连续单一除草剂应用情况下的转基因直播稻田杂草群落动态

【背景】转基因抗除草剂水稻种植将导致连年连续使用单一目标除草剂,势必会影响杂草群落结构的变化,但其变化规律至今还不十分明确。【方法】于2011~2013年,连续3年在直播种植抗草铵膦转基因Bar68-1水稻田中,使用灭生性除草剂草铵膦,持续观察期间杂草群落结构变化,并与常规选择性除草剂丙草胺—苄嘧磺隆（丙·苄）的应用情况进行对比,以揭示由于种植转基因抗除草剂水稻而使用单一除草剂对稻田杂草群落结构的影响。【结果】草铵膦和丙·苄连续使用后,杂草的物种丰富度和总杂草密度均逐年显著降低。随草铵膦使用年限增加,控草效果持续提高并达到优良水平,而常规选择性除草剂丙·苄的长期使用,致使多年生杂草双穗雀稗演替为群落的优势种,杂草密度呈逐年增加的趋势,导致生物多样性指数显著降低。【结论与意义】抗除草剂转基因水稻种植,在抗性杂草演化之前,不会因单一灭生性除草剂的应用而导致杂草群落迅速朝不良方向演替。长期的群落演替还需要进一步研究观察。     

Evolutionary-thinking in agricultural weed management

Agricultural weeds evolve in response to crop cultivation. Nevertheless, the central importance of evolutionary ecology for understanding weed invasion, persistence and management in agroecosystems is not widely acknowledged. This paper calls for more evolutionarily-enlightened weed management, in which management principles are informed by evolutionary biology to prevent or minimize weed adaptation and spread. As a first step, a greater knowledge of the extent, structure and significance of genetic variation within and between weed populations is required to fully assess the potential for weed adaptation. The evolution of resistance to herbicides is a classic example of weed adaptation. Even here, most research focuses on describing the physiological and molecular basis of resistance, rather than conducting studies to better understand the evolutionary dynamics of selection for resistance. We suggest approaches to increase the application of evolutionary-thinking to herbicide resistance research. Weed population dynamics models are increasingly important tools in weed management, yet these models often ignore intrapopulation and interpopulation variability, neglecting the potential for weed adaptation in response to management. Future agricultural weed management can benefit from greater integration of ecological and evolutionary principles to predict the long-term responses of weed populations to changing weed management, agricultural environments and global climate.     

Increasing habitat connectivity in agricultural landscapes as a weed management strategy reconciling ecology and agronomy

While studies have explored how habitat amount drives weed assemblages in agroecosystems, knowledge remains limited of the effects of habitat connectivity. The response-effect trait framework provides insights into the mechanisms underpinning the relationship between landscape structure and the taxonomic diversity and abundance of weed assemblages. This study evaluated how habitat connectivity and habitat amount affect weed diversity and abundance in winter cereal fields, and whether these effects are driven by the functional composition of weed assemblages. We sampled weeds in 27 winter cereal fields. We measured habitat connectivity and habitat amount provided by wooded, grassland and cropland elements. We selected five traits related to the dispersal, establishment, and competitive abilities of weed species likely to respond to landscape structure: seed number per plant, type of reproduction, seed dry mass, plant vegetative height and seed germination rate. The functional composition of weed assemblages was assessed using community weighted mean trait values. Weed diversity and abundance were used as proxies of weed management. The taxonomic approach did not reveal any effect of landscape structure on weed diversity and abundance. Only the grassland elements that contributed to habitat connectivity, and to a lesser extent to habitat amount, drove the functional composition of weed assemblages. High habitat amount favoured species with many seeds, while high habitat connectivity favoured species with fewer seeds, a higher ability to reproduce vegetatively and higher seed germination rates. In turn, higher seed germination rates increased weed evenness and reduced weed abundance. Some of these relationships were influenced by the presence of rare species. Overall, high connectivity provided by grassland elements increases weed evenness and reduces weed abundance by shaping weed functional composition. Our study suggests that land-use planning policies that enhance the connectivity provided by grassland elements could be considered as a weed management strategy reconciling ecology and agronomy.     

