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1.
Chrysanthemoides monilifera ssp rotundata (L) T Norl (Bitou bush) is a serious environmental weed along the southeast coast of Australia. The herbicide glyphosate is commonly used to control C monilifera on the New South Wales coastline, but there have been few studies examining the effects of this herbicide on invertebrate communities in the field, especially on sand dunes. Control and impact sites were selected in coastal hind dunes heavily infested with C monilifera, and the impact sites were sprayed with a 1:100 v/v dilution of glyphosate-isopropyl 360 g AE litre(-1) SL (Roundup Biactive). Leaf litter invertebrates were sampled before spraying and after spraying by collecting fixed areas of leaf litter in both the control and impact sites. Samples were sorted for particular invertebrates involved in leaf litter decomposition and some of their predators. This study did not identify any significant direct or indirect effects on leaf litter invertebrate abundance or community composition in the four months following herbicide application. The litter invertebrate assemblages were highly variable on a small spatial scale, with abiotic factors more strongly regulating leaf litter invertebrate numbers than glyphosate application. These results conflict with previous studies, indicating that the detrimental indirect effects herbicide application has on non-target litter invertebrates may depend upon the application rate, the vegetation community and structure and post-spray weather.  相似文献   

2.
The biodiversity of farmed landscapes is, in the context of agricultural intensification, a key aspect with regard to improving the sustainability of agroecosystems. Olive groves are undergoing rapid changes because of the spread of intensive farming systems, which may have negative environmental impacts. This paper reports a survey on the aboveground flora and seed banks in five olive groves located in Andalusia (Southern Spain). In this study, the following three management systems have been compared: no‐tillage, with the mowing of spontaneous weedy vegetation; no‐tillage, with the mowing of planted cover crops (Poaceae); and conventional tillage practices. Results showed that coverage and an abundance of vegetation are favored by spontaneous weedy vegetation with mowing management, while the richness of aboveground species was affected by landscape diversity and the presence of edges, which increases the richness and diversity of aboveground flora species in olive groves. Seed bank composition showed a low relationship with aboveground flora in the three cover crop management systems. The multivariate analysis performed pointed to those seed species that have a major influence on the aboveground flora communities of each of the three agricultural systems. The seed bank was clearly impoverished in terms of both abundance and species richness after the long‐term conventional tillage practices. We conclude that the intensive long‐term conventional tillage dramatically reduces weed communities in olive orchards and the subsequent ecosystem services provided by them.  相似文献   

3.
The annual plant Impatiens glandulifera (Himalayan balsam) is the most widespread invasive non‐native weed in the British Isles. Manual control is widely used, but is costly and laborious. Recently, biological control using the rust fungus Puccinia komarovii var. glanduliferae has been trialled. We designed an experiment to assess the impact of these control methods on invertebrate communities in relation to unmanaged and uninvaded habitats, and to determine whether mycorrhizal inoculation aided post‐control recovery of these communities. Sixty invaded and twenty uninvaded field soil blocks were transplanted to the experiment site, where a mycorrhizal inoculum was added to half of all blocks. Biological and mechanical control treatments were applied to twenty invaded blocks independently; the twenty remaining invaded blocks were left intact. Above‐ and belowground invertebrate samples were collected from the blocks at the end of the growing season. Overall, aboveground invertebrate abundance increased with the removal of I. glandulifera, and several groups showed signs of recovery within one growing season. The effect of mechanical control was more variable in belowground invertebrates. Biological control did not affect aboveground invertebrate abundance but resulted in large increases in populations of belowground Collembola. Our experiment demonstrates that mechanical removal of I. glandulifera can cause rapid increases in invertebrate abundance and that its biological control with P. komarovii var. glanduliferae also has the potential to benefit native invertebrate communities.  相似文献   

