bluuebunny/crossref_metadata_2025 huggingface dataset:
Pattern and dynamics of the ground vegetation in south Swedish Carpinus betulus forests: importance of soil chemistry and management
Authors: Brunet Jòrg , Falkengren‐Grerup Ursula , Tyler Germund
Published: July 2006

The vegetation and environmental conditions of south Swedish hornbeam Carpinus betulus forests are described with data from 35 permanent sample plots The main floristic gradient of the ground vegetation is closely related to acid‐base properties of the top soil base saturation, pH and organic matter content Other floristic differences are related to tree canopy cover and the distance of the sample plots to the Baltic coast Species richness of herbaceous plants typical of forests increases with soil pH, The number of other herbaceous species, occurring in both forests and open habitats, and of woody species is not related to pH Comparisons of vegetation data from 1983 and 1993 show relatively small compositional differences of the herbaceous forest flora The number of other herbaceous species increased considerably m those plots where canopy trees had been cut after 1983 The number of new species in managed plots increases with soil pH Species losses and gains of the herbaceous forest flora between 1983 and 1993 are generally lower as compared with other herbaceous species and woody species However, the ground cover of herbaceous forest species, especially of Oxalis acetosella and Lamium galeobdolon, was considerably lower in 1993 as compared to 1983 in both unmanaged and managed plots Possible explanations for this decrease are current soil acidification and drought during the growing season
Colonization dynamics and relative abundance of three plant species (Antennaria dioica, Hieradum pilosella and Hypochoeris maculata) in dry semi‐natural grasslands
Authors: Eriksson Ove
Published: July 2006

The objective of this study was to examine how population recruitment depends on seed size, and if relative abundance depends on colonization, in three plant species inhabiting dry semi‐natural grasslands All three species, Antennaria dioica, Hieracium pitosella and Hvpochoeris maculata belong to the same family, Asteraceae, and possess similarly structured wind‐dispersed fruits, achenes with pappus They occupy the same range of habitats, but are not equally abundant The seed size hierarchy is Hypochoeris Hieracium Antennaria Results from experiments suggest that recruitment is promoted by small disturbances, but limited also by seed availability Seed size differences explain interactions during recruitment, Hypochoeris“wins” over the other two species, and Hteracium wins over Antennaria Seed arrival order did not alter this hierarchy A model of relative abundance of the species was developed, based on observed differences in recruitment and seed output from local populations The model was able to predict observed relative abundance patterns at a large spatial scale, especially at marginal sites along road verges (Hieracium Hypochoeris Aniermaria), but not at smaller scales, where Antennaria was more frequent than Hypochoeris The results support a metapopulation approach to abundance patterns in landscapes, and, more specifically, they support the hypothesis that species abundance reflects colonizing ability An additional implication is that single source populations may be of great importance for species persistence in landscapes, a conclusion which has bearing on development of conservation and management plans for endangered habitats
Population and community level responses in Anas ‐species to patch disturbance caused by an ecosystem engineer, the beaver
Authors: Nummi Petri , Pöysä Hannu
Published: July 2006

We studied the response of a guild of three Anas‐species, to patch disturbance caused by the beaver Castor canadensis in southern Finland during 1988–1996 Of the three species, the teal Anas crecca increased in beaver ponds during the first two years of beaver occupation compared to the situation before the beaver The mallard Anas platyrhynchos and wigeon Anas penelope did not respond to beaver flooding during the first two years Also dominance relations changed upon inundation The mallard usually was more numerous than the teal before the beaver, but the reverse was the case during beaver occupation The study shows that some animal guilds may benefit from disturbance although species dominance relations may change And, that this change in dominance can be caused by an ecosystem engineer, the beaver
Secondary succession and summer herbivory in a subarctic grassland: community structure and diversity
Authors: Zobel Kristjan , Moora Mari , Brown Valerie K. , Niemela Pekka , Zobel Martin
Published: July 2006

A field experiment was established in a subarctic grassland in the Finnish Lapland to study the role of summer herbivory in plant community succession Perennial vegetation and moss cover were removed in an area of 324 m2 The site was divided into four blocks, of which two were fenced to prevent herbivory by large mammals (reindeer, hare)

Early successional changes in the vegetation were assessed Mean species richness per 3 × 3 m plot was consistently higher in the fenced area, indicating that herbivory can suppress small‐scale diversity Herbivory affected the height of several plant species However, there was no correlation between frequency and height of individual species There was a weak indication that taller species were more successful m early succession when grazed Light competition is apparently not a key process determining successional change Thus, in early stage of succession, summer herbivory has little effect on diversity by limiting light competition, and most species are equally successful in grazed and ungrazed plots There was some indirect evidence about competitive interactions in the developing community However, unlike temperate grasslands, large mammal herbivory and competition for light seem not to be important determinants of community change in this subarctic grassland (at least what concernes early successional stages) This may be explained by the harshness of local climate, and abundance of light due to the polar day
Landscape characteristics associated with the occurrence of the flying squirrel Pteromys volans in old‐growth forests of northern Finland
Authors: Mönkkönen Mikko , Reunanen Pasi , Nikula Ari , Inkeröinen Jouko , Forsman Jukka
Published: July 2006

