bluuebunny/crossref_metadata_2025 huggingface dataset:
Variation in plant performance in a grassland: Species‐specific and neighbouring root mass effects
Authors: Herben Tomáš , Brezina Stanislav , Skálová Hana , Hadincová Vera , Krahulec František
Published: February 2009

Question: What characteristics of local biotic neighbourhood is the best proxy of competitive effects experienced by plants in a herbaceous community: (1) total above‐ground biomass, (2) root mass or (3) relative above‐ground abundance of selected species?

Location: Grassland at ca. 1100 m a.s.l. in the Krkonoše Mts., northern Czech Republic.

Methods: We implanted two phytometer species, Antho‐xanthum alpinum and Festuca rubra, into a mountain grassland, and examined their response to local variation in (1) total above‐ground biomass, (2) root mass at three soil depths, and (3) relative abundance of individual species above‐ground. Results: Performance of both phytometer species was determined much more consistently by the mass of neighbouring roots and by species composition of neighbours than by the total above‐ground biomass. The two phytometer species showed different responses to these parameters. The most important relationships were (1) negative relationship between performance of Anthoxanthum and mass of neighbouring roots at 0–3 cm, (2) positive relationship between performance of Festuca and mass of neighbouring roots at 3–6 cm, and (3) negative relationship between performance of Festuca and relative abundance of Festuca in the neighbourhood.

Conclusions: Neighbouring root mass and above‐ground species composition are better determinants of biotic interactions than total above‐ground biomass of neighbours in the studied mountain grassland. However, the relationships found are not necessarily due to variation in competitive intensity but can be due to other hidden factors as well, e.g. local availability of resources.
Invasion of woody species into temperate grasslands: Relationship with abiotic and biotic soil resource heterogeneity
Authors: Pärtel Meelis , Helm Aveliina
Published: February 2009

Question:Invasion of woody species into grasslands is a global phenomenon. This is also topical in semi‐natural temperate grasslands that are no longer profitable for agricultural management. Trees and grasses interact through harsh root competition, but below‐ground processes have been neglected in the dynamics of semi‐natural grasslands. Trees are thought to have a competitive advantage in resource‐rich and heterogeneous soils. We tested whether soil resource quantity and heterogeneity differ between paired temperate semi‐natural grasslands and forests (former grasslands), and whether this was caused abiotically by varying soil depth or biotically by fine roots.

Location:Thin‐soil calcareous alvar grasslands with overgrown parts (youngPinus sylvestrisforests) in W. Estonia.

Methods:The quantity and spatial heterogeneity of soil resources (moisture and nutrients), soil depth, and root parameters (mass, length and specific length) were measured in 1‐m transects of 11 samples in 26 paired grasslands and forests. The quantity and heterogeneity of soil resources were compared between vegetation types and related to soil depth and root parameters.

Results:Soil resources were lower and more heterogeneous in forests than in grasslands. The invasion of woody species was enhanced abiotically by deeper soil. Root mass was larger in the forests, but root length was longer in the grasslands. Both root mass and specific root length were more heterogeneous in the forests. Forest root length was negatively correlated with transient soil moisture patches and positively correlated with more persistent nutrient‐rich patches. No such relationship was found in grasslands.

Conclusions:Abiotic soil heterogeneity (local deep‐soil patches) supports woody species invasion, but the trees themselves also biotically make soils more heterogeneous, which further enhances woody species invasion. Large trees use soil resources patchily, making soils biotically poorer and more heterogeneous in resources. The dynamics of temperate semi‐natural grasslands are strongly linked to below‐ground ecological processes, and high soil heterogeneity can be both the cause and the outcome of woody species invasion.
Edge effects on epiphytic communities in a Mediterranean Quercus pyrenaica forest
Authors: Belinchón Rocío , Martínez I. , Escudero A. , Aragón G. , Valladares F.
Published: February 2009

Question: What are the edge effect responses of epiphytic lichen communities in Mediterranean Quercus pyrenaica forest?

Location: Central Spain.

Methods: We established ten transects perpendicular to a road dissecting a well conserved remnant of Q. pyrenaica forest into two sections. Transects extended from the forest/road edge to 100 m into the forest. Data were collected from seven plots in each transect at different distances from the edge. Variables were grouped into stand scale variables (distance to edge, number of trees per plot, mean diameter per plot, irradiance) and tree scale variables (diameter and height of sampled trees, aspect of the sampled square and relative height of the square). We used General Mixed Linear Models and constrained ordination techniques to test the hypothesis that the spatio‐temporal heterogeneity of light and water controls the occurrence of lichens and bryophytes along the edge‐interior gradient in the Q. pyrenaica forest.

