|
|
The effect of habitat continuity and management on species composition and diversity
Hubáčková, Barbora ; Münzbergová, Zuzana (advisor) ; Mudrák, Ondřej (referee)
Semi-natural grasslands of the eastern Moravia have big potential to host species-rich plant communities. However, changes in land-use during the second half of the last century were rapid and vast and many grasslands had been ploughed over. In the early 80s some arable lands were sown with low diversity clover-grass mixture and transferred back to grassland. Restoration of grasslands on former arable fields is a major challenge. Their colonisation by grassland species may be complicated by initial seeding productive low diversity seed mixtures. The aim of this study was to estimate differences in species composition and species diversity between ex-arable artificially seeded grasslands and fragments of grasslands with continuity over 70 years in the north part of White Carpathian Mts., SE Czech Republic and identify species traits limiting species ability to colonize the ex-arable grasslands. Target plant species (total of 137) were surveyed on 66 grasslands. Surveyed grasslands were according to continuity and type of management. Coordinates of centroids from each polygon (i. e. surveyed grassland) were used to treat the spatial correlation of the surveyed grasslands. The effect of continuity on species composition and diversity was tested after accounting for differences in the management and...
|
|
|
Ecological and ethological aspects of bird-building collisions
Semeráková, Anna ; Sedláček, Ondřej (advisor) ; Koleček, Jaroslav (referee)
Collisions with artificial structures represent one of the most significant cause of bird mortality worldwide. Accounting for hundreds of millions bird deaths each year, bird-building collisions represent a particular problem. Although the bird's vision system is perfectly adapted to the orientation during fast flight, birds are often confused due to the transparency or reflectivity of the glass. Moreover, light pollution of urban areas interferes with the physiological geomagnetic and polarized light compass in birds, which causes the night migrants to disorient. The bird-building collision frequency variates in time and space. Throughout the day, largest number of fatal collisions occurs during early morning. Throughout the year, the peak in the numbers of fatal strikes appears in the course of autumn migration. Local species abundance did not appear to be the most important predictor of collision probability. Species traits making birds highly prone to collisions are small body size, high flight speed, long distance of migration and feeding strategy requiring rare and temporary food sources. Aggressive males during the mating period and inexperienced post-fledging juveniles are among the most vulnerable individuals. Based on taxon-specific ecological traits, some bird families were identified to...
|
|
|
Bird diversity and life-history patterns along gradients of productivity and its variation
Tószögyová, Anna ; Storch, David (advisor) ; Remeš, Vladimír (referee) ; Field, Richard (referee)
Geographical variability in species richness and life-history strategies shows remarkable and well-documented patterns generated by various processes that have not yet been fully revealed. However, the pronounced correlation between spatial patterns in species and trait diversity and spatial gradients in environmental conditions indicates that the environment may modulate these processes. The mechanisms related to environmental productivity (energy availability), as a strong predictor of biodiversity, have been hypothesized to explain the cause of these broad- scale biodiversity patterns. Still, there is no consensus in the explanation, as many of the environmental and biotic factors are strongly interrelated. We have derived testable predictions that allowed disentangling the mechanisms responsible for spatial distributions of life-histories and species richness. The patterns in spatial distribution of many avian traits across the striking productivity gradient in South Africa show a slow-fast continuum in life-history strategies. High environmental productivity in tropics may result in stable populations that favour slow life-history strategies; birds can utilize stable food resources - low food seasonality selects for small clutch sizes, long parental care and high juvenile survival. The...
|
guest ::
