bluuebunny/crossref_metadata_2025_split huggingface dataset:
The role of the seed bank, seed rain and the timing of disturbance in gap regeneration
Authors: Pakeman R.J. , Small J.L. 
Published: February 2009

Abstract. Question: Does the degree and timing of disturbance contribute significantly to the pattern and process of regeneration in plant communities as a consequence of the availability and number of species of propagules present?Location: Acid grassland at 230 m a.s.l., eastern Scotland, UK.Methods : Plots were surface disturbed or had their soil profile inverted at monthly intervals at 12 dates during a year. Seed bank and seed rain were assessed at each treatment time. The effect of disturbance intensity and timing on the regenerating vegetation was assessed.Results: Removing the seed bank significantly slowed regeneration, as it contributed 43 % of developing cover after one year where it was present.At an individual seed level, seed in the seed rain had a much higher likelihood of contributing to the regenerating vegetation than a seed in the seed bank. Some species showed a reliance on the seed bank for regeneration, and hence there was a significant difference in the vegetation that developed between plots with the seed bank intact and those where it was removed. Winter disturbed plots (little seed rain) had slower rates of re‐vegetation than summer disturbed plots. Timing had little effect on species composition, though a significantly higher cover of perennial forb species developed on the winter disturbed plots.Conclusion: Removing the contribution of the seed bank had a greater effect on the composition of regenerating vegetation than the effect of seasonal variation on the seed rain.
Contrasting impacts of a native and an invasive exotic shrub on flood‐plain succession
Authors: Bellingham Peter J. , Peltzer Duane A. , Walker Lawrence R. 
Published: February 2009

Abstract. Question: How do Coriaria arborea, an N‐fixing native shrub, and Buddleja davidii, a non‐N‐fixing exotic shrub, affect N:P stoichiometry in plants and soils during early stages of primary succession on a flood‐plain?Location: Kowhai River Valley, northeast South Island, New Zealand.Methods: We measured soil and foliar nutrient concentrations, light levels, plant community composition and the above‐ground biomass of Coriaria and Buddleja in four successional stages: open, young, vigorous and mature.Results: Coriaria occurred at low density but dominated above‐ground biomass by the vigorous stage. Buddleja occurred at 5.3 ± 1.0 stems/m2 in the young stage and reached a maximum biomass of 520–535 g.m‐2 during the young and vigorous stages. Mineral soil N increased with above‐ground Coriaria biomass (r2= 0.45), but did not vary with Buddleja biomass. In contrast, soil P increased with Buddleja biomass (r2= 0.35), but not with Coriaria biomass. In early successional stages, 70–80% of the species present were exotic, but this declined to about 15% by the mature stage. Exotic plant species richness declined with increasing Coriaria biomass, but no other measures of diversity varied with either Coriaria or Buddleja biomass.Conclusion: These results demonstrate that Buddleja dominates early succession and accumulates P whereas Coriaria dominates later succession and accumulates N. A key ecosystem effect of the invasive exotic Buddleja is alteration of soil N:P stoichiometry.
Epiphytic macrolichen communities along regional gradients in northern Norway
Authors: Werth S. , Tømmervik H. , Elvebakk A. 
Published: February 2009

Abstract.Question:What are the relative influences of human impact, macroclimate, geographic location and habitat related environmental differences on species composition of boreal epiphytic macrolichen communities?Location:Troms county in northern Norway.Methods:Detrended Correspondence Analysis revealed the main gradient structure in lists of epiphytic macrolichen species from deciduous forests. By Canonical Correspondence Analysis with variance partitioning, the relative amount of variance in macrolichen species composition attributable to human impact, macroclimate, spatial context and environmental differences was quantified.Results:There was no significant effect of human impact on species composition of epiphytic macrolichens of deciduous forests. Macroclimate was the most important factor determining epiphytic macrolichen communities, which were also strongly influenced by ecological differences such as forest stand properties.Conclusions:Epiphytic macrolichen communities are determined by a macroclimatic gradient from the coastline to the interior of central north Norway. In marked contrast, the species composition of epiphytic macrolichen communities seems to be unaffected by human impact in the study area, where air pollution was marginal.
Prediction of plant cover from seed bank analysis in a semi‐arid plant community on gypsum
Authors: Olano J.M. , Caballero I. , Loidi J. , Escudero A. 
Published: February 2009