Results: Microclimatic parameters vary in a non‐linear way; edge and interior stands showed the most divergent and extreme values. Although the micro‐environment within Mediterranean forests is heterogeneous, interior conditions are apparently suitable for the performance of some specific forest epiphytes. Consequently, species richness does not show significant differences along the gradient. Total epiphytic cover increases towards the forest interior, but distance to the edge together with other predictors at the tree scale (aspect and height of the square) are the most relevant predictors for the composition and structure of these communities.

Conclusions: Composition and structure of epiphytic communities in a Mediterranean semi‐deciduous forest are affected by the edge between the forest and the road constructed. Since some extremely rare lichens only occur at interior stands, the conservation of these threatened elements requires urgent conservation measures because well preserved and unmanaged forests in the Mediterranean region are very rare.
Harvester ants (Messor barbarus) as disturbance agents in Mediterranean grasslands
Authors: Azcárate Francisco M. , Peco Begoña
Published: February 2009

Questions:1. Do disturbances by harvester ants (Messor barbarusL.) affect soil properties? 2. Do they alter seed distribution? 3. Do they show a different species composition? 4 Are these changes related to seed size (length and weight)?

Location:Mediterranean grasslands in central Spain, near Madrid.

Methods:We recorded autumn seed banks and spring vegetation in middens, trunk trails and controls. Soil properties were also measured in middens and controls. The effect of seed weight and length was analysed after transforming data into phylogenetically independent contrasts.

Results:Soil under middens is more silty and higher in potassium, organic matter and pH. Seed density and seed bank species richness increased greatly in middens, while vegetation species richness was significantly lower in comparison to control samples. Abundance changes in this disturbance type were positively correlated with seed weight, both in seed bank and vegetation. In contrast, we only detected a slight increase in bare ground on foraging trunk trails, with no clear effects on seed bank and vegetation composition.

Conclusions:Midden development is a mechanism that generates heterogeneity which favours the survival of certain large‐seeded species mainly predated by ants in Mediterranean grasslands. This effect may partially neutralize the dominance of small seeded species expected from the seed predation process.
Post‐fire regeneration of Mediterranean plant communities at a regional scale is dependent on vegetation type and dryness
Authors: Arnan Xavier , Rodrigo Anselm , Retana Javier
Published: February 2009

Question: We tested whether (1) the change in composition and structure of whole plant communities after fire is directly related to regeneration of the dominant tree species in the canopy; (2) the change in structure and composition of plant communities several years after fire decreases with the proportion of obligate seeders and (3) the proportion of obligate seeders in plant communities increases with the dryness gradient.

Location: Catalonia (NE Spain)

Methods: We measured floristic differences between burned and long‐since burned sites in eight vegetation types across a climate gradient. We compared 22 sites burnt in 1994 in paired plots with 22 sites that had not been burnt since the 1940s. In each site we placed plots in burned and long‐since burned areas, where we identified the presence and abundance of all plant species.

Results: When the tree canopy recovers, structure and composition of the vegetation also return to the long‐since burned community; when tree canopy does not recover, composition of the post‐fire community varies compared to the long‐since burned one. A higher proportion of obligate seeders in the pre‐fire community promotes quicker regeneration of the original community. The proportion of obligate seeders increased along the dryness gradient.

Conclusions: Regeneration of plant communities after fire depends on the vegetation type before the fire. Regeneration increases when the dominant tree or shrub species persists after fire and with a higher proportion of obligate seeders in the pre‐fire community. The proportion of obligate seeders varies along the dryness gradient, which suggests that vegetation in drier areas (when seeders are more abundant) recovers earlier than in moister areas.
Flooded forests: Death by drowning, not herbivory
Authors: White T.C.R.
Published: February 2009

Abstract. Trees on small islands formed when a new hydroelectric dam was filled are said to have been killed by leaf‐cutter ants that were no longer regulated by their armadillo predators. This top‐down hypothesis is questioned and an alternative bottom‐up hypothesis is proposed: the trees died because their roots were flooded.
Seed bank diversity in mesic grasslands in relation to vegetation type, management and site conditions
Authors: Wellstein Camilla , Otte Annette , Waldhardt Rainer
Published: February 2009

Questions: 1. Do different management types (i.e. hay meadow, silage meadow, meadow‐pasture, pasture) have different impact on the size and composition of the seed bank of mesic grassland (Arrhenatheretalia)? 2. How strong is the effect of management on the seed bank in relation to above‐ground vegetation, edaphic factors and land‐use history? 3. Are there differences in C‐S‐R plant strategy types and seed longevity under different management regimes?

