陆地生态系统氮饱和监测指标及氮沉降控制研究进展

土壤和大气中存在较多的氮,但大多以稳定态的有机氮和氮气形式存在,被植物生长利用的可获得性氮素较少。工业革命以来,人口数量剧烈增长及生活方式的改变带来的化石燃料燃烧、化肥施用和畜禽养殖等活动向大气中排放了大量活性氮,提高了植物可获得性氮水平,并影响到陆地生态系统氮循环和碳循环。长期的氮沉降在全球多个地区引起了氮饱和问题,使得全球工业发达地区及其周边陆地生态系统面临退化风险,我国所在的东亚地区逐步成为继欧洲和北美之后的第三大氮沉降区。严峻的事实及不断加重的氮沉降污染趋势,迫使我们亟需借鉴发达国家的经验以开展相关研究。文章综述了从20世纪80年代起在氮饱和研究中采用的多种氮饱和监测指标,涵盖了陆地生态系统土壤、植被、水体、气体等多个部分的最新进展。文章还总结了我国氮饱和研究的现状,并提出了一些改进措施,以期对我国开展氮沉降观测、氮沉降模拟实验及氮沉降控制有所借鉴。     

北极陆地生态系统的碳循环与全球温暖化

根据最新研究资料，综述并分析了全球温暖化与北极陆地生态系统碳循环的关系，指出近代全球大气ＣＯ２和ＣＨ４浓度显著增加，并呈现日益加剧的趋势；这些温室气体的浓度上升与全球温暖化密切相关，自本世纪７０年代开始，北极地区的夏季温度显著上升．通过分析北极陆地生态系统的碳循环及其基本特征，发现北极陆地生态系统是一个巨大的土壤碳库，占全球土壤碳库总量的２３７％—３２３％；虽然该系统目前起着大气ＣＯ２汇的作用，但大气ＣＯ２浓度增加导致的气温上升将对北极土壤碳库和ＣＯ２的源汇功能产生深刻影响．     

自然生态系统中厌氧氨氧化和反硝化耦合反应研究进展

厌氧氨氧化和反硝化反应是氮循环系统的两个关键环节,它们对平衡整个生态系统氮的收支、改善水体氮的污染、减少温室气体的排放均具有重要意义.在阐述厌氧氨氧化和反硝化生物反应及微生物学机理的基础上,着重综述了二者在水生和陆地两个生态系统中的耦合反应:①探讨了厌氧氨氧化和反硝化反应在不同环境背景下发生的介质及N₂的产生速率和贡献比率,发现水生生态系统中厌氧氨氧化对N₂产生的贡献率相对陆地生态系统占有较大比重.②分析了调控厌氧氨氧化和反硝化反应的细菌群落和功能基因,反应系统占主导的微生物种类随环境发生变化,其中厌氧氨氧化菌Candidatus brocadia作为主导细菌出现频率较高.③二者耦合过程中的影响因素包括环境因素与底物因素.其中,环境因素中厌氧氨氧化与反硝化耦合的最适pH为6.7~8.3,且溶解氧含量过高时也会对耦合反应产生抑制作用;在底物环境中,有机物含量或C/N过高会促进反硝化作用,但同时也会抑制厌氧氨氧化的发生.建议以后能够加大对于厌氧氨氧化和反硝化耦合反应全球尺度的研究,特别是对于陆地生态系统,还应加深对厌氧氨氧化反应速率与反硝化反应速率之间关系的理论与应用研究;同时,在实际应用中,需要在确定厌氧氨氧化菌和反硝化菌最佳生长基础上,建立耦合体系理论预测数学模型,量化两类功能性微生物的耦合效果.      

陆地生态系统碳水通量特征研究进展

CO₂/H₂O通量特征对于揭示微尺度生态系统的区域碳循环规律及机制具有重要意义。陆地生态系统作为全球生态系统重要组成部分,其CO₂/H₂O通量变化深刻影响着全球碳循环和水循环平衡。本文综述了碳通量、水汽通量的研究方法,归纳了各类研究方法的研究进展,评述了各类方法的优势与不足。总结了我国包括森林、草地、农田、荒漠等不同陆地生态系统碳通量和水汽通量的最新研究进展,对碳通量和水汽通量的影响环境因子进行了总结分析,最后从模拟尺度以及影响因子角度,分析了目前碳水通量研究存在的问题难点及未来发展趋势。     

不同国家农用地土壤环境标准比较与启示

农用地土壤环境质量影响农产品质量、人体健康和生态安全.经过十几年的修订,我国于2018年发布了《土壤环境质量农用地土壤风险管控标准(试行)》(GB15618-2018).与国外发达国家相比,我国土壤污染防治依然处于起步阶段,当前有关农用地土壤环境标准相关的综述研究相对较少.本文系统梳理了国内外17个国家或地区的农用地土...     

22种常用除草剂对蚯蚓(Eisenia fetida)的急性毒性

为评价农药对土壤动物的影响,采用滤纸法和人工土壤法测定了22种常用除草剂对赤子爱胜蚓(Eisenia fetida)的急性毒性.滤纸法染毒48 h,特丁净、丙草胺、精异丙甲草胺、乙草胺和莎稗磷对蚯蚓为中等毒性,其LC50值为10.32(8310～12.23)～34.69(29.16～43.99) μg·cm-2;其次为...     

