The impact of increasing heavy metal stress on the diversity and structure of the bacterial and actinobacterial communities of metallophytic grassland soil     

Lisa Bamborough  Stephen P. Cummings 《Biology and Fertility of Soils》2009,45(3):273-280

A study was undertaken to investigate the bacterial community found in metallophytic grassland soil contaminated with Zn and Pb. We hypothesised that such communities would be tolerant of additional heavy metal stress due to phylogenetic and functional adaptation. In microcosm experiments, lasting 51 days, denaturing gradient gel electrophoresis (DGGE) analyses was used to compare the total bacterial and actinobacterial communities in non-amended soils and those to which additional Pb and Zn concentrations were added. There was a decrease in total bacterial diversity with each addition of Pb and Zn; in contrast, the actinobacterial community diversity remained unaffected. The community structures were analysed using multivariate analyses of the DGGE profiles. Total bacterial community profiles showed two distinct groups sharing less than 80% similarity, irrespective of Pb and Zn addition. The first contained profiles sampled during the first 7 days of the experiment; the second contained those sampled from day 10 onwards. Actinobacterial profiles from those that were non-amended showed a similar distribution to those of the total bacterial community. However, in soil amended with fivefold additional Pb and Zn, all the profiles shared more than 80% similarity. Raup and Crick analyses suggested that total bacterial soil communities were subject deterministic selection becoming significantly similar as the experiment progressed, but this was inhibited by the highest concentration of additional Pb and Zn. Actinobacterial communities showed a similar response but were less affected by elevated Pb and Zn concentrations. These data indicate that the diversity of the actinobacterial community was not negatively affected by additional heavy metal stress in contrast to total bacterial community diversity.  相似文献   

The “Crex crex” lament: Estimating landowners willingness to pay for corncrake conservation on Irish farmland     

Stephen Hynes  Nick Hanley 《Biological conservation》2009,142(1):180-188

This paper considers farmers’ willingness to pay (WTP) to conserve an endangered Irish farmland bird, the corncrake (Crex crex). An Irish National Farm Survey is used to produce individual farm-level WTP estimates for the year 2006. These figures are then aggregated to obtain a total value figure for the farming community of corncrake conservation in Ireland. We focus on the willingness to pay of farmers rather than the WTP of the general Irish population, as farmers will ultimately be the ones that will have to take responsibility if targets set out in the All Ireland Action Plan for corncrake conservation are to be achieved. Quantifying willingness to pay on the part of farmers can help inform the design of agri-environment schemes aimed at improving conservation of many bird species on farmland. Results indicate that the non-market benefit of corncrake conservation in Ireland may significantly outweigh the costs of existing conservation schemes.  相似文献   

Strong impacts of belowground tree inputs on soil nematode trophic composition     

Aidan M. Keith  Rob W. Brooker  Stephen J. Chapman  René van der Wal 《Soil biology & biochemistry》2009,41(6):1060-1065

Trees have a key role in determining the composition of soil biota via both above and belowground resource-based mechanisms, and by altering abiotic conditions. We conducted an outdoor mesocosm experiment to investigate the relative impact of above and belowground tree inputs on soil nematode trophic composition, and examine whether tree-driven impacts differed between contrasting species (birch and pine). For both species, we created a factorial design of litter addition and root presence treatments. The litter addition treatment was equivalent to natural levels of litterfall; tree saplings were planted in mesocosms for the root presence treatment and an unplanted control treatment was established that had no litter or root inputs. Litter addition had a limited impact on soil nematode community composition: it primarily decreased omnivore and predatory nematode abundance in birch but had few other effects on the nematode community. By contrast, root presence markedly altered nematode community composition through changes in a range of trophic groups. For both birch and pine, there were significant increases in total, fungivore and predatory nematode abundance in root presence treatments, and furthermore, total and fungivore abundances were positively related to root biomass. Root presence of these contrasting tree species also had a distinctive impact on some specific nematode trophic groups; pine roots promoted bacterivore abundance while birch roots promoted root-hair feeding nematode abundance. These findings suggest strong bottom-up effects of belowground tree inputs, and indicate that particular components of the nematode community may be affected differently by resource quantity and quality. Consequently, we suggest that, in the short-term, belowground rather than aboveground tree inputs have a strong impact on soil food web structure and complexity.  相似文献   

Nitrogen and Phosphorus Remediation by Three Floating Aquatic Macrophytes in Greenhouse-Based Laboratory-Scale Subsurface Constructed Wetlands     

Robert F. Polomski  Milton D. Taylor  Douglas G. Bielenberg  William C. Bridges  Stephen J. Klaine  Ted Whitwell 《Water, air, and soil pollution》2009,197(1-4):223-232

In the greenhouse and container nursery production industry there is potential for runoff of nitrogen (N) and phosphorus (P), which may contaminate surface and groundwater. Since the 1950s constructed wetlands (CWs), as a simple, low-technology method, have been shown to effectively treat agricultural, industrial, and municipal wastewater. We investigated the N and P attenuating potential of three floating hydrophytes planted in a laboratory-scale subsurface flow (SSF) CW system. Over an 8-week period plants were supplied with N and P (0.39 to 36.81 mg·L^?1 N and 0.07 to 6.77 mg·L^?1 P) that spanned the rates detected in nursery runoff between the discharge and inflow locations of a commercial nursery currently employing CWs. Whole plant dry weight was positively correlated with N and P supplied. Highest N recovery rates were exhibited by water hyacinth (Eichhornia crassipes [Mart.] Solms.) and water lettuce (Pistia stratiotes L.). P recovery rates were similar for water hyacinth, water lettuce, and dwarf redstemmed parrotfeather (Myriophyllum aquaticum [Vell.] Verdc.). These floating hydrophytes can be cultivated in a SSF CW to remediate runoff losses of N and P. The possibility exists for integrating them into a polycultural remediation system that includes emergent aquatic macrophytes for processing and polishing nursery/greenhouse wastewater.  相似文献   