4.
The germinable soil seedbank was determined at two sites in central Queensland on four separate occasions between February 1995 and October 1996. These sites were infested with parthenium weed ( Parthenium hysterophorus L.), a serious invasive exotic weed. During this period, the seedbank varied between 3282 and 5094 seeds m−2 at the Clermont site, and between 20 599 and 44 639 seeds m−2 at the Moolayember Creek site. Parthenium hysterophorus exhibited a very abundant and persistent seedbank, accounting for 47–73% of the seedbank at Clermont and 65–87% of the seedbank at Moolayember Creek. The species richness and species diversity of the seedbank, and the seed abundance of many species, was lower at Moolayember Creek during spring (the time of year when the most dense infestations of the weed originate). Parthenium hysterophorus seedlings also emerged more rapidly from the soil samples than did those of all other species. Hence, it seems that various aspects of the weed's seed ecology, including abundance and the persistence of its seedbank and the rapid emergence of its seedlings, are major factors contributing to its aggressiveness in semiarid rangeland communities in central Queensland. The domination by P . hysterophorus of the seedbanks of these sites suggests that the weed is having a substantial negative impact on the ecology of these plant communities. The diversity of these seedbanks was found to be lower in comparison with that observed in other grassland communities that were not dominated by an invasive weed species. Hence, the prolonged presence of P . hysterophorus may have substantially reduced the diversity of these seedbanks, thereby reducing the ability of some of the native species to regenerate in the future.  相似文献   

5.
The aim of this study was to determine the weed suppression potential of soil steaming plus activating compounds (KOH or CaO) to boost soil temperature. Different combinations between the compounds and rates were tested in experiments carried out in the field and in a controlled environment. Treatment effects were assessed on field weed vegetation and on seedbank and seedling emergence of three winter ( Alopecurus myosuroides , Matricaria chamomilla and Raphanus raphanistrum ) and four spring annuals ( Amaranthus retroflexus , Echinochloa crus-galli , Fallopia convolvulus and Setaria viridis ), were assessed on field weed vegetation. Neither maximum soil temperature (from 72 to 85°C) nor duration of high temperature in the 3 h following application consistently affected weed suppression. In the field, no significant effects on total weed density were recorded, but there were some significant effects on individual species. The weed seedbank was clearly suppressed by activated steaming: total seedling emergence was inversely related to increasing KOH rates both in the 0–10 and 10–20 cm soil layers, while for CaO the relationship was significant only in the 0–10 cm layer. Winter annuals were more sensitive to KOH than CaO and spring annuals had a more pronounced species-specific response to treatments. There was a strong negative relationship between compound rate and seedling emergence for all species. Alopecurus myosuroides was the most sensitive to the steam-alone treatment (77% reduction), whereas M. chamomilla and E. crus-galli were the least sensitive. Results from this study indicate that the type and rates of activating compounds for soil steaming must be adjusted to the weed community composition.  相似文献   

6.
The presence of weeds in crop fields often causes yield reductions. However, the effects of weed diversity have not been fully examined. This study tested the hypothesis that, holding density constant, increased weed species richness would decrease the effects of competition on spring wheat target plant performance. Measurements were taken from circular neighbourhoods (16.5 cm radius) with a single spring wheat plant surrounded by combinations of Setaria viridis , Avena fatua , Kochia scoparia , Thlaspi arvense and spring wheat plants, representing all combinations of neighbour species at four density levels. Using regression models, we found that species richness had no significant direct effect on spring wheat biomass, yield, or relative growth rate and that there were no significant neighbour species interaction terms. For weedy target plants, the presence of negative interaction terms suggested that increasing species richness had negative effects on growth of individual weed species. Additional analysis suggested that increased species richness may limit competitive ability of dominant weeds. Although we found no evidence of a direct effect of weed species richness on crop performance, increased weed species richness had no negative effect on spring wheat performance. Further, species richness of the weed community appears to influence weedy plant performance, which may offer a future opportunity to influence crop performance.  相似文献   

