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11.
Biotic, abiotic and performance aspects of the Nevada Desert Free-Air CO2 Enrichment (FACE) Facility 总被引:3,自引:0,他引:3
DeaN. N. Jordan Stephen F. Zitzer † George R. Hendrey ‡ Keith F. Lewin ‡ JohN. Nagy ‡ Robert S. Nowak § Stanley D. Smith James S. Coleman¶ Jeffrey R. Seemann§ 《Global Change Biology》1999,5(6):659-668
Arid and semiarid climates comprise roughly 40% of the earth’s terrestrial surface. Deserts are predicted to be extremely responsive to global change because they are stressful environments where small absolute changes in water availability or use represent large proportional changes. Water and carbon dioxide fluxes are inherently coupled in plant growth. No documented global change has been more substantial or more rapid than the increase in atmospheric CO2. Free Air CO2 Enrichment (FACE) technology permits manipulation of CO2 in intact communities without altering factors such as light intensity or quality, humidity or wind. The Nevada Desert FACE Facility (NDFF) consists of three 491 m2 plots in the Mojave Desert receiving 550 μL L–1 CO2, and six ambient plots to assess both CO2 and fan effects. The shrub community was characterized as a Larrea–Ambrosia–Lycium species complex. Data are reported through 12 months of operation. 相似文献
12.
Multiple introductions,admixture and bridgehead invasion characterize the introduction history of Ambrosia artemisiifolia in Europe and Australia
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Lotte A. van Boheemen Eric Lombaert Kristin A. Nurkowski Bertrand Gauffre Loren H. Rieseberg Kathryn A. Hodgins 《Molecular ecology》2017,26(20):5421-5434
Admixture between differentiated populations is considered to be a powerful mechanism stimulating the invasive success of some introduced species. It is generally facilitated through multiple introductions; however, the importance of admixture prior to introduction has rarely been considered. We assess the likelihood that the invasive Ambrosia artemisiifolia populations of Europe and Australia developed through multiple introductions or were sourced from a historical admixture zone within native North America. To do this, we combine large genomic and sampling data sets analysed with approximate Bayesian computation and random forest scenario evaluation to compare single and multiple invasion scenarios with pre‐ and postintroduction admixture simultaneously. We show the historical admixture zone within native North America originated before global invasion of this weed and could act as a potential source of introduced populations. We provide evidence supporting the hypothesis that the invasive populations established through multiple introductions from the native range into Europe and subsequent bridgehead invasion into Australia. We discuss the evolutionary mechanisms that could promote invasiveness and evolutionary potential of alien species from bridgehead invasions and admixed source populations. 相似文献
13.
The Environmental Exposure Unit (EEU) is a 924 m3 facility (Kingston General Hospital, Ontario) in which uniform concentrations of various pollens in HEPA-filtered air at
known rates of laminar airflow can be maintained. This facility provided a unique opportunity to compare several air samplers
without the environmental variation inherent in outdoor comparisons. The purpose of this study was to conduct a quantitative
comparison of pollen measurements using the Rotorod, Burkard™ Personal Volumetric Air Sampler, Air-O-Cell™ and a 37 mm open-faced
filter cassette with a microporous filter in the EEU. Pollen samples were taken during clinical trials being conducted in
the Unit. Raw pollen counts/m3 obtained using the different methods were corrected using published particle collection efficiencies for the particle size
(∼
∼20 μm) and airflow. Data were analyzed by ANOVA/Tukey HSD. No statistically significant differences were found between pollen
concentrations determined by Rotorod, Air-O-Cell and filter cassette. Pollen levels determined by the Burkard were up to 2
times higher than the other sampling methods. Relative standard deviations were similar for the Rotorod, Burkard, and filter
cassette and higher for the Air-O-Cell. This study demonstrated that, under our conditions, the Rotorod sampler provides consistent
and reliable measurements of ragweed pollen concentrations. 相似文献
14.
Brice A. McPherson Nadir Erbilgin David L. Wood Pavel Svihra Andrew J. Storer Richard B. Standiford 《Agricultural and Forest Entomology》2008,10(4):315-321
1 Sudden oak death is caused by the apparently introduced oomycete, Phytophthora ramorum. We investigated the role of bark and ambrosia beetles in disease progression in coast live oaks Quercus agrifolia. 2 In two Marin County, California sites, 80 trees were inoculated in July 2002 with P. ramorum and 40 were wounded without inoculation. Half of the trees in each group were sprayed with the insecticide permethrin [cyclopropanecarboxylic acid, 3‐(2,2‐dichloroethenyl)‐2,2‐dimethyl‐(3‐phenoxyphenyl) methyl ester] to prevent ambrosia and bark beetle attacks, and then were sprayed twice per year thereafter. After each treatment, sticky traps were placed on only the permethrin‐treated trees. Beetles were collected periodically in 2003. 3 Inoculated trees accounted for 95% of all beetles trapped. The ambrosia beetles Monarthrum scutellare and Xyleborinus saxeseni and the western oak bark beetle Pseudopityophthorus pubipennis were the most abundant of the seven species trapped. 4 Permethrin treatment delayed initiation of beetle attacks and significantly reduced the mean number of attacks per tree. Beetles did not attack any wounded or noncankered inoculated trees. 5 Trees with larger cankers trapped more beetles early in the disease. Once permethrin lost effectiveness, the number of beetle entrance tunnels was a more reliable predictor of subsequent trap catch than was canker size. 6 Beetles were initially attracted to P. ramorum cankers in response to kairomones generated in the host‐pathogen interaction. After beetles attacked the permethrin‐treated trees, aggregation pheromones most probably were the principal factor in beetle colonization behaviour. 相似文献
15.