Prediction of weed density: the increase of error with prediction interval, and the use of long-term prediction for weed management

1. This paper addresses the errors that are associated with the long-term prediction of weed densities, and the effect of these errors on the performance of weed management decisions based on those long-term predictions.
2. A model of weed population dynamics was constructed and its parameters were estimated from experimental observations of population dynamics of the weed species Stellaria media in a crop rotation.
3. The observations showed that estimates of weed population growth rate differed between two locations.
4. The model was used to analyse error propagation for predicted weed densities in an enlarged prediction interval. It is concluded that errors due to an uncertain population growth rate increase linearly with the length of the prediction interval, and thus pose an upper limit to the horizon for long-term predictions.
5. It is shown that a limited ability to predict weed densities does not necessarily impair the practical use of weed population dynamic models in planning for long-term weed control programmes.     

Aspects of herbicide activity and persistence under low level polyethylene covers

In an experiment prepared in autumn, weed numbers were not affected by covering the soil with clear perforated polyethylene. Weed growth was enhanced, however, and the fresh weight at the time of polyethylene removal in spring was more than three times greater on the covered compared with the uncovered areas. In a similar experiment prepared in spring, covering with perforated polyethylene increased weed numbers by a factor of two and weed fresh weight by a factor of seven. The performance of a number of herbicides used in carrots, in terms of percentage reduction in weed number and weed fresh weight, was similar under covers and in the open. The most effective weed control was achieved with broad-spectrum herbicide treatments, particularly under the polyethylene, since surviving weed seedlings grew rapidly in the protected environment. When weed control was good, covering enhanced carrot yield. Measurement of the distribution of herbicide residues in the soil demonstrated that persistence was increased and movement in the soil decreased by covering with polyethylene.     

Restoring a seasonal wetland using woven black plastic weed mat to overcome a weed threshold

Little information is available on the use of woven black polypropylene weed control mat in ecological restoration. At a 6.5‐ha area of fertile Vertosol soil ex‐farmland near Perth, Western Australia, concerted efforts to control weed using conventional methods such as herbicides, fire and cultivation proved ineffective. After 5 years, weeds still dominated the site, and native plant establishment was poor. Small‐scale preliminary trials of various weed suppression coverings were then undertaken, with plastic weed mat the most cost‐effective in overcoming the weed threshold, permitting native tree seedling establishment. In a larger‐scale trial of weed mat over the whole site, weeds were controlled and high levels of native plant establishment achieved, with a diverse range of understorey, midstorey and overstorey species providing 56% projected foliage cover. This ensured that completion criteria were finally satisfied. These results suggest that weed mat may be effective for weed control in large‐scale restoration where conventional methods have failed, as long as ultimate removal or decomposition and other issues are addressed.     

长期稻鸭共作对稻田杂草群落组成及物种多样性的影响

2000~2003年连续4年研究了稻鸭共作条件下田间杂草群落的特征及其动态变化规律。结果表明,在长期稻鸭共作条件下,田间杂草密度逐年降低,下降趋势符合阻滞模型y=k+a·e^bx,模型参数b反映了杂草种群的下降速率。在稻田6种主要杂草中,水虱草(Fimbristylis miliaceae)、陌上菜(Lindernia procumbens)、丁香蓼(Ludwigia prostrata)种群数量降低较快,鸭舌草(Monochoria vaginalis)、异型莎草(Cyperus difformis)次之,稗(Echinochloa crusgalli)最慢。稻鸭共作使稻田杂草群落的物种多样性持续降低,群落均匀度提高,群落相似性与稻鸭共作前相比逐年降低。说明稻鸭共作改变了田间杂草的群落结构,有利于限制杂草的发生危害。随着稻鸭共作的连年进行,对田间杂草的控制效果逐渐上升,4年后达99%以上。稻鸭共作是稻田替代化学除草的一种非常有效的生物、生态控草措施,具有显著的经济和生态效益。     

Cereal weeds variation in middle Egypt: Role of crop family in weed composition

Cereals occupies a major part in the diet of humans globally, participating more to our daily protein and calorie intake than any other crop. The present study highlight the weed flora of cereal crops compared to other crops in middle Egypt and their distribution. Ninety-two weed species were recorded in the all studied crops, cereal and other crops; in the studied area belong to 67 genera and 20 families. Egyptian clover; showed the highest numbers of both weed species and genera followed by wheat, on contrast the lowest weed species and genera numbers were recorded associated with Solanaceous crops tomato and pepper. Wheat crops exhibited the highest number of weed species, among cereals, followed by maize crop, while the lowest weed species number was detected in barley crop. Chenopodium murale, Cynodon dactylon, Convolvulus arvensis and Malva parviflora were the most frequent species in winter cereals, while Echinochloa colona, P. oleraceae were the most frequent weeds in summer cereals. Chorological analysis of the recorded weed species showed that cosmopolitan elements showed the highest numbers in total weed flora Differences in weed species compositions were fundamentally influenced by seasonal priority. Based on TWINSPAN and Ward classifications, crop family showed slightly effect as a factor affecting weed composition.     