We investigated whether the occurrence of the flying squirrel, a declined virgin forest species, was accounted for by the structure of the landscape in northeastern Finland We sampled 20 forest areas (1–77 km2 in size) in 1995 for the occurrence of the species using a sampling plot method Landscape structure around occupied and unoccupied areas were compared using seven different radii ranging from 100 m lo 10 km Classified satellite images were analyzed with Geographic Information System (GIS) Ten areas could be determined to be occupied by the flying squirrel Results showed that occupied areas did not deviate from unoccupied ones in total area In unoccupied areas there were more mature pine‐spruce forests, and less matrix habitat at the home range scale (100 m and 200 m radii) than in occupied areas Further more, in unoccupied forest areas open habitats (clear‐cuts, open fens) were more common than in occupied ones at distances between 200 m and 2 km around sampling plots These differences resulted from both larger mean patch size of and smaller mean nearest neighbor distance between open habitat patches m unoccupied than in occupied forest areas According to a logistic regression analysis, information on the amount of open habitat within 1 km radius alone correctly classified 75% of the areas into occupied and unoccupied ones The probability of the presence of flying squirrel decreases with the increasing amount of open habitat within 1 km The results suggest that increasing the amount of open habitats (e g clear‐cutting) at the local scale has a negative impact on the flying squirrel It is obvious that in the present situation where the population has severely declined and its optimal habitat is still diminishing, every patch suitable for the species ‐ whether occupied or not ‐may be important for the population persistence
Establishment and interactions of carabid populations: an experiment with native and introduced species
Authors: Niemelä Jari , Spence John R. , Cárcamo Héctor
Published: July 2006

The ground beetle Pterostichus melanarius (Coleoptera, Carabidae), of European origin, is abundant and wide‐spread in the northern United States and southern Canada Three field enclosures were used in a four‐year experiment in Alberta, Canada, to examine whether the species is able to establish in natural aspen‐poplar forest, and to test the hypothesis that it has an adverse effect on the native carabid assemblage After introduction to the enclosures P melanarius maintained breeding populations in them, establishing that the forest is suitable habitat for the species, and suggesting that the species will eventually invade from nearby populations Pterostichus melanarius had no negative effect on population size or body mass of the native carabid species However, the two most abundant native species (Ptero‐stichus adstrictus and P pensvlvanicus) appeared to be more active (measured as escape rate) in compartments where they co‐occurred with P melanarius Although the three enclosures were just a few metres apart, one of them consistently yielded the highest densities of all carabid species This difference was correlated with high abundance of earthworms and low litter accumulation Relatively low densities of P melanarius may explain the lack of negative interspecific interactions in forests, although such effects are suggested by data from urban and agricultural environments where P melanarius is more abundant
Spring home range, spatial organisation and activity of stoats Mustela erminea in a South Island Nothofagus forest, New Zealand
Authors: Alterio Nic
Published: July 2006

This radio‐tracking study reports the spring home range, spatial organisation and activity of 11 stoats Mustela erminea in a New Zealand Nothofagus forest, 1,5 yr after significant seedfall when rodent density was low, but stoat density was high. The average home range of 4 male stoats was 223 (SE = 45) ha, significantly larger than the average range area of 94 (SE = 13) ha recorded for 7 female stoats. Stoats were generally tolerant of sharing space and did not maintain intra‐ or intersexual territorial spacing systems. There was no evidence of temporal avoidance with several stoats of the same sex showing slight attraction to one another. However, stoats still may avoid one another when in close proximity. Long‐term radio‐tracking studies are required to determine the general patterns of spacing behaviour in stoats, Male stoats showed higher levels of activity during daylight than females.
Evidence that humidity influences snake activity patterns: a field study of the Malayan pit viper Calloselasma rhodostoma
Authors: Daltry Jennifer C. , Ross Toby , Thorpe Roger S. , Wüster Wolfgang
Published: July 2006

Multivariate statistical methods were used to elucidate which environmental factors influence the activity patterns of free‐living Malayan pit vipers, Calloselasma rhodostoma. Fourteen adult snakes were implanted with miniature radiotransmitters and located a total of 887 times in 5 months. The pit vipers usually remained coiled on the ground for several consecutive days before moving at night to a new site. Partial correlation tests revealed that the frequency and distance of movements to new sites by tagged snakes were highly positively correlated with ambient relative humidity, but not with rainfall, ambient temperature or the lunar cycle. This finding was corroborated by the frequency with which active non‐tagged C. rhodostoma were encountered at night, In each site, the proportion of the snakes’ bodies exposed to view was positively correlated with ambient humidity, and the snakes retreated to areas with deeper undergrowth when ambient humidity was low. Overt thermoregulatory behaviour was not observed, and implanted thermosensitive transmitters revealed that the snakes were passive thermoconformers.

