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Grassland Area (grassland + area)
Selected AbstractsOviposition preferences of Maculinea alcon as influenced by aphid (Aphis gentianae) and fungal (Puccinia gentianae) infestation of larval host plantsECOLOGICAL ENTOMOLOGY, Issue 1 2009ERVIN ÁRNYAS Abstract 1.,The influence of infestation of the larval host plant Gentiana cruciata on the egg-laying preferences of the xerophilous ecotype of Alcon Blue butterfly (Maculinea alcon) was studied in a semi-dry grassland area (Aggtelek Karst Region, Northern Hungary). 2.,We examined whether oviposition patterns of females differed when G. cruciata stems were uninfested compared with when they were infested by an aphid (Aphis gentianae) or a rust (Puccinia gentianae) species. 3.,Females laid more than 90% of their eggs on fertile, uninfested G. cruciata stems, although these stems comprised only , 50% of the total stems available. Stems infested by aphids were similar to uninfested ones in properties that had a strong correlation with egg numbers, and yet there were significantly fewer eggs on infested stems than on intact ones. 4.,Females never laid eggs on parts of Gentiana stems infested by aphids, and the presence of Lasius paralienus ants, which have a mutualistic interaction with Aphis gentianae, did not increase the repulsive effect of aphids. Infection of Gentiana by Puccinia did not influence the egg-laying behaviour of females, even though the flowers and buds of infested stems exhibited a delayed development. 5.,Aphid infestation can influence butterfly oviposition patterns through both direct and indirect effects. The presence of aphids directly excluded oviposition, but our data also indicated the possibility of an indirect effect of aphid infestation. Stems that had no aphids at the last egg counting, but were infested prior to it, had significantly fewer eggs than those that were never infested. [source] Prediction of butterfly diversity hotspots in Belgium: a comparison of statistically focused and land use-focused modelsJOURNAL OF BIOGEOGRAPHY, Issue 12 2003Dirk Maes Abstract Aim, We evaluate differences between and the applicability of three linear predictive models to determine butterfly hotspots in Belgium for nature conservation purposes. Location, The study is carried out in Belgium for records located to Universal Transverse Mercator (UTM) grid cells of 5 × 5 km. Methods, We first determine the relationship between factors correlated to butterfly diversity by means of modified t -tests and principal components analysis; subsequently, we predict hotspots using linear models based on land use, climate and topographical variables of well-surveyed UTM grid cells (n = 197). The well-surveyed squares are divided into a training set and an evaluation set to test the model predictions. We apply three different models: (1) a ,statistically focused' model where variables are entered in descending order of statistical significance, (2) a ,land use-focused' model where land use variables known to be related to butterfly diversity are forced into the model and (3) a ,hybrid' model where the variables of the ,land use-focused model' are entered first and subsequently complemented by the remaining variables entered in descending order of statistical significance. Results, A principal components analyses reveals that climate, and to a large extent, land use are locked into topography, and that topography and climate are the variables most strongly correlated with butterfly diversity in Belgium. In the statistically focused model, biogeographical region alone explains 65% of the variability; other variables entering the statistically focused model are the area of coniferous and deciduous woodland, elevation and the number of frost days; the statistically focused model explains 77% of the variability in the training set and 66% in the evaluation set. In the land use-focused model, biogeographical region, deciduous and mixed woodland, natural grassland, heathland and bog, woodland edge, urban and agricultural area and biotope diversity are forced into the model; the land use-focused model explains 68% of the variability in the training set and 57% in the evaluation set. In the hybrid model, all variables from the land use-focused model are entered first and the covariates elevation, number of frost days and natural grassland area are added on statistical grounds; the hybrid model explains 78% of the variability in the training set and 67% in the evaluation set. Applying the different models to determine butterfly diversity hotspots resulted in the delimitation of spatially different areas. Main conclusions, The best predictions of butterfly diversity in Belgium are obtained by the hybrid model in which land use variables relevant to butterfly richness are entered first after which climatic and topographic variables were added on strictly statistical grounds. The land use-focused model does not predict butterfly diversity in a satisfactory manner. When using predictive models to determine butterfly diversity, conservation biologists need to be aware of the consequences of applying such models. Although, in conservation biology, land use-focused models are preferable to statistically focused models, one should always check whether the applied model makes sense on the ground. Predictive models can target mapping efforts towards potentially species-rich sites and permits the incorporation of un-surveyed sites into nature conservancy policies. Species richness distribution maps produced by predictive modelling should therefore be used as pro-active conservation tools. [source] Grassland diversity related to the Late Iron Age human population densityJOURNAL OF ECOLOGY, Issue 3 2007MEELIS PÄRTEL Summary 1Species-rich semi-natural grasslands in Europe developed during prehistoric times and have endured due to human activity. At the same time, intensive grassland management or changes in land use may result in species extinction. As a consequence, plant diversity in semi-natural calcareous grasslands may be related to both historical and current human population density. 2We hypothesize that current vascular plant diversity in semi-natural calcareous grasslands is positively correlated with the Late Iron Age (c. 800,1000 years ago) density of human settlements (indicated by Late Iron Age fortresses and villages) due to enhancement of grassland extent and species dispersal, and negatively correlated with current human population density due to habitat loss and deterioration. 3We described the size of the community vascular plant species pool, species richness per 1 m2 and the relative richness (richness divided by the size of the species pool) in 45 thin soil, calcareous (alvar) grasslands in Estonia. In addition to historical and current human population density we considered simultaneously the effects of grassland area, connectivity to other alvar grasslands, elevation above sea level (indicating grassland age), soil pH, soil N, soil P, soil depth, soil depth heterogeneity, geographical east,west gradient, precipitation and spatial autocorrelation. 4Both the size of the community species pool and the species richness are significantly correlated with the Late Iron Age human population density. In addition, species richness was unimodally related to the current human population density. The relative richness (species ,packing density') was highest in the intermediate current human population densities, indicative of moderate land-use intensity. 5Community species pool size decreased non-linearly with increasing soil N, and was highest at intermediate elevation. Small-scale richness was greater when sites were well connected and when the elevation was intermediate. Spatial autocorrelation was also significant for both species pool size and small-scale richness. 6In summary, human land-use legacy from prehistoric times is an important aspect in plant ecology, which could be an important contributor to the current variation in biodiversity. [source] Landscape Patterns of Tropical Forest Recovery in the Republic of Palau,BIOTROPICA, Issue 4 2001Bryan A. Endress ABSTRACT A GIS (geographic information systems) database was constructed from aerial photographs, a vegetation map, and topographic map data of the Ngeremeduu Bay Drainage Area (NBDA), Palau, to examine relationships between upland land cover dynamics, environmental variables, and past land use. In 1992, 82.9 percent of the NBDA was forest, 16.6 percent was grassland, and 0.5 percent consisted of village areas. Between 1947 and 1992, there was a 11.2 percent reduction of grassland area primarily due to a 10.9 percent increase in forest cover. These land cover changes led to larger, more continuous stretches of forest and numerous, highly fragmented grassland patches. Significant relationships (P 0.001) were found between the spatial distribution of forest and grassland cover and slope, elevation, soil pH, and percent soil organic matter. These patterns, however, may have resulted from past farm site selection rather than from ecological relationships. Our results indicate that areas of forest expansion were significantly (P 0.001) associated with the location of abandoned agricultural communities. In addition, over 92 percent of areas of forest expansion occurred within 100 m of established forest. These results suggest that the proximity of established forest facilitate forest recovery following human disturbance. [source] | ||||||||||