bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stress tolerance abilities and competitive responses in a watering and fertilization field experiment
Authors: Liancourt P. , Corcket E. , Michalet R. 
Published: February 2009

AbstractQuestion:Do water gradients produce patterns of responses to stress and competition similar to those induced by nutrient gradients?Location:French Alps.Methods:We established a split‐plot design in a calcareous grassland, with watering and fertilization as main plot treatments and competition as subplot treatment. We followed individual and competitive responses of transplants of the three potential dominant grass species: Bromus erectus, Brachypodium rupestre and Arrhenatherum elatius, in all plots during two growing seasons. Changes in natural relative abundances of the three grass species were also monitored.Results:The growth and the relative abundance of A. elatius were primarily stimulated by nutrient addition and those of B. rupestre by water addition, whereas B. erectus decreased in abundance and had a very low flexibility with enhanced resource supply. Competition intensity increased for all species with both watering and fertilization and the ranking in competitive responses did not change with treatments: A. elatius > B. rupestre > B. erectus.Conclusions:Patterns of dominance were efficiently explained by stress tolerance abilities and competitive responses for dry and poor sites, and wet and rich sites for B. erectus and A. elatius respectively, whereas competitive responses were poor predictors of dominance for B. rupestre in wet and nutrient‐poor sites. Further studies are needed to assess the potential role of other processes, such as increasing competitive effect on light with increasing age as well as interference, to explain the dominance of this conservative competitor type of species in wet and nutrient‐poor sites.
The fate of seeds in Mediterranean soil seed banks in relation to their traits
Authors: Traba Juan , Azcárate Francisco M. , Peco Begoña 
Published: February 2009

AbstractQuestion:Is there any change in seed density and species richness in Mediterranean surface soil banks during summer? Are there any relationships between these summer variations and seed traits (weight, length and shape), without and with controlling the phylogenetic effect?Location:Central Spain.Methods:Samples of the surface soil seed bank were collected in two Mediterranean systems, grassland and scrubland, at two points in the year: immediately after the summer production peak and immediately prior to the autumn germination peak. We used Canonical Correspondence Analysis ordination to check for changes in floristic composition and ANOVAs to check for changes in seed density and species richness between summer and autumn samples. We used multiple regression analysis to analyse the relationship between summer variations in soil seed density and form traits, with and without controlling phylogenetic relations.Results:Soil seed density dropped significantly during the summer in the two systems (28% in grasslands, repeated measures ANOVA test;F= 58.19,P< 0.01; 72% in scrublands, repeated measures ANOVA test;F= 75.67,P< 0.001). Species richness, however, only dropped significantly in the scrubland (32%; repeated measures ANOVA test;F= 9.17,P< 0.05). Variation in the floristic composition of the shallow banks was only significant in the scrubland.Changes in shallow bank density were related significantly to seed morphology features, with greater drops in species with heavier seeds in grasslands and species with longer seeds in scrubland.Conclusions:Our results show a substantial loss of seeds in the uppermost soil layer during the summer period between the point of peak production and the autumn germination peak. This drop was clearer in the scrubland than in the grassland. Longer and/or heavier seeds underwent the greatest declines in density at the end of summer, indicating a more intense effect of post‐dispersal predation on large‐seeded species.
Effects of altitude and topography on species richness of vascular plants, bryophytes and lichens in alpine communities
Authors: Bruun Hans Henrik , Moen Jon , Virtanen Risto , Grytnes John‐Arvid , Oksanen Lauri , Angerbjörn Anders 
Published: February 2009