These findings seem lo contradict much of the current literature which shows temperature to be the dominant abiotic factor affecting reptilian activity, but most herpetologists have considered only temperate forms. Ambient temperature in our tropical study site was warm and relatively constant throughout the year (mean daily range = 24‐ 33°C), so the pit vipers could passively maintain body temperature within a fairly narrow range, with a daytime mean of 29.4°C. Ambient relative humidity, on the other hand, was very variable, and confining exposure and activity to periods of high ambient humidity may be necessary to avoid dehydration
The effects of arable field margin management on the abundance and species richness of Araneae (spiders)
Authors: Baines M. , Hambler C. , Johnson P. J. , Macdonald D. W. , Smith H.
Published: July 2006

The effects of ten different management regimes on the abundance and species richness of Araneae on pre‐existing and newly expanded zones of field margins surrounding arable fields are compared in a large‐scale experiment conducted between 1987 and 1991. Most of the management regimes involved varying the Liming and frequency with which the field margins were cut. There was no evidence of consistent temporal trends in the abundance and species richness of Araneae on either the existing or expanded zones of the field margins during the first four years of the experiment. However, lowest numbers were recorded before expansion of the margins in 1987, and highest numbers in the final sample, in 1991. Araneae remained less abundant, and less species rich, on the newly expanded than on the existing zones of the field margins four years after they were set‐aside'. Culling reduced both abundance and species richness. Regimes which included culling in mid‐summer had a greater impact which persisted for longer than did those involving cutting in spring and autumn. Removal of cut material was associated with lower species richness than leaving it in situ. Sowing the margins with a wild flower seed mixture was associated with increased abundance and species richness of Araneae. Annual spraying with a broad‐spectrum, non‐persistent herbicide reduced the abundance of Araneae but the effect was not detectable until several months after the application of the spray. Both the species richness and abundance of Araneae were positively correlated with a measure of vegetation height made on the field margins in September, on both the pre‐existing and newly expanded zones of the margins. The extent to which management practices which benefit Araneae are compatible with both the management requirements for various other taxa. and the overriding constraint of effective pernicious weed control on field margins, is discussed.
Topographical constraints and home range quality
Authors: Powell Roger A. , Mitchell Michael S.
Published: July 2006

The topography of an area affects the animals that live in at. Using digitized topographic maps of our mountainous study area in North Carolina. USA, and using radio telemetry data for locations of black bears Ursus americanus, we tested the hypotheses that topography influences home ranges of black bears and that topography affects access to resources by black bears. Use of space by bears correlated positively with steepness of slope but negatively with relative elevation. The perimeters of bears” home ranges aligned with ridges and valleys more than expected by chance and home ranges were oriented on major topographic features, such as watersheds and basins. Bears’ homo ranges had lower resource values than was optimal for their home range locations and access to resources was limited by topography'. Ignoring topography may lead researchers to misunderstand the ecology and behavior of animals that live in mountainous areas.
Global patterns in species richness of pelagic seabirds: the Procellariiformes
Authors: Chown Steven L. , Gaston Kevin. J. , Williams Paul H.
Published: July 2006

Quantitative information on large scale spatial patterns of biodiversity remains poor, especially for pelagic systems. In this paper the regional diversity of procellariiforms is mapped worldwide at the species level. These seabirds do not display a conventional latitudinal gradient of decreasing species richness towards high latitudes, but rather are most speciose between 37° and 59°S in all ocean basins. Based on data for foraging ranges, areas with the highest species richness and the most species with smaller range sizes are all found in the vicinity of New Zealand and its sub‐Antarctic islands. In contrast, data for breeding ranges show islands in the southern Indian and Atlantic oceans to have the highest number of breeding species, while these islands and New Zealand have the most species with smaller range sizes. No northern hemisphere regions are amongst the top ten grid cells for foraging and breeding species richness, although Hawaii has the highest species richness of procellariilforms north of the equator. Northern Baja California. Madeira, the Canary islands, and the west coast of South America are all important sites of narrow endemism in the northern hemisphere. High species richness and narrow endemism coincide with areas of significant longline fishing activity in the southern hemisphere. Near‐minimum sets based on one and three representations demonstrate that if all procellariiform species are to be retained, large areas of the ocean and almost all breeding sites require conservation.
Species‐range size distributions in Britain
Authors: Gaston Kevin J. , Quinn Rachel M. , Blackburn Tim M. , Eversham Brian C.
Published: July 2006

