,探讨了群落特征变化对植被-土壤系统碳密度的影响.结果表明,调查植被群落盖度从坡耕地阶段的85%波动增加到乔木阶段的100%.物种数量、Margalef指数、Shannon-Wiener指数、Pielou指数和Simpson指数总体呈现出先快速增加后缓慢降低直至趋向稳定的变化特征,演替中期(白桦)达到峰值.植被各组分(地上生物、地下根系、枯落物)的生物量和碳密度在演替过程中呈指数函数关系增加,即白桦以前增加缓慢,白桦和油松阶段显著增加(P<...     

Local to global perspectives on forest and land fires in Southeast Asia

Forest and land fires are not new to the landscapes of Southeast Asia. Nevertheless, strikingly different perspectives persist about the significance of fires in the tropics to environmental changes and human well-being and consequently how they should be managed. Our synthesis of papers in this special issue suggests both trade-offs and complementarities in various policy responses with differing objectives. There are, however, at least three domains with high potential of meeting multiple objectives. First, is through identification, and improved management, of ecosystems vulnerable to fire under current and future climate. Agriculture, forestry and human settlements on peat land areas in Indonesia are candidates for such a focus. Second, is through building adaptive capacities to manage fire and related land and water resources. Investments in capacity at multiple levels are needed, but particularly at fairly local levels where stakeholders have strong incentives to manage fires appropriate to local contexts. Third, is through building awareness that fire management does not universally equate to fire suppression. Severe smoke haze episodes, for example, are also a result of timing of fires, and some fire-adapted ecosystems may depend on fire to persist. Finally, we emphasize that effective fire management is unlikely to be realized without greater engagement by research and policy with stakeholders in thoroughly exploring the full range of land and fire management options. Negotiation, compensation and trade-offs are probably inevitable.     

骆马湖浮游植物演替规律及驱动因子

江苏骆马湖作为南水北调工程的重要调蓄湖泊,水生态系统结构变化不容忽视.为研究骆马湖浮游植物群落结构演替规律及其与环境因子的关系,于2014~2018年进行了逐月监测.研究期间骆马湖总氮、高锰酸盐指数、电导率等参数呈逐年升高趋势,氟离子浓度呈逐年下降趋势.共鉴定有浮游植物7门71属,月均生物量变化范围0.16~5.51mg·L^-1.硅藻和绿藻为绝对优势门类,其次为甲藻及隐藻;主要优势属为针杆藻（Synedra sp.）、隐藻（Chroomonas spp.）、直链硅藻（Aulacoseira spp.）、锥囊藻（Dinobryon sp.）、栅藻（Scenedesmus spp.）、脆杆藻（Fragilaria spp.）、转板藻（Mougeotia sp.）、纤维藻（Ankistrodesmus sp.）和裸藻（Euglena spp.）.2014~2018年骆马湖浮游植物群落结构年际差异较大,其变化主要体现在浮游植物生物量的再分配,硅藻和绿藻继续保持优势外甲藻和蓝藻的优势度增加.非度量多维尺度分析显示,骆马湖浮游植物群落变化与总氮、氟离子、水温、总磷、溶解氧、pH、电导率和高锰酸盐指数等因素有关,广义可加模型同样显示总氮、氟离子浓度和水温是主导骆马湖浮游植物群落结构变化的主要因素.总氮、氟离子浓度是影响浮游植物群落年际变化的环境因子,而水温是引起浮游植物群落季节变化的主要因子.结合近几年管理部门采取的措施,浮游植物群落年际变化可能与骆马湖实行禁止采砂和拆除围网等管理修复措施有关.     

江汉湖群典型湖泊生态系统健康评价——以梁子湖、洪湖、长湖、斧头湖、武湖为例

湖泊生态系统健康评价对湖泊生态健康状况评定、环境问题诊断和湖泊生态系统管理具有重要意义.根据江汉湖群实际情况和生态特点,选取江汉湖群五大湖泊—梁子湖、长湖、洪湖、斧头湖和武湖为研究对象,采用野外调查、资料收集并结合GIS技术的研究方法,从生物、水质、生境特征及生态压力4个方面选择15个代表性评价指标,构建江汉湖群典型湖泊生态系统健康评价指标体系,并利用基于模糊综合评价模型的评价方法,对江汉湖群五大湖泊生态系统健康进行评价.结果表明,江汉湖群五大湖泊生态健康综合评价得分值为5.47~7.46,梁子湖得分最高,其余依次为斧头湖、洪湖、长湖和武湖.从湖泊生态系统健康等级看,五大湖泊中梁子湖和斧头湖处于比较健康状态,而洪湖、长湖和武湖处于亚健康状态.通过实例分析表明,本研究建立的湖泊生态系统健康评价方法能够较客观系统地评价江汉湖群生态系统健康状况,具有较高的可行性和可靠性,可作为江汉湖群健康诊断的评价方法.本文研究结果可为江汉湖群的分类管理提供较为重要的参考依据.     