Recent Ogallala Aquifer Region Drought Conditions as Observed by Terrestrial Water Storage Anomalies from GRACE

Recent severe drought events have occurred over the Ogallala Aquifer region (OAR) during the period 2011–2015, creating significant impacts on water resources and their use in regional environmental and economic systems. The changes in terrestrial water storage (TWS), as indicated by the Gravity Recovery and Climate Experiment (GRACE), reveals a detailed picture of the temporal and spatial evolution of drought events. The observations by GRACE indicate the worst drought conditions occurred in September 2012, with an average TWS deficit of ~8 cm in the northern OAR and ~11 cm in the southern OAR, consistent with precipitation data from the Global Precipitation Climatology Project. Comparing changes in TWS with precipitation shows the TWS changes can be predominantly attributable to variations in precipitation. Power spectrum and squared wavelet coherence analysis indicate a significant correlation between TWS change and the El Nino‐Southern Oscillation, and the influence of equatorial Pacific sea surface temperatures on TWS change is much stronger in the southern OAR than the northern OAR. The results of this study illustrate the value of GRACE in not just the diagnosis of significant drought events, but also in possibly improving the predictive power of remote signals that are impacted by nonregional climatic events (El Nino), ultimately leading to improved water resource management applications on a regional scale. Editor’s note : This paper is part of the featured series on Optimizing Ogallala Aquifer Water Use to Sustain Food Systems. See the February 2019 issue for the introduction and background to the series.     

Wildlife Connectivity Approaches and Best Practices in U.S. State Wildlife Action Plans

As habitat loss and fragmentation threaten biodiversity on large geographic scales, creating and maintaining connectivity of wildlife populations is an increasingly common conservation objective. To assess the progress and success of large‐scale connectivity planning, conservation researchers need a set of plans that cover large geographic areas and can be analyzed as a single data set. The state wildlife action plans (SWAPs) fulfill these requirements. We examined 50 SWAPs to determine the extent to which wildlife connectivity planning, via linkages, is emphasized nationally. We defined linkage as connective land that enables wildlife movement. For our content analysis, we identified and quantified 6 keywords and 7 content criteria that ranged in specificity and were related to linkages for wide‐ranging terrestrial vertebrates and examined relations between content criteria and statewide data on focal wide‐ranging species, spending, revenue, and conserved land. Our results reflect nationwide disparities in linkage conservation priorities and highlight the continued need for wildlife linkage planning. Only 30% or less of the 50 SWAPs fulfilled highly specific content criteria (e.g., identifying geographic areas for linkage placement or management). We found positive correlations between our content criteria and statewide data on percent conserved land, total focal species, and spending on parks and recreation. We supplemented our content analysis with interviews with 17 conservation professionals to gain specific information about state‐specific context and future directions of linkage conservation. Based on our results, relevant literature, and interview responses, we suggest the following best practices for wildlife linkage conservation plans: collect ecologically meaningful background data; be specific; establish community‐wide partnerships; and incorporate sociopolitical and socioeconomic information. Acercamientos a la Conectividad de Vida Silvestre y las Mejores Prácticas en los Planes de Acción de Vida Silvestre Estatales en los Estados Unidos     

Toxicity and biochemical impact of certain oxime carbamate pesticides against terrestrial snail,Theba pisana (Müller)

Abstract

The bran toxic baits (0.5 % w/w) of five oxime carbamate pesticides; aldicarb, aldoxycarb, methomyl, oxamyl and thiofanox were tested for their molluscicidal activity against Theba pisana snails under Laboratory conditions. In addition, the in vivo effects of these compounds on seven vital enzymes namely Acetylcholin‐esterase (AchE), glutathion‐S‐transferase (GST), glutamic oxlaoacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), acid phosphatase (AcP), alkaline phosphatase (AIP), and adenosine triphosphatase (ATPase) activities of the snail tissue were also investigated after 1,3, and 5 days of exposure. The results showed that methomyl was the most potent candidate, whereas thiofanox was the least effective one against the snails. LT₅₀’s values of aldicarb, aldoxycarb, methomyl, oxamyl and thiofanox were 5.77, 4.69, 2.31, 3.97 and 6.67 days, respectively. Results of the potency of the tested pesticides against AchE activity were in harmony with the toxicity of these compounds to snails. AchE, AcP, and AIP activities were inhibited by the tested pesticides. GST activity was inhibited by aldicarb but stimulated by oxamyl and thiofanox. Methomyl and oxamyl lead to significant elevation of GOT and GPT, whereas thiofanox treated snail induced a reduction of both enzymes activities. Aldicarb and aldoxycarb caused significant induction of ATPase activity.     

北盘江梯级水电开发对陆生生态的影响研究

水电开发工程在当今社会发展中发挥着重要作用,尤其是梯级水电开发,但是其发展对环境的影响更是备受关注。本文以北盘江梯级水电开发项目为研究对象,主要采用3S技术研究方法,针对流域梯级水电开发对陆生生态系统的影响进行分析,确定陆生生态环境影响评价识别因子,做出针对植物、植被,陆生动物,黑叶猴自然保护区和自然景观生态体系影响的具体分析。经研究结果表明：梯级电站建设主要不利影响是改变了河流自然生态系统,对适应原生境的动物造成不利影响,使其栖息地缩小或丧失,水库淹没和施工占地及移民安置活动对区域土地资源、自然保护区的影响,对自然景观生态体系的影响。