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Biology Hyvonen, T. and J. Salonen. 2002. Weed species diversity and community composition in cropping practices at two intensity levels - a six-year experiment. Plant Ecol. 154
405 220 227 Gering, J.C., T.O. Crist and J.A. Veech. 2003. Additive partitioning of species diversity across multiple spatial scales: implications
Bird migration constitutes a redistribution of bird diversity that radically changes the composition of the bird community worldwide. It comprises about 19% of the world’s bird species. Several studies have indicated that changes in avian community structure and differences in bird richness in different seasons are mainly driven by seasonality and by winter harshness, and that the associated costs increase with the distance involved. Western Mexico is an important wintering area for most passerines that breed in western North America, and that travel long on the long-distance Central and Pacific migration routes. In this study, we examined bird species richness and diversity during the breeding and wintering seasons in the Central Sierra Madre Occidental (SMO), North Durango (Mexico) in relation to i) tree species diversity, ii) tree dimension, iii) forest stand density and site quality, iv) density and dimension of snag trees, and v) various climate variables. The overall aim of the study was to determine how the observed associations between bird species diversity and variables i-v are affected by the season considered (breeding or wintering). The diversity of bird species in the breeding season was not affected by any of the climate and forest stand variables considered. In contrast, bird species diversity in the wintering season was significantly and weakly to moderately associated with climate variables, tree species diversity and stand density, although not with density or dimension of snag trees. Bird species diversity was higher at lower elevations and in drier and warmer locations of the SMO. The association detected is therefore mainly a local migratory phenomenon.
. Härdtle , W. , B. Redecker , T. Assmann and H. Meyer . 2005 . Vegetation responses to environmental conditions in floodplain grasslands: prerequisites for preserving plant species diversity . Basic Appl. Ecol. 7 : 280 – 288
This study describes plant species diversity in well preserved dry coastal dune systems along the southern Baltic coast. Variations in diversity and in distributional character of plant species and plant communities throughout the study areas result mainly because of the interplay between plant succession, exposure, disturbance and resource availability. Environmental indicator values, used to describe dynamics in dune habitats, show a decline of light and temperature with increased distance to the sea, accompanied by higher soil moisture due to accumulation of organic matter. Species richness and species diversity showed a humped-shaped curve along a coast-to-inland gradient. The highest species richness of vascular plants and cryptogamic species were found in plant communities of grey dunes at intermediate levels of environmental and disturbance gradients, which confirms the intermediate disturbance theory.
In two arid/semiarid regions, we studied diversity of algae in lakes and pools with salinity ranging from 0.1‰ up to 39‰ In plankton and periphyton of 34 lakes in northern Kazakhstan, we found 252 species belonging to 113 genera of 8 algal divisions. In 24 pools with experimental salinity ranges in the Negev desert of Israel, we recorded 86 species from 47 genera of 6 algal divisions. The dominant groups of both arid regions are represented by widespread species of diatoms, green algae, and cyanobacteria in similar proportions. Alkaliphiles among the indicators of acidification and betamesosaprobionts among the indicators of saprobity prominently prevail in both regions. The indices of saprobity in lakes (1.48–2.7) and in pools (0.75–2.18) reflect a low-trophic loading. Oligohalobes-indifferents are most common in both arid regions. Cluster analysis based on data containing 420 species revealed 9 clusters, of which the highly diverse communities of low mineralized lakes and pools and the low diversity communities of highly-mineralized lakes and pools are separated at the highest dissimilarity level. CCA analysis revealed correlation of the algal species diversity preferences with salinity level in lakes in Kazakhstan and in pools of Israel, which are more impacted by arid factors. These results point to mineralization being the most important variable defining the diversity levels irrespective of the type and location of reservoirs in the arid regions.