Abstract. Question: Does the seed bank filter annual plant composition and determine cover at the species level?Location: 510 m a.s.l., central Spain.Methods: Seven transects and 136 quadrats were established in a semi‐arid gypsum system. Seed bank samples were collected in each quadrat in September. The community was sampled the following April. For each quadrat we measured slope, microslope, landform, elevation, perennial cover and crust cover. Seed bank was estimated using the direct emergence method in glasshouse. Relationship among seed bank and annual community was assessed by Mantel correlations. Above‐ground cover for the five most abundant species was modelled with GLMs.Results: Seed bank density was the best predictor for annual community cover; perennial cover and landform were also included in the model. Species composition between September seed bank and April annual community cover was also highly related according to the Mantel test. This relationship was constant, even when the effect due to other abiotic (landform, microslope) or biotic (perennial cover, crust cover) parameters were partialled out. Microslope, elevation and seed bank density were the best parameters to predict spring cover of the five most abundant species.Conclusions: Above‐ground and below‐ground community compartments are strongly related in terms of abundance and species composition. This relationship is filtered by several environmental factors (e.g. perennial cover, landform, microslope) that exert a strong control at community and individual levels. Our results support the hypothesis that annual community performance is affected by seed bank pattern.
On hierarchical diversity decomposition
Authors: Ricotta Carlo 
Published: February 2009

Abstract. Question: According to Whittaker's proposal, ecologists have traditionally viewed β‐diversity as the ratio between γ‐diversity and average α‐diversity. More recently, an alternative way of partitioning diversity has been ‘rediscovered’for which β‐diversity is obtained as the difference between γ‐diversity and average α‐diversity. This additive way of partitioning diversity has rapidly become a very popular framework for hierarchical diversity decomposition at various spatial scales. The question for this study is: Can we highlight any relation between these two ways of partitioning diversity, or do these methods really capture different facets of spatial turnover in species composition?Methods: First the properties that a diversity measure should possess for enabling additive decomposition into α‐, β‐, and γ‐components are reviewed. Next, attention is drawn to the relationships between additive and multiplicative diversity decomposition.Results: It is shown that the additive model is closely related to its multiplicative counterpart through a simple logarithmic transformation.Conclusions: Contrary to the current assumption, both methods for partitioning diversity are not as different as they appear. Hence, the supposed superiority of additive diversity partition over multiplicative diversity decomposition is largely unjustified.
Tempo and mode of vegetation dynamics over 50 years in a New Zealand alpine cushion / tussock community
Authors: Mark Alan F. , Wilson J. Bastow 
Published: February 2009

Abstract. Question: What are the tempo and mode of long‐term succession and of demographic processes in an alpine community, especially: tenacity, transition patterns, predictions, growth of individual cushion plants, cyclic succession, spatial patterns? Location: A low‐alpine mixed cushion /turf /snow‐tussock / shrub community in southeastern New Zealand.Methods: The distribution of seven plant cover‐types was recorded at 1024 fixed points in an 8 m × 8 m plot at approximately decade intervals for 50 years. The diameters of eight Donatia novae‐zelandiae cushions were monitored.Results: The process was essentially first‐order Markovian. There was a change in transition frequencies about 1980. The tenacity of the two major cover types — cushion and turf — was high, but that of cushion decreased about 1980 as some of its area was taken over by turf. The original informal prediction of 1955 that the cushion/turf would increase proved to be correct, probably because of paludification of the site. A prediction of 1987 made from observed transitions that cushion would dominate over turf has proved untrue because of a change in the transition probabilities in the 1980s, of unknown cause. There is a ten‐fold range in diameter growth rates among the eight cushions measured, but the mean rate of 5.3 mm.a‐1 is similar to that reported from other alpine and arctic sites. As cushions aged, turf colonized their centres, and in two cases new cushions colonized into this turf: consistent with cyclic succession. The pattern of transitions was compatible with a general interpretation of cyclic succession, but not definitive.Conclusions: Change is slow in this alpine community, and tenacity high. The change in transition frequencies about 1980, the invasion of individual cushions, and the decrease in spatial autocorrelation all suggest that cushions established on the site as a result of the clearance of woody vegetation after 1400 AD. Paludification may be causing some loss of tussock grass. A tendency for the cushions to break up, and the shallow peat accumulated below them, may indicate that they are the first generation of cushions on the site. Though these cushions are breaking up, other cushions are establishing, and cushions will continue to be an important part of the vegetation dynamics which may be part of a cyclic succession.
Spatial pattern and neighbour effects onHelianthemum squamatumseedlings in a Mediterranean gypsum community
Authors: Escudero Adrián , Romão Roberto L. , de la Cruz Marcelino , Maestre Fernando T. 
Published: February 2009

