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South-facing Slopes (south-facing + slope)
Selected AbstractsEpidemiology of Heterobasidion abietinum and Viscum album on silver fir (Abies alba) stands of the PyreneesFOREST PATHOLOGY, Issue 1 2010J. Oliva Summary In the last two decades, stand decline and increased mortality has affected silver fir (Abies alba) forests in the Spanish Pyrenees. Simultaneously severe occurrences of the root rot fungus Heterobasidion annosum s.l. and of the mistletoe Viscum album have been reported. We aimed to improve the understanding of the epidemiology of both pathogens in our region. All H. annosum isolates found on silver fir were typed as H. abietinum. H. abietinum was more frequently observed where cuttings had targeted fir trees rather than other species. H. abietinum fruiting bodies were observed in the most recently cut stumps. V. album was more abundant on more dominant fir trees, and in southern aspect stands. The number of V. album colonies in the stand correlated (R2 = 0.40) with silver fir mortality. Stands with a high level of V. album infection tended to have a smaller percentage of basal area in species other than silver fir, and they tended to be located on more south-facing slopes. H. abietinum was widespread in silver fir forests of the Pyrenees. Our data suggest that, in the Pyrenees, the observed H. abietinum incidence may represent a combination of both primary and secondary spread of the pathogen. Favouring mixed forests should be tested as a potential control method for V. album. The correlation between silver fir mortality and V. album infection warrants further study, as the observed tree mortality could have occurred due to other factors than V. album, such as drought damage. [source] Habitat selection by Ortolan Buntings Emberiza hortulana in post-fire succession in Catalonia: implications for the conservation of farmland populationsIBIS, Issue 4 2009MYLES H. M. MENZ The Ortolan Bunting Emberiza hortulana is a long-distance migrant that has suffered major population declines across much of its European breeding range. While northern populations are bound largely to farmland, Mediterranean populations are largely confined to habitats subject to recurrent wildfires. Habitat selection of the Ortolan Bunting was assessed in a recently burnt area in Catalonia at landscape and habitat scales. A Zero-inflated Poisson procedure was used to model the abundance of birds in relation to landscape and habitat variables. The most parsimonious landscape model predicted the highest abundance on south-facing slopes, with a gradient above 10°. The most parsimonious habitat model showed a positive quadratic effect of bare ground and regenerating oak Quercus spp., with predicted optima for abundance around 20,30% and 20% cover, respectively. There was a clear relationship between predicted abundance of the Ortolan Bunting and post-fire regenerating oak shrubs. South-facing, moderately sloping areas were favoured and bare ground was a key feature of the species' habitat. A matrix combining patches of sparse oak shrubs and patches of bare ground appears to be the optimal breeding habitat in the Mediterranean. The maintenance or provision of similar habitat features, especially patches of bare ground, may prove crucial for the conservation of rapidly declining Ortolan Bunting populations on farmland across temperate Europe. [source] Relationships between expanding pinyon,juniper cover and topography in the central Great Basin, NevadaJOURNAL OF BIOGEOGRAPHY, Issue 5 2008Bethany A. Bradley Abstract Aim, Increasing geographical range and density of conifers is a major form of land-cover change in the western United States, affecting fire frequency, biogeochemistry and possibly biodiversity. However, the extent and magnitude of the change are uncertain. This study aimed to quantify the relationship between changing conifer cover and topography. Location, The central Great Basin in the state of Nevada, USA. Methods, We used a series of Landsat Thematic Mapper satellite images from 1986, 1995 and 2005 to map change in pinyon,juniper woodlands (Pinus monophylla, Juniperus spp.) in the montane central Great Basin of Nevada. We derived fractional greenness for each year using spectral mixture analysis and identified all areas with an above average increase in greenness from 1986 to 1995 and 1995 to 2005. Results, Areas with high fractional greenness in 2005 were most likely to occur at elevations between 2200 and 2600 m a.s.l. Increases in fractional greenness between 1986 and 2005 were most likely to occur at elevations below 2000 m a.s.l. and on south-facing slopes. However, relationships between elevation and increasing greenness for individual mountain ranges varied considerably from the average trend. Fractional greenness values measured by Landsat suggest that the majority of pinyon,juniper woodlands have not reached their maximum potential tree cover. Main conclusions, Expansion of pinyon,juniper at low elevations and on south-facing slopes probably reflects increasing precipitation in the 20th century, higher water use efficiency caused by increasing atmospheric CO2 in the late 20th century and livestock grazing at the interface between shrubland and woodland. Identification of the spatial relationships between changing fractional greenness of pinyon,juniper woodland and topography can inform regional land management and improve projections of long-term ecosystem change. [source] Lineage diversification and historical demography of a sky island salamander, Plethodon ouachitae, from the Interior HighlandsMOLECULAR ECOLOGY, Issue 24 2008DONALD B. SHEPARD Abstract Sky islands provide ideal opportunities for understanding how climatic changes associated with Pleistocene glacial cycles influenced species distributions, genetic diversification, and demography. The salamander Plethodon ouachitae is largely restricted to high-elevation, mesic forest on six major mountains in the Ouachita Mountains. Because these mountains are separated by more xeric, low-elevation valleys, the salamanders appear to be isolated on sky islands where gene flow among populations on different mountains may be restricted. We used DNA sequence data along with ecological niche modelling and coalescent simulations to test several hypotheses related to diversifications in sky island habitats. Our results revealed that P. ouachitae is composed of seven well-supported lineages structured across six major mountains. The species originated during the Late Pliocene, and lineage diversification occurred during the Middle Pleistocene in a stepping stone fashion with a cyclical pattern of dispersal to a new mountain followed by isolation and divergence. Diversification occurred primarily on an east,west axis, which is likely related to the east,west orientation of the Ouachita Mountains and the more favourable cooler and wetter environmental conditions on north slopes compared to south-facing slopes and valleys. All non-genealogical coalescent methods failed to detect significant population expansion in any lineages. Bayesian skyline plots showed relatively stable population sizes over time, but indicated a slight to moderate amount of population growth in all lineages starting approximately 10 000,12 000 years ago. Our results provide new insight into sky island diversifications from a previously unstudied region, and further demonstrate that climatic changes during the Pleistocene had profound effects on lineage diversification and demography, especially in species from environmentally sensitive habitats in montane regions. [source] | ||||||||||