Large-scale Aerial Images Capture Details of Invasive Plant Populations

Satellite and high-altitude aerial remote sensing have been used to measure dense infestations of invasive weeds over very large areas but have limited resolution and cannot be used to detect sparsely distributed weeds. Ground-based methods have provided detailed measurements of invasive weeds but can measure only limited areas. Here we test a novel approach that uses a lightweight airplane, flying at 72 km • h^-1 and 100-m altitude, to rapidly collect high-resolution images over relatively large areas. We obtained 1 987 images, each representing 48.5 m² of mixed-grass prairie with 2-mm resolution (ground sample distance). From these images we were able to reliably measure small patches and even individual plants of the invasive forb Dalmatian toadflax (Linaria dalmatica [L.] P. Mill.). Ground-based measurements of aboveground toadflax biomass were highly correlated (R² > 0.93) with point-intercept and visual-estimate cover measurements from aerial images. The time required to analyze images ranged from 4 to 45 seconds for presence/absence data and from 1 to 6 minutes for cover data. Toadflax was present in 795 of 1 987 images but exceeded 1% cover in only 99 images. Given the observed variation among images in toadflax cover, at least 400 images were needed to precisely estimate the mean toadflax cover of 0.2%. These results suggest that such high-resolution aerial imagery could be used to obtain detailed measurements of many invasive weed populations. It may be most useful for identifying incipient weed infestations and expanding the scale at which population-level attributes of weed populations can be effectively measured.     

入侵植物美洲商陆与3种牧草的竞争效应研究

以美洲商陆（Phytolacca americana）和紫花苜蓿‘吉利’（Medicago sativa ‘Ghillie’）、拉巴豆‘润高’（Dolichos lablab ‘Rongai’）、甜高粱‘大力士’（Sorghum dochna ‘Hunnigreen’）为试验材料,采用复合De Wit取代试验方法,探讨入侵植物与牧草间的竞争效应。结果表明：美洲商陆与3种牧草低密度混种下,其株高与生物量均显著低于单种的美洲商陆;在高密度混种下,美洲商陆与拉巴豆混种时的差异最显著,其株高比单种降低53.52%~81.95%,生物量比单种降低90.22%~98.67%;在美洲商陆与拉巴豆两者的竞争关系中,美洲商陆相对产量（relative yield,RY）值均极显著小于1.0,拉巴豆RY值在中、高密度下均大于1.0,且拉巴豆对美洲商陆的攻击力系数（aggressivity,A）显著大于0,表明两者混种时,拉巴豆的攻击力大于美洲商陆,混种阻碍了美洲商陆的生长,拉巴豆对美洲商陆具有较强的控制潜力。     

Human Infrastructure and Invasive Plant Occurrence Across Rangelands of Southwestern Wyoming,USA

Although human influence across rural landscapes is often discussed, interactions between the native, natural systems and human activities are challenging to measure explicitly. We assessed the distribution of introduced, invasive species as related to anthropogenic infrastructure and environmental conditions across southwestern Wyoming. to discern direct correlations as well as covariate influences between land use, land cover, and abundance of invasive plants, and assess the supposition that these features affect surrounding rangeland conditions. Our sample units were 1 000 m long and extended outward from target features, which included roads, oil and gas well pads, pipelines, power lines, and featureless background sites. Sample sites were distributed across the region using a stratified, random design with a frame that represented features and land-use intensity. In addition to land-use gradients, we captured a representative, but limited, range of variability in climate, soils, geology, topography, and dominant vegetation. Several of these variables proved significant, in conjunction with distance from anthropogenic features, in regression models of invasive plant abundance. We used general linear models to demonstrate and compare associations between invasive plant frequency and Euclidian distance from features, natural logarithm transformed distances (log-linear), and environmental variables which were presented as potential covariates. We expected a steep curvilinear (log or exponential) decline trending towards an asymptote along the axis representing high abundance near features with rapid decrease beyond approximately 50–100 m. Some of the associations we document exhibit this pattern, but we also found some invasive plant distributions that extended beyond our expectations, suggesting a broader distribution than anticipated. Our results provide details that can inform local efforts for management and control of invasive species, and they provide evidence of the different associations between natural patterns and human land use exhibited by nonnative species in this rural setting, such as the indirect effects of humans beyond impact areas.     