7.
MAYOR  DESSAINT 《Weed Research》1998,38(2):95-105
The role of three weed management strategies on weed populations and community dynamics was investigated from 1989 to 1994. These were chemical weed control (CH), integrated weed control (IN) and mechanical weed control (ME). Weed populations and communities were analysed by univariate (species richness, rank:frequency diagrams) and multivariate (correspondence analysis) methods. Species richness of the soil seedbank differed with weed management strategies and over time, with an observed annual number of species that ranged from 18 to 32. The seedbank was dominated by the same pool of species in all cases, but these species responded differently among years and management strategies; their rank (relative abundance) and densities changed between strategy and within a strategy among the years. In the last 2 years of the study, the soil seedbank was characterized mainly by #Capsella bursa-pastoris  相似文献   

8.
Very little research has been done on weed seedbank communities in the northern Great Plains region of the USA. The objectives of this study were to evaluate the effects of management systems on the weed seed banks and to assess the relationship between the weed seed banks and the above-ground weed communities. The seed banks were sampled along a range of areas of above-ground weed diversity in organic and conventional spring wheat production fields near Big Sandy, Montana, over 2 years. Eight 1 m × 0.33 m areas were selected in each field to encompass a wide range of above-ground weed diversity and soil cores were taken in each area to a depth of 20 cm and split in half at 10 cm. The number of seeds recovered from the top 10 cm of soil and the 10–20 cm depth were significantly affected by the sampling year and an interaction between the cropping system and the sampling year. The year was the only significant predictor affecting the weed seedbank diversity at both depths. A significant interaction between the management system and the year observed at the 10–20 cm sampling depth reflected the higher rate of decrease in diversity occurring between 2005 and 2006 in the conventionally managed fields compared with the organic fields. A multivariate ordination indicated that, although the year played a significant role in determining the weed seedbank communities, the management system had a role only during 2006. We failed to detect strong correlations between the above-ground and underground weed communities. The results of this study suggest that, in the studied region, yearly fluctuations in environmental factors have significant impacts on the weed seed banks.  相似文献   

9.
Jordan  Zhang  & Huerd 《Weed Research》2000,40(5):397-410
The importance of interactions between arbuscular-mycorrhizal fungi (AMF) and weeds of agro-ecosystems is reviewed. Considerable evidence suggests that AMF can affect the nature of weed communities in agro-ecosystems in a variety of ways, including changing the relative abundance of mycotrophic weed species (hosts of AMF), and non-mycotrophic species (non-hosts). These effects may merely change the composition of weed communities without affecting the damage that these communities cause. However, it is quite plausible that interactions with AMF can increase the beneficial effects of weeds on the functioning of agro-ecosystems. Through a variety of mechanisms, weed:AMF interactions may reduce crop yield losses to weeds, limit weed species shifts, and increase positive effects of weeds on soil quality and beneficial organisms. If beneficial effects of AMF on the composition and functioning of weed communities can be confirmed by more direct evidence, then AMF could provide a new means of ecologically-based weed management. Intentional management will be required to increase diversity and abundance of AMF in many cropping systems, but these actions (e.g. conservation tillage and use of cover and green-manure crops) typically will confer a range of agronomic benefits in addition to potential improvements in weed management.  相似文献   

10.
Weed species diversity may benefit from organic farming due to enhanced temporal diversification of crop species in a rotation and omission of herbicide applications. However, in intensively managed conventional systems, little evidence exists as to what extent diversified crop rotations contribute to higher weed species richness. Using an on-farm approach, the effect of crop rotation (organic, conventional diverse (CD) and conventional simple (CS) crop rotations) and weed control (with vs. without) on weed species richness, cover, community composition and crop biomass, was analysed in 24 winter wheat fields. Weed species with beneficial functions for invertebrates and birds were analysed separately. Weed species richness was higher in the organic crop rotation, but did not differ between CD and CS crop rotations. Weed control treatment reduced species richness in both conventional rotations, but not in the organic one. Redundancy analyses revealed that crop rotation intensity accounted for the largest part of the explained variation in weed species composition. Results from the study indicate that the maintenance of weed species richness and conservation of species with important ecological functions requires not only temporal diversification of crop species in the rotation, but also an adjustment of weed control strategies.  相似文献   

