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Figure 3 in Brown bear (Ursus arctos L.) habitat use patterns in two regions of northern Pindos, Greece - management implications
No full textFigure 3. The habitat suitability map produced by the ecological niche factor analysis for the Grevena study site. Habitat suitability is presented by a greyscale gradient. The lighter the colour the more suitable habitat location for the bear.Published as part of Mertzanis, Georgios, Kallimanis, Athanasios S., Kanellopoulos, Nikolaos, Sgardelis, Stefanos P., Tragos, Athanasios & Aravidis, Ilias, 2008, Brown bear (Ursus arctos L.) habitat use patterns in two regions of northern Pindos, Greece - management implications, pp. 301-315 in Journal of Natural History 42 (5-8) on page 311, DOI: 10.1080/00222930701835175, http://zenodo.org/record/466662
Figure 2 in Brown bear (Ursus arctos L.) habitat use patterns in two regions of northern Pindos, Greece - management implications
No full textFigure 2. The habitat suitability map produced by the ecological niche factor analysis for the Gramos study site. Habitat suitability is presented by a greyscale gradient. The lighter the colour the more suitable habitat location for the bear.Published as part of Mertzanis, Georgios, Kallimanis, Athanasios S., Kanellopoulos, Nikolaos, Sgardelis, Stefanos P., Tragos, Athanasios & Aravidis, Ilias, 2008, Brown bear (Ursus arctos L.) habitat use patterns in two regions of northern Pindos, Greece - management implications, pp. 301-315 in Journal of Natural History 42 (5-8) on page 310, DOI: 10.1080/00222930701835175, http://zenodo.org/record/466662
How does plant species composition change from year to year? A case study from the herbaceous layer of a submediterranean oak woodland
No full textOver millions of years there is a long-term increase in species richness, accompanied by substantial turnover in species composition. However, little is known about species temporal turnover over shorter, ecologically relevant time periods, such as years. In the present study, we examine the inter-annual temporal turnover in species composition in 100 m(2) plots of the herbaceous layer in a submediterranean oak woodland over six years. We found that approximately half of the accumulated number of species over the six years is accommodated as temporal turnover. We also found that species temporal turnover in undisturbed control plots was not significantly different from that in plots where vegetation was recovering naturally without assistance, i.e., plots undergoing ecological succession. Only in the most disturbed (continuously overgrazed) plots temporal turnover was low to non-existent. We therefore suggest that diversity estimates based on a single year of observations may seriously underestimate species richness or the detrimental effects of disturbance, at least at the 100 m(2) scale. Furthermore, we found that, with the exception of the heavily grazed plots, short-lived species (annuals and biennials) did not display significantly greater temporal turnover than long-lived (perennial) species. Our analysis also supports that the space for time substitution applies in the patterns of species turnover. Spatial species turnover was comparable to temporal turnover. Species that are observed in many plots are also present in many years, and vice versa. Also, the similarity in species composition decreased as the time period between observations increased, as is the case with distance decay. Overall we conclude that the patterns of species turnover in time resemble those in space, and thus temporal turnover makes an important contribution to total biodiversity that should not be ignored
Examining the relationship between total species richness and single island palaeo- and neo-endemics
No full textRecently, Emerson and Kolm (2005) hypothesized that diversity begets speciation (DBS hypothesis). The relationship between total species richness and single island endemic diversity (as a proportion of the total species richness of the island) has been used as evidence for the DBS hypothesis. This relationship has been documented in oceanic archipelagos, but many criticisms have been raised on whether this relationship truly supports the DBS hypothesis. In this study we tested if this hypothesis holds in the Aegean archipelago (a continental archipelago with continuous human presence over millennia). Endemism in the Aegean includes mainly neo-endemic species but also relictual populations of formerly more widespread species (i.e. palaeo-endemics). Contrary to the DBS hypothesis, we found that total species richness was not significantly correlated to single island endemics (neither neo-endemics nor palaeo-endemics) as a proportion of the island flora. Furthermore, we found that neo-endemic diversity (either as species richness or as a proportion of the islands flora) is mainly correlated to island maximum elevation, while area and isolation were less important. So if this ratio is indeed an index of speciation, then an alternative explanation might be that elevation (interpreted as a proxy for habitat heterogeneity) is the driver of speciation in our case. Palaeo-endemics, on the other hand, were present in only six of the largest islands in the Aegean and their diversity was strongly correlated only with island area, perhaps implying that larger islands support larger population sizes that buffer stochastic extinctions risks. (C) 2010 Elsevier Masson SAS. All rights reserved
The herb layer restoration potential of the soil seed bank in an overgrazed oak forest
No full textWe investigated the potential contribution of the persistent soil seed bank in post-disturbance restoration of the herb layer in a long-term overgrazed, mixed oak forest (NW Greece). We examined the impacts of grazing on plant richness and density in the soil seed bank in regard to the different dispersal and life strategy types of the herb layer taxa. Soil seed bank was qualitatively and quantitatively analyzed and contrasting plant guilds were defined according to life strategy type and dispersal mode. Soil seed bank differences between a) the upper and lower soil layers and b) plant functional guild pairs (ruderals vs. non ruderals, including typical forest taxa, and physically-vs. animal-dispersed plants) were statistically tested in overgrazed and sporadically grazed plots. Moreover, correlations in soil seed bank species dominance between overgrazed and sporadically grazed plots were examined by Spearman's Rank correlation. The majority of seeds were found in the upper (0-5 cm) soil layer. Seed density in the deeper (5-10 cm) soil layer was rather poor and did not differ significantly between overgrazed and sporadically grazed plots. In the upper soil layer, both seed density and plant species richness were significantly lower in the overgrazed plots. Overgrazing reduced both species richness and seed density of non-ruderal species in general and typical forest herbs in particular, while it did not affect ruderal species richness and density. Plant species richness and seed density of animal-dispersed taxa were reduced by overgrazing while physically-dispersed species were not affected; it is therefore concluded that large herds of grazers fenced in relatively small areas cannot act as efficient dispersal vectors of the former species. Our findings suggest that, upon cessation of grazing, the soil seed bank is rather inadequate to restore the herb layer of overgrazed forest sites