Decomposition dynamics of invasive alligator weed compared with native sedges in a Northland lake

Invasive weeds have been shown to alter ecosystem processes such as decomposition and nutrient cycling. However, little is known about the effects of introduced biocontrol agents on these processes. This study examined the effects of alligator weed (Alternanthera philoxeroides) and its biocontrol agent, the alligator weed flea beetle (Agasicles hygrophila), on nutrient cycling in a northern New Zealand lake. Alligator weed litter decomposed significantly faster than either of two native sedge species (Schoenoplectus tabernaemontani, Isolepis prolifer) in a litterbag experiment. In addition, the presence of the alligator weed flea beetle resulted in large amounts of decaying alligator weed litter entering the lake in early summer. Both the timing and magnitude of this litter input were uncharacteristic of seasonal biomass dynamics of the native sedges. Combined with alligator weed?s rapid decomposition, this indicates altered patterns of nutrient cycling at the lake, with potential flow-on effects including facilitation of further weed invasion.     

不同施肥方式对稻麦两熟制小麦田杂草群落的影响

为揭示不同施肥方式对稻麦两熟制区麦田杂草的影响,以连续4年固定施肥田为对象,于2014年小麦收获前进行了杂草群落调查,研究不同施肥、秸秆还田小麦田间杂草种类、密度、高度、杂草多样性指数的差异,并对杂草种群分布与肥料因子进行典范分析. 结果表明：36个试验小麦田中共记录杂草20种,分属11科19属. 其中,菵草、泥胡菜、牛繁缕、蛇床广泛分布于各试验田块. 长期施肥可减少麦田杂草种类及发生密度,但会增加麦田杂草高度,其中阔叶杂草在试验设定的各施肥措施下种类及发生密度均显著下降;纯施化肥、有机肥配施化肥,特别是施用有机无机复混肥的田块中,杂草群落多样性指数和均匀度指数低,优势度指数较高,容易使单一优势杂草种类暴发,造成严重危害;秸秆还田配施有机肥化肥处理麦田环境中杂草多样性指数、均匀度指数相对较高,优势度指数相对较低,杂草群落的结构较复杂,群落相对稳定,且杂草密度较低,对小麦生长危害较轻.     

Impact of Fertilizing Pattern on the Biodiversity of a Weed Community and Wheat Growth

Weeding and fertilization are important farming practices. Integrated weed management should protect or improve the biodiversity of farmland weed communities for a better ecological environment with not only increased crop yield, but also reduced use of herbicides. This study hypothesized that appropriate fertilization would benefit both crop growth and the biodiversity of farmland weed communities. To study the effects of different fertilizing patterns on the biodiversity of a farmland weed community and their adaptive mechanisms, indices of species diversity and responses of weed species and wheat were investigated in a 17-year field trial with a winter wheat-soybean rotation. This long term field trial includes six fertilizing treatments with different N, P and K application rates. The results indicated that wheat and the four prevalent weed species (Galium aparine, Vicia sativa, Veronica persica and Geranium carolinianum) showed different responses to fertilizer treatment in terms of density, plant height, shoot biomass, and nutrient accumulations. Each individual weed population exhibited its own adaptive mechanisms, such as increased internode length for growth advantages and increased light interception. The PK treatment had higher density, shoot biomass, Shannon-Wiener and Pielou Indices of weed community than N plus P fertilizer treatments. The N1/2PK treatment showed the same weed species number as the PK treatment. It also showed higher Shannon-Wiener and Pielou Indices of the weed community, although it had a lower wheat yield than the NPK treatment. The negative effects of the N1/2PK treatment on wheat yield could be balanced by the simultaneous positive effects on weed communities, which are intermediate in terms of the effects on wheat and weeds.     

