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401.
M. K. MACPHAIL 《The New phytologist》1984,96(1):131-147
402.
Insufficient productivity has driven population declines in grassland breeding waders with high levels of predation limiting
productivity in many wetland reserves. We studied hatching and fledging success of Lapwings Vanellus vanellus in two continental river floodplains (Havel and Oder) differing in water regime and density of Red Foxes Vulpes vulpes to assess the effects of increased water tables as a management option. Nest predation rates were high on dry sites as well
as on flooded grasslands in all areas irrespective of fox litter density. Carnivores formed the majority of the predators
identified and eggshell remains suggested that mustelids took proportionally more nests at low fox densities. At unsuccessful
nests on flooded grassland, an increasing incidence of nocturnal disturbances prior to predation indicated an influx of carnivores
as the sites dried out. Brood survival depended on the availability of wet features, and productivity was thus linked to water
tables in June in one area (Havel). Productivity was insufficient to maintain local populations in all areas and years except
for two occasions related to increased water tables. Retaining high water tables throughout the breeding season therefore
remains an important management option for waders on continental wet grasslands. 相似文献
403.
This paper presents a systematic comparison of liquid chromatography (LC) and supercritical fluid chromatography (SFC) for Chiralcel OD and Chiralpak AD chiral stationary phases (CSPs), performed using various chiral compounds having a known or potential pharmaceutical activity. The chiral recognition mechanisms involved in LC and SFC for the enantiomeric separation of β-blockers have been studied more particularly. As a general rule, it appears that the presence of polar functions, like primary or secondary hydroxyl or amine functions, may result in marked discrepancies in selectivity between LC and SFC. This result is peculiar to cellulose- and amylose-derived CSPs, for which the interactions involved in chiral recognition mechanism are not always well balanced, contrary to what happens for independent CSPs. In the case of chiral resolution of polar solutes or polymer-type CSPs, the analyst should try both the LC and SFC techniques to be able to choose the more stereoselective one. © 1995 Wiley-Liss, Inc. 相似文献
404.
Abstract Despite the enormous contribution of invertebrates to global biodiversity and ecosystem function, the patterns and causes of insect responses to tropical rainforest destruction and fragmentation remain poorly understood. We studied the responses of beetles to these factors in a fragmented upland rainforest landscape in north‐east Queensland, Australia. Beetles were sampled using flight interception traps from six replicate sites in rainforest interior, rainforest edge, small rainforest remnants and pasture, interspersed across about 600 km2. Beetles from 10 family/subfamily groups were sorted to species. There were three major findings. First, converting rainforest into pasture has a very strong negative effect on beetle diversity and species composition. Very few beetle species were present in pasture and none of the most abundant species was more abundant in pasture than rainforest. Second, beetle assemblages appeared to respond to climate. Beetle species composition in drier rainforest habitats was different from that of moister rainforest and there were species unique to each rainforest type. Third, beetle species composition differed between small remnants and interior rainforest: drier‐associated species were more abundant in small remnants, whereas wetter‐associated species were more abundant in interiors. Edges tended to be intermediate. We argue that this pattern can be attributed to a fragmentation effect mediated by differences in microclimate rather than by floristic, structural, or area and isolation effects. 相似文献
405.
406.
Charlotte J. KuceraCynthia K. Faulk G.Joan Holt 《Journal of experimental marine biology and ecology》2002,272(2):147-158
Spotted seatrout are capable of spawning in a wide range of salinities. Along the Texas Gulf Coast, bay salinities increase from an average of 14 ppt in Galveston Bay to an average of 40 ppt in Lower Laguna Madre due to the negative gradient of freshwater inflow from north to south. Tagging studies have shown that the majority of spotted seatrout do not migrate between adjacent bay systems. Spawning salinity has been shown to affect many properties of eggs including the diameter and salinity of neutral buoyancy. Spotted seatrout from two historically different salinity regimes (Matagorda Bay (MB) and Upper Laguna Madre (ULM)) were kept in the laboratory and induced to spawn in three salinities: 20, 30, and 40 ppt. The purpose of this study was to evaluate eggs at each of the three salinities and between the two bay systems. Two-way ANOVA showed a significant effect on the egg diameter of bay and spawning salinity, and a significant interaction between bays and spawning salinity. No significant difference in size at hatch was found between spawning salinities or between bays. Hatch rates in spawning salinity were >90% in all cases. Regression of wet weight on spawning salinity was highly significant for both bays. Eggs spawned in 20 ppt have the largest wet weight and eggs spawned in 40 ppt have the smallest wet weight, irrespective of parental bay origin. Percentage of water varied between 92% for 20 ppt spawned eggs and 86% in 40 ppt spawned eggs. Neutral Buoyancy Salinity (NBS) of eggs increased with increasing spawning salinity. Eggs spawned by the Upper Laguna Madre fish held at 20 ppt were not positively buoyant at 20 ppt. The results of this study suggest that spotted seatrout are locally adapted to the prevailing salinity regime within an estuary. 相似文献
407.
