Search results for "species diversity."
showing 10 items of 160 documents
The effect of Quaternary climatic changes on plant distribution and evolution
1998
Abstract Climatic oscillations in the Quaternary have played a major role in changing the geographical distribution of plant species. Recent molecular work has provided new insights into the location of glacial refugia and routes of postglacial expansion. A comparative analysis shows that phylogeographic patterns in Europe appear to be less congruent than in North America. The change of geographical distribution has also provided opportunities for speciation through isolation, and hybridization after secondary contact. However, a complete understanding of the significance of the Quaternary climatic changes for plant speciation requires further research into the estimation of reliable and ac…
Determinants of macroinvertebrate diversity in headwater streams: regional and local influences
2003
Summary 1 Multiscale determinants of diversity and the relationship between regional (RSR) and local richness (LSR) have recently attracted increased attention, yet such studies on stream organisms remain scarce. We studied the relationships among RSR, β-diversity, LSR and local environmental variables in 120 headwater streams in Finland. Approximately similar-sized areas of eight drainage systems were defined as regions, and 15 stream riffles (= locality) per region were sampled. 2 RSR showed a strong positive relationship with mean LSR (R2 = 0·686), and there was no sign of curvilinearity within the observed range of RSR. RSR was also positively, although non-significantly, related to β-d…
Helminth communities of owls (strigiformes) indicate strong biological and ecological differences from birds of prey (accipitriformes and falconiform…
2012
We compared the helminth communities of 5 owl species from Calabria (Italy) and evaluated the effect of phylogenetic and ecological factors on community structure. Two host taxonomic scales were considered, i.e., owl species, and owls vs. birds of prey. The latter scale was dealt with by comparing the data here obtained with that of birds of prey from the same locality and with those published previously on owls and birds of prey from Galicia (Spain). A total of 19 helminth taxa were found in owls from Calabria. Statistical comparison showed only marginal differences between scops owls (Otus scops) and little owls (Athene noctua) and tawny owls (Strix aluco). It would indicate that all owl …
Assessment of Classifiers and Remote Sensing Features of Hyperspectral Imagery and Stereo-Photogrammetric Point Clouds for Recognition of Tree Specie…
2018
Recognition of tree species and geospatial information on tree species composition is essential for forest management. In this study, tree species recognition was examined using hyperspectral imagery from visible to near-infrared (VNIR) and short-wave infrared (SWIR) camera sensors in combination with a 3D photogrammetric canopy surface model based on RGB camera stereo-imagery. An arboretum with a diverse selection of 26 tree species from 14 genera was used as a test area. Aerial hyperspectral imagery and high spatial resolution photogrammetric color imagery were acquired from the test area using unmanned aerial vehicle (UAV) borne sensors. Hyperspectral imagery was processed to calibrated …
The effect of forest fuel harvesting on the fungal diversity of clear-cuts
2012
Abstract The removal of logging residues and stumps from clear-cuts has become a common forestry practice. Forest fuel harvesting decreases the initially low volume of dead wood in managed forests, but the biodiversity effects are poorly known. We studied the effects of forest fuel harvesting on decomposer fungi on clear-cut Norway spruce stands in central Finland. The number of occurrences and taxa of polypores, saprotrophic agarics and pleurotoid agarics were determined on 10 forest fuel harvested and 10 control clear-cuts 4–5 years after logging. In total, we recorded 148 fungal taxa. The total number of taxa, the number of polypore occurrences, and the number of polypore species within …
Species richness-standing crop relationship in stream bryophyte communities: patterns across multiple scales
2001
Summary 1 We tested for a unimodal (‘hump-backed’) relationship between species richness and standing crop at various spatial scales in stream bryophyte communities. Bryophyte species and their biomasses were determined from 20 to 25 quadrats in eight river and six stream sites in northern Finland. 2 Regression analyses revealed a quadratic relationship between richness and biomass in only two of the river sites and a positive correlation in one other. A quadratic relationship was detected in three stream sites and richness increased linearly with biomass in another. 3 We also tested for the hump-shaped pattern across individual stream boulders, representing an elevational gradient from con…
Revision of Sarcocornia (Chenopodiaceae) in South Africa, Namibia and Mozambique
2010
Abstract Sarcocornia comprises ca. 20–24 perennial, halophytic herb and shrub species. The genus is distinct from other genera in the Salicornioideae in having flowers that are more or less equal in size, arranged in a row, and with seeds that have a membranous hairy testa and lack perisperm. Sarcocornia is distributed worldwide, mainly in regions characterized by warm-temperate and, to a lesser extent, subtropical climates. The representatives of this genus are found in habitats such as estuarine salt marshes, tidal mud flats, coastal cliffs, inland salt pans, and salt-laden alluvia of intermittent semi-desert and desert streams. Some South African taxa also occur in inland (semi-desert) q…
The effects of protection measures on fish assemblage in the Plemmirio marine reserve (Central Mediterranean Sea, Italy): A first assessment 5years a…
2013
This 2-year study was aimed to investigate the early effects of protection measures on fish assemblage in the Plemmirio marine reserve and to evaluate its level of enforcement. Sampling was carried out by means of underwater visual census techniques in four sampling sites within the reserve boundaries and eight outside the reserve. Results showed significant inside/outside differences in the multivariate abundance of fish assemblage. These results were confirmed and exemplified by significant univariate differences between locations for total abundance, Species Richness and diversity of the fish assemblage; values of these metrics were higher inside the reserve than outside. Small fish size…
The helminth community of the skink Chalcides sexlineatus from Gran Canaria (Canary Islands).
2012
AbstractA survey of the gastrointestinal helminth communities of a population of Chalcides sexlineatus Steindachner, a small skink endemic to Gran Canaria island (Canary Archipelago, Spain), was conducted to determine the prevalence, abundance and species diversity of intestinal parasites in these reptiles. Only three parasite species were found, one cestode, Oochoristica agamae Baylis, 1919 and two nematodes, Parapharyngodon micipsae (Seurat, 1917) and Pharyngodonidae gen. sp. Helminth infracommunities of C. sexlineatus showed low values of abundance and species richness and diversity, being more similar to the helminth community of Tarentola boettgeri boettgeri (Steindachner) rather than …
The southernmost beech (Fagus sylvatica) forests of Europe (Mount Etna, Italy): ecology, structural stand-type diversity and management implications
2013
The southernmost European beech forests are located in the upper forest vegetation belt on Mount Etna volcano. Their standstructural patterns were analysed to assess the effects of the site-ecological factors and previous management practices on the forest structure. Five main structural-silvicultural types were identified among the main beech forest types: coppice, highmountain coppice (HMCo), high forest, coppice in conversion to high-forest and non-formal stand. A detailed standstructural analysis was carried out through measured dendrometric parameters and derived structural characters linked to both the horizontal and the vertical profiles. Plant regeneration processes were also assess…