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Temporal Turnover (temporal + turnover)
Selected AbstractsSpatiotemporal changes of beetle communities across a tree diversity gradientDIVERSITY AND DISTRIBUTIONS, Issue 4 2009Stephanie Sobek Abstract Aim, Plant and arthropod diversity are often related, but data on the role of mature tree diversity on canopy insect communities are fragmentary. We compare species richness of canopy beetles across a tree diversity gradient ranging from mono-dominant beech to mixed stands within a deciduous forest, and analyse community composition changes across space and time. Location, Germany's largest exclusively deciduous forest, the Hainich National Park (Thuringia). Methods, We used flight interception traps to assess the beetle fauna of various tree species, and applied additive partitioning to examine spatiotemporal patterns of diversity. Results, Species richness of beetle communities increased across the tree diversity gradient from 99 to 181 species per forest stand. Intra- and interspecific spatial turnover among trees contributed more than temporal turnover among months to the total ,-beetle diversity of the sampled stands. However, due to parallel increases in the number of habitat generalists and the number of species in each feeding guild (herbivores, predators and fungivores), no proportional changes in community composition could be observed. If only beech trees were analysed across the gradient, patterns were similar but temporal (monthly) species turnover was higher compared to spatial turnover among trees and not related to tree diversity. Main conclusions, The changes in species richness and community composition across the gradient can be explained by habitat heterogeneity, which increased with the mix of tree species. We conclude that understanding temporal and spatial species turnover is the key to understanding biodiversity patterns. Mono-dominant beech stands are insufficient to conserve fully the regional species richness of the remaining semi-natural deciduous forest habitats in Central Europe, and analysing beech alone would have resulted in the misleading conclusion that temporal (monthly) turnover contributes more to beetle diversity than spatial turnover among different tree species or tree individuals. [source] Distribution of aquatic vascular plants in lowland rivers: separating the effects of local environmental conditions, longitudinal connectivity and river basin isolationFRESHWATER BIOLOGY, Issue 3 2005BENOÎT O. L. DEMARS Summary 1. Changes in species distributions along rivers have rarely been observed independently of changes in environmental conditions and meaningful comparison between different catchments is made difficult by the limited geographical distribution of species. This study presents a new approach to quantify the effect of the spatial structure of lowland river networks on aquatic plant distribution and to explore the potential underlying processes using species life-history characteristics. 2. Twenty-five species of aquatic vascular plants recorded in 62 sites across five calcareous river basins were used to investigate (i) the temporal turnover of plant species, (ii) the habitat utilisation of species, (iii) the trade-offs between different plant life-history characteristics and (iv) the relationship between species life-history characteristics and habitat utilisation. 3. The annual plant turnover within a 3-year period was, although significant, extremely low. It suggests that results from spatial surveys conducted over 3 years should not be undermined by temporal changes. 4. Spatial connectivity along and between rivers was more important than in-channel physical characteristics in shaping species assemblages. Neither chemical factors (ammonium, phosphate) nor extrinsic biotic competitors (filamentous green algae) significantly influenced plant distribution. 5. The most common combinations of life-history characteristics were neither related to environmental conditions nor to spatial isolation. Instead, they could reflect natural selection processes associated with larger scales than those considered in this study. 6. Plant distribution was most strongly related to the dispersal and regeneration abilities of the plants, supporting the hypotheses relating to longitudinal connectivity. The hypothesis that different growth forms would be associated with different in-channel physical features was not verified. As expected, there were no substantial differences in plant life-history characteristics between river basins. [source] Acacia species turnover in space and time in an African savannaJOURNAL OF BIOGEOGRAPHY, Issue 1 2001William J. Bond Aim Patterns of species turnover along environmental gradients are better studied than their causes. Competitive interactions, or physiological tolerance are most often cited as determinants of turnover. Here we investigate differential tree species response to disturbance by fire and mammal browsing as causes of changing dominance of species within and among sites along an altitudinal gradient. Methods We documented the distribution of two Acacia species using maps and sample transects. We explored possible causes of species turnover by studying differences between the species in tolerance to grass competition using pot experiments, to browsers by observing patterns of shoot damage, and to fire by comparing the size structure of populations burnt at different frequencies and intensities. Results Acacia karroo woodlands were rare and occur at higher elevations than the much more common A. nilotica woodlands. Woodland composition seems set to change in future since the pattern of dominance was reversed in juvenile stages. A. karroo juveniles were very widespread and far more abundant than A. nilotica juveniles. A. karroo juveniles were most abundant in tall fire-prone grasslands and were rare on grazing lawns whereas A. nilotica showed the reverse pattern. In the pot experiments, growth of both species was suppressed by grasses but there were no significant differences in response between the two species. Juveniles of A. karroo were more heavily browsed than those of A. nilotica. However juveniles of A. nilotica were less tolerant of frequent intense burns than juvenile A. karroo. Main conclusions Disturbance gradients, from high fire frequency and low herbivore density at high altitudes, to lower fire frequency and higher herbivore density at low altitudes, are responsible for the shift in community structure along the spatial gradient. Differential responses to browsing and fire may also explain temporal turnover from A. nilotica in the past to A. karroo in the present. Changes in the area burnt annually, and in faunal composition, suggest a landscape-scale shift from grazing-dominated short-grass landscapes in the 1960s, favouring A. nilotica, to fire-dominated tall grasslands in the 1990s favouring A. karroo. We suggest that species turnover due to differential responses along disturbance gradients may be much more widespread than the current paucity of studies suggests. [source] Inter-annual variability in amphibian assemblages: implications for diversity assessment and conservationAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 6 2010Carola Gómez-Rodríguez Abstract 1.Diversity assessments and conservation management should take into account the dynamic nature of populations and communities, particularly when they are subject to highly variable and unpredictable environmental conditions. 2.This study evaluates the inter-annual variability in the assemblage composition (temporal turnover) of an amphibian community breeding in a highly dynamic habitat, a Mediterranean temporary pond system, during a 4-year period. 3.A comprehensive framework is provided to evaluate temporal turnover from data of a differing nature (species richness, presence/absence and relative abundance) and, especially, to discern variation in richness (species loss) from changes in the identity or abundance of species (species replacement). 4.Results show that the pond amphibian assemblages in Doñana National Park exhibited high inter-annual variability during the study period, both in the number of species, species identity and their relative abundance. This result provides evidence for the inadequacy of surveys conducted only in one breeding season to characterize the species assemblage associated with a given pond. Besides, it suggests that a given pond offers different breeding opportunities over time, being suitable for different species depending on the year. This alternation will contribute to the medium-term preservation of all species in the assemblage. 5.It is highly relevant to preserve the natural dynamism and spatial variability of temporary pond systems, which will favour the conservation of populations through their intrinsic variability. Copyright © 2010 John Wiley & Sons, Ltd. [source] | ||||||||||