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1.
In agricultural landscapes in central Europe, species richness of the herbaceous plant community may be compromised by processes associated with forest fragmentation, habitat loss, and management practices. We examined variability in species richness and composition of the herbaceous layer in 229 plots located in 23 forest fragments (0.1 to 255 ha), in a representative upland agricultural landscape in central Bohemia, in relation to the most important site environmental factors, edge effects, and site history. The influence of environmental factors on the composition of vegetation in the herb layer was evaluated using generalized additive models, which enabled us to analyze highly non-linear and non-monotonic relationships. Total species richness and number of red-listed and ancient forest species were significantly influenced by type of forest vegetation, light quality, soil pH, slope aspect, and distance from the forest edge. Implications of the significant explanatory variables corresponded well to previous findings, with the exception of distance from the forest edge, for which we found a positive relationship with species richness for distances up to 200 m toward the forest interior. Plant species with low colonization ability occupied plots with increasing frequency from edge to forest interior, while fast-colonizing species showed the opposite trend. Apart from the edge effect, forest continuity should be considered for its important contribution to the richness of ancient forest and red-listed species, whereas the effect of forest fragment size appeared to be generally weak. These results do not negate the importance of large forest fragments for the maintenance of herb layer species richness, but specifically emphasize the essential contribution of the core habitats of these forests. In summary, we showed that the negative effects of habitat fragmentation on the richness of ancient forest and red-listed species and on herb layer species in total can be largely attributed to either the edge effect itself or to aggregate effects of forest edge and forest continuity.  相似文献   

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Haloperidol (50 mg/kg, i.p.) treatment was given once to two different groups of pregnant Charles Foster rats on gestational day 9 and 14, these being respectively the critical periods of neural morphogenesis and rapid neural cell proliferation in this species. Pregnant control rats were similarly treated with equal volume of vehicle. The pups born were subjected to open-field exploratory behaviour and elevated plus-maze behaviour tests of anxiety and learned helplessness test of depression at 9 weeks of age. The results indicate that prenatal haloperidol treatment on gestational day 14 induces a significant increase in open-field ambulation and faecal droppings whereas haloperidol treatment on gestational day 9 caused significantly decreased rearing and unaltered ambulation in rat offsprings. Rat offsprings treated with haloperidol on gestational day 9 and 14 also displayed significant anxiogenic behaviour pattern on elevated plus-maze. Significantly increased number of escape failures were observed in learned helplessness tests indicating presence of depression in haloperidol treated rat offsprings. These behavioural alterations were found to be more marked in rat offsprings treated with haloperidol on gestational day 14. The results suggest that prenatal single exposure of high dose of haloperidol during critical period of neural cell proliferation leaves a lasting imprint on offsprings resulting in abnormal emotional state.  相似文献   

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Vole demographics are often modified close to wooded environments. Population monitoring in such settings reveals substantial edge effects, although these have seldom been quantified. This study compares the abundance of common voleMicrotus arvalis (Pallas, 1778) populations at various distances from three types of wooded environment (hedgerow, copse and forest) and in two types of habitat (temporary and permanent grassland). In temporary grassland, substantial edge effects were detected along the boundaries of forests and hedgerows. At 100 m from the forest edge, voles were twice more abundant than at 50 m, four times more than at 25 m and eight times more than at 5 m. In permanent grassland, the edge effect was such that voles were practically absent up to 100 m from the forest edge. For both types of grassland, the edge effect was more pronounced for forest habitat than for hedgerows, that is, for elements with a large surface area of wooded environment. Our results suggest that landscape context may greatly affect the local abundance of voles. Given the considerable damage done byM. arvalis, the presence of wooded patches in grassland areas leads to lower vole densities in adjacent areas and this might be an alternative method to controlM. arvalis as a pest species.  相似文献   

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Protected areas have been increasingly encroached upon by light pollution. This paper examines whether patch geometry and land development intensities in protected areas affect the light pollution levels in 22 Korean national parks. Light pollution levels were assessed based on mean nighttime radiance of these national parks derived from nighttime satellite images. Total floor areas of buildings in the parks and in a 1 km buffer zone outside the park boundaries were calculated to assess land development intensities both inside and surrounding the parks. Two landscape metrics (patch area and fractal dimension) were measured to assess the patch geometry of the parks. Results show that the mean nighttime radiances in the Korean national parks are significantly affected by total floor areas in the 1 km buffer zone, but not by the total floor area within the park. This suggests that skyglow caused by artificial light in periphery is a major source of light pollution in the Korean national parks. In other words, light pollution can be seen as an ecological edge effect in protected areas where land development is stringently restricted. This conclusion is also supported by significant effects of two patch geometry variables, i.e., light pollution was more severe in a protected area with smaller size and a more complex shape. Based on these findings, it is suggested to make protected areas larger and more simple-shaped to protect biodiversity from light pollution. Managing lights in periphery of protected areas is also suggested.  相似文献   

