bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of plot size on the ordination of vegetation samples
Authors: Otypková Zdenká , Chytry Milan 
Published: February 2009

AbstractQuestions: Do ordination patterns differ when based on vegetation samples recorded in plots of different size? If so, how large is the effect of plot size relative to the effects of data set heterogeneity and of using presence/absence or cover‐abundance data? Can we combine plots of different size in a single ordination?Methods: Two homogeneous and two heterogeneous data sets were sampled in Czech forests and grasslands. Cover‐abundances of plant species were recorded in series of five or six nested quadrats of increasing size (forest 49‐961 m2; grassland 1‐49 m2). Separate ordinations were computed for plots of each size for each data set, using either species presences/absences or cover‐abundances recorded on an ordinal scale. Ordination patterns were compared with Procrustean analysis. Also, ordinations of data sets jointly containing plots of different size were calculated; effects of plot size were evaluated using a Monte Carlo test in constrained ordination.Results: The results were consistent between forest and grassland data sets. In homogeneous data sets, the effect of presence/absence vs. cover‐abundance was similar to, or larger than, the effect of plot size; for presence/absence data the differences between ordinations of differently sized plots were smaller than for cover‐abundance data. In heterogeneous data sets, the effect of plot size was larger than the effect of presence‐absence vs. cover‐abundance. The plots of smaller size (= 100 m2 in forests, = 4 m2 in grasslands) yielded the most deviating ordination patterns. Joint ordinations of differently sized plots mostly did not yield patterns that would be artifacts of different plot size, except for plots from the homogeneous data sets that differed in size by a factor of four or higher.Conclusions: Variation in plot size does influence ordination patterns. Smaller plots tend to produce less stable ordination patterns, especially in data sets with low ß‐diversity and species cover‐abundances. Data sets containing samples from plots of different sizes can be used for ordination if they represent vegetation with large ß‐diversity. However, if data sets are homogeneous, i.e. with low ß‐diversity, the differences in plot sizes should not be very large, in order to avoid the danger of plot size differences distorting the real vegetation differentiation in ordination patterns.
Competitive effects of herbaceous vegetation on tree seedling emergence, growth and survival: Does gap size matter?
Authors: Vandenberghe Charlotte , Freléchoux François , Gadallah Fawziah , Buttler Alexandre 
Published: February 2009

AbstractQuestion: What is the effect of gap size on the seedling emergence, growth and survival of four common tree species in wooded pastures?Location: A pasture in the Jura mountains, Switzerland.Methods: Seeds were sown in a complete three‐way factorial design with eight blocks in May 2003. Each block consisted of a competition treatment (four gap sizes including zero) and a mowing treatment (mown and unmown). Emergence, survival and total biomass of tree seedlings of three species (Picea abies, Acer pseudoplatanus and Fagus sylvatica) were measured. A fourth species (Abies alba) failed to germinate.Results: Gaps had a positive influence on the early stages of tree development for all species. Larger gaps favoured growth and survival more than small gaps. Seedling growth was higher when vegetation around the openings was mown. Mowing the vegetation at gap size zero enhanced both growth and survival compared to unmown vegetation. Mown gaps larger than zero had increased seedling desiccation but decreased seedling predation. Species showed similar trends in their emergence and growth responses to gap size and mowing treatments but for Picea emergence rate was higher and survivorship was lower than for Acer and Fagus.Conclusions: Gap size does matter for tree seedling success but even in more favourable large gaps only a small percentage of seedlings emerged and survived. The effects of gaps on tree seedling establishment are complex as a result of interactions between biotic and abiotic changes caused by gaps.
Broad‐scale vegetation‐environment relationships in Eurasian high‐latitude areas
Authors: Virtanen Risto , Oksanen Jari , Oksanen Lauri , Razzhivin Vladimir Yu 
Published: February 2009