太湖湖滨湿地沉积物营养元素分布特征及其环境意义

针对当前修复湖滨湿地去除氮磷营养盐长期效果的不确定性,以东太湖自然湖滨湿地与东部滨岸区、竺山湾修复湖滨湿地为代表,采用放射性核素210Pb计年法测定湖滨湿地沉积物的年代,据此计算出沉积速率,并结合沉积物柱中粒度组成与碳氮磷的含量变化,推算出自然湖滨湿地沉积物中碳氮磷的平均蓄积量.结果表明:太湖自然湖滨湿地与修复湖滨湿地沉积物的颗粒组成均以粉砂粒为主.东太湖自然湖滨湿地沉积物的平均沉积速率为:芦苇群落,0.74cm/a;茭草群落,0.69cm/a;香蒲群落,1.24cm/a;牛鞭草群落,1.27cm/a;荷群落,0.81cm/a.近40a来,东太湖自然湖滨湿地单位面积(cm2)沉积物中碳氮磷的蓄积量平均为:总有机碳1408.0mg,总氮138.2mg,总磷14.31mg.对于修复湖滨湿地而言,随着植物群落的发育演替,营养元素在修复湖滨湿地系统内可以不断累积,其沉积物库的蓄积量潜力很大,在控制外源污染输入的前提下,湖滨湿地具有净化水质的长期环境效应.     

How Climate and Vegetation Influence the fire Regime of the Alaskan Boreal Biome: The Holocene Perspective

We synthesize recent results from lake-sediment studies of Holocene fire-climate-vegetation interactions in Alaskan boreal ecosystems. At the millennial time scale, the most robust feature of these records is an increase in fire occurrence with the establishment of boreal forests dominated by Picea mariana: estimated mean fire-return intervals decreased from ≥300 yrs to as low as ∼80 yrs. This fire-vegetation relationship occurred at all sites in interior Alaska with charcoal-based fire reconstructions, regardless of the specific time of P. mariana arrival during the Holocene. The establishment of P. mariana forests was associated with a regional climatic trend toward cooler/wetter conditions. Because such climatic change should not directly enhance fire occurrence, the increase in fire frequency most likely reflects the influence of highly flammable P. mariana forests, which are more conducive to fire ignition and spread than the preceding vegetation types (tundra, and woodlands/forests dominated by Populus or Picea glauca). Increased lightning associated with altered atmospheric circulation may have also played a role in certain areas where fire frequency increased around 4000 calibrated years before present (BP) without an apparent increase in the abundance of P. mariana. When viewed together, the paleo-fire records reveal that fire histories differed among sites in the same modern fire regime and that the fire regime and plant community similar to those of today became established at different times. Thus the spatial array of regional fire regimes was non-static through the Holocene. However, the patterns and causes of the spatial variation remain largely unknown. Advancing our understanding of climate-fire-vegetation interactions in the Alaskan boreal biome will require a network of charcoal records across various ecoregions, quantitative paleoclimate reconstructions, and improved knowledge of how sedimentary charcoal records fire events. In this paper, charcoal refers to macroscopic (≥180 μm) as opposed to microscopic (< 180 μm) particles unless indicated otherwise. Radiocarbon ages were converted to calibrated years before AD 1950 using the atmospheric calibration data set (Stuiver et al. 1998).     

草海湿地生态系统健康评价

贵州省威宁草海是贵州最大的天然高原淡水湖泊,同时也是我国亚热带高原湿地生态系统的典型代表,成为中国西南地区迁徙水禽的重要越冬地和停歇地。但草海湿地生态系统由于人类活动加剧引起的其功能作用会削弱、生物多样性会降低、水体富营养化等生态环境问题多方面的影响导致其表现出明显的生态脆弱性,尤其是在其生态系统的生态环境方面表现尤为突出。如果草海受到多方面的影响不及时加以制止和消除,将直接威胁着草海湿地生态系统的稳定。本文首先从湿地的生态特征、功能和社会经济环境三个方面的30个主要影响草海生态健康的因子进行分析,并对每个因子的健康状况进行调查、分析说明。其次,利用模糊综合评价模型中的层次分析法对草海生态健康影响的30个主要因子进行了整合分析,并对草海现在的健康状况应用平均加权原则进行了评估。最后,针对草海目前的健康状况,对草海今后的防治提出了相关建议。