The detailed forms of species‐range size distributions in Britain are determined and contrasted for ten taxonomic assemblages (liverworts, vascular plants, molluscs [aquatic and terrestrial], dragonflies, macro‐moths. butterflies, birds [breeding and wintering], mammals). All are strongly right‐skewed when range sizes are untransformed. A logarithmic transformation fails to normalise the distribution for all but one group, and the distributions for several groups are not readily normalised at all. Taxa with larger median range sizes have species‐range size distributions that are less strongly right‐skewed. The median observed range sizes of species in each of the taxonomic groups fall, in terms of decreasing range size, in the sequence wintering birds < breeding birds < mammals < butterflies < terrestrial molluscs < dragonflies < aquatic molluscs < vascular plants < moths < liverworts. Despite the difficulties in deriving a simple and sensible mechanistic model for range size distributions, this is likely to be the most important next step towards understanding their forms.
Vertical stratification of rainforest collembolan (Collembola: Insecta) assemblages: description of ecological patterns and hypotheses concerning their generation
Authors: Rodgers D. J. , Kitching R. L.
Published: July 2006

We describe a complex vertical stratification of collembolan assemblages from rainforest leaf litter samples and identify distinct assemblages associated with forest floor, lower canopy and upper canopy samples. Leaf litter samples were collected from the forest floor and deposits of leaf litter suspended in epiphytes in the canopy of a subtropical rainforest site at Lamington National Park in southeast Queensland. The patterns of relationship among assemblages of Collembola extracted from these samples were examined using a variety of analyses of a matrix of similarities between samples. The results of ANOSIM analyses showed that forest floor, lower canopy and tipper canopy samples formed discrete groups. These results permit a discussion of these groups as three distinct collembolan assemblages. Analysis of the dissimilarities between these assemblages revealed a gradient of similarity from the forest floor through the lower to the upper canopy. This gradient represents a more complex vertical stratification than has previously been identified in rainforest canopy arthropods. We suggest that limitations on the dispersal of some forest floor species into the canopy may be responsible for this pattern. We also identify a second gradient of similarities among these assemblages. We show that dissimilarity among samples from forest floor is significantly lower than dissimilarity among samples from within the lower canopy, and that the level of dissimilarity between samples from within the upper canopy is significantly higher again. We suggest that dispersal barriers and higher probabilities of extinction in upper canopy collembolan colonies may be responsible for higher heterogeneity of species composition and abundance among samples from the upper canopy. We outline a number of testable hypotheses aimed at determining the importance of these processes in producing the patterns we have observed.
The effect of depletion and predictability of distinct food patches on the timing of aggression in red deer stags
Authors: Schmidt Karoline T. , Seivwright Linzi J. , Hoi Herbert , Staines Brian W.
Published: July 2006

For group‐foraging ungulates, forage is generally widely and relatively evenly dispersed. However, for free‐ranging red deer Cervus elaphus supplementary winter feeding provides distinct patches of predictable food. These patches differ in size, but also in temporal distribution and depletion rate. Interference competition is known to increase with increasing spatial clumping (decreasing patch size), but the influence of temporal clumping and the predictability of food occurrence has received much less attention. Therefore in this study we investigated the effects of different degrees of spatial and temporal clumping of food on interference competition during feeding. Patch size was the main parameter influencing participation in feeding as well as interference competition during feeding on the respective patch. Temporal dispersion and the predictability of food occurrence were however, important parameters for the timing of aggressive interactions. Generally, aggression occurs during feeding and increases with decreasing patch size. But when depletion rate was high food availability was predictably short and the patch occurred predictably (such as hay), middle ranking stags increased aggression already prior to feeding at the respective patch. We suggest that in this way they confirmed hierarchy outside feeding on the quickly depleted patch and as a result gained actual feeding time when feeding on the respective patch. With the patch occurring predictably but varying in size the number of participating subordinates varied concomitantly with variation in patch size. Subordinates assessed patch profitability and left without having fed when patch size was too small for an efficient participation. When patch size was predictably small enough to be defended exclusively (feed blocks), subordinate stags did not assess profitability each time but did not participate at all in feeding at the respective patch. The relative importance of these various food‐related parameters (patch size depletion rate, predictability) influencing feeding competition and the timing of aggression will vary with group size, rank, alternative food sources, physical characteristics of the food as well as different hierarchy systems of the feeding animals.
Testing for spatial autocorrelation in ecological studies
Authors: Koenig Walter D. , Knops Johannes M. H.
Published: July 2006

We describe a statistical method appropriate for the analysis of spatial autocorrelation in data varying in time as well as space. In particular, the technique was developed lo address the issue of geographic synchrony in ecological variables that may change markedly from year to year such as population density of animals or seed production of trees. The method yields ‘modified correlograms” that test for significant autocorrelation between sites located within any given range of distances apart. This technique facilitates detecting and understanding spatial processes m a variety of ecological phenomena, including testing the plausibility of causational hypotheses using cross‐correlational analyses. Several examples are discussed, including population densities of squirrels in Finland, winter densities of two hawk species in California, and acorn production and radial growth by individual blue oak Quercus douglasii trees in central coastal California.
Interspecific competition between larvae is not an important strncturing force in mixed communities of Rana and Bufo on an English sand‐dune system
Authors: Bardsley Louise , Beebee Trevor J. C.
Published: July 2006