AbstractQuestion:Do, in a semi‐arid gypsum environment, neighbours condition the spatial patterns of emergence, survival and height ofHelianthemum squamatumseedlings?Location:Vicinity of Chinchón, province of Madrid, Spain (40°11′N, 3° 35′W, 550 m a.s.l.)Methods:We evaluated the effects of neighbours on the survival and growth of naturally emergingHelianthemumseedlings in a semi‐arid area during a two‐year period. We followed a two‐fold approach based on the use of neighbour models for seedling survival and growth and spatial point pattern analyses for seedling emergence, taking into account the germination date.Results:Seedlings appeared clumped in the vicinity of matureHelianthemumindividuals. The neighbour models fitted showed that interactions with neighbours were extremely important for the survival and growth ofHelianthemumseedlings. These models also suggest that the effects of neighbours on these variables vary with changes in spatial scale and in the abiotic conditions. Some species exerted negative or positive effects onHelianthemumseedlings only at certain spatial scales, and others exerted negative or positive effects at earlier stages of seedling development, but none later andvice versa.Conclusions:We suggest that the observed patterns are mainly influenced by small‐scale modifications in soil conditions and microclimate created by neighbours, which change in time and space.
Disturbance history of a European old‐growth mixed‐species forest—A spatial dendro‐ecological analysis
Authors: Splechtna Bernhard E. , Gratzer Georg , Black Bryan A. 
Published: February 2009

AbstractQuestion:We were interested if and how variation in frequency and/or size of disturbances affect the dynamics of a montane old‐growth forest in Central Europe.Location:The forest, co‐dominated by Fagus sylvatica, Picea abies and Abies alba, is located in Lower Austria and represents one of the few sizable virgin forests in Central Europe.Methods:We extracted cores from 100 trees using systematic grid sampling (grid cell size 10 m × 10 m) on each of four 1‐ha plots distributed across the old‐growth remnant of 300 ha. We inferred disturbance events from rapid early growth and release events. For defining release criteria, we applied the boundary line method. We investigated the spatial structure of current age and gap distributions and past disturbance events in grid cells, using a pair density statistic.Results:The disturbance histories indicate decades with peaks and also extended periods without disturbance. Some peaks occurred synchronously at three of the four plots (1910s, 1930s, 1960s and 1980s). Peaks and gaps in the disturbance chronologies widely agreed with peaks and gaps in the age distributions. Most disturbance events during single decades showed a random spatial distribution.Conclusions:There is considerable variation in disturbance frequency and/or severity over time. Most disturbance events will rather thin the stand than clear larger areas at once. Following scattered disturbance two pathways occur: (1) gap expansion leading to creation of larger gaps, and (2) gap closure by lateral encroachment or by subcanopy trees growing into the canopy.
Is seed dormancy under environmental control or bound to plant traits?
Authors: Jurado Enrique , Flores Joel 
Published: February 2009

AbstractQuestions:Is dormancy selected as a means by which a seed defers germination until suitable environmental conditions occur? Are plant species in frost‐free and drought‐free environments less likely to have some form of dormancy than species from environments with frost and/or drought? Are there any relationships between dormancy and three important plant traits: seed size, plant longevity, and growth form?Methods:Data from the literature including 3164 species were compiled. We quantified the relationship between dormancy and seed size (1795 species), plant longevity (183 species), and growth form (3164 species).Results:Plant species of environments with frost and/or drought were more likely to possess some form of seed dormancy (morphological, physiological, morphophysiological, or physical) than species in more benign environments. Seeds exhibiting some form of dormancy were lighter in weight and generally more prevalent among herbaceous species. Woody plants had a larger proportion of non‐dormant seeds. There was a broad overlap in seed size between species with dormant and non‐dormant seeds. We also found no significant relationship between seed dormancy and plant longevity.
Spatial relationships between tree species and gap characteristics in broad‐leaved deciduous woodland
Authors: Koukoulas Sotirios , Blackburn George Alan 
Published: February 2009

AbstractQuestions:1. What are the spatial patterns of all trees, individual tree species, trees within particular height classes, all gaps and gaps with specific properties across the study site in broad‐leaved deciduous forest at a range of scales? 2. Are patterns of the above features spatially associated? 3. Are these patterns indicative of gap creation mechanisms and phases of regeneration?Location:Frame Wood, New Forest, UK.Methods:Ripley'sK‐function analysis was applied to spatial information derived from airborne remotely sensed imagery to characterize the patterns of trees and gaps and to test for spatial interactions between these patterns. The patterns of trees and gaps with specific physical and spatial properties were analysed.Results:The pattern of all tree species combined was random for most scales;Quercus roburfollowed the same random pattern, whileFagus sylvaticaandBetula pendulawere clustered over most spatial scales. Large gaps (> 250 m2) and larger trees (> 17.5 m) were randomly distributed, while smaller gaps and smaller trees were clustered. Significant spatial relationships were demonstrated between the patterns of different tree species and between trees within different size classes, as well as between the patterns of trees and gaps with specific properties.Conclusions:Small gap patterns and field evidence indicated that progressive gap enlargement is the most likely creation mechanism for large gaps (> 250 m2). Clustered patterns of younger individuals were indicative of patches of past regeneration. As a complement to field‐based data, data derived from remotely sensed imagery provides spatially comprehensive information with which to further investigate woodland stand/community processes and gap dynamics.
Is there limiting similarity in the phenology of fleshy fruits?
Authors: Burns K.C. 
Published: February 2009