稻鸭共作及其它控草措施对稻田杂草群落的影响

运用群落生态学方法研究了稻鸭共作、人工除草、化学除草3种控草措施对稻田杂草群落特征的影响及其对田间杂草的控制作用.结果表明,稻鸭共作显著降低了田间杂草的发生密度,对稻田主要杂草鸭舌草(Monochoriavaginalis)、异型莎草(Cyperusdifformis)、矮慈姑(Sagittariapygmaea)的防效均达到95%以上,总体控草效果显著优于化学除草和人工除草.稻鸭共作使稻田杂草群落的物种丰富度及Shannon-Wiener多样性指数略有降低,但Pielou均匀度指数显著提高,表明群落物种组成有了很大的改变,降低了原来优势杂草的发生危害.在不同控草措施作用下,稻田杂草群落的结构组成也发生了一定的变化,稻鸭共作区群落组成为陌上菜(Linderniaprocumbens)+异型莎草+水虱草(Fimbristylismiliacea),Whittaker群落指数显著高于化学除草、人工除草及对照区,表明稻鸭共作对田间杂草群落结构影响较大.从Sorensen群落相似性指数及以其为距离测度指标的聚类分析结果中也可得到同样的结论.     

Factors affecting the cost of weed biocontrol programs in New Zealand

Many national schemes for setting priorities for invasive weed management have emphasized the current or future impacts of the weed more than the cost or feasibility of control, perhaps because the latter may be difficult to estimate. As part of a project to improve prioritization of weed biocontrol targets in New Zealand, we investigated factors that were hypothesized to influence the cost of conducting weed biological control, using data from New Zealand programs. Taxonomic isolation of the target weed, relative to commercially important plants and native flora was not a significant influence on program cost, although we present evidence that disease, which to date has only affected agents released against taxonomically isolated weed targets, has masked the importance of taxonomic isolation in New Zealand. Opposition to biocontrol has caused delays, but has not had a major influence on the cost of biocontrol in New Zealand, probably because weed species with the greatest potential for opposition were identified during feasibility studies and avoided, or because conflicts were resolved by conducting cost-benefit analyses that were minor components of the total program costs. Only two factors explained virtually all the variance in program cost: program type (repeat programs were cheaper than novel/pioneering programs); and the number of agent species released. The predicted cost of future weed biocontrol programs can now be incorporated into decision-making tools ranking New Zealand weed biocontrol targets. Efficiencies in future programs are most likely to be gained by better agent selection so that fewer agents are released. For repeat programs this could be achieved by waiting until monitoring has been conducted overseas, so that the best agents or combination of agents can be selected for any particular weed. This reiterates the need for better post-release evaluation of weed biocontrol agent effectiveness worldwide.     

Density of adult hoverflies (Dipt., Syrphidae) in sown weed strips and adjacent fields

In 1992 and 1993, studies examined numbers of adult hoverflies in sown weed strips, adjacent fields and a field boundary in the Swiss plateau, near Bern. Hoverflies were observed quantitatively and were divided according to their larval food. In both years, distinctly more aphidophagous and aquatic hoverflies were observed in the weed strips than in the adjacent fields. Copro- and phytophagous hoverflies were observed in very low numbers and they were almost entirely confined to the weed strips and the field boundary. The weed strips contained a high density of flowering plants and therefore proved to be very attractive feeding places for all hoverflies. Numbers of aphidophagous hoverflies declined slightly with increasing distance from the weed strips. Possible impacts of weed strips in encouraging aphidophagous hoverflies and their potential as aphid antagonists are discussed.     

江苏省棉区棉田杂草群落发生分布规律的数量分析

在对江苏省四大主产棉区８２个样点７２７块田地共５７．５ｈｍ＾２棉田杂草群落及草害进行７级目测法调查采集数据后,对其进行主成分分析（ＰＣＡ）,并赋以生态学意义的解释。研究表明,江苏省棉田杂草的发生和分布与轮作种植制度和地理区域性密切相关,其中轮作制度导致的田间水分的巨大差异是决定杂草群落结构特征的最深刻的原因,导致全省水旱轮作棉田的杂草群落有趋向性。而地理区域构成的土壤、气候等生态因子的显著影响表现     

Wild and Weed Azuki Beans in Japan

Wild azuki bean, a progenitor of an Asiatic food legume (Vigna angularis var.nipponensis: Fabaceae), and its weed form are distributed widely in the Japanese Archipelago. The straggling or climbing wildform occurs in sleeve or mantle plant communities, and the weakly climbing or bushy weed form is found in relatively open human-disturbed habitats. The wild form has small seeds with a black-mottled pattern on green or grey skin; the weed form has larger seeds with variable color patterns. Wild and weed forms have black, easily dehiscent pods, distinct from their cultivated counterpart which has red large seeds and indehiscent light-colored pods. The wild form is not utilized, but the weed form is recognized by farmers and has several folk names as a weed, a contaminated form of azuki bean, and a substitute for azuki as a food. The frequent occurrence of weed azuki bean in Japan is attributable to adaptation of the wildform to lack of climbing support in human-disturbed habitats, escape from old cultivars, and natural establishment from the derivatives of hybrids between cultivars and wild forms.     