Abstract Severe Tropical Cyclone ‘Larry’ caused damage to 10 long‐term 0.5 ha monitoring plots in the rain forests of Queensland's Wet Tropics on 20 March 2006. We assessed the community‐level damage and the impact of the cyclone on the most abundant tree species in each plot. Damage was positively correlated with distance from the cyclone eye, though some plots received less damage than predicted owing to topographic shielding. Damage was patchy within plots, which is reflected in the range of damage‐classes recorded for each species, but there are broad trends in the type of response shown by different species. At the plot level, some species were either more susceptible or less susceptible to damage than the rest of the community. Species tended to show similar patterns of damage between plots with different community damage ratings. We discuss these response types in terms of adaptive tolerance to particular wind speeds and the trade‐off between frequently losing canopy volume in light winds, or rarely suffering substantial damage. We suggest that increased frequency of intense cyclones may affect the distribution of some species in the future, with those species most susceptible to high levels of damage at lower wind speeds becoming restricted to leeward‐facing slopes and upland areas away from the coast, and an increased abundance of resilient species in lowland coastal areas. 相似文献
408.
Ecological demands were studied in Elaphrus cupreus, a frequent species, and E. uliginosus, one of the most endangered carabids in Europe. Ecological experiments were performed in the laboratory and the field in
northern Germany. Abundance was measured using the mark-and-recatch method. Both species prefer sites with water content changes
lower than 25%. E. uliginosus prefers higher temperatures than E. cupreus and niche breadth was on average wider in E. cupreus than in E. uliginosus. E. uliginosus is restricted to grassland sites with a low fraction (>0 and 25%) of bare soil. E. cupreus was mainly found on sites having >75–100% bare soil. This preference of E. uliginosus can be referred to its high temperature demands using open regions for warming up and its predatory behaviour using hideouts
for a rapid predatory push. The wider niche structure and lower temperature demand of E. cupreus allows the inhabitation of cooler alder woods. It prefers large fractions of bare soil because its predatory behaviour is
to run randomly on the soil. Thus, E. uliginosus demands wet extensively grazed grassland where cattle produces low fractions of bare soil, while E. cupreus prefers intensively grazed sites in grassland or alder woods. 相似文献
409.
The enantiomeric purities of optically active intermediates for β-adrenergic blocking agents prepared via enzyme-assisted processes can be determined rapidly and with high accuracy using HPLC on commercially available columns with chiral supports [Chiralcel OD, OB; Chiralpak OT(+)]. The dependence of the resolution parameters on the substitution pattern of both hydroxy compounds and their esters is reported. © 1993 Wiley-Liss, Inc. 相似文献
410.
Abstract Cyclones have been instrumental in shaping the structural and floristic composition of tropical forests, including tropical rainforests of north Queensland, Australia. The response of tropical riparian rehabilitation sites to cyclonic wind damage, however, is currently unknown. This lack of knowledge may severely hamper long‐term success of riparian restoration efforts, particularly in light of predictions that cyclones in north Queensland may become less frequent but more severe. In this study, we examined the extent, type and magnitude of damage inflicted on revegetation works in the Tully‐Murray floodplain of north Queensland by Severe Tropical Cyclone Larry. We compared wind damaged in 20 paired revegetated and associated rainforest remnant sites, using (i) gross community damage scores, (ii) mean weighted damage scores, and (iii) type of damage sustained by individual plants. Overall, wind damage due to Severe Tropical Cyclone Larry was surprisingly similar in revegetated and remnant sites. Both gross community damage scores and mean weighted damage scores did not differ between paired revegetated and remnant sites. In contrast, the type of damage sustained by individual plants was not independent of site, with a larger proportion in revegetated sites sustaining severe damage compared with remnant sites. This larger proportion of severely damaged individuals in revegetated sites was at least in part due to the significantly higher proportion of pioneers at these sites. The pioneer species Homalanthus novoguineensis was particularly susceptible to wind damage. The potential effects of spatial differences, such as consistent bias due to size, shape or exposure between the remnants and revegetated sites, on our results are discussed. In light of our results, we recommend that future revegetation sites include fewer pioneer species that are highly susceptible to wind damage, more pioneer species that are resistant to wind damage, and alteration of pioneer species distribution within planting matrices. 相似文献