AbstractQuestion:How is tundra vegetation related to climatic, soil chemical, geological variables and grazing across a very large section of the Eurasian arctic area? We were particularly interested in broad‐scale vegetation‐environment relationships and how well do the patterns conform to climate‐vegetation schemes.Material and Methods:We sampled vegetation in 1132 plots from 16 sites from different parts of the Eurasian tundra. Clustering and ordination techniques were used for analysing compositional patterns. Vegetation‐environment relationships were analysed by fitting of environmental vectors and smooth surfaces onto non‐metric multidimensional scaling scattergrams.Results:Dominant vegetation differentiation was associated with a complex set of environmental variables. A general trend differentiated cold and continental areas from relatively warm and weakly continental areas, and several soil chemical and physical variables were associated with this broad‐scaled differentiation. Especially soil chemical variables related to soil acidity (pH, Ca) showed linear relationships with the dominant vegetation gradient. This was closely related to increasing cryoperturbation, decreasing precipitation and cooler conditions. Remarkable differences among relatively adjacent sites suggest that local factors such as geological properties and lemming grazing may strongly drive vegetation differentiation.Conclusions:Vegetation differentiation in tundra areas conforms to a major ecocline underlain by a complex set of environmental gradients, where precipitation, thermal conditions and soil chemical and physical processes are coupled. However, local factors such as bedrock conditions and lemming grazing may cause marked deviations from the general climate‐vegetation models. Overall, soil chemical factors (pH, Ca) turned out to have linear relationship with the broad‐scale differentiation of arctic vegetation.
Biodiversity and ecosystem functioning: It is time for dispersal experiments
Authors: Zobel Martin , Öpik Maarja , Moora Mari , Pärtel Meelis 
Published: February 2009

AbstractThe experimental study of the relationship between biodiversity and ecosystem function has mainly addressed the effect of species and number of functional groups. In theory, this approach has mainly focused on how extinction affects function, whereas dispersal limitation of ecosystem function has been rarely discussed. A handful of seed introduction experiments, as well as numerous observations of the effects of long‐distance dispersal of alien species, indicate that ecosystem function may be strongly determined by dispersal limitation at the local, regional and/or global scales.We suggest that it is time to replace biodiversity manipulation experiments, based on random draw of species, with those addressing realistic scenarios of either extinction or dispersal. Experiments disentangling the dispersal limitation of ecosystem function should have to take into account the probability of arrival. The latter is defined as the probability that a propagule of a particular species will arrive at a particular community. Arrival probability depends on the dispersal ability and the number of propagules of a species, the distance a species needs to travel, and the permeability of the matrix landscape. Current databases, in particular those in northwestern and central Europe now enable robust estimation of arrival probability in plant communities.We suggest a general hypothesis claiming that dispersal limitation according to arrival probability will have ecosystem‐level effects different from those arising due to random arrival. This hypothesis may be rendered more region‐, landscape‐ or ecosystem‐specific by estimating arrival probabilities for different background conditions.
Is vegetation inside Carex sempervirens tussocks highly specific or an image of the surrounding vegetation?
Authors: Yu Fei‐Hai , Krüsi Bertil , Schütz Martin , Schneller Jakob , Wildi Otto 
Published: February 2009