Location: Lahn‐Dill Highlands in central‐western Germany. Methods: Above‐ground vegetation and the soil seed bank of 63 plots (at 21 sites) in mesic grasslands were studied. Differences between management types in quantitative seed bank traits and functional characteristics were tested by ANOVA. The impact of management, above‐ground vegetation, site conditions and land‐use history on seed bank composition were analysed by partial CCA.

Results: Management had no significant impact on species richness and density of the seed bank but significantly influenced their floristic composition and functional characteristics. CCA revealed that even after adjustment for soil chemical parameters and above‐ground vegetation management still had significant impact on seed bank composition. ANOVA revealed that silage meadows contained higher proportions of R‐strategy compared to hay meadows. In contrast, in hay meadows and meadow‐pastures proportions of S‐strategy were higher than in silage meadows.

Conclusions: The type of grassland management has little impact on quantitative seed bank traits. Management types with a high degree of disturbance lead to an increase of species following a ruderal strategy in the seed bank. Irrespective of management type only a limited proportion of characteristic grassland species is likely to re‐establish from the seed bank after disappearance from above‐ground vegetation.
Relationships between soil hydrology and forest structure and composition in the southern Brazilian Amazon
Authors: Jirka Stefan , McDonald Andrew J. , Johnson Mark S. , Feldpausch Ted R. , Couto Eduardo G. , Riha Susan J.
Published: February 2009

Question: Is soil hydrology an important niche‐based driver of biodiversity in tropical forests? More specifically, we asked whether seasonal dynamics in soil water regime contributed to vegetation partitioning into distinct forest types.

Location: Tropical rain forest in northwestern Mato Grosso, Brazil.

Methods: We investigated the distribution of trees and lianas ≥ 1 cm DBH in ten transects that crossed distinct hydrological transitions. Soil water content and depth to water table were measured regularly over a 13‐month period.

Results: A detrended correspondence analysis (DCA) of 20 dominant species and structural attributes in 10 × 10 m subplots segregated three major forest types: (1) high‐statured upland forest with intermediate stem density, (2) medium‐statured forest dominated by palms, and (3) low‐statured campinarana forest with high stem density. During the rainy season and transition into the dry season, distinct characteristics of the soil water regime (i.e. hydro‐indicators) were closely associated with each vegetation community. Stand structural attributes and hydro‐indicators were statistically different among forest types.

Conclusions: Some upland species appeared intolerant of anaerobic conditions as they were not present in palm and campinarana sites, which experienced prolonged periods of saturation at the soil surface. A shallow impermeable layer restricted rooting depth in the campinarana community, which could heighten drought stress during the dry season. The only vegetation able to persist in campinarana sites were short‐statured trees that appear to be well‐adapted to the dual extremes of inundation and drought.
Spatial pattern in the organic layer and tree growth: A case study from regenerating Picea mariana stands prone to paludification
Authors: Lavoie Martin , Harper Karen , Paré David , Bergeron Yves
Published: February 2009

Questions: 1. How does the spatial structure of the organic layer affect tree sapling physiology? 2. Are the organic layer and Picea mariana height growth spatially structured at different scales? 3. Does microtopography influence the accumulation of organic matter and does organic layer thickness affect height growth?

Locations: Picea mariana forests, northwestern Quebec, Canada.

Methods: We assessed the spatial pattern of each variable in one wildfire site and one harvest site using semivariograms and correlograms. We measured the cross‐correlation between relative elevation and organic layer thickness, and between organic layer thickness and growth using cross‐correlograms.

Results: Picea mariana height growth was autocorrelated to a greater extent in the wildfire site (103 m) than in the harvest site (43 m). The spatial structure of organic layer thickness was similar in both sites. Deeper depressions in the harvest site, as illustrated by spatial variance in relative elevation at short distances (ca. 50 m), and by high autocorrelation values, increased the accumulation of organic matter within 20 m.

Conclusions: The interaction between microtopography and organic matter accumulation led to paludification and poor growth of Picea mariana at the harvest site. Paludification at the wildfire site was independent of microtopography and was probably a result of stand development.
Integrating ecological features of species in spatial pattern analysis of a plant community
Authors: Pottier J. , Marrs R.H. , Bédécarrats A.
Published: February 2009

Objective: This empirical study was designed to explore the role of ecological features of species in the spatial patterning of a grassland community.

Location: Banks of the river Rhône in France.

Material and Methods: First, we explored the spatial pattern of 29 species recorded in the community using spatial autocorrelation analysis of species cover values. Second, we then explored the relationship between the patterns found and a set of life attributes that characterized the ecological features of species for resource foraging or dispersion. Finally, we explored the spatial relationship of groups of species that shared the same ecological features using cross‐correlation analysis.