Widespread occurrence of both metabolic and target‐site herbicide resistance mechanisms in Lolium rigidum populations          下载免费PDF全文

Heping Han  Qin Yu  Mechelle J Owen  Gregory R Cawthray  Stephen B Powles 《Pest management science》2016,72(2):255-263

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Response to low‐dose herbicide selection in self‐pollinated Avena fatua          下载免费PDF全文

Roberto Busi  Marcelo Girotto  Stephen B Powles 《Pest management science》2016,72(3):603-608

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Soil and tree biomass carbon sequestration potential of silvopastoral and woodland-pasture systems in North East Scotland     

Marvin R. Beckert  Pete Smith  Allan Lilly  Stephen J. Chapman 《Agroforestry Systems》2016,90(3):371-383

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Recurrent selection with reduced 2,4‐D amine doses results in the rapid evolution of 2,4‐D herbicide resistance in wild radish (Raphanus raphanistrum L.)          下载免费PDF全文

Michael B Ashworth  Michael J Walsh  Ken C Flower  Stephen B Powles 《Pest management science》2016,72(11):2091-2098

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Dynamic Models for Longitudinal Butterfly Data     

Emily B. Dennis  Byron J. T. Morgan  Stephen N. Freeman  David B. Roy  Tom Brereton 《Journal of Agricultural, Biological & Environmental Statistics》2016,21(1):1-21

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不同生物质炭输入水平下旱作农田温室气体排放日变化研究   总被引：1，自引：0，他引：1  

宋敏  蔡立群  齐鹏  Stephen Yeboah  张仁陟  罗珠珠  潘占东  卢廷超 《中国生态农业学报》2016,24(10):1300-1309

在陇中黄土高原干旱半干旱区,采用小区定位试验,对不同生物质炭水平(0 t·hm~(-2)、10 t·hm~(-2)、20 t·hm~(-2)、30 t·hm~(-2)、40 t·hm~(-2)、50 t·hm~(-2))下农田土壤温室气体(CO_2、N_2O和CH_4)的日排放通量及其影响因子进行连续观测,并确定1 d中不同生物质炭处理水平下的最佳观测时间。结果表明:6个生物质炭输入水平处理下,春小麦地土壤CH_4、N_2O和CO_2通量变化趋势与气温日变化轨迹大体一致,均表现为白天排放量大于夜间,并在4:00—5:00时,出现对CH_4通量的吸收峰,以及N_2O与CO_2的排放低谷;全天内各处理CH_4平均排放通量依次为:10.14mg·m~(-2)·h~(-1)、7.82mg·m~(-2)·h~(-1)、6.57mg·m~(-2)·h~(-1)、-0.10mg·m~(-2)·h~(-1)、1.05mg·m~(-2)·h~(-1)和2.89mg·m~(-2)·h~(-1),N_2O平均排放通量依次为:288.79mg·m~(-2)·h~(-1)、201.78mg·m~(-2)·h~(-1)、157.14mg·m~(-2)·h~(-1)、112.06mg·m~(-2)·h~(-1)、154.60mg·m~(-2)·h~(-1)和164.02mg·m~(-2)·h~(-1),CO_2平均排放通量依次为:85.44 mg·m~(-2)·h~(-1)、80.91 mg·m~(-2)·h~(-1)、76.49 mg·m~(-2)·h~(-1)、65.29 mg·m~(-2)·h~(-1)、67.19 mg·m~(-2)·h~(-1)和69.10 mg·m~(-2)·h~(-1);当生物质炭输入量小于30 t·hm~(-2)时,土壤CH_4、N_2O、CO_2排放通量随其输入量增加而显著减小,但当其输入量超过30 t·hm~(-2)时,3种温室气体排放通量则呈显著增大趋势;当生物质炭输入水平为30 t·hm~(-2)时,春小麦土壤全天表现为CH_4的吸收汇,其余各水平处理下的土壤表现为CH_4的弱排放源;6种处理水平下,全天春小麦地土壤表现为N_2O、CO_2的排放源。0~5 cm的土壤温度及水分(y)与生物质炭输入量(x)回归方程分别为y=-0.017 6x+16.585(R~2=0.302 6,r=-0.55,P0.05)和y=0.056 5x+13.626(R~2=0.815 1,r=0.903,P0.05),生物质炭输入量与0~5 cm的土壤水分呈显著正相关关系;无生物质炭输入处理下3种温室气体的吸收或排放通量与地表温度及5 cm地温均呈显著正相关关系,其他各处理也表现出不同程度的正相关关系。因此,当生物质炭输入水平为30 t·hm~(-2)时,更有利于CH_4、N_2O和CO_2 3种温室气体的增汇减排;生物质炭输入水平差异引起的土壤温度及水分差异可能是不同生物质炭处理CH_4、N_2O和CO_2日排放通量产生差异的主要原因;由矫正系数及最佳时段温室气体排放量与累积排放量回归分析可得,3种温室气体的最佳同期观测时间为8:00—9:00。  相似文献