AbstractQuestions: How do species diversity, frequency and composition in tussocks differ from those in similar sized plots outside tussocks? Does the extent of the differences depend on community types or environmental conditions?Location: A sub‐alpine grassland in the Swiss National Park.Methods: In each of the two communities (short grass and tall graminoid) differing in species composition, grazing intensity and soil nutrient availability, relevés were made in 40 pairs of small circular plots, with one plot located inside a randomly selected Carex sempervirens tussock and the other outside.Results: We found 92 vascular species, of which 46 had a frequency higher than 5%. Species richness (S), pooled cover, Shannon's diversity (H) and cumulative species number (CS) were higher outside than inside the C. sempervirens tussocks, but evenness (J) was lower. S, H and CS differed more in the tall graminoid community than in the short grass community. However, dissimilarity between the paired relevés inside and outside tussocks did not differ between the two communities. Of the 46 most frequent species, 12 were statistically more and only one less frequent outside than inside the tussocks. Vegetation inside and outside tussocks could be clearly distinguished in the ordination space.Conclusion: Vegetation inside C. sempervirens tussocks is different from that in the surrounding area and represents an impoverished but homogenized version of the surrounding vegetation. Although tussocks of C. sempervirens were systematically avoided by grazers, there is little evidence that tussocks facilitate the species growing inside them.
Specific leaf area as a superior predictor of changes in field layer abundance during forest succession
Authors: Dahlgren Johan P. , Eriksson Ove , Bolmgren Kjell , Strindell Magnus , Ehrlén Johan 
Published: February 2009

AbstractQuestion: How accurately can a suite of suggested functional traits predict plant species response to succession from semi‐open woodland to closed deciduous canopy forest?Location: Southeastern Sweden.Methods: Abundance of 46 field‐layer plant species in a temperate deciduous forest, measured as frequency of occupied plots, was estimated in 1961, 1970 and 2003. Abundance change over time across species was tested for correlations with functional traits and literature information on habitat preference.Results: Increase in abundance was positively correlated with specific leaf area (SLA), weakly negatively correlated with seed mass and not significantly correlated with plant height or start, peak and length of the flowering period. Change in abundance was correlated with the Ellenberg light indicator value, whereas no correlations were found with Ellenberg values for nitrogen, calcium and moisture, or forest preference according to the literature.Conclusions: SLA was a better predictor of how field layer plants responded to succession from semi‐open woodland to closed canopy forest than empirically‐derived measures of habitat preference. The same holds for SLA in relation to seed size, indicating that interactions in the established life‐cycle phase are more important than the recruitment phase for species response to succession.
The role of successional stage, vegetation type and soil disturbance in the invasion of the alien grass Cortaderia selloana
Authors: Domènech Roser , Vilà Montserrat 
Published: February 2009

AbstractQuestion: This paper studies the establishment and performance of Cortaderia selloana (Pampas grass), an alien South American ornamental species that is invading many parts of the world. We asked whether (1) early successional stages were the most susceptible to C. selloana invasion; (2) soil microdisturbances increased invasion at any point of succession, and (3) C. selloana invasion of later successional stages was modulated by vegetation typeLocation: Delta del Llobregat (Catalonia, NE Spain).Methods: We monitored survival and growth of transplanted C. selloana seedlings in disturbed and non‐disturbed plots throughout a successional gradient with an age range of < 1 to > 10 years in different vegetation types and within the area of influence of coexisting species with similar growth form.Results: Although seedling survival was extremely low in all treatments, our results revealed that early successional stages were not the most easily invaded since we found no significant differences in the percentage survival of C. selloana along the successional gradient. However, survival and seedling bio‐mass were enhanced by soil disturbance at any seral stage. This result suggested that inhibition ruled C. selloana invasion. Invasibility neither depended on the invaded vegetation type nor on the co‐existing species with similar growth form. Finally, C. selloana invasion was not enhanced by decreasing competition with Phragmites australis, a native coexisting species because survival rates after a year were not significantly different. However, Phragmites increased C. selloana leaf length probably due to shading.Conclusions: C. selloana recruitment appears to be positively affected by soil disturbance but it is independent of successional stage or vegetation type.
Flood‐deposited wood creates regeneration niches for riparian vegetation on a semi‐arid South African river
Authors: Pettit Neil E. , Naiman Robert J. 
Published: February 2009