We investigated the roles of competition and predation in the structuring of mixed anuran communities (Rana temporaria and Bufo bufo) in an English sand‐dune system. Rana temporaria breeds earlier in spring than B. bufo. but the latter species was numerically superior in all ponds at the study site. We measured survival and growth rates of larvae in three duplicate sets of natural ponds. In one set we removed B. bufo spawn, leaving only R. temporaria: in a second sel we removed R. temporaria spawn, leaving only B. bufo: and in a third set we left boih together. The third set also contained substantial numbers of predatory fish (Perea fluviatilis and Gasterosteus aeuleatus). Rana temporaria survival was lower than that of B, bufo in all ponds, on average by sixfold. Rana temporaria fared better on its own than in the mixed‐species ponds, but lower survival in the latter ponds was probably due to fish predation rather than to Inierspecific competition. By eonlrast, B. bufo survival was sevenfold higher in mixed‐species compared with single‐species ponds, probably because they are distasteful to fish and thus benefited indirectly from fish‐predation of invertebrates, Protothieca rieharsi. a mediator of interference competition between anuran larvae under laboratory conditions, was present in some of the dune ponds but was not correlated with larval growth inhibition. Taken together the evidence implicated predation of larvae and intraspecific competition, rather than interspecific competition, as the dominant structuring forces in this community.
Predation on artificial nests in a forest dominated landscape – the effects of nest type, patch size and edge structure
Authors: Huhta Esa , Jokimäki Jukka , Helle Pekka
Published: July 2006

We studied the effects of forest patch size and forest edge structure on nest predation in a boreal coniferous forest landscape. The following predictions were tested. Nest predation should be higher in small than in large stands, in edges than in interior areas of forest stands, and in barren forest/clear–cut edges created by forestry than in natural forest/open marsh edges. Four types of artificial above ground nests (total of 261) were used; open cup nests with reindeer Rangifer t. tarandus hair, open cup nests with domestic hen Gallus domesticus feathers, and unlined open cup and nest–box nests. Nests were baited with one Japanese quail Coturnix coturnix japonica egg. Nest–boxes were depredated significantly less than open cup nests of all types. No edge‐ or stand size–related nest predation was found. The predation rate, regardless of the nest type, did not differ relative to the edge type and vegetation characteristics. However, better horizontal visibility of open cup nests due to more open vegetation structure increased predation risk in man–made edges compared to inherent edges. The results suggest that edge–related nest predation is absent or weak in forest dominated landscapes. This may be due to predator types present in the landscape and/or predators habitat use in forest dominated areas. Therefore, it might be that findings documented in other areas, such as in agricultural dominated landscapes, cannot be directly applied to managed forest landscapes.
Dietary and microtopographical selectivity of Greenland white‐fronted geese feeding on Icelandic hayfields
Authors: Kristiansen J. N. , Fox A. D. , Stroud D. A. , Boyd H.
Published: July 2006

The feeding ecology of Greenland white‐fronted geese Anser albifrons flavirostris was studied during .spring staging in Iceland 1997. Geese feeding on Poa pratense dominated hayfields (> 80% cover) were highly selective, selecting for Deschampsia caespitosa which comprised only 10% of the sward. Geese fed most on the south‐facing fringes of Deschampsia tussocks. Subsequent analysis showed that the southern fringes of Deschampsia tussocks supported significantly greater biomass (27% greater mass of green material) and that leaves growing on the southern faces had significantly higher protein content than those on the northern faces (33.9% vs 30.5%)‐ It appears that the geese maximise their nutritional intake in spring by selecting the grass species of highest quality and taking the most nutritious parts of the plants.
Breeding habitat selection and larval performance of two anurans in freshwater rock‐pools
Authors: Laurila Anssi
Published: July 2006

I studied breeding habitat choice of common toad Bufo bufo and common frog Rana temporaria in 221 freshwater rock‐pools on 15 small islands in the southwestern coast of Finland. I monitored tadpole growth rate in a number of rock‐pools differing in size, competitors and predator regime. Furthermore, I carried out a short‐term field experiment to investigate the effects of different predators on larval survival. Rana bred in pools of virtually all sizes, although the very smallest ones were usually avoided. A logistic regression analysis showed that the amount of aquatic macrophyte vegetation and pool surface area were the most important pool characters for Rana. Bufo preferred the largest pools, and pool surface area was by far the most important habitat variable. Rana avoided pools with the lowest pH. but was more common than expected at pools with pH around 6. In Bufo such an effect was not found, but this may be due to relatively low number of pools occupied by Bufo. In Rana there was a positive correlation between pool area and tadpole body length in early June, but two weeks later this relationship was not significant. In Bufo tadpole body size was not significantly affected by pool area. Presence of predators or presence of the other tadpole species did not affect growth or tadpole body size in either Rana or Bufo. A short‐term experiment in wading pools indicated that both species suffered heavy mortality in the presence of a diving beetle larva. In the presence of predatory fish, mortality of Bufo did not differ from controls, whereas mortality was high among Rana tadpoles. It appears that although predators prey heavily on Rana tadpoles, they do not exclude Rana from larger rock‐pools. However, it is not evident from this study why Bufo avoids smaller pools.
Plant colonisation in small forest–floor patches: importance of plant group and disturbance traits
Authors: Jonsson Bengt Gunnar , Esseen Per‐Anders
Published: July 2006