Lake Hévíz is the largest natural thermal lake of Europe, harboring special bacterial communities. The aim of the present study was to gain information about the distribution and species diversity of the sediment microbiota, with special focus on Actinobacteria, by using cultivation-based and -independent molecular methods. Samples from two depths were taken in two different locations in October 2007. 245 strains were isolated, grouped to 85 OTUs by ARDRA, and identified by 16S rDNA sequencing. Most of the strains showed highest sequence similarity with Bacillus and related genera. Strains belonging to the phylum Actinobacteria were identified as members of Arthrobacter, Brachybacterium, Brevibacterium, Curtobacterium, Friedmanniella, Gordonia, Kocuria, Microbacterium, Micrococcus, Micromonospora, Mycobacterium, Rhodococcus, Streptomyces and Williamsia . Two clone libraries were constructed from H3M and H4M samples, providing 288 and 192 clones which were grouped to 150 and 125 OTUs, respectively, by ARDRA. The two most abundant group of the H4M library were OP8-related. The phylum Proteobacteria was represented mostly by δ -Proteobacteria, other relevant groups were Cyanobacteria, Bacteroidetes, Acidobacteria and β -Proteobacteria. The H3M library was dominated by Cyanobacteria, Verrucomicrobia, β -Proteobacteria, γ -Proteobacteria and δ -Proteobacteria. Chloroflexi, Bacteroidetes, Spirochetes and Firmicutes were scarce. Results from the clone libraries were compared to the length-heterogeneity-PCR fingerprints of the communities.
Different components of biodiversity may vary differently since species diversity was considered to be determined by resource availability but functional diversity was related to partitioning of niche space. Moreover, the harsh or benign conditions may result in different niche space partitioning by the coexisting species. For example, in harsh environments niche differentiation may be stronger resulting in higher functional diversity. In this study, we investigate species diversity and functional diversity along a south-to north-facing slope gradient with different resource availability in a sub-alpine meadow. Our results indicate that the patterns of species diversity and functional diversity are not consistent along this gradient. Both species richness and Shannon index of diversity increased, but functional diversity slightly decreased or changed a little from south-to north-facing slope. Moreover, these two components formed a quadratic relationship. Soil water content (SWC) was the limiting resource along this gradient. On one hand, it determined the species diversity; on the other hand, it also influenced functional diversity via affecting niche differentiation and species trait pool. In conclusion, functional diversity was determined by both species richness and niche differentiation with the influence of soil water content.
The identification of the drivers of diversity in understorey plant assemblages is a major challenge in forest ecology. However, it is not yet fully understood whether the same factors consistently affect different facets of species organization, such as species richness, composition and turnover. Here, we compare the influence of fine-scale environmental variables and spatial organization on the herb-layer flora of two unmanaged and ecologically different forest stands in the Muniellos Biosphere Reserve, Northern Spain. The aims of our study are to identify the most important factors influencing different facets of herb-layer plant organization, and to test whether the effect of such drivers is consistent across facets and forest types. We used Generalized Linear Models, Redundancy Analysis and Multiple Regression on Distance Matrices to model, respectively, the response of species richness, species composition and species turnover to spatial distances as well as to several environmental factors, including forest structure, light conditions, soil and topographical features. We observed a substantial consistency among variables affecting the different facets of ground-layer species organization within stands, with a subset of topographical variables with a transversal effect across facets. Although potential solar radiation was the main variable influencing species richness in the two stands, the factors shaping species composition and turnover varied across forest types: in the beech stand, slope and canopy openness were the main determinants of herb-layer species diversity and turnover; in the oak stand, the main drivers of species composition were related to topography and spatial structure, while spatial distance was the main driver of species turnover. Our study shows that the ecological processes driving fine-scale variation of ground-layer plant richness and composition are similar to those driving species turnover. Although the ecological factors shaping different facets may be the same, we highlight that, at least in temperate forests, these factors are system-specific and vary according to forest types.
Monthly changes in species diversity of aquatic macrophytes (richness and Simpson’s diversity index) were studied in relation to various limnological predictors (including their time lag effects) of two tropical ponds, over a period of three years, using regression analysis with correction for temporal autocorrelation.The monthly mean ± SD number of total plant species was 6±2 and 2±1 in Pond 203 and Pond 206, respectively, with significant pond effect. Immediate and 2-months lag of water temperature in the ‘species rich’ pond (Pond 203) appeared to be the significant predictors for Simpson’s diversity index and total plant species richness, respectively. Secchi depth (1-month lag) was found to be the significant predictor for Simpson’s diversity index in ‘less species rich’ pond (Pond 206), while total plant species richness was not found to be influenced by any limnological predictor. Comparative literature review on maximum number of plant species per pond revealed low richness in tropical and subtropical ponds than their temperate counterparts. Among different growth forms, maximum number of emergent and submerged plant species per pond was also less in tropical climates.