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Schneider NA  Low M  Arlt D  Pärt T 《PloS one》2012,7(2):e31517
Nest predation risk generally increases nearer forest-field edges in agricultural landscapes. However, few studies test whether differences in edge contrast (i.e. hard versus soft edges based on vegetation structure and height) affect edge-related predation patterns and if such patterns are related to changes in nest conspicuousness between incubation and nestling feeding. Using data on 923 nesting attempts we analyse factors influencing nest predation risk at different edge types in an agricultural landscape of a ground-cavity breeding bird species, the Northern Wheatear (Oenanthe oenanthe). As for many other bird species, nest predation is a major determinant of reproductive success in this migratory passerine. Nest predation risk was higher closer to woodland and crop field edges, but only when these were hard edges in terms of ground vegetation structure (clear contrast between tall vs short ground vegetation). No such edge effect was observed at soft edges where adjacent habitats had tall ground vegetation (crop, ungrazed grassland). This edge effect on nest predation risk was evident during the incubation stage but not the nestling feeding stage. Since wheatear nests are depredated by ground-living animals our results demonstrate: (i) that edge effects depend on edge contrast, (ii) that edge-related nest predation patterns vary across the breeding period probably resulting from changes in parental activity at the nest between the incubation and nestling feeding stage. Edge effects should be put in the context of the nest predator community as illustrated by the elevated nest predation risk at hard but not soft habitat edges when an edge is defined in terms of ground vegetation. These results thus can potentially explain previously observed variations in edge-related nest predation risk.  相似文献   

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The existence of the nervous form of Chagas disease is a matter of discussion sinceCarlos Chagas described neurological disorders, learning and behavioural alterationsin Trypanosoma cruzi-infected individuals. In most patients, theclinical manifestations of the acute phase, including neurological abnormalities,resolve spontaneously without apparent consequence in the chronic phase of infection.However, chronic Chagas disease patients have behavioural changes such as psychomotoralterations, attention and memory deficits, and depression. In the present study, wetested whether or not behavioural alterations are reproducible in experimentalmodels. We show that C57BL/6 mice chronically infected with the Colombian strain ofT. cruzi (150 days post-infection) exhibit behavioural changes as(i) depression in the tail suspension and forced swim tests, (ii) anxiety analysed byelevated plus maze and open field test sand and (iii) motor coordination in therotarod test. These alterations are neither associated with neuromuscular disordersassessed by the grip strength test nor with sickness behaviour analysed bytemperature variation sand weight loss. Therefore, chronically T.cruzi-infected mice replicate behavioural alterations (depression andanxiety) detected in Chagas disease patients opening an opportunity to study theinterconnection and the physiopathology of these two biological processes in aninfectious scenario.  相似文献   

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C G Janson  M J During 《Genomics》2001,78(1-2):3-6
Over the past decade, viral vectors have slowly gained mainstream acceptance in the neuroscience and genetics communities for the in vivo study of gene function [1]. Using stereotactic techniques, it is possible to characterize neuroanatomical relationships through the delivery of neurotropic viral vectors to specific brain regions. More sophisticated studies combine viral vectors with other methods of genetic manipulation such as germline transgenic mice. As more is learned about the properties of different viral vectors, it has become possible to use viral vectors to test hypotheses about the function of genes, through targeted in vivo delivery to the central nervous system (CNS). The effects of gene expression in the brain can be measured on the molecular, biochemical, electrophysiological, morphological, and behavioral levels. We propose that viral vectors should be considered as part of an integrated functional genomics platform in the CNS.  相似文献   

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Alkaline phosphatase (from chicken intestinal sources) was shown to contain a considerable amount of polyanionic phosphorus which was released by basic digestion. The polyanionic phosphorus of alkaline phosphatase is not associated with protein or polyalcohols and does not exhibit a visible or ultraviolet absorption spectrum. Alkaline phosphatase and abiogenic inorganic polyphosphate were found to incorporate 32P-orthophosphate under similar experimental conditions. It has been previously reported that this enzyme will incorporate 32P-orthophosphate into its protein phosphoserine without the apparent concomitant utilization of an energy source. This reported phosphorylation was immediately reversible upon dilution of the phosphorylated enzyme with unlabelled orthophosphate, which indicates that the initial phosphorylation was an exchange reaction. These observations suggest that this polyanionic phosphorus from alkaline phosphatase may be inorganic polyphosphate.  相似文献   