AbstractQuestion:What is the relationship between species richness of vascular plants, bryophytes and macrolichens, and two important gradients in the alpine environment, altitude and local topography?Location:Northernmost Fennoscandia, 250–1525 m a.s.l. corresponding to the range between timberline and mountain top.Methods:The vegetation was sampled in six mountain areas. For each 25 vertical metres, the local topographic gradient from wind‐blown ridge to snowbed was sampled in quadrats of 0.8 m × 0.8 m. Patterns in species richness were explored using Poisson regression (Generalized Linear Models). Functional groups of species, i.e. evergreen and deciduous dwarf‐shrubs, forbs, graminoids, mosses, hepatics and lichens were investigated separately.Results:Functional groups showed markedly different patterns with respect to both altitude and topography. Species richness of all vascular plants showed a unimodal relationship with altitude. The same was true for graminoids, forbs and lichens analysed separately, but forb richness peaked at much higher altitudes than total richness. The richness of dwarf‐shrubs decreased monotonically with altitude, whereas richness of mosses and liverworts showed an increasing trend. Significant interactions between altitude and local topography were present for several groups. The unimodal pattern for total plant species richness was interpreted in terms of local productivity, physical disturbance, trophic interactions, and in terms of species pool effects.Conclusions:Patterns in local species richness result from the action of two opposing forces: declining species pool and decreasing intensity of competition with altitude.
A long‐term study of neighbour‐regulated demography during a decline in forest species diversity
Authors: Yi‐ching Lin , Augspurger Carol K. 
Published: February 2009

AbstractQuestion:Did disturbance, no density‐dependence of the dominant species, and negative neighbourhood interactions on rare species affect tree demography during a decline in species diversity associated with the increase ofAcer saccharumfrom 1939–2001?Hypotheses:1. The rise in dominance ofA. saccharumwas because of its advantage in disturbances and lack of density‐dependence of its demography. 2. Rare species were not favoured by disturbances, including those from Dutch elm disease, and demonstrated negative neighbourhood interactions withA. saccharum.Location:Brownfield Woods in Illinois, USA.Methods:Historical maps of trees (≥ 7.6 cm DBH) from 1939, 1951, 1988, and 2001 in 16 quadrats (48 m × 68 m) were used to compare demography of eight tree species. Effects of disturbances, density‐dependence, and neighbourhood interactions on mortality and recruitment of tree species within a 6‐m radius of individual target trees were studied.Results:A. saccharumdemonstrated a demographic advantage over rare species. It had lower mortality and higher recruitment rates. Disturbances facilitated recruitment ofA. saccharum, but did not enhance rare species. Density‐dependence of both mortality and recruitment ofA. saccharumoccurred, but population projection models indicated that ecological conditions became more favourable forA. saccharumin the past 62 years. Furthermore, negative neighbourhood interactions were detected between rare species andA. saccharum. The increase in neighbouringA. saccharumsignificantly increased mortality and reduced recruitment of the rare species.Conclusions:The general disturbance regime, enhanced by Dutch elm disease, in Brownfield Woods facilitated the rise of dominance ofA. saccharum. Meanwhile, rare species declined as a result of their disadvantage in disturbance and negative neighbourhood interactions withA. saccharum.
Tree rings show competition dynamics in abandoned Castanea sativa coppices after land‐use changes
Authors: Fonti Patrick , Cherubini Paolo , Rigling Andreas , Weber Pascale , Biging Gregory 
Published: February 2009

AbstractQuestions:As a consequence of socio‐economic changes, many Castanea sativa coppices have been abandoned and are now developing past their usual rotation length. Do we have to expect changes in stand structure and composition of abandoned Castanea sativa coppice invaded by other species? Is a tree ring‐based approach adequate to early recognise changes in inter‐specific competitive interaction?Location:Lowest alpine forest belt of the southern Swiss Alps.Methods:We selected a 60‐year old abandoned Castanea sativa coppice stand with sporadic Fagus sylvatica and Quercus cerris mixed in. Using tree‐ring based indices we analysed differences in the species‐specific response to competition. Analyses were performed by comparing how subject dominant trees (10 Castanea, 5 Fagus, 5 Quercus) have differently faced competition from their immediate Castanea coppice neighbourhood, taking into account the changes over time and space.Results:Although no species appears yet to have made a difference in the surrounding coppice mortality, there are species‐specific differences in growth dominance, which indicate potential successional processes. Castanea sativa growth dominated in the early stages of stand development. However, after approximately 30–35 yr Fagus sylvatica and Quercus cerris became much more dominant, indicating a change in competitive potential that does not favour Castanea sativa.Conclusions:Without interventions this coppice will develop into a mixed stand. A tree‐ring based approach allows an early recognition of forthcoming changes in stand composition and structure and is likely to be an important tool for forest landscape management.
Restoration of lichen diversity in grass‐dominated vegetation of coastal dunes after wildfire
Authors: Ketner‐Oostra R. , van der Peijl M.J. , Sýkora K.V. 
Published: February 2009

