林火干扰对兴安落叶松林下植被多样性和生物量的影响

以寒温带大兴安岭受林火干扰的兴安落叶松林下植被为研究对象,采用植物多样性测度方法和收获法,分析火烧强度和自然恢复年限对林下植被物种多样性和生物量的影响。结果表明:在不同火烧强度的影响下,林下植被物种多样性有所降低,Shannon-Wiener指数表现为随林火强度呈递减趋势,Margalef指数表现出未过火区中度火烧迹地轻度火烧迹地重度火烧迹地的规律;火烧降低了林下植被的总生物量,主要降低的是灌木生物量;重度火烧和轻度火烧后草本生物量有所提升,但提升量不足以改变总生物量降低的趋势。在自然恢复过程中,Margalef指数表现为先升高后降低的单峰变化趋势,而Pielou指数的变化趋势与之相反;恢复年限与植被生物量呈正相关关系,草本生物量在经过5 a恢复后逐渐达到一个稳定期,灌木生物量在1~10 a的自然恢复期内持续增长。     

林火对大兴安岭典型植被土壤理化性质的影响

以大兴安岭地区西部呼中国家级自然保护区2008年受火烧干扰的林分为研究对象,对2个典型林型落叶松林和白桦林不同火烧强度的土壤理化性质进行了分析。结果表明:2个林型在不同火烧强度的作用下,其土壤含水率、土壤密度、pH值、有机质及营养元素质量分数等理化性质表现出显著的差异性。     

基于稀疏表示的森林火灾火焰识别研究

为了实现森林火灾的智能识别,提出一种基于稀疏表示的林火火焰自动识别方法.以林火火焰和5类干扰物体为研究对象,每类对象从视频图像中随机选取50帧作为训练样本,150帧作为测试样本.对每幅图像提取疑似火焰区域,求取面积变化率、颜色、纹理和形状特征参数.所有训练样本的特征向量构建训练样本特征字典,对每个测试样本利用l1最小化范数计算其在训练字典上的投影系数,根据最小重构残差进行分类识别.结果表明,稀疏表示方法的识别率可达到93.56％,为林火火焰识别提供了一个有效的解决方案.     

长白山红松阔叶林主要树种树皮抗火性的分析与排序

应用因子分析法对长白山红松阔叶林8种乔木树皮的5种性状进行统计分析,得出了树皮抗火性顺序.对树皮抗火性由强到弱的排序为:春榆(胸径52.9 cm)、紫椴(胸径13.5 cm)、蒙古栎(胸径82.8cm)、色木槭(胸径32.5 cm)、水曲柳(胸径31.0 cm)、白牛槭(胸径13.5 cm)、色木槭(胸径34.2 cm...     

杉木火力楠混交林林内火环境的初步研究

采用常规方法,分别于1987.9.24和1988.9.24两次对福建省尤溪县林业科学研究所西坑试验点6年生杉木火力楠混交林的火环境进行定位观测,结果表明:混交林的日均相对湿度、凋落叶的含水量、土层0～40cm土壤含水量分别比杉木纯林高3％、22.27％和4.41％,混交林内日均光照强度仅为杉木纯林的55％,林内日均气温比杉木纯林低0.5℃。因此,杉木火力楠混交林在一定程度上降低了林分的燃烧性。     

油茶芽苗砧嫁接的技术环节

从生产实际出发，评述了油茶芽苗砧嫁接技术在圃地选择，选种催芽，荫棚架设，接穗选取，嫁接，栽植，栽后管理等技术环节的应用及注意事项。     

火生态因子对草原的效应及有计划用火的研究

火烧可以提高禾草类的生物量25—30%,可以快速地(当年)大幅度提高羊草种群的生物量达100%以上。火烧提高羊草的抽穗率,促进草群更新复壮。火烧可以有效地抑制针茅种群的增长,并改变群落中的种群分布格局,促进羊草种群形成均匀分布格局,扩大羊草种群在群落中的生态位。火烧对草原的总生产力不发生负效应,一次火烧的正效应可持续2—3年。基于以上的结果,我们认为锡林郭勒草原区中,东部含有羊草的草原群落,可在春季四月下旬进行火烧,将会取得良好的效果。     

Characterisation of a Quantitative Resistance to Vector Transmission of Tomato yellow leaf curl virus in Lycopersicon pimpinellifolium

Two wild genotypes from the same species Lycopersicon pimpinellifolium, WVA106 (susceptible) and INRA-Hirsute (so-called ‘resistant’), were compared with respect to their reaction to Tomato yellow leaf curl virus isolate Réunion (TYLCV-Mld[RE]), using both whitefly-mediated inoculation and graft inoculation. Disease incidence and symptom severity were scored. Presence and quantification of viral DNA were assessed by dot blot hybridisation. Upon insect inoculation, accession INRA-Hirsute showed a moderate resistance against TYLCV that was overcome by a high inoculation pressure obtained by increasing the cumulative number of inoculative whiteflies. Temporal analyses of the disease progress in relation to this criterion exhibited that the protection was quantitative, mainly reducing the TYLCV-Mld[RE] incidence by at maximum 50% at low inoculation pressure. When graft inoculated, the final TYLCV-Mld[RE] disease incidence was 100% in both susceptible and resistant genotypes with severe symptoms, suggesting a reduction of virus transmission by a vector resistance as a possible mechanism. Implications of using such type of resistance in breeding programmes are discussed.     

Determining landscape extent for succession and disturbance simulation modeling

Dividing regions into manageable landscape units presents special problems in landscape ecology and land management. Ideally, a landscape should be large enough to capture a broad range of vegetation, environmental and disturbance dynamics, but small enough to be useful for focused management objectives. The purpose of this study was to determine the optimal landscape size to summarize ecological processes for two large land areas in the southwestern United States. We used a vegetation and disturbance dynamics model, LANDSUMv4, to simulate a set of nine scenarios involving systematically varied topography, map resolution, and model parameterizations of fire size and fire frequency. Spatial input data were supplied by the LANDscape FIRE Management Planning System (LANDFIRE) prototype project, an effort that will provide comprehensive and scientifically credible mid-scale data to support the National Fire Plan. We analyzed output from 2,000 year simulations to determine the thresholds of landscape condition based on the variability of burned area and dominant vegetation coverage. Results show that optimal landscape extent using burned area variability is approximately 100 km² depending on topography, map resolution, and model parameterization. Variability of dominant vegetation area is generally higher and the optimal landscape sizes are larger in comparison to those features determined from burned area. Using the LANDFIRE project as a case study, we determined landscape size and map resolution for a large mapping project, and showed that optimal landscape size depends upon geographical, ecological, and management context. This paper was written and prepared by U.S. Government employees on official time, and therefore is in the public domain and not subject to copyright. The use of trade or firm names in this paper is for reader information and does not imply endorsement by the U.S. Department of Agriculture of any product or service.     

湘西州森林防火与气象条件关系

利用1950~1988、2005~2015年湘西州森林火灾相关资料,1960~2015年湘西州8县(市)气象观测站温度、湿度资料,采用线性和曼-肯德尔(MK)突变检验的分析方法,对湘西州森林防火与气象条件关系进行研究。通过研究得出气象条件和森林火灾关系非常紧密,每年的春冬季节是森林火灾的高发期;确定森林火险预报模型为I=D×4+(100-H)×0.4+T+F+r,将森林火险等级划分为五级;对湘西州森林防火预警预报系统进行研发,将森林防火气象预报预警模型与突发事件预警信息发布的业务充分融合。