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Edge effects are a well-known result of habitat fragmentation. However, little has been published on fragmentation, isolation and the intrusive influence from the surrounding matrix at the landscape level. The objectives of the present study are to evaluate the presence of dogs in the Brasília National Park (BNP) in relation to habitat type and the influence from the surrounding matrix. In addition, this study examines the response of the native mammal fauna to the presence of dogs. Track stations were built along dirt roads in the BNP and subsequently examined for the presence or absence of tracks. We used a stepwise logistic regression to model the occurrence of five mammal species relative to habitat variables, with an α =0.05 to determine whether to enter and retain a variable in the model. A simulation of each species occurrence probability was conducted using a combination of selected habitat variables in a resource selection probability function. Results indicate a negative relationship between distance from the BNP edge and the probability of dog occurrences. From an ecological perspective, the presence of dogs inside the BNP indicates an edge effect. The occurrence of the maned wolf was positively associated with distance from a garbage dump site and negatively associated with the presence of dog tracks. The maned wolf and giant anteater seem to avoid areas near the garbage dump as well as areas with dog tracks. There is no support for the possible existence of a feral dog population inside the BNP, but the effects of free-ranging dogs on the wildlife population in such an isolated protected area must not be neglected. Domestic dog Canis familiaris populations and disease control programs should be established in the urban, sub-urban and rural areas surrounding the BNP, along with the complete removal of the garbage dump from the BNP surroundings.  相似文献   

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Animal and clinical studies have shownrespiratory muscle dysfunction caused by treatment withglucocorticoids. The present study was designed to investigate whetheranabolic steroids are able to antagonize the loss of diaphragm forceinduced by long-term low-dose methylprednisolone (MP) administration.Male adult rats were randomized to receive saline or MP (0.2 mg · kg1 · day1sc) during 9 mo, with or without nandrolone decanoate (ND; 1 mg · kg1 · wk1im) during the last 3 mo. The ~10% reduction in force generation ofisolated diaphragm bundles induced by MP was completely abolished byaddition of ND. The MP-induced decrease in number of fibers expressingtype IIb myosin heavy chains was not reversed by ND. MP slightlyreduced type I, IIa, and IIx fiber cross-sectional areas(CSA), but not type IIb fiber CSA. Addition of ND abolished thereduction in IIa and IIx fiber CSA. The MP-induced alterations inglycogenolytic activity and fatty acid oxidation capacity were notreversed by ND. In conclusion, the marked reduction in diaphragm forcecaused by long-term low-dose MP was completely abolished by addition ofND. ND in part also antagonized the effects of MP on diaphragmmorphology but showed no beneficial effects on biochemical changes.

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Eriophyoid mites are excellent candidates for ethological research using the approaches of behavioural ecology and sociobiology. These tiny haplodiploid mites are highly specialized plant parasites, producing galls, forming nests, inhabiting refuges or living freely on plants. They reproduce via spermatophores deposited on a substrate and without pairing, which is a fascinating, though still poorly understood, mode of reproduction widespread in some groups of arthropods. Eriophyoid males can be involved in external sperm competition. In some species they also guard pre-emergent females and deposit spermatophores beside them. Although slow-walking, the minute eriophyoid mites can disperse for long distances on air currents or specific animal carriers. After landing on a plant they can distinguish between suitable and unsuitable hosts. Biological observations on a deuterogynous species indicate that parasociality could occur among eriophyoid mites. Many eriophyoids are of economic importance. Knowledge of their behaviour may promote understanding their ecology, may resolve problems in their phylogeny and may help developing methods for their control. In this paper, attention is directed to dispersal modes of eriophyoid mites, their feeding and host acceptance, spermatophore deposition and mating, defence against predators, and social behaviour.  相似文献   

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格氏栲群落林窗边缘效应研究   总被引:17,自引:2,他引:17  
应用Shannon—Wiener物种多样性指数、Simpson生态优势度指标以及边缘效应强度指数,对福建三明格氏栲保护区森林群落林窗的边缘效应现象进行了研究.格氏栲群落的38个林窗样地不同部位上述指标的测定结果表明,用物种多样性指数测定的林窗边缘效应强度值为0.7~1.3左右;而用生态优势度值测定的林窗边缘效应强度值为0.3~1.8左右,林窗边缘区由于边缘效应的作用有增大物种多样性的趋势,林窗的面积及林窗所在的森林群落类型,都对处于不同发育阶段的林窗的边缘效应强度产生影响.从而为格氏栲群落生物多样性保护与森林经营管理提供理论基础.  相似文献   

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通过对典型农业生态工程结构的研究,分析了生态农业系统的运行机制.结果表明,结构多样性与主导性关系的协调问题,是目前制约农业生态系统良性循环的根本问题.山东省西单村农业生态系统之所以前期能够保持持续稳定发展,后期出现减缓趋势,主要原因也是由于其系统的结构多样性比较高,结构多样性指数最高达0.6556,结构链内部各组分之间的协调性超过90%;而系统实际主导性则较低,结构主导性指数最高为0.2574,系统的最高协调性指数只有0.1327.因此,要保证系统的可持续发展,必须保证系统结构的协词性.  相似文献   

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