Seed bank composition and above-ground vegetation in response to grazing in sub-Mediterranean oak forests (NW Greece)
No full textWe investigate the persistent soil seed bank composition and its relation to the above-ground flora of grazed and non-grazed sub-Mediterranean deciduous oak forests of NW Greece. Twenty-eight taxa were recorded in the soil seed bank and 83 taxa (70 taxa in plots of seed bank sampling) in the above-ground vegetation. The dominant tree species and many woodland species found in the above-ground vegetation were absent from the soil seed bank. Similarity between the soil seed bank and the above-ground vegetation decreased with grazing, and grazing led to a decrease of species richness in above-ground vegetation and soil seed bank. Beta diversity of vegetation among grazed and among non-grazed plots did not differ, but was significantly higher between grazed and non-grazed areas. Beta diversity of the soil seed bank declined with grazing. When applying classification tree and logistic regression analyses, non-grazed forest sites are clearly differentiated by the presence of Phillyrea latifolia, Euphorbia amygdaloides and Brachypodium sylvaticum. PCA ordination of above-ground species composition reflected a gradient from sites grazed by ruminants to non-grazed sites, but no clear structure was detected in the seed bank
The herb layer restoration potential of the soil seed bank in an overgrazed oak forest
No full textWe investigated the potential contribution of the persistent soil seed bank in post-disturbance restoration of the herb layer in a long-term overgrazed, mixed oak forest (NW Greece). We examined the impacts of grazing on plant richness and density in the soil seed bank in regard to the different dispersal and life strategy types of the herb layer taxa. Soil seed bank was qualitatively and quantitatively analyzed and contrasting plant guilds were defined according to life strategy type and dispersal mode. Soil seed bank differences between a) the upper and lower soil layers and b) plant functional guild pairs (ruderals vs. non ruderals, including typical forest taxa, and physically-vs. animal-dispersed plants) were statistically tested in overgrazed and sporadically grazed plots. Moreover, correlations in soil seed bank species dominance between overgrazed and sporadically grazed plots were examined by Spearman's Rank correlation. The majority of seeds were found in the upper (0-5 cm) soil layer. Seed density in the deeper (5-10 cm) soil layer was rather poor and did not differ significantly between overgrazed and sporadically grazed plots. In the upper soil layer, both seed density and plant species richness were significantly lower in the overgrazed plots. Overgrazing reduced both species richness and seed density of non-ruderal species in general and typical forest herbs in particular, while it did not affect ruderal species richness and density. Plant species richness and seed density of animal-dispersed taxa were reduced by overgrazing while physically-dispersed species were not affected; it is therefore concluded that large herds of grazers fenced in relatively small areas cannot act as efficient dispersal vectors of the former species. Our findings suggest that, upon cessation of grazing, the soil seed bank is rather inadequate to restore the herb layer of overgrazed forest sites
Biogeographical determinants for total and endemic species richness in a continental archipelago
No full textWe examined the relationship between plant species richness and biogeographical variables (island area, island maximum elevation, distance from nearest inhabited island, distance from nearest mainland) using a data set comprising 201 islands of the Aegean archipelago. We found that endemic species richness was strongly correlated to total species richness. Single-island endemic species richness was most strongly correlated to island maximum elevation, and then to island area, with an apparent small island effect for islands smaller than 47 km(2). Total species richness was most strongly correlated to island area (with no apparent small island effect), and less strongly correlated to island maximum elevation. Distance from the mainland or other inhabited islands displayed limited predictive value in our data set. The slope of the relationship between species richness and geographical factors (island area, elevation, distance from island/mainland) was steeper for endemic species richness than for total richness. Finally, the different scales of endemicity (single-island endemics, island group endemics and Aegean regional endemics) displayed similar qualitative trends and only differed quantitatively. Thus, we conclude that different biogeographical factors act as drivers for total species richness than for endemic species richness
Multiple-Facet Diversity Patterns of Aquatic Vegetation in Lakes along a Trophic Gradient
No full textThe EU Water Framework Directive foresees the ecological assessment of surface waters against identified pressures. Nutrient loading is the main pressure impairing the ecological quality of lake ecosystems, and aquatic macrophytes are considered good indicators of ecological response. In this study, we statistically assessed different aspects of aquatic plant (macrophyte) diversity in response to different trophic levels in Mediterranean lakes. We used 5690 relevés of aquatic vegetation, distributed over 305 transects, sampled in 18 freshwater lake ecosystems during 2013–2016. Our results show a significant decrease in taxonomic alpha diversity in lakes with a total phosphorus content above 100 μg/L. Syntaxonomic diversity followed the species richness pattern as well. Functional richness decreased along the trophic gradient, while functional dispersion was higher in lakes with high trophic levels. Taxonomic and functional beta partitioning presented changes in assembly processes leading to greater community homogeneity in lakes with higher trophic levels. In summary, we found no redundancy between taxonomic and functional diversity indices. These results provide novel insights into aquatic plant assembly processes of impacted freshwater lakes needed to forward conservation and restoration practices
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