入侵植物角果毛茛种子萌发特性的研究

为探讨入侵植物角果毛茛（Ceratocephalus testiculatus）种子的萌发特性,以温度、赤霉素（GA₃）、硝酸钾（KNO₃）和浓硫酸腐蚀时间（SACT）等为参试因素的正交试验来研究其种子萌发响应特性。预试验结果表明：在自然条件下角果毛茛种子萌发耗时长,萌发率低,处理14 d后才开始有种子萌发,28 d后的最终萌发率仅为10%左右,存在种子休眠机制。正交试验研究结果表明,4个参试因素均能极显著地促进该种子萌发（P<0.01）,处理7 d后种子陆续萌发,萌发处理14 d时发芽势可达68.89%,萌发处理28 d时最高发芽率可达83.33%,成功解除了角果毛茛的种子休眠。各参试因素对角果毛茛种子萌发率和发芽势的影响顺序相同,均为温度 >SACT >KNO₃ >GA₃。最有利于种子萌发率的因素水平组合为A₃B₄D₄E₅,即萌发温度为10℃,赤霉素浓度为150 mg·L^-1,硝酸钾浓度为1.50 g·L^-1,浓硫酸腐蚀时间为10 min;发芽势的最优水平组合为A₃B₃D₂E₄,即萌发温度为10℃,赤霉素浓度为100 mg·L^-1,硝酸钾浓度为0.50 g·L^-1,浓硫酸腐蚀时间为8 min。     

Landscape Factors Influencing the Abundance and Dominance of the Invasive Plant Potentilla Recta

Little is known about the relative importance of environmental, biotic, historical, and spatial factors that influence invasive plant abundance, dominance, and distribution across landscapes. We identified factors that influence the abundance and dominance of Potentilla recta L. (sulfur cinquefoil) in bunchgrass grasslands of northeastern Oregon to better understand the conditions under which it becomes a major component of plant communities. We estimated P. recta stem density and dominance from field measurements across the landscape and used classification and regression tree analyses to assess the importance of environmental, biotic, spatial, and historical factors in explaining P. recta presence, stem density, and dominance. Plots were sampled within a systematic grid with 250-m spacing within our 6.5-km² study landscape. At each sample point we recorded P. recta presence, stem density, and dominance as well as 11 biological, environmental, spatial, and historical variables. P. recta was widely distributed, with stem densities in occupied plots averaging 5.8 stems • m^-2 and dominance values ranging from 1% to 52%. Percent cover of bare ground was the most important variable to predict the presence of P. recta, though the model fit was poor, likely because the entire study area is suitable for P. recta establishment. A strong relationship between P. recta dominance and habitat type (r² = 67.5%) was found, with dominance greatest in old fields on relatively flat slopes (mean dominance of 34.1%). Dominance estimates were ≤ 1% in plots located in forest, shrub, and grassland habitats. Factors that make old fields susceptible to dominance remain unknown, though microsite conditions that increase P. recta seedling survival rates and limited native propagule availability due to previous cultivation may be involved. Since old fields are found throughout the region, are highly susceptible to P. recta invasion, and represent a source of seeds, containment and restoration activities should focus on these areas.     

北方草坪绿地的建植与管理

随着社会、经济的进步,两个文明建设的深入,国土绿化步伐的加快,我国草坪业正以前所未有的速度向前发展.近年来草坪绿地的建植事业在我国城乡建设、体育运动场、旅游景点、园林环保等领域日益受到重视,如何建成高质量的草坪绿地,则是大多数从事草坪、园林工作者所关心的问题,因此,就北方草坪绿地的建植与养护管理作一简要介绍.     

电厂燃煤管理方法探讨

本文通过对煤炭从生产源头到进入火电厂的管理措施,设备的管理,工作人员技能培训和思想上的监督等一些方法来提高工作的整体效率和在燃料口上为电厂的燃料成本做好坚实的把控,从而使电厂的效益得以提升,煤的资源得以高效利用。     

Plant Community and Target Species Affect Responses to Restoration Strategies

Increases in Kentucky bluegrass and smooth bromegrass on northern Great Plains rangelands have the potential to negatively impact ecosystem function, lower plant diversity, and alter seasonal forage distribution, but control strategies are lacking in the region. A project was initiated on a heavily invaded 16-ha grassland that had not been grazed or hayed for at least 20 yr. Five restoration treatments and a control were initiated in 2003 on communities dominated by 1) smooth bromegrass (Bromus inermis Leyss.), 2) Kentucky bluegrass (Poa pratensis L.), 3) warm-season native grasses, 4) a mix of introduced species, and 5) smooth bromegrass and Kentucky bluegrass. Restoration treatments were 1) late-April burn, 2) late-April burn followed by imazapic at 511.62 mL ai · ha^?1, 3) imazapic only at the same rate, 4) mowing, 5) mowing followed by litter removal, and 6) control. We found that treatment responses were affected by target species, community category, and year. Generally, burning followed by the herbicide imazapic reduced Kentucky bluegrass in the species composition, but smooth brome was reduced by mowing followed by raking. Burning followed by imazapic reduced live grass biomass in all community categories except the native the year following treatment, but by the third year of the study live grass biomass was maintained across all treatments. In the third year of the study, responses of Kentucky bluegrass, other invasive species, and native grasses to restoration treatment differed depending on community. The use of burning plus imazapic was promising for control of Kentucky bluegrass but its use by producers may be limited by yield reductions in early years. Our data suggest management strategies should vary depending on whether the goal is to reduce one or several invaders, specific invader identity, and community type in which the invader is growing. We also found that the most effective strategy was an adaptive management approach, one where treatments are chosen in response to changes in community composition and depending on resource conditions.