AbstractQuestion: The formation of large woody debris (LWD) piles during floods has significant impacts on riparian succession through pioneering plants often establishing in association with wood. We assess the importance of LWD for seed regeneration of riparian plants after a century‐scale flood disturbance in a semi‐arid environment.Location: The Sabie River within Kruger National Park in the semi‐arid northeast of South Africa.Methods: Our approach was to quantify the riparian soil seed bank, to record the frequency of establishment of riparian plants in woody debris piles, and to conduct experimental out‐plantings of common riparian trees in plots with and without LWD.Results: We found the abundance and diversity of seedlings were higher in soils taken from wood piles than from open reference areas, and most seedlings were herbaceous species. Surveys indicated that numbers of seedlings recorded within woody debris were significantly greater than in open reference areas or within established vegetation. Seedling establishment in various cover‐types also varied for different riparian tree species. Experimental out‐planting of seedlings of two riparian tree species (Philenoptera violacea and Combretum erythrophyllum) revealed that, after 433 days, planted seedlings survived only in woody debris piles.Conclusion: LWD formed after a large flood creates heterogeneous patches that may influence post‐disturbance regeneration of riparian vegetation by providing a variety of environmental niches for seedlings establishment. We suspect that higher seedling survival in LWD is due to increased moisture (particularly in the dry season) and nutrients, and protection from seasonal flooding and herbivory.
Long‐term dynamics of the hemiparasiteRhinanthus angustifoliusand its relationship with vegetation structure
Authors: Ameloot Els , Verheyen Kris , Bakker Jan P. , De Vries Yzaak , Hermy Martin 
Published: February 2009

AbstractQuestions:1. How are the long‐term dynamics of the root hemiparasiteRhinanthus angustifoliusrelated to vegetation structure, grassland management and climate? 2. DoesR. angustifoliushave a long‐term impact on standing crop and community composition?Location: A formerly fertilized grassland, part of a larger brook valley system in the nature reserve ‘Drentsche Aa’, near Groningen, The Netherlands.Methods: Vegetation development has been monitored since 1973 in 54 permanent plots in nine management regimes without fertilizer application.Results: 1. The hemiparasite established when standing crop was less than 600 g.m−2and performed best under annual haymaking using machinery. Since its appearance, the population fluctuated stochastically, with two peaks. Coinciding collapses in six adjacent grasslands and comparison with an integrated climatic index suggest that the population collapses are induced by spring drought. 2. We did not find a relationship between total standing crop andR. angustifoliuscover. Cover of grasses was negatively related to the abundance of the hemiparasite in the same and the previous year. Forb cover tended to increase with the parasite.Conclusions:R. angustifoliusshows stochastic population fluctuations, mainly determined by spring drought, to which this species is probably highly vulnerable because of its parasitic and annual life style without a persistent seed bank. The hemiparasite also shows long‐term relationships with grass cover (negative) and forb cover (positive), but it seems to have no lasting impact on standing crop.
Relationship between soil nutrient availability and plant species richness in a tropical semi‐arid environment
Authors: Perroni‐Ventura Yareni , Montaña Carlos , García‐Oliva Felipe 
Published: February 2009

AbstractQuestion:What is the relationship between soil fertility and plant species richness in the ‘fertile islands’ occurring beneath two species of legume (Cercidium praecoxandProsopis laevigata)?Location:Tehuacán‐Cuicatlán region, central Mexico.Methods:Plant richness was measured in three micro‐environments (below canopies ofC. praecox, below canopies ofP. laevigataand in areas without canopies). The concentration of soil nutrients (C, N and P), C and N in the microbiota, and processes of ecosystem functioning (net C mineralization rate and N mineralization) were measured. The relationship between soil variables and plant richness were assessed with ANCOVAs.Results:Soil nutrients and species richness increases markedly under fertility islands. There were higher concentrations of C and N in the soil, faster rates of C mineralization, and higher species richness underP. laevigatacanopies. The relationship between soil fertility and species richness was always positive except for total N, ammonium and net C mineralization rate underC. praecox, and for available P underP. laevigata.Conclusions:The sign of the relationship between soil fertility and species richness varies according to the nutrient and the micro‐environment. Positive relationships could result from between species complementarity and facilitation. Negative relationships could be explained by a specific limitation threshold for some soil resources (P and N for plants and C for the soil microbiota) which eliminate the possibilities of between species complementarity and facilitation above that threshold. As in all observational studies, these relationships should be considered only correlational.
Within‐stand spatial structure and relation of boreal canopy and understorey vegetation
Authors: Kembel Steven W. , Dale Mark R.T. 
Published: February 2009