沟叶结缕草草坪杂草群落的时空动态

杂草群落结构的异质性是群落动态的主要属性.基于物种频度和幂函数法则,对沟叶结缕草草坪杂草群落在时间维度上的物种结构和空间异质性的变化进行了研究.结果表明： 从2007到2009年,沟叶结缕草草坪3年共发生杂草43种,隶属19科,其中,禾本科、菊科、莎草科和茜草科杂草在草坪杂草中占据优势,多年生杂草占杂草比例最大,并呈逐年上升趋势;杂草群落具有比随机分布更高的空间异质性;杂草优势种年内随季节变化明显,表现出“双子叶杂草－单子叶杂草－双子叶杂草”、“多年生杂草－一年生杂草－多年生杂草”交替出现的规律;杂草群落的空间异质性在夏季大于冬季,多样性和均匀性在夏秋季大于冬春季,在夏季表现出高异质性的杂草种类比其他季节多;杂草群落空间异质性、多样性年际间变化不显著,均匀性呈逐年降低趋势.
     

Weed development in spring wheat after contrasting soil tillage and nitrogen management

Soil tillage and nitrogen (N) management effects on weed species composition were evaluated in 2013 and 2014 on a clayey soil after 5‐years of organic management at the Royal Agricultural University's Harnhill Manor Farm, UK. Three tillage systems – Conventional Tillage (CT), and High and Low Intensity Non‐inversion Tillage (HINiT & LINiT) – were compared at four N fertiliser rates of 0, 70, 140 and 210 kg N ha^?1. Broad‐spectrum herbicide was applied before soil operations across the site in both years. Previous organic management legacy of high weed biomass promoted greater weed prevalence in 2013 while 2‐years of herbicide inclusion reduced weed biomass. Contrasting weather conditions across the seasons affected weed incidence. In the 2014 wet season, early weed dry weight (DM) was higher under HINiT than CT and LINiT, while no differences were observed in the 2013 dry year. At midseason, weed DM was higher under HINiT than CT and LINiT in both years, which was related to higher DM of the dominant weeds Stellaria media (L.) Vill. and Sinapis arvensis L. Grass weed DM was higher under non‐inversion tillage than CT. N fertilisation increased midseason total weed DM and weed prevalence at harvest. Spring wheat yield was the highest under CT while LINiT produced 17% higher yields than HINiT. Despite higher but still tolerable weed prevalence under both non‐inversion tillage systems and with the application of N, weeds alone was not the only yield‐limiting factor. However, results show that CT is the most reliable option for weed control in changing weather, while N fertilisation rates needs to be considered.     

Weed performance in crop rotations with and without leys and at different nitrogen levels

Weed populations were studied from a 26-year-old field experiment in southern Sweden with three different 6-year crop rotations, each with four rates of nitrogen application. The rotations differed in that one had a two-year legume-grass ley, another had a two-year grass ley, and that the third had spring wheat followed by a repeatedly harrowed fallow. The leys and the fallow were followed by turnip rape, winter wheat, oats and barley which was undersown in the two ley rotations. Data on weed biomass, collected in one season, were subjected to multivariate analysis.
Winter turnip rape had the highest weed biomass. However, of the several weed species, only Matricaria perforata Merat was important in wheat (the crop following turnip rape in the rotation). The weed flora did not differ consistently between rotations. We conclude that none of the three rotations had developed any major weed problems under the past weed management regime (herbicides applied to cereal crops).
There was no consistent effect of nitrogen fertilisation on total weed biomass in any of the three rotations. However, when comparing the weed floras in winter wheat, turnip rape and oats, the unfertilised plots differed from the plots receiving nitrogen. In the two latter crops, the abundant, low-growing annual Stellaria media (L.) Vil. performed best in fertilised plots with dense stands. Equisetum arvense L., the most abundant perennial weed, was important only in unfertilised plots.     

江苏省棉区棉田杂草群落发生分布规律的数量分析

在对江苏省四大主产棉区８２个样点７２７块田地共５７．５ｈｍ＾２棉田杂草群落及草害进行了７级目测法调查采集数据后,对其进行主成分分析,并赋以生态学意义的解释,研究表明,江苏省棉田杂草的发生和分布与轮作种植制度和区域性化作制度导致的田间水分的巨大差异是决定杂草群落结构特征的最深刻的原因,导致全省水旱轮作棉 杂草群落有趋同性。