It has been proposed that the interaction between life–history attributes of different organisms and distrbance characteristics play an important role in determining the successional pattern following a disturbance event. We compared the responses of vascular plants and bryophytes (mosses and hepatics) to variation in disturbance size and severity in an old‐growth boreal forest during a four–year period. The experiment included two patch sizes (0.25 and 2.5 m2) and two levels of severity: humus patches (removal of vegetation) and mineral soil patches (removal of both vegetation and humus layer). Treatments were chosen to reflect some aspects of disturbance by uprooting. Species richness was significantly affected by both disturbance size and severity but the response differed among plant groups. In vascular plants, species numbers were highest in humus patches while mosses were more numerous in mineral soil patches, the most severe disturbance. In contrast, severity had no effect on hepatics. Plant recovery was more rapid in bryophytes than in vascular plants. Species richness of bryophytes had exceeded that of adjacent, undisturbed vegetation after 2‐3 yr. We attribute the contrasting response of the plant groups to differences in regeneration strategies. As a group, bryophytes had a greater variety of regeneration methods than vascular plants, with several types of asexual propagules and abundant production of spores in some species. In contrast, clonal ingrowth dominated in vascular plants while seedlings were rare. Thus, our analysis supports the view that plant response to patchy disturbance is strongly dependent on the interplay among disturbance traits and specific attribtites of different plant groups.
Stability of pre‐ and post‐fire spatial structure of pine trees in Aleppo pine forest
Authors: Ne'eman Gidi , Izhaki Ido
Published: July 2006

The study reported here describes for the first time the similarity between pre‐ and post‐fire spatial patterns of the trees in a Mediterranean pine forest demonstrating that the pre‐fire ancestor microsite is occupied also by the next generation. Although Aleppo pine Pinus halepensis Mill, is an obligatory post‐fire seeder, it is adapted to regenerate in its pre‐fire growing microsite. thus keeping suitable growing sites from generation to generation. We studied the effect of the dead burned adult pines on the density and size of their recruited saplings 2, 5, 11 and 20 yr after fire. A comparison of pine sapling density and size was made between the “near” zone (under the former effect of the burned canopy) and the‘far’zone (beyond the former effect of the burned canopy).

In the site 2 yr after fire, seedling density was 56% higher in the “far” zone than in the‘near’zone, but seedling .size was similar. However in the site 20 yr after fire, densities were similar in both zones, but the size was bigger by 89% in the “near” zone. Thus, population recruitment after fire seems to peak near the burned pine trees rather than at u distance from them, in contrast to Janzen's original‘distance hypothesis’ model suggested for undisturbed rainforest. Mere we present a new hypothetical model for the spatial pattern of post‐fire regeneration of obligate seeder tree species forming open forests. It is proposed that in such trees the microsites which were kept by the burned adult trees, which are killed by the fire, are also the favorable regeneration microsite for the post‐fire generation.
The importance of scale and spatial variables for the fungivorous beetleBolitophagus reticulatus(Coleoptera, Tenebrionidae) in a fragmented forest landscape
Authors: Rukke BJoørn Arne , Midtgaard Fred
Published: July 2006

Effects of isolation, habitat size and several microhabitat variables on presence/absence of the monophagousBolitophagus reticulatus(L.) (Coleoptera. Tenebrionidae) were investigated in 58 forest fragments in an agricultural landscape (15 km2) in south‐eastern Norway, All potential habitats of the beetle, deadFomes fomentarius(L,) Kiekx basidiocarps (n = 587), were collected from trees (n = l85) within the study area. The basidiocarps were dissected and the number ofB, reticulatusspecimens (larvae, pupae and adults) counted. The material was analysed at four distinguishable spatial scales; basidiocarp‐. tree‐, tree‐group‐ and forest island level. Different patterns of beetle presence emerged at the different scales, increasing habitat size and decreasing degree of isolation increased the probability of B, reticulatus presence at three (basidiocarp‐, tree‐ and forest island level) and one (tree level) scales, respectively, whilst no such trends were found at the fourth level (tree‐group level). Increasing insolation and thereby higher ambient temperatures, indicated by several microhabitat variables, improved the probability of beetle presence amongst the trees. The number of beetle specimens correlated positively with an increase in the habitat size at the tree level.
Resource quality and the colonisation and succession of coprophagous dung beetles
Authors: Gittings Tom , Giller Paul S.
Published: July 2006