AbstractQuestion:Can lichen diversity of an earlier succession stage be restored in dune grassland after fire in a region with high nitrogen deposition?Location:Calcium‐poor coastal dunes in the Wadden district, The Netherlands.Methods:We sampled dune grassland by using a large continuous transect of 4 m × 4 m blocks on both a south slope and a west slope. The sampling was conducted in the lichen‐rich Violo‐Corynephoretum in 1966, in the vegetation dominated by tall graminoids in 1990 and in the recovering vegetation for eight years after a wildfire in 1993. Vegetation succession in the blocks is visualised in stacked bar graphs and ordination diagrams (DC A). In 1966 relevés were made within the blocks, and from 1990 until 2001 permanent quadrats were studied.Results:Between 1966 and 1990 the lichen‐rich open grassland became dominated by tall graminoids and developed partly into a dwarf‐shrub heath, resulting in a severe loss of lichen diversity. After the fire a lush vegetation of tall graminoids with an abundant moss cover developed. In 2001 the vegetation was still very different from the lichen‐rich vegetation in 1966.Conclusions:Fire alone will not change dunes dominated by tall graminoids into open lichen‐rich grasslands in an area with high aerial nitrogen deposition. After fire, additional intervention is recommended, such as large‐scale clearing of the burned vegetation and actively promoting deposition of sand, either blown in from foredunes, from re‐activated blow‐outs or artificially brought to the site.
Variables influencing the distribution of epiphytic lichens in heterogeneous areas: A case study for Liguria, NW Italy
Authors: Giordani Paolo 
Published: February 2009

AbstractQuestions:What are the most relevant environmental variables influencing the distribution and the species richness of epiphytic lichens in heterogeneous areas of the Mediterranean region? What is the relative importance of substrate‐ vs. environmental‐related variables? How do climatic and disturbance factors interact?Location:The study was carried out in the Liguria region (northwestern Italy). This is a complex region where steep environmental gradients occur over a few kilometres of longitude and latitude.Methods:Data on lichen species frequencies, collected on the basis of stratified random sampling, were analyzed using non‐metric multidimensional scaling (NMS) and DCA. Indicator Value Analysis (IVA) analysis was used to find indicator species for the environmental predictors.Results:In the survey area, epiphytic lichen distribution depends on both substrate‐ and environment‐related factors. Climatic variables (in particular average yearly temperature and rainfall), anthropogenic pressures (particularly harvesting and atmospheric pollution), bark pH and texture were associated with the main axes of variability in the dataset. Mean annual rainfall is the best predictor for epiphytic lichen richness in the survey area. The particular effects of the Mediterranean region (e.g. the influence of forest fires) and of heterogeneous areas (the variability of diversity in relation to habitat) were pointed out. Several indicator species, closely linked to particular ecological conditions, were found for both substrate‐and environment‐related variables.Conclusions:The main variables involved seemed to be the same reported for other areas, but their relative importance and their spatial scale of action were in some cases different, probably due to the geomorphological and climatic heterogeneity of the survey area. The significant influence of climatic predictors and disturbance factors on epiphytic lichens was confirmed, suggesting that these organisms may be used successfully to describe ecological trends in natural environments, also providing practical information at ecosystem level.
The influence of carbon—nutrient balance on herb and woody plant abundance in temperate forest understories
Authors: Graves James H. , Peet Robert K. , White Peter S. 
Published: February 2009