11.
The dissipation behaviour of metsulfuron-methyl, tribenuron-methyl, thifensulfuron-methyl, triasulfuron and amidosulfuron were studied in soil following post-emergence spring applications to cereal crops. Incorporation or removal of straw and different fertilizer applications had no influence on the disappearance time (DT50) of the herbicides. However, in laboratory trials dissipation of metsulfuron-methyl, triasulfuron and amidosulfuron at higher application rates was accelerated after incorporation of straw into the soil. The addition of straw decreases soil pH thereby causing faster hydrolysis of the compounds. Addition of nitrogen fertilizer increased the half-lives (t1/2) of the herbicides. Combination of both straw and N fertilizer, however, had no effect. Neither straw nor N influenced the degradation of tribenuron-methyl and thifensulfuron-methyl.
The DT50 of all herbicides investigated varied from 6 to 17 days in the field trials. Except for amidosulfuron, herbicides could not be detected 38–68 days after application. In the laboratory, t1/2 values were higher than those in the field at 75 days (amidosulfuron), 63 days (metsulfuron-methyl), 35 days (triasulfuron) and 13 days (tribenuron-methyl). Only the t1/2 of thifensulfuron-methyl was at 29 h faster under laboratory conditions. T1/2 values of all herbicides were influenced by their initial concentration. The t1/2 values of amidosulfuron and tribenuron-methyl at 1 mg a.i. kg−1 soil were 2–2.5 times higher than at the recommended field application rate of 42 μg a.i. kg−1 soil.  相似文献   

12.
以内蒙古荒漠区短脚锦鸡儿灌木为研究对象,采用野外调查法分析灌丛对植物群落的影响,采用传统培养法,结合分子鉴定法分析灌丛对土壤微生物群落的影响。结果表明:(1)灌丛内植物群落多度和总生物量显著大于灌丛外,但是物种丰度和Shannon-Wiener指数灌丛内外无显著差异;(2)随土壤深度的增加,表层土与深层土的土壤可培养细菌丰度和真菌多度差异不显著,其余土壤微生物群落多样性特征均表现为:表层土显著大于深层土;(3)灌丛对土壤微生物群落具有正效应,且表层土正效应最大;(4)灌丛对植物群落的促进作用大于对土壤微生物群落的作用。  相似文献   

13.
In order to better understand the effects of urbanization on weed communities, the distribution of weed communities in Shanghai, China, was systematically investigated. The diversity of weed communities and four environmental factors, including the relative light intensity, soil moisture, soil compaction and soil pH, were measured in 1375 plots along an urban–rural gradient. The species diversity indices in each area along the urban–rural gradient were compared by using a one‐way ANOVA. The weed communities were identified by using clustering methods that were based on relative dominance information. A canonical correspondence analysis was used to reveal the relationships between the species composition and the environmental factors at the community level and the Spearman's rank correlation test was used to test the relationship between the number of weed communities and each environmental factor. A total of 183 species, belonging to 41 families and 123 genera, was recorded. It was found that the species richness, Shannon–Wiener diversity index and Pielou evenness index followed a unimodal curve along the urban–rural gradient. The 1375 plots were divided into 133 weed community types. All four environmental factors significantly affected the species composition of the weed communities, but only soil compaction had significant effects on the number of weed communities. It was concluded that the diversification of habitat type and environmental change along the urban–rural gradient led to more weed communities in rural areas and fewer weed communities in urban areas. Based on the species' habitats and distribution patterns, the weeds were divided into “widespread”, “urban” and “rural”.  相似文献   