AbstractQuestion: How do spatial patterns and associations of canopy and understorey vegetation vary with spatial scale along a gradient of canopy composition in boreal mixed‐wood forests, from younger Aspen stands dominated by Populus tremuloides and P. balsamifera to older Mixed and Conifer stands dominated by Picea glauca? Do canopy evergreen conifers and broad‐leaved deciduous trees differ in their spatial relationships with understorey vegetation?Location: EMEND experimental site, Alberta, Canada. Methods: Canopy and understorey vegetation were sampled in 28 transects of 100 contiguous 0.5 m × 0.5 m quadrats in three forest stand types. Vegetation spatial patterns and relationships were analysed using wavelets.Results: Boreal mixed‐wood canopy and understorey vegetation are patchily distributed at a range of small spatial scales. The scale of canopy and understorey spatial patterns generally increased with increasing conifer presence in the canopy. Associations between canopy and understorey were highly variable among stand types, transects and spatial scales. Understorey vascular plant cover was generally positively associated with canopy deciduous tree cover and negatively associated with canopy conifer tree cover at spatial scales from 5–15 m. Understorey non‐vascular plant cover and community composition were more variable in their relationships with canopy cover, showing both positive and negative associations at a range of spatial scales.Conclusions: The spatial structure and relation of boreal mixed‐wood canopy and understorey vegetation varied with spatial scale. Differences in understorey spatial structure among stand types were consistent with a nucleation model of patch dynamics during succession in boreal mixed‐wood forests.
Effects of grazing intensity in grasslands of the Espinal of central Chile
Authors: del Pozo Alejandro , Ovalle Carlos , Casado Miguel A. , Acosta Belén , de Miguel José M. 
Published: February 2009

AbstractQuestion: How is grazing intensity associated with species and morpho‐functional traits (MFTs) composition, productivity and richness of annual dominated grasslands? Have native and exotic species similar associations to this gradient?Location: Anthropogenic grassland in the Espinal vegetation in the sub‐humid area of the mediterranean type climate region of Chile (35°58’ S, 72°17’ W).Methods: Data were obtained from a long‐term (eight years) experiment with six stocking rates (1 to 3.5 sheep/ha). Detrended Correspondence Analysis (DCA) and regression analysis were used to determinate the relationship between grazing intensity and biomass, richness, abundance and traits of the species.Results: The first DCA axis was related to grazing intensity and explained most of the floristic variation (69.3%); the abundance of some non‐native species, e.g. Vulpia megalura were highly correlated with this axis. In the DCA for MFTs the first axis explained 87% of the variance and was also related to grazing intensity; the abundance of small size plants and shallow roots increased with grazing intensity. The relative abundance of grasses and composites, but not of legumes, changed with stocking rate: as grazing intensity increased composites became the predominant species to the detriment of grasses. The above‐ground biomass measured in exclusion cages declined with increasing grazing pressure. The richness of exotic species was greater compared to native ones at low stocking rates, but they converge to similar values at higher stocking rates. However, the relative abundance of exotic species was greater than 75% in all stocking rates.Conclusions: Grazing intensification has large effects in the structure of grassland in central Chile. With grazing intensities greater than 1 sheep/ha species characteristics change; evolving in a few years (6–8) towards a similar community regardless of the stocking rate. The overgrazed community has more native than exotic species richness, possibly due to greater defence traits against herbivory of this group of species.