Results: We found a significant relationship between the spatial pattern and life attributes of the species highlighting three groups of species: (1) species characterized as competitors, reproducing by runner clonal organs and forming large, dense patches; (2) species characterized as competitive‐rud‐erals, dispersing exclusively by seed production and forming small periodic patches; and (3) species classified as CSR, characterized by rosette morphology and short rhizomes as clonal organs without any significant spatial autocorrelation. Spatial segregation was found between group 1 and group 2 up to 14 m; no significant cross‐correlation between groups 1 and 3 between 0 and 3.5 m, and association between groups 2 and 3 up to 14 m.

Conclusions: These results helped to understand how species attributes (relative to stature or dispersion abilities); external factors (such as disturbance) and biotic processes (competition) interplay in structuring the plant community under study in space.
Leaf dry matter content and lateral spread predict response to land use change for six subalpine grassland species
Authors: Gross Nicolas , Suding Katharine Nash , Lavorel Sandra
Published: February 2009

Question: Land‐use change has a major impact on terrestrial plant communities by affecting fertility and disturbance. We test how particular combinations of plant functional traits can predict species responses to these factors and their abundance in the field by examining whether trade‐offs at the trait level (fundamental trade‐offs) are linked to trade‐offs at the response level (secondary trade‐offs).

Location: Central French Alps.

Methods: We conducted a pot experiment in which we characterized plant trait syndromes by measuring whole plant and leaf traits for six dominant species, originating from contrasting subalpine grassland types. We characterized their response to nutrient availability, shading and clipping. We quantified factors linked with different land usage in the field to test the relevance of our experimental treatments.

Results: We showed that land management affected nutrient concentration in soil, light availability and disturbance intensity. We identified particular suites of traits linked to plant stature and leaf structure which were associated with species responses to these environmental factors. Leaf dry matter content separates fast and slow growing species. Height and lateral spread separated tolerant and intolerant species to shade and clipping.

Discussion and Conclusion: Two fundamental trade‐offs based on stature traits and leaf traits were linked to two secondary trade‐offs based on response to fertilization shade and mowing. Based on these trade‐offs, we discuss four different species strategies which could explain and predict species distributions and traits syndrome at community scale under different land‐uses in subalpine grasslands.
Tree morphology in seasonally dry montane forest in Argentina: Relationships with shade tolerance and nutrient shortage
Authors: Easdale Tomás A. , Gurvich Diego E. , Sersic Alicia N. , Healey John R.
Published: February 2009

Question: How does form (leaf and trunk morphology) relate to function (tolerance of shade and nutrient storage) in trees?

Location: Los Toldos montane valley in NW Argentina.

Methods: We analysed the relationships amongst (1) ten vegetative and four reproductive traits across 40 tree species, (2) a distribution based measure of recruitment under shade and (3) a distribution based measure of recruitment over a soil fertility gradient.

Results: Ordinations revealed three main axes of species’ morphological differentiation: (1) evergreen species had leaves with a lower specific leaf area, greater tensile resistance and slower decomposition rate, denser wood and thinner bark than deciduous species; (2) tall tree species that lack spines and are anemochorous were separated from short, spinescent and zoochorous species and (3) species were distinguished according to clonal growth, seed mass and pollination syndromes. Notably, species’ recruitment under shade and over a soil fertility gradient were independent of each other, but both were correlated with species’ scores along the first axis of morphological variation (tolerant species have attributes that favour resource conservation). Different sets of traits were correlated with recruitment under shade and over a soil fertility gradient when traits where assessed individually. Amongst shade tolerant species, recruitment under shade was negatively correlated with species’ maximum height, suggesting differential responses to vertical gradients of light.

Conclusions: These results provide new evidence of integration between leaf and stem morphology which is consistent with an evolutionary compromise between high rate of resource acquisition and resource conservation. Generalizations about the functional value of individual morphological characteristics and of ‘strategies’ vary with the resolution of analyses.
Shrub encroachment in the Alps gives rise to the convergence of sub‐alpine communities on a regional scale
Authors: Anthelme Fabien , Villaret Jean‐Charles , Brun Jean‐Jacques
Published: February 2009

Question: How does Alnus alnobetula colonization affect plant communities in sub‐alpine grasslands undergoing land abandonment on a regional scale?

Location: Savoie, French Alps.

Methods: Variations within and between communities were monitored in 243 plots within three types of stands representing an A. alnobetula colonization chronosequence from grassland to dense vegetation. They were tested for species richness, species strategies and species distribution through multivariate analysis. Regional variations were assessed at three sites along a rain shadow gradient.