AbstractQuestion:We present a general structural carbon—nutrient balance hypothesis parallel to Bryant et al.'s defensive chemistry hypothesis. Our hypothesis suggests that because herb species require a lower investment of carbon per unit length of stem than do woody plants, herbs should be at a competitive advantage where the leaf area of plants in the ground layer is limited by light (or fixed carbon, C) rather than soil resources (R) such as nutrients or water. We test the derivative predictions that in temperate deciduous forests (1) herb cover and species richness increase as soil resources increase, and (2) woody ground‐layer cover, density, and species richness increase as soil resources decrease.Location:To maximize generality, the eight temperate deciduous forest sites were dispersed along an 800 km band from the Coastal Plain of eastern North Carolina to the Central Basin of middle Tennessee, USA.Methods:Soil nutrients and moisture, herb cover and woody stem densities were observed in six plots at each site, randomly located in high, medium, and low herb cover areas. Multiple regression, correlation, and Redundancy Analysis ordination were used to test predictions.Results:Plants with herbaceous (low C:R) stems are generally abundant where soil moisture and basic cations (Ca, Mg) are high (low C:R environments), and woody (high C:R) plant cover, basal area, stem density, and species richness are all greatest on dry or nutrient‐poor soils (high C:R environments). Plots with intermediate soil resource availability and herb cover have the most species, and maximum herb species richness occurs at higher soil resource levels than maximum woody species richness.Conclusions:Our observations are consistent with our structural carbon—nutrient balance hypothesis.
Sample size and the detection of a hump‐shaped relationship between biomass and species richness in Mediterranean wetlands
Authors: Espinar J.L. 
Published: February 2009

AbstractQuestions:What is the observed relationship between biomass and species richness across both spatial and temporal scales in communities of submerged annual macrophytes? Does the number of plots sampled affect detection of hump‐shaped pattern?Location:Doñana National Park, southwestern Spain.Methods:A total of 102 plots were sampled during four hydrological cycles. In each hydrological cycle, the plots were distributed randomly along an environmental flooding gradient in three contrasted microhabitats located in the transition zone just below the upper marsh. In each plot (0.5 m × 0.5 m), plant density and above‐ and below‐ground biomass of submerged vegetation were measured. The hump‐shaped model was tested by using a generalized linear model (GLM). A bootstrap procedure was used to test the effect of the number of plots on the ability to detect hump‐shaped patterns.Result:The area exhibited low species density with a range of 1—9 species and low values of biomass with a range of 0.2 ‐87.6 g‐DW/0.25 m2. When data from all years and all microhabitats were combined, the relationships between biomass and species richness showed a hump‐shaped pattern. The number of plots was large enough to allow detection of the hump‐shaped pattern across microhabitats but it was too small to confirm the hump‐shaped pattern within each individual microhabitat.Conclusion:This study provides evidence of hump‐shaped patterns across microhabitats when GLM analysis is used. In communities of submerged annual macrophytes in Mediterranean wetlands, the highest species density occurs in intermediate values of biomass. The bootstrap procedure indicates that the number of plots affects the detection of hump‐shaped patterns.
Changes in the abundance, composition and species richness of mountain vegetation in relation to summer grazing by reindeer
Authors: Eskelinen Anu , Oksanen Jari 
Published: February 2009

AbstractQuestion:How do reduced levels of summer grazing by reindeer affect the abundance, composition and species richness of mountain plant communities?Location:Arctic‐alpine mountain vegetation 700–850 m a.s.l., Saana Conservation Area, northwestern Finnish Lapland.Methods:Permanent plots were established in 1990 and resampled in 1999 or 2001. The number of reindeer had considerably declined from the 1980s to the 1990s and we followed the recovery of vegetation. The comparisons between 1990 and 1999/2001 were made at seven sites differing in their original grazing pressure.Results:At the initially heavily grazed sites, lichen abundances increased, but at the lightly grazed sites the abundances of lichens decreased. Graminoids declined at all sites, but the change seemed to be greatest at the most heavily grazed sites. Forbs increased slightly across all sites. At the species level, lichens and graminoids responded most notably to the reduction of grazing pressure. Individual species responses in shrubs were variable and among forbs, typical species of species‐richDryasheaths increased. Total species richness increased at all sites and the change was greater at heavily grazed sites. This increase resulted mainly from increased bryophyte and lichen species richness but also from a slight increase in vascular plant species richness.Conclusions:These results suggest that lichens are the group most responsive to the reduction of heavy summer grazing by reindeer and that lichens and forbs typical in arctic‐alpineDryasheaths are favoured over graminoids under reduced grazing. Heavy grazing decreases overall species richness with the most pronounced effects on bryophyte and lichen species richness. The results support the hypothesis that heavy summer grazing may shift the composition of mountain plant communities towards that of grasslands and show how this shift may be reversed under reduced grazing.
Structure of biological soil crust communities inCallitris glaucophyllawoodlands of New South Wales, Australia
Authors: Thompson Wendy A. , Eldridge David J. , Bonser Stephen P. 
Published: February 2009