AbstractQuestion:Is there evidence for limiting similarity in the timing of fruit production by a bird‐dispersed plant community? Is the rate of fruit removal in each plant species inversely related to fruit availability in other species? Can simple measurements of fruit phenologies (i.e. temporal changes in fruit availability) obscure important fruit attributes that influence their removal by birds?Location:Vancouver Island, British Columbia, Canada.Methods:Periods of fruit availability were measured in ten woody angiosperm species for two years. In the second year, the fate of individual fruits was quantified to disentangle dates of fruit maturation, removal and mortality from measurements of availability.Results:Null model analyses of fruit availability distributions showed no evidence for limiting similarity. However, fruit removal rates of most plant species were correlated with their relative abundance in the community, indicating fruits were removed more rapidly when other fruits were less abundant. Species with similar periods of fruit availability often had different dates of fruit maturation, rates of fruit removal and fruit persistence times, indicating fruit availability measurements can obscure important bird‐fruit interactions.Conclusions:Competition for dispersers appears to occur. However, it has not resulted in limiting similarity in fruit availability distributions. A likely explanation for this discrepancy is that fruit availability distributions often confound several important fruit attributes that can independently influence fruit removal by birds.
Effects of fire severity and initial tree composition on understorey vegetation dynamics in a boreal landscape inferred from chronosequence and paleoecological data
Authors: Lecomte Nicolas , Simard Martin , Bergeron Yves , Larouche Alayn , Asnong Hans , Richard Pierre J.H. 
Published: February 2009

AbstractQuestion and Location:How does soil burn severity and early post‐fire tree composition affect long‐term understorey vegetation dynamics in the coniferous forests of eastern Canada?Method:Vegetation dynamics were assessed using paleoecological methods and a chronosequence analysis of extant stands. The relation between environmental factors and succession was evaluated using ordination techniques on the chronosequence data. Understorey succession was studied by regression analysis on the chronosequence data and through within‐site Markovian transition probabilities between successive 1‐cm layers of plant macroremains from soil organic matter profiles.Results:Initial tree composition (Picea mariana and Pinus banksiana) had little effect on understorey composition. Soil burn severity (measured as the thickness of the residual forest floor humus) significantly affected temporal changes in understorey species. Following fires of high severity, stands underwent a gradual paludification with a net increase in Sphagnum and ericaceous shrubs (Ledum groenlandicum), and a decrease in feathermosses. Paludification was accelerated after low severity fires, which led to the dominance of Sphagnum less than 200 years after fire, and of L. groenlandicum shortly after fire. In situ paleo‐ecological work confirmed results obtained with the chronosequence analysis.Conclusions:One vegetation gradient related to time after disturbance is insufficient to account for the full complexity of long‐term changes in understorey composition following fire. Current forestry practices that protect the forest floor humus may induce a premature paludification.
Vegetation change shows generic features of non‐linear dynamics
Authors: Gassmann Fritz , Klötzli Frank , Walther Gian‐Reto 
Published: February 2009

AbstractQuestion:In non‐linear physical, or chemical, systems dynamic instability limits predictability and external fluctuations cause interesting, and sometimes counter intuitive, effects. We ask how these generic properties of complex systems are seen in vegetation change.Methods:An interacting particle system is used to simulate possible developments of a plant community that was observed for 30 years on a test area in the Lüneburger Heide (Germany). We investigate simulated trajectories for five plant types over several decades. The internal updating rule, simulating the interactions between the five plant types, is completely deterministic, the only sources of stochasticity being the initial conditions and the external climatic variations.Results:Though the results of our simulation model share many aspects with those of stochastic models with probabilistic transition matrices, the solution manifold of our non‐linear model goes beyond the possibilities of stochastic models. Among many stable developments, chaotic trajectories were also found. Climatic fluctuations increased the frequency of certain plant types. These properties of vegetation dynamics match the long‐term field observations. They reflect generic features of complex systems.Conclusions:The presented non‐linear model can provide insights into the dynamics of vegetation change, even though the mechanisms observed in the real world are modelled only in a rather general way. The rich behavioural repertoire, resulting from deterministic internal dynamics, can simulate observed properties that are beyond the possibilities of models with probabilistic internal dynamics.