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41.
CRAIG A. FAULHABER NOVA J. SILVY ROEL R. LOPEZ DAVID H. LAFEVER PHILIP A. FRANK MARKUS J. PETERSON 《The Journal of wildlife management》2008,72(5):1161-1167
Abstract: We used radiotelemetry to locate daytime forms of endangered Lower Keys marsh rabbits (LKMRs; Sylvilagus palustris hefneri) throughout their range so we could determine habitat characteristics of diurnal cover. We typically found forms (n = 1,298) of 36 rabbits in brackish wetlands in patches of saltmarsh or buttonwoods. In freshwater wetlands, forms (n = 54) were located most often in patches of freshwater hardwoods embedded in or adjacent to freshwater marshes. Forms (n = 942) in brackish wetlands were characterized by thick groundcover (>75%), whereas those (n = 42) in freshwater wetlands had both thick groundcover and canopy vegetation. The mean minimum convex polygon around forms of 15 rabbits was 1.4 ha (SD = 1.7), with smaller ranges characterized by thick bunchgrasses or clump-forming sedges. To increase the amount of annual space usable by LKMRs, managers should provide more saltmarsh habitat interspersed with buttonwoods and enhance ground cover in existing habitat. 相似文献
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Previous observations have shown that slugs found favourableconditions for reproduction in wildflower strips and that theycaused high damage to oilseed rape adjacent to the strips. Inthe current study slug numbers and damage were estimated inwildflower strips and at different distances from the stripsinto winter wheat crops, from 1994 to 1996. Slug damage wasestimated using an index of defoliation and slug numbers andactivity were measured using wheat bran traps. Investigationsbegan when winter wheat seedlings emerged and lasted for fiveweeks. Slug damage was never severe in any of the fields studied.In most fields, slug damage was higher close to the wildflowerstrips than at greater distances from the strips. The decliningslug damage with increasing distances from the wildflowers stripswas related to the distribution pattern of juvenile Arion lusitanicus,suggesting that this species was responsible for the higherdamage near the strips. Other slug species (Deroceras reticulatum,Arion fasciatus, Deroceras laeve) were more or less evenly distributedover the field or were almost entirely confined to the wildflowerstrips. Results showed that winter wheat was not at risk fromslug feeding in spite of the establishment of wildflower stripsand that therefore the application of molluscicide along thestrips is unnecessary. (Received 23 June 1997; accepted 17 October 1997) 相似文献
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As the first part of a comprehensive study of the hormonal control of lateral root initiation and development, the effect of surgical treatments such as removal of the root tip, one or more cotyledons, the young epicotyl, or combination of these treatments, on the induction and emergence of lateral roots on the primary root of pea seedlings has been examined. Results show that removal of the root tip leads to a rapid but transitory increase in the number of lateral primordia, the largest number arising in the most apical segment of decapitated roots suggesting the accumulation of acropetally moving promoter substances in this region. The cotyledons appear to be the main source of promoter substances for both the induction and emergence of lateral roots, although one or more promoters also appear to be produced in the epicotyl. The data further indicate that the root tip is possibly the source of a substance which moves basipetally and interacts with acropetally moving promoters to regulate the zone for lateral primordia initiation; the root tip also appears to be the source of a powerful inhibitor of lateral root emergence. 相似文献
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1) Large temperature differences have a measurable effect onectothermic power consumption both at rest and during locomotion,yet this question remains to be satisfactorily addressed inecological studies looking at optimal foraging strategy andperformance. 2) Acclimation may influence the enzyme complementpresent in ectotherms and this could influence the energeticcost and efficiency of locomotion for ectotherms. 3) There maybe an optimal temperature for ectothermic locomotion and thismay vary from species to species, yet we measure power consumptionduring locomotion uniformly at 30°C. 4) Endothermic locomotionas demonstrated by birds is temperature sensitive, as was shownby Paladino and King (1984). Although the locomotory cost maynot change, thermoregulatory adaptations allow the bird to usethe heat produced during locomotion in the cold to reduce thermoregulatorypower requirements. 5) Avian hypothermia and inactivity is nota last ditch effort to save energy, but a strategy that allowsendotherms to conserve energy reserves during inactivity orstressful environmental conditions. 相似文献
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Secondary productivity is one portion of energy flow in a community,which includes the ingestion and assimilation of energy, andthe expenditure of energy in metabolism by consumer organisms.The purpose of this paper is to describe the ecological significanceof energy flow in consumers and to discuss methods of measuringits components. Data pertaining to 20 terrestrial animal populationsare presented. About 20% of the energy assimilated by invertebratesis manifested as net production, while only about 2% of theassimilated energy is represented by net production in populationsof birds and mammals. The relationship between production andmetabolism appears to depend on the capacity for homeothermy.For a given amount of assimilated energy, homeotherms produceless than heterotherms. 相似文献
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In 1995, slug damage and numbers of slugs were estimated intwo grass strips and adjacent rape fields. Investigations beganas soon as rape seedlings emerged and lasted for five weeks.Slug damage to rape plants 1 m from the grass strips was significantlyhigher than at greater distances from the strips. Derocerasreticulatum was the most abundant slug species recorded in bothgrass strips and adjacent rape fields. Arion lusitanicus andArion fasciatus were much less abundant than D. reticulatum.In one field, D. reticulatum declined steadily with increasingdistance from the grass strips and therefore appeared to havecaused the majority of severe damage to rape plants close tothe strips. This finding was surprising because until now severeslug damage in oilseed rape beside semi-natural habitats hasbeen observed only where A. lusitanicus was abundant. (Received 12 November 1997; accepted 26 January 1998) 相似文献