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Habitat Parameters (habitat + parameter)
Selected AbstractsEffects of plant diversity, plant productivity and habitat parameters on arthropod abundance in montane European grasslandsECOGRAPHY, Issue 4 2005Jörg Perner Arthropod abundance has been hypothesized to be correlated with plant diversity but the results of previous studies have been equivocal. In contrast, plant productivity, vegetation structure, abiotic site conditions, and the physical disturbance of habitats, are factors that interact with plant diversity, and that have been shown to influence arthropod abundance. We studied the combined effect of plant species diversity, productivity and site characteristics on arthropod abundance in 71 managed grasslands in central Germany using multivariate statistics. For each site we determined plant species cover, plant community biomass (productivity), macro- and micronutrients in the soil, and characterized the location of sites with respect to orographic parameters as well as the current and historic management regimes. Arthropods were sampled using a suction sampler and classified a priori into functional groups (FGs). We found that arthropod abundance was not correlated with plant species richness, effective diversity or Camargo's evenness, even when influences of environmental variables were taken into account. In contrast, plant community composition was highly correlated with arthropod abundances. Plant community productivity influenced arthropod abundance but explained only a small proportion of the variance. The abundances of the different arthropod FGs were influenced differentially by agricultural management, soil characteristics, vegetation structure and by interactions between different FGs of arthropods. Herbivores, carnivores and detritivores reacted differently to variation in environmental variables in a manner consistent with their feeding mode. Our results show that in natural grassland systems arthropod abundance is not a simple function of plant species richness, and they emphasize the important role of plant community composition for the abundance patterns of the arthropod assemblages. [source] Dynamics in a butterfly,plant,ant system: influence of habitat characteristics on turnover rates of the endangered lycaenid Maculinea alconECOLOGICAL ENTOMOLOGY, Issue 5 2007JAN CHRISTIAN HABEL Abstract 1.,Maculinea alcon, a myrmecophilic, stenotopic lycaenid butterfly is restricted to wet heathlands, bogs, and nutrient-poor hay meadows. Due to intensification of agriculture and decrease of extensively grazed meadows, many suitable habitats have disappeared and the remaining ones are highly fragmented and deteriorated. 2.,Historical distribution data and a comparison with the present occupation of patches show the decline of this critically endangered butterfly in north-west Germany. Most of the populations in north-west Germany are small and often geographically isolated. 3.,In summer 2002, two-thirds of 77 investigated potential patches were unoccupied as a result of unsuitable habitat structure and habitat fragmentation. 4.,Several habitat parameters were highly significantly correlated with the presence of M. alcon, in particular the distribution pattern of the host plant Gentiana pneumonanthe. Furthermore, butterflies were absent from many patches with an incidence probability below 50% with respect to patch size and isolation. 5.,In the nature reserve Lüneburger Heide, part of the study area, M. alcon populations have been observed since 1995. Typical turnover of local populations could be detected during these years. Extinctions and re-colonisations have stabilised the presence of this species in a metapopulation in this nature reserve. 6.,These data show the importance of different factors on different spatial levels influencing the presence of this endangered butterfly. [source] Disturbance history influences the distribution of stream invertebrates by altering microhabitat parameters: a field experimentFRESHWATER BIOLOGY, Issue 5 2008MICHAEL EFFENBERGER Summary 1. We investigated the effects of local disturbance history and several biotic and abiotic habitat parameters on the microdistribution of benthic invertebrates after an experimental disturbance in a flood-prone German stream. 2. Bed movement patterns during a moderate flood were simulated by scouring and filling stream bed patches (area 0.49 m2) to a depth of 15,20 cm. Invertebrates were investigated using ceramic tiles as standardized substrata. After 1, 8, 22, 29, 36 and 50 days, we sampled one tile from each of 16 replicates of three bed stability treatments (scour, fill and stable controls). For each tile, we also determined water depth, near-bed current velocity, the grain size of the substratum beneath the tile, epilithic algal biomass and standing stock of particulate organic matter (POM). 3. Shortly after disturbance, total invertebrate density, taxon richness and density of the common taxa Baetis spp. and Chironomidae were highest in stable patches. Several weeks after disturbance, by contrast, Baetis spp. and Hydropsychidae were most common in fill and Leuctra spp. in scour patches. The black fly Simulium spp. was most abundant in fill patches from the first day onwards. Community evenness was highest in scour patches during the entire study. 4. Local disturbance history also influenced algal biomass and POM standing stock at the beginning of the experiment, and water depth, current velocity and substratum grain size throughout the experiment. Scouring mainly exposed finer substrata and caused local depressions in the stream bed characterized by slower near-bed current velocity. Algal biomass was higher in stable and scour patches and POM was highest in scour patches. In turn, all five common invertebrate taxa were frequently correlated with one or two of these habitat parameters. 5. Our results suggest that several ,direct' initial effects of local disturbance history on the invertebrates were subsequently replaced by ,indirect' effects of disturbance history (via disturbance-induced changes in habitat parameters such as current velocity or food). [source] Breeding requirements of Nahan's Francolin, Francolinus nahan, in Budongo forest reserve, UgandaAFRICAN JOURNAL OF ECOLOGY, Issue 3 2010Eric Sande Abstract The Nahan's Francolin Francolinus nahani is a globally threatened species associated with remnant forests of the eastern equatorial lowlands of the Democratic Republic of the Congo and Uganda. We studied the species in the Budongo Forest Reserve during March 1998 to January 2000 in an attempt to document some aspects of breeding requirements. We located nests by physically searching the forest and through following radio-tagged adults. We measured demographical and habitat parameters associated with each nest. Our data suggest that trees of large diameter at breast height with appropriate buttress formation are important for long-time survival of Nahan's Francolins. Résumé Le francolin de Nahan Francolinus nahani est une espèce menacée au niveau mondial qui est liée à des forêts résiduelles dans les plaines équatoriales de l'est de la République Démocratique du Congo et d'Ouganda. Nous avons étudié cette espèce de mars 1998 à janvier 2000 dans la Réserve forestière de Budongo pour tenter de documenter certains aspects de ses exigences en matière de reproduction. Nous avons localisé des nids en fouillant la forêt et en suivant des adultes équipés de radio-émetteurs. Nous avons mesuré des paramètres démographiques et de l'habitat associés à chaque nid. Nos données laissent penser que les arbres qui ont un grand diamètre dbh avec une formation de soutien appropriée sont importants pour la survie des francolins de Nahan à long terme. [source] | ||||||||||