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811.
812.
S?ren Furbo Anne G. Mortensen Bente Laursen Carsten Christophersen Inge S. Fomsgaard 《Chemoecology》2011,21(2):59-66
Degradation of biochanin A, 400 μg (1.41 μmol) per gram of dry soil, was studied and the initial degradation products, dihydrobiochanin
A, pratensein and genistein were identified and quantified. The maximum concentrations of these compounds were determined
as 166 pmol/g dry soil after 2 days of incubation, 175 pmol/g dry soil after 1 day and 1,236 pmol/g dry soil after 1 day,
respectively. Biochanin A and the initially formed products degrade too fast to be responsible for clover soil sickness (DT90 <20 days), but could be precursors for the responsible compounds. The immediate degradation products from biochanin A are
all biologically active and are the prime candidates for a reduction of weed pressure caused by clover. 相似文献
813.
Kristen M. Waring Danielle M. Reboletti Lauren A. Mork Ching-Hsun Huang Richard W. Hofstetter Amanda M. Garcia Peter Z. Fulé T. Seth Davis 《Environmental management》2009,44(4):824-835
Predicted climate warming is expected to have profound effects on bark beetle population dynamics in the southwestern United
States. Temperature-mediated effects may include increases in developmental rates, generations per year, and changes in habitat
suitability. As a result, the impacts of Dendroctonus frontalis and Dendroctonus mexicanus on forest resources are likely subject to amplification. To assess the implications of such change, we evaluated the generations
per year of these species under three climate scenarios using a degree-day development model. We also assessed economic impacts
of increased beetle outbreaks in terms of the costs of application of preventative silvicultural treatments and potential
economic revenues forgone. Across the southwestern USA, the potential number of beetle generations per year ranged from 1–3+ under
historical climate, an increase of 2–4+ under the minimal warming scenario and 3–5+ under the greatest warming scenario. Economic
benefits of applying basal area reduction treatments to reduce forest susceptibility to beetle outbreaks ranged from 7.75/ha (NM) to7.75/ha
(NM) to 95.69/ha (AZ) under historical conditions, and 47.96/ha (NM) to47.96/ha (NM) to 174.58/ha (AZ) under simulated severe drought conditions.
Basal area reduction treatments that reduce forest susceptibility to beetle outbreak result in higher net present values than
no action scenarios. Coupled with other deleterious consequences associated with beetle outbreaks, such as increased wildfires,
the results suggest that forest thinning treatments play a useful role in a period of climate warming. 相似文献
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815.
Indra?Elena?C.?EscobarEmail author Vilma?M.?Santos Danielle?Karla?A.?da?Silva Marcelo?F.?Fernandes Uided?Maaze?T.?Cavalcante Leonor?C.?Maia 《Environmental management》2015,55(6):1433-1445
The aim of this study was to describe the impact of re-vegetation on the restoration of microbial community structure and soil microbiological properties in sand dunes that had been affected by mining activity. Soil samples were collected during the dry and rainy seasons from a chronosequence (1, 9, 21 years) of re-vegetated dunes using a single preserved dune as a reference. The composition of the fatty acid methyl esters and soil microbial properties were evaluated. The results showed that the changes in microbial community structure were related to seasonal variations: biomarkers of Gram-positive bacteria were higher than Gram-negative bacteria during the dry season, showing that this group of organisms is more tolerant to these stressful conditions. The microbial community structure in the natural dune was less affected by seasonal variation compared to the re-vegetated areas, whereas the opposite was observed for microbiological properties. Thus, in general, the proportion of saprobic fungi was higher in the natural dune, whereas Gram-negative bacteria were proportionally more common in the younger areas. Although over time the re-vegetation allows the recovery of the microbial community and the soil functions, these communities and functions are different from those found in the undisturbed areas. 相似文献
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Gary?Mahoney Alex?G.?StewartEmail author Nattalie?Kennedy Becky?Whitely Linda?Turner Ewan?Wilkinson 《Environmental geochemistry and health》2015,37(4):689-706
While scientific understanding of environmental issues develops through careful observation, experiment and modelling, the application of such advances in the day to day world is much less clean and tidy. Merseyside in northwest England has an industrial heritage from the earliest days of the industrial revolution. Indeed, the chemical industry was borne here. Land contamination issues are rife, as are problems with air quality. Through the examination of one case study for each topic, the practicalities of applied science are explored. An integrated, multidisciplinary response to pollution needs more than a scientific risk assessment. The needs of the various groups (from public to government) involved in the situations must be considered, as well as wider, relevant contexts (from history to European legislation), before a truly integrated response can be generated. However, no such situation exists in isolation and the introduction of environmental investigations and the exploration of suitable, integrated responses will alter the situation in unexpected ways, which must be considered carefully and incorporated in a rolling fashion to enable solutions to continue to be applicable and relevant to the problem being faced. This integrated approach has been tested over many years in Merseyside and found to be a robust approach to ever-changing problems that are well described by the management term, “wicked problems”. 相似文献
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820.
Size-assortative pairing across three developmental stages in the Zeus bug, Phoreticovelia disparata
Therésa M. Jones G?ran Arnqvist Kathryn B. McNamara Mark A. Elgar 《Behavioral ecology and sociobiology》2012,66(7):995-1003
The mechanisms underlying size-assortative pairing have received considerable attention. Typically, pairing is assumed to occur at, or just prior to, the adult phase of the life cycle. However, in many invertebrates, males commence associations with juvenile females who are more than a single moult away from sexual maturity. These species are ideal to explore the importance of reproductive and survival benefits as mechanisms driving size-assortative pairing. In the Zeus bug, Phoreticovelia disparata, adult males are found riding on juvenile (fourth and fifth instar) and adult females—a behaviour that is costly for females but has survival benefits for males. Using a combination of field collections and laboratory manipulations, we show that pairing is size-assortative both within and between female age classes and that riding males are smaller than non-riding males. In a series of mating trials, we revealed that males attempt to ride any female but that their riding success is dependent on female age. We also provide the first direct evidence of female resistance to male riding attempts in P. disparata. We propose that size-assortative pairing arises through adaptations that have evolved to minimise the potential costs of sexual conflict. We suggest that the selective pressure on males to maximise survival benefits is sufficiently high that it outweighs the reproductive benefits of discriminating against fourth instar females. Finally, given that female resistance is under direct selection in juvenile females, it is likely to be the main form of selective pressure for adult females. 相似文献