14.
The influence of herbicides on weed community dynamics is an issue of agroecological concern. A field study was initiated in 1986 with zero-, minimum-, and conventional-tillage systems. In 1989 and 1990, the fourth and fifth years of study, weed community diversity and relative composition were assessed prior to and following the application of post-emergence non-residual herbicides. Weed communities were assessed at the level of tillage system to balance the effect of different crop sequences and crop-herbicide combinations within each comparison. In general, herbicides did not reduce community diversity when compared by Shannon's H’and dominance-diversity curves. An increase in species richness and evenness, as assessed by Shannon's E and Margalef's DMG occurred in some cases. Differences in relative community composition among tillage systems were apparent before the application of herbicides, but disappeared following herbicide application. The use of herbicides in this study reduced weed densities, maintained weed diversity, and inhibited community changes that were due to changing tillage systems.  相似文献   

15.
Livestock ranching is one of the main productive activities in arid regions of the world.Grazing produces changes in animal as well as plant communities(e.g.richness,abundance and species dominance relationships).Ants are good biological indicators due to the environmental fidelity of some of their community parameters.We described the functional structure of the ant community in the central Monte of Mendoza,Argentina,and examined the effect of grazing using richness,diversity and the functional group scheme.We used pitfall traps to sample ants at a reserve with 30-year cattle exclusion and at an adjacent ranch.Eleven of the 27 recorded species showed significant differences in their abundance and two species were absent at the ranch.While richness and diversity did not reflect these differences,functional groups did.Hot Climate Specialists were more abundant at the ranch while Cryptic Species and Generalized Myrmicinae increased at the reserve.This study supports the utility of the functional group scheme to study the effects of grazing disturbance in ant communities of arid regions.  相似文献   

16.
R H LI  †  & S QIANG 《Weed Research》2009,49(4):417-427
The diversity and composition of floating weed seed communities were surveyed in 27 sites across the main rice-growing regions in China with the aim of better understanding weed seed dispersal via irrigation water. Seed of 74 species, belonging to 20 families, were identified from floating matter on the water surface in lowland rice fields. Thirty-five species from three families: Poaceae (15), Asteraceae (11), and Polygonaceae (9), accounted for 47% of all species identified. Species with seed maturing in the summer accounted for 64% of the weed seed and their mean relative abundance was 0.74. Species richness, Shannon–Wiener index and Pielou evenness index were significantly different among the floating weed seed communities. The diversity of weed seed communities in the Yangtze river valley was higher than that in other sites, and some sites were dominated by only a few weed species, such as Beckmannia syzigachne , Alopecurus aequalis , A. japonicus , and Polypogon fugax. At all sites, the dominant weed seeds reflected the dominant weed species in the previous crop. The 27 sample sites of weed seed communities can be clustered into two groups on the basis of previous crop, either lowland rice or sites with previous crops of winter fallow, winter wheat or oilseed rape. Canonical correspondence analysis (CCA) revealed that irrigation frequency, previous crop, and latitude, but not soil type or longitude, significantly affected species composition. The numbers of floating weed seed species were high in lowland rice fields; composition was affected by previous crops and irrigation frequency. Filtering irrigation water and collecting and removing floating weed seeds from the water surface could be integrated into weed management practices to control weeds in lowland rice fields.  相似文献   

17.
K French  E Watts 《Weed Research》2015,55(6):537-545
To investigate the impact of invasion by Chrysanthemoides monilifera ssp. monilifera (boneseed) on plant communities, sites that were invaded and uninvaded were surveyed across Tasmania, South Australia and Victoria, Australia. Above‐ground cover abundance was estimated and samples of the seed bank from invaded and uninvaded sites in each state were collected and germinated in the glasshouse. We compared species richness and composition between invaded and uninvaded sites for both above‐ground and below‐ground samples. Across this broad geographic area, C. monilifera invaded sites had 25% fewer species than uninvaded sites and twice as many exotic species. Most growth forms showed reduced richness in invaded sites. There were no differences in the composition of native species communities between invaded and uninvaded sites in most regions, except South Australia. The composition of the seed bank differed from the above‐ground vegetation, but was similar within each state. Herbs and grasses were most abundant. The species composition of the seed bank was different in invaded sites only in Victoria, suggesting that invasion may negatively influence the capacity of the seed bank to restore vegetation in some areas. However, the underlying mechanisms for the observed patterns were not tested in this study. The capacity of all sites to regenerate effectively from the seed bank was limited and, in order to ensure the conservation of biodiversity into the future, monitoring of species richness at smaller scales, particularly those where management of C. monilifera has occurred, will be needed to ensure management can facilitate the establishment of missing species. This study suggests that C. monilifera impacts a range of functional groups and different species across its distribution and is therefore non‐selective in how it influences changes in communities.  相似文献   

