The polyphagous carabid beetle Abax parallelepipedus has been shown to be capable of controlling slugs within a lettuce crop in previous studies. This report describes experiments undertaken in plots within a polythene tunnel. Field slugs, Deroceras reticulatum, were introduced to plots containing either large or small lettuce plants, at 30 slugs per plot. The plots were further subdivided into those with or without six beetle predators. Slug numbers were assessed after two weeks, and were found to be affected by plant size, both with and without the presence of predators. These two factors had an additive effect, with both small plant size and the presence of beetles causing significant reductions in slug numbers. Plots with beetles contained either males or females, and females were shown to be significantly better at reducing slug numbers than males, particularly within plots of small plants. The four principal treatments (combinations of two plant sizes and the presence/absence of beetles) generated four distinct patterns of slug distribution within the plots. The potential of the residual slug populations to inflict further damage was measured in a subsequent crop of seedling lettuces. It appeared that the beetles were generally incapable of capturing slugs within large lettuce plants, but were effective predators at soil level. Possible reasons for the survival of fewer slugs in plots with small plants, both with and without the presence of predators, are discussed. 相似文献
1. 1. The concept of intermittent, microclimate cooling during rest periods has been investigated due to the logistical and ergonomic problems associated with backpack cooling systems
2. 2. In an attempt to improve intermittent cooling applications, the use of industrial/commercial air conditioners (ICAC) as a source of cool air was conceived
3. 3. In the current study, a prototype of a pressurized air distribution unit (PADU) which can be incorporated into existing ICAC was designed and fabricated
4. 4. In a successful test, an ICAC circulated air and cooled it down to the set temperature, while the PADU pumped 5101/min (the specified air volume for one person) of 15°C into each air cooling vest, 4601/min to the body and 501/min to the face, through filters and 10 ft/1 in. diameter supply line
5. 5. The PADU is necessary to increase the air pressure in the system, creating the required air volume
6. 6. This promising concept adapts existing ICAC to provide adequate amounts of clean, cool air to individuals working in thermally stressful environments
7. 7. This development effectively increases the conditioned air sources available for use in decreasing heat storage and increasing personal comfort in military or civilian scenarios where work is conducted in protective garments.
Author Keywords: Personal cooling; heat stress; microclimate cooling; work/rest cycle; human-environment system 相似文献
Photosynthetic photon flux density (PPFD) fluctuations were quantified in crops of beans (Phaseolus vulgaris L.) in the field as the canopy developed between July and October. Two different methods were used to select sunflecks and
shadeflecks. Four ranges of zenith angles (60–70°, 50–60°, 40–50° and 30–40°) were selected for analysing PPFD fluctuations.
At the base of the canopy, sunflecks contributed 18%, 53%, 10% and 4% during the 1st, 3rd, 5th and 7th week of growth, respectively.
At a height of 20 cm above the soil surface, the respective contributions were 28% and 21% during the 6th and 7th weeks. Sunfleck
lengths of 0–5 s were the most frequent, with the greatest number being found with smaller zenith angles. The proportion of
short duration sunflecks increased as the growth period advanced. The number of long sunflecks decreased with time, with very
few longer than 100 s by the 5th and 7th weeks. The distributions of sunfleck irradiance were similar to normal distributions
and irradiance ranged in μmol m−2 s−1 from 600–900, 800–1500 and 1000–1600 respectively at zenith angles of 50–60°, 40–50° and 30–40°. A multiple regression showed
that short sunflecks (<100 s) depended on zenith angle, plant height, and leaf and stem area index (Ls), whereas long sunflecks (>100 s) depended on zenith angle and Ls. Shadefleck distributions were similar to those for sunflecks but there were fewer of the shortest examples and more of the
longest. The best statistical distribution to describe sunflecks and shadeflecks was the gamma distribution, which could provide
the basis for the future development of a good model for sunfleck and shadefleck distributions.