Abstract:Question:What is the nature of the relationships between cover, diversity and abundance of biological soil crusts, cover and diversity of vascular plants, and annual rainfall, soil texture and forestry practices inCallitris glaucophyllawoodlands? Location: Arid and semi‐aridCallitris glaucophylla‐domi‐nated woodlands of eastern Australia.Methods:We documented soil crust‐forming mosses, lichens and liverworts at 83 woodland sites along a gradient of declining rainfall. Linear and non‐linear regression were used to examine relationships between soil crust species and attributes of vascular plant communities, and a similarity matrix (species abundance X sites) was subjected to Non‐metric Multi‐Dimensional Scaling (MDS), and Analysis of Similarities (ANOSIM) to show the degree of association between groups of taxa, and soil texture, rainfall classes and forestry practices.Results: We collected 86 taxa. Mosses were dominated by the familyPottiaceae, and lichens were dominated by squamulose forms. Average annual rainfall was highly correlated with soil crust community composition, and loamy soils supported a greater cover and diversity of taxa compared with sandy soils. Increases in tree cover were associated with significant, though weak, increases in abundance, but not diversity, of crusts. Crusts tended to be more diverse in areas that (1) had a sparse cover of ground‐storey plants; (2) were relatively stable ‐ as indicated by the proportion of perennial and/or native plants; (3) had more stable soil surfaces; and (4) were unlogged. Litter cover, overstorey thinning, and livestock grazing had no appreciable effect on crust diversity or cover.Conclusions:Callitris glaucophyllawoodlands provide substantial habitat for soil crust organisms, and the dense tree cover and closed canopies ofCallitrisdo not appear to have a major influence on the structure of biological crust communities. Unlike other woodland systems, relatively few patches would be required to reserve a high diversity of crust species.
Variation in tree growth, mortality and recruitment among topographic positions in a warm temperate forest
Authors: Tsujino Riyou , Takafumi Hino , Agetsuma Naoki , Yumoto Takakazu 
Published: February 2009

Abstract:Questions: Do the population dynamics of trees differ among topographic positions and, if so, how does topographic position affect the population dynamics of species that are distributed in a topography‐specific manner? Which is the most important life stage in determining vegetation patterns?Location: Primary and secondary warm temperate evergreen broad‐leaved forest (40 ‐ 280 m a.s.l.) on the western part of Yakushima Island, Japan.Methods: Mortality, recruitment, DBH growth and distribution of stems (= 5 cm DBH) in a 2.62‐ha plot were surveyed in 1992 and 2002 to determine the relationships between population parameters and (1) topography and (2) distribution patterns of 17 common tree species.Results: Common species (n = 17) were classified into three distribution pattern groups: group A, distributed mainly on convex slopes; group B, on concave slopes, and group C, not aggregated with respect to topographic position. Stem mortality, recruitment and DBH growth were greater in group A than in group B within each topographic class. The hierarchy of stem mortality among topographic classes for groups A and B was convex > planar > concave. Stem recruitment density was relatively high on the convex and concave slopes, respectively, for groups A and B.Conclusions The topographical positions of adult trees were not always most suited for adult survival and growth. For group A, the distribution pattern of adults was determined in the juvenile stage, while this was not the case for group B. Studies of juvenile stages are important for understanding the demographic basis of vegetation distribution patterns.