18.
IKUENOBE  & AYENI 《Weed Research》1998,38(6):397-404
A range of herbicides was evaluated for the control of Chromolaena odorata (L.) K & R in oil palm at the Nigerian Institute for Oil Palm Research. Glufosinate-ammonium quickly dessicated treated foliage but weed plants soon recovered. Glyphosate-isopropylamine and glyphosate-trimesium produced similar results, both formulations controlling treated vegetation and suppressing regrowth for up to 12 weeks after treatment. Triclopyr and hexazinone + diuron were effective for up to 20 WAT, whereas imazapyr controlled regrowth for up to 36 WAT. Regrowth of the weed from its roots was better suppressed when the foliage was left undisturbed for 4–7 days after herbicide treatment. Repeated annual applications of triclopyr, hexazinone + diuron, the two formulations of glyphosate or imazapyr progressively reduced the biomass of C . odorata in the plots. In particular, imazapyr effectively eliminated the weed after the second application. Taking crop tolerance into consideration, the most promising herbicide treatments were glyphosate at 2.4 kg a.i. ha−1 and low rates (0.5 kg a.i. ha−1 or less) of imazapyr.  相似文献   

19.
Imperata cylindrica (L.) Raeuschel is a dominant and infamous grass weed in the savannah of West Africa. Research to reduce the weed to non-damaging levels is a priority activity at many agricultural institutions. The successful development and implementation of long-term I. cylindrica management strategies depend on the ability to predict changes in weed composition after I. cylindrica has been controlled effectively. The weed flora and soil seedbank were assessed from 329 fields dominated by this species in the fringes of the humid forest (HFF), coastal/derived savannah (CDS) and in the southern Guinea savannah (SGS) in 1996 and 1997. The objectives of the study were to correlate species composition of the weed flora with that of the soil seedbank and to determine the effect of management factors and soil properties on the composition of the weed flora. Species richness in the weed flora and in the weed seedbank was higher in the SGS than in the CDS and HFF. Mean weed density per field was generally higher in the HFF (156 ± 25.0 weeds m–2) than in the CDS (108 ± 8.1 weeds m–2) and in the SGS (92 ± 6.3 weeds m–2). Weed composition varied with agroecological zone as well as with management factors and soil properties. Sørenson's index of similarity was low (mean=0.20) in all zones, indicating poor similarity between the weed flora above-ground and the soil seedbank.  相似文献   

20.
This study was carried out to propose a simple abundance index (AI) of weed species, to describe the ranking of weeds in weed communities, and to evaluate weed flora. Based on a 4 year weed survey program conducted in Tehran province, the Thomas methodology for determining the relative abundance (RA) in weed communities was applied and a new, improved method (called the AI method) was introduced. Sixty-one irrigated wheat fields were selected using a stratified sampling procedure. The boundaries of each county in the province formed the strata. For the Thomas method, the data were summarized for each county using five quantitative measures for determining the RA of each species. For the AI method, three quantitative measures were used, including frequency, uniformity, and mean field density. In the Thomas method, the mean field density had a significant role in determining the RA of a species, while the frequency and uniformity had a less significant role. However, for determining the AI, the frequency and uniformity had a higher value than the mean field density. Higher values for these two parameters for a particular species indicates that this species was more compatible with the soil and climate conditions in which it was growing, while higher values for the mean field density for a particular species indicates that the species had a higher competitive or reproductive ability than other species. In the Thomas method, the weed species with a low mean density were less abundant and not a serious weed for agroecosysytems but, in the AI method, an invasive weed could be detected before the colonization stage.  相似文献   

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