In order to examine the degree of resource selectivity in a north temperate dung beetle assemblage und to identify major parameters that influence such selectivity, the occurrence of adult dung beetles (Aphodius. GeotrupesandSphaeridium) in up to five different types of dung over a period of up to 25 d was examined in a series of field experiments using standardised dung pats. There were significant physical and chemical differences in dung quality between dung types and over time during succession. Dung beetle species showed distinct preferences for particular types of dung which were generally similar in data sets from both pitfall traps and dung pat samples. Species also showed distinct patterns of successional occurrence. Ordinations produced by Canonical Correspondence Analysis, based on species occurrences in dung types and over time, usually selected dung pat age as the most important environmental variable influencing dung beetle assemblages. Dung quality parameters contributed a significant element of structure to the species ordinations but ordinations using dung types or dung quality parameter values as the environmental variables were very similar in terms of sample and species placement within the ordination for each data set. Most importantly the CCA ordinations clearly grouped species according to their breeding behaviour. Early‐successional species laid eggs in the soil, or in silken egg cocoons, which allowed them to exploit wet dung. Mid and late‐successional species laid eggs in the dung pat: late‐successional species could exploit normally wetter dung types than mid‐successional species, probably due to increased crust formation and drying as the dung pat ages. Thus, species appear to be differentially adapted to exploit varying types of dung microhabitats. Therefore, where two or more species of large herbivores are present, dung quality preferences probably constitute an important niche dimension.
Variation in the diet of red foxes on Scottish moorland in relation to prey abundance
Authors: Leckie F. M. , Thirgood S. J. , May R. , Redpath S. M.
Published: July 2006

The diet of red fox Vulpes vulpes was investigated through analysis of 340 scats collected during 1992‐1996 from moorland in south‐west Scotland. Rodents, game‐birds, lagomorphs, carrion and insectivores were the most frequently occurring food types. Fox diet and prey abundance were compared between heather dominant and grass dominant habitat types within the study area. Rodents were the most frequently occurring food type in each habitat and occurred in 63% of seats overall. Rodents occurred more often in scats from grass dominant sites while gamebirds and lagomorphs were more frequent in scats from heather dominant sites. The occurrence of rodents in winter fox scats increased with rodent abundance. In contrast, the occurrence of gamebirds in winter fox scats was unrelated to gamebird abundance but negatively related to rodent abundance. It appeared that foxes switched to gamebirds in years, or habitats, where rodents were uncommon.
Geographic variation inAgama impalearisfrom Morocco: evidence for historical population vicariance and current climatic effects
Authors: Brown Richard P. , Znari Mohammed
Published: July 2006

Morphological and molecular surveys of within‐island geographic variation in lizards have revealed patterns of geographic variation that reflect both population vicariance and in situ selection‐mediated responses to the ecological heterogeneity of the islands. This study tested different models of differentiation in a continental species, the agamidAgama impalearis, in which spatial separation is much greater than that in island species. Patterns of among‐site differentiation in morphology were described and a character‐resampling technique used to investigate their robustness. Putative causes were evaluated by testing multivariate patterns of differentiation against models based on historical and present‐day effects using matrix association randomization tests. This strongly suggested the action of both vicariance/secondary contact and current climatic conditions in shaping the patterns of morphological variation. The former appears to be the result of range contraction into refugia separated by the Atlas mountain range during glacial conditions, with subsequent secondary contact during warmer interglacial periods, Scalation showed a very clear association with geographic difference in thermal regime, even after the vicariance/gene‐flow induced non‐independence had been taken into account. This latter finding indicates that patterns observed in other lizards are quite general.
Epiphytic macrolichens in managed and natural forest landscapes: a comparison at two spatial scales
Authors: Dettki Holger , Esseen Per‐Anders
Published: July 2006

To maintain biodiversity in managed forests we must understand how forestry affects various organisms across a wide range of spatial and temporal scales. We compared landscape structure, forest structure, and species richness and abundance of epiphytic macrolichens in three pairs of natural and managed boreal forest landscapes. Study landscapes (2500 ha) were located within and adjacent to three of the largest forest reserves in Sweden (Reivo, Muddus, Jelka). The structural heterogeneity within landscapes was higher in managed forests whereas within‐stand structural heterogeneity was higher in natural landscapes. Species richness of macrolichens at the stand level (sample plot) was 23% higher in natural forests but there was no difference at the landscape level. Most (86%) of the common species were more frequent in natural landscapes. Lichen abundance (estimated by lichen litter) was two times higher in natural than in managed landscapes, 5.6 and 2.7 kg ha‐1 forest (pooled data), respectively. Both species richness and abundance were negatively related to cutting level (number and basal area of cut stumps) and positively related to stand variables (stand age, stem density and basal area). Lichen‐rich forest stands were more numerous but covered a smaller area and were more isolated in managed landscapes. This may in turn have important consequences for dispersal of lichen propagules to second‐growth forests. In conclusion, the results suggest that effects of forestry on epiphyte diversity and abundance are strongly related to the spatial scale (stand or landscape). To enhance biodiversity in managed forests we must increase structural heterogeneity at the whole range of spatial and temporal scales.
Effects of wrack burial in salt‐stressed habitats: Batis maritima in a southwest Atlantic salt marsh
Authors: Pennings Steven C. , Richards Christina L.
Published: July 2006