Received: 10 November 1997 / Accepted: 2 April 1998 相似文献
How does the morphogenesis of a widespread epiphytic lichen interact with the environment, leading to amazingly polymorphic and wind-tolerant fruticose thalli? A series of photographs showed that the normal branches were basically even and flat with isotomic-dichotomous branchings. Numerous deviations from this basic regular pattern were found and traced back to their origins in the asymmetry of the branches’ cross sections. This was observed quantitatively (statistically testable) in the field, while the thalli were growing. This large variability in growth of single branches was a prerequisite for the polymorphism seen in complete thallus growth forms. The structure and distribution of the mentioned important asymmetries in branch cross sections can best be explained by the effect of grazing on cortex and phycobiont layer. Very small-scale growth observations and experimental simulation confirmed this. In thalli with many such small-scale variations in branch growth the overall thallus growth form became wind acclimated as a result of the selective effect of wind exposure on the thallus phenotype: branches growing windwardly grew more slowly. Such thalli were well protected from being dislodged by wind, and they desiccate slowly as demonstrated by a previous study. 相似文献
Overwintered adult apple blossom weevils, Anthonomus pomorum (L.) (Coleoptera: Curculionidae), colonise apple trees, Malus domestica Borkh. (Rosaceae), in early spring. Information gained from a suitable monitoring technique could serve as a guide to determining the accurate timing for control measures. To assess tree colonisation by flight and crawling, Plexiglas flight traps and commercial screen traps developed for different curculionid species were used. Refuges were mimicked by a newly designed shelter trap based on transparent bubble wrap. The trap catches were contrasted to the limb jarring technique. Microclimate and weather conditions were determined over a trial period of one and a half months. The shelter traps caught a high number of weevils irrespective of weather conditions, and thus performed better than both flight and screen traps. The temperature level within the shelter traps was slightly, but significantly, higher than on the trunk, indicating that weevils exploit microclimatic differences and occupy thermally favourable refuges. The seasonal culmination of colonisation as determined by shelter traps coincided with that as determined by the two methods used to monitor weevil movement towards host trees (flight traps and screen traps). The data indicated that not only flight, but also crawling as quantified by the screen traps contributes substantially to spring colonisation. Captures by all three types of traps over the spring season were significantly positively correlated with each other, but in most respects not with the results of the limb jarring. We conclude that the newly designed shelter trap will be useful for accurately monitoring the seasonal course of colonisation and holds promise for determining the timing of interventions. 相似文献
Climate change is a major threat to species worldwide, yet it remains uncertain whether tropical or temperate species are more vulnerable to changing temperatures. To further our understanding of this, we used a standardised field protocol to (1) study the buffering ability (ability to regulate body temperature relative to surrounding air temperature) of neotropical (Panama) and temperate (the United Kingdom, Czech Republic and Austria) butterflies at the assemblage and family level, (2) determine if any differences in buffering ability were driven by morphological characteristics and (3) used ecologically relevant temperature measurements to investigate how butterflies use microclimates and behaviour to thermoregulate. We hypothesised that temperate butterflies would be better at buffering than neotropical butterflies as temperate species naturally experience a wider range of temperatures than their tropical counterparts. Contrary to our hypothesis, at the assemblage level, neotropical species (especially Nymphalidae) were better at buffering than temperate species, driven primarily by neotropical individuals cooling themselves more at higher air temperatures. Morphology was the main driver of differences in buffering ability between neotropical and temperate species as opposed to the thermal environment butterflies experienced. Temperate butterflies used postural thermoregulation to raise their body temperature more than neotropical butterflies, probably as an adaptation to temperate climates, but the selection of microclimates did not differ between regions. Our findings demonstrate that butterfly species have unique thermoregulatory strategies driven by behaviour and morphology, and that neotropical species are not likely to be more inherently vulnerable to warming than temperate species. 相似文献
Anthropogenic global warming has major implications for mobile terrestrial insects, including long-term effects from constant warming, for example, on species distribution patterns, and short-term effects from heat extremes that induce immediate physiological responses. To cope with heat extremes, they either have to reduce their activity or move to preferable microhabitats. The availability of favorable microhabitat conditions is strongly promoted by the spatial heterogeneity of habitats, which is often reduced by anthropogenic land transformation. Thus, it is decisive to understand the combined effects of these global change drivers on insect activity. Here, we assessed the movement activity of six insect species (from three orders) in response to heat stress using a unique tracking approach via radio frequency identification. We tracked 465 individuals at the iDiv Ecotron across a temperature gradient up to 38.7°C. In addition, we varied microhabitat conditions by adding leaf litter from four different tree species to the experimental units, either spatially separated or well mixed. Our results show opposing effects of heat extremes on insect activity depending on the microhabitat conditions. The insect community significantly decreased its activity in the mixed litter scenario, while we found a strong positive effect on activity in the separated litter scenario. We hypothesize that the simultaneous availability of thermal refugia as well as resources provided by the mixed litter scenario allows animals to reduce their activity and save energy in response to heat stress. Contrary, the spatial separation of beneficial microclimatic conditions and resources forces animals to increase their activity to fulfill their energetic needs. Thus, our study highlights the importance of habitat heterogeneity on smaller scales, because it may buffer the consequences of extreme temperatures of insect performance and survival under global change. 相似文献