Results: We detected a convergence of the understorey communities along an A. alnobetula colonization gradient at all sites, associated with a reduction in species richness and the replacement of stress related strategists by competitor strategists. This convergence was unaffected by the rain shadow gradient although it was a key factor of plant distribution.

Conclusions: The dense cover and the soil properties provided by A. alnobetula stands buffered the heterogeneity of sub‐alpine communities induced by a rain shadow gradient throughout the study region. It facilitated the development a homogeneous understorey community dominated by competitor related strategists while excluding grasslands stress adapted species through competition processes. The resulting community, although species‐poor, has an interesting conservation value. Accordingly, as a ‘native invader’, A. alnobetula does not display typical traits of biological invaders. Future experimental research on the interactions between A. alnobetula and components of the understorey would be particularly interesting in a severe environment that promotes facilitation among plants.
Variation in juvenile survival and related physiological traits among dipterocarp species co‐existing in a Bornean forest
Authors: Aiba Masahiro , Nakashizuka Tohru
Published: February 2009

Question: What environmental factors and physiological traits determine the juvenile survival rates of 11 dipterocarp species (Dipterocarpaceae) co‐occurring in a Bornean tropical rain forest?

Location: Tropical northwestern Borneo.

Methods: In 248 quadrats, distributed over 12 ha, the juvenile (height< 2.0 m) survival of 11 shade‐tolerant dipterocarp species was monitored for one year. The probability of survival for each species was expressed as a logistic function of plant height and three environmental factors: canopy openness, soil water potential and conspecific individual density. The correlation between survival under shaded conditions and several physiological traits of juveniles was tested by normal Pearson correlation and a phylogeny based manner using independent contrasts.

Results: Seven species had increased survival under more open canopies, one species had increased and two species had decreased survival at drier sites. Six species had higher survival as the density of conspecifics increased, whereas two species had lower survival. The magnitudes of the effects for the three environmental factors were similar. However, the interspecific difference in survival was largely determined by a dependence of small seedlings on the light environment. Survival under low light was correlated positively with root dry mass and negatively with total leaf area of juveniles.

Conclusions: Responses of seedlings to the fine‐scale gradient of light availability were considerably different among the 11 species. Species that suffered increased mortality under low light had a set of structural traits that would potentially allow rapid growth under bright conditions. Differential performance along the light gradient may contribute to the stable coexistence of these species.
Relationship between size hierarchy and density of trees in a tropical dry deciduous forest of western India
Authors: Bagchi Sumanta
Published: February 2009

Questions: Density dependence is thought to restrict exponential growth as well as give rise to size structure in populations. Size hierarchy in trees from tropical dry deciduous forests is studied to ask (1) whether nature of competition is symmetric or asymmetric and (2) what is the self thinning trajectory under a natural gradient of tree density.

Location: Western India.

Methods: Density was measured as the number of trees in 10‐m radius circular plots (n= 96) and size was measured at DBH. Size variation was evaluated by the Gini coefficient (n= 1239 trees).

Results: Size inequality between neighbours decreased with density but in a non‐linear manner. In the backdrop of existing theory this indirectly suggests that competitive interactions may be symmetric over a ‘depletive’ resource such as below‐ground water (rather than a ‘pre‐emptive’ resource such as light), which is very plausible in a semi‐arid environment. The self thinning coefficient derived from the relationship between stem diameter and density (γ∼−1/4), is higher than expected from existing models of allometric plant growth (γ=−1/3) which are based on above‐ground interactions alone. Seen in conjunction, these results suggest that above‐ground structures, such as stem size, do not adequately represent the outcome of competitive interactions when below‐ground resources, such as water, may be more important under semi‐arid conditions.

Conclusions: The non‐linear relationship between size inequality and density indicates that there exists a density threshold beyond which investment in above‐ground biomass becomes sluggish in semi‐arid, deciduous forests. Since current allometric models do not incorporate below‐ground biomass for trees, these data suggest that a more comprehensive allometric growth model may have higher predictive power and wider applicability.
Do vine species in neotropical forests see the forest or the trees?
Authors: Nesheim Ingrid , Økland Rune H.
Published: February 2009

Questions: Is the occurrence of vine species in neotropical rain forests primarily determined by properties of the forest (environmental factors), by properties of the trees (tree species or tree size) or are vines randomly distributed?

Location: Maya Biosphere Reserve, Guatemala.

Methods: In five 1‐ha plots that span variation from unlogged forest to forest impacted by recurrent human disturbance we recorded the presence of all climbing vine species on every tree. The presence of all free standing vine species and 11 environmental variables were recorded in 100‐m2 subplots. The