In coastal salt marshes, mats of wrack (dead plant stems) that are deposited on the marsh by high tides can kill underlying vegetation and initiate secondary succession. The importance of wrack disturbance in northwest Atlantic salt marshes has been a topic of recent debate. The importance of wrack disturbance in southwest Atlantic salt marshes, which experience a very different climate regime than do northern marshes, has rarely been examined. Working in a Georgia salt marsh, we documented a pattern of positive association between wrack and Batis maritima biomass, and conducted experiments that indicated that wrack was beneficial to Batis maritima. Sampling indicated that natural wrack deposition was correlated with areas of vigorous Batis growth and mild soil conditions. Natural wrack deposition occurred primarily at the highest elevations occupied by Batis maritima (the high Batis zone). Batis plants in the high zone were taller, with more and larger leaves, and contained several times the biomass/unit area than Batis plants at lower elevations. High zone soils had lower salinities, better percolation rates, and a lower organic content than did soils from lower elevations. Experimental manipulations demonstrated that deposition of wrack was partially responsible for these patterns. In each of two experiments, soil salinities were lower and plants taller and larger in the presence of wrack compared to in its absence. Although wrack lowered salinities and enhanced plant growth, the effects were not large enough to completely explain the differences between Batis zones. Instead, wrack probably reinforced pre‐existing gradients in flooding and salinity caused by differences in elevation and terrestrial runoff.

Our results contrast with previous studies from northern marshes. Because of geographic differences in climate and plant phenology, northern marshes are more likely than southern marshes to receive patches of wrack thick enough to kill underlying vegetation. Plants covered by thin layers of wrack, as commonly occurs in southern marshes, may often grow through the wrack rather than suffer mortality. Also because of climatic differences, wrack is more likely to benefit plants by ameliorating salinity stress in southern marshes, where soil salinities are often hypersaline, than in northern marshes where soils are rarely hypersaline. Although ecological processes may differ between northern and southern salt marshes, these differences may be predictable based on an understanding of geographic variation in climate.
Host‐specialization and species diversity in fish parasites: phylogenetic conservatism?
Authors: Sasal Pierre , Desdevises Yves , Morand Serge
Published: July 2006

The pattern of parasite species diversification and specialization, appreciated by host range, is investigated in fish parasites. We test whether host range is linked with phylogeny at a high taxonomic level, and if there is a relationship between host range and host species diversification. For this purpose we used two sets of data, one on macro‐parasites of marine fishes of the Mediterranean Sea and the other on macro‐parasites of marine and freshwater fishes of Canada. Similar patterns of host range among parasitic groups were found. Our findings suggest that habitat (marine vs freshwater) and geographic localization (Canada vs Mediterranean region) play little role in determining the observed patterns of host range. We highlight the potential influence of phylogeny (high‐taxonomic level) on the level host range in parasites. We find that parasites with free‐swimming larval stages and with direct life cycles have a narrower range of host species than do parasites with indirect life cycle, even if we cannot control for phylogenetic effects because of the lack of variation of life cycles within each parasitic group. Finally, a positive relationship was found between the number of known hosts and parasite species diversity in the case of Mediterranean parasite species. The relationship between host range and species diversification should be related to the mechanism of cospeciation.
Insect diversity of Acacia canopies in Mkomazi game reserve, north‐east Tanzania
Authors: Krüger Oliver , McGavin George C.
Published: July 2006

Here we analyse one of the largest insect samples taken so far from a tropical savannah habitat. We used insecticidal mist blowing to spray the canopy of 3i trees of six Acacia species, and obtained 41 099 insects of 492 recognisable taxonomic units (RTUs). In most cases, there were significant differences between individual trees between and within tree species with regard to their insect community. After we performed a standardisation procedure because of unequal sample size, cluster analysis showed that most tree species formed more or less distinct clusters, indicating a moderate level of insect host specificity. Considered by tree localities, clear clusters were visible only if one tree species was sampled. This finding suggests that there is no significant overlap in the insect communities between tree species at a local scale. We carried out a multivariate analysis of insect diversity using four different diversity measurements. Results differed depending on the measurement used and no significant association of simple tree characteristics, such as height, with insect diversity was detectable. Instead, time of the day and ant biomass seem to be of greater importance. These results emphasise the importance of using different diversity measurements to evaluate habitats with regard to their conservation value.