Functional ecology of shrub seedlings after a natural recruitment event at the Nevada Desert FACE Facility 总被引:1,自引:0,他引:1
DAVID C. HOUSMAN STEPHEN F. ZITZER† ‡ TRAVIS E. HUXMAN§ STANLEY D. SMITH 《Global Change Biology》2003,9(5):718-728
Seedling recruitment is an important determinant of community structure in desert ecosystems. Positive photosynthetic growth and water balance responses to increasing atmospheric carbon dioxide (CO2) concentrations ([CO2]) are predicted to be substantial in desert plants, suggesting that recruitment could be stimulated. However, to date no studies have addressed the response of perennial plant recruitment in natural populations of desert shrubs exposed to elevated [CO2]. In April 1997, we employed Free‐Air Carbon Dioxide Enrichment (FACE) in order to increase atmospheric [CO2] in an undisturbed Mojave Desert ecosystem from ambient (~~ 370 µmol mol?1) to elevated CO2 (~~ 550 µmol mol?1). From 1997 to 2001 we seasonally examined survival, growth, gas exchange and water potential responses of Larrea tridentata and Ambrosia dumosa seedlings that germinated in Fall, 1997. Recruitment densities were not influenced by [CO2] in either species, although a two‐fold higher adult Ambrosia density under elevated [CO2] resulted in two‐fold higher seedling density (0.87 vs 0.40 seedlings m?2). Mortality was greatest for both species during the first summer (1998), despite above‐average rainfall during the previous Winter–Spring. A significant [CO2] × time interaction revealed that early survival was greater under elevated CO2, whereas a significant species time interaction revealed that overall survival was greater for Ambrosia (28%) than for Larrea (15%), regardless of [CO2]. Microsite (understorey or interspace) alone had no significant influence on survival. Significant species, microsite and species × microsite effects on growth (seedling height, stem diameter and canopy size) were found, but elevated CO2 had minimal impact on these parameters. Photosynthetic rates (Asat) for both species were higher at elevated [CO2] during certain seasons, but not consistently so. These results suggest that increased atmospheric [CO2] may enhance carbon (C) assimilation and survival of aridland perennial shrubs during favourable growing conditions, but that it may not counteract the effects of prolonged drought on mortality. 相似文献
16.
N Münevver PINAR 《植物学报(英文版)》2003,45(12)
The airborne ragweed pollen spectrum was investigated in the air of Ankara, Turkey for aperiod of ten years (1990-1999) using a Burkard seven-day volumetric recording trap. In our study period,long distance transported Ambrosia pollen has been registered. Daily pollen levels varied from low to highin Burge's system. In last three years, the pollen concentration of Ambrosia showed a clear increasingtendency. Our results prove that ragweed pollen may be an important threat for ragweed sensitive patientsin Ankara city in near future. 相似文献
17.
S. T. E. Lommen S. Ciappetta A. Ghiani R. Asero R. Gentili H. Müller-Schärer 《Plant biosystems》2017,151(6):1094-1100
Ragweed allergy is one of the primary causes of seasonal allergies in Europe and its prevalence is expected to rise. The leaf beetle Ophraella communa, recently and accidentally established in N-Italy and S-Switzerland, represents a promising approach to control ragweed, but negative side effects should be excluded before its use. Since biotic and abiotic stresses are known to influence the allergenicity of pollen, we set out to assess the effect of sub-lethal defoliation by O. communa on the quantity and quality of ragweed pollen. Seventeen sister pairs (including six clones) of ragweed plants were grown in controlled conditions. One of each pair was exposed to O. communa as soon as the plant started to produce reproductive structures. After 10 weeks of exposure, plant traits were measured as a proxy for pollen quantity. Pollen quality was assessed by measuring its viability and allergenicity. Generally, plants produced very few male flowers and little amount of pollen. Damage by the beetle was severe with most of the leaf tissue removed, but no treatment effect was found on any of the quantitative and qualitative traits assessed. In conclusion, O. communa did not increase the amount or allergenicity of ragweed pollen grains in our experimental conditions. 相似文献
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20.
豚草卷蛾与苍耳螟的资源生态位研究 总被引:2,自引:0,他引:2
引进的豚草卷蛾和本地的苍耳螟是取食豚草的重要天敌昆虫。为了进一步明确两种天敌种问的竞争作用,定量研究了豚草卷蛾和苍耳螟在寄主植物种类和空间上的生态位指数。结果表明,在寄主植物种类上,豚草卷蛾只取食豚草和苍耳;苍耳螟可取食豚草、苍耳、黄花蒿、向日葵、万寿菊、国庆菊、菊芋、麦杆菊;苍耳螟的生态位宽度指数(Hurbert标准值0.228)明显大于豚草卷蛾(0.069),两者的食物资源生态重叠程度较小(Horn’s指数0.318);豚草卷蛾和苍耳螟对常用资源的利用率分别为93.5%(豚草)和59.3%(苍耳)。在相同寄主植物上,两种天敌的空间生态位表现为:随着寄主植物的生长发育,两种天敌的生态位重叠程度减小;高龄幼虫的生态位宽度指数大于低龄幼虫。在食物生态位上,豚草卷蛾主要取食新发生的幼嫩枝,并且一旦蛀入形成虫瘿后很少发生转移,而苍耳螟除低龄幼虫喜蛀食幼嫩枝外,高龄幼虫的取食部位常常发生转移,从枝型较细的幼嫩枝转向枝型较粗的老龄枝。两种天敌对豚草和苍耳实际选择作用以及对常用资源利用率存在明显差异,因此,形成竞争的程度较小,在对豚草的控制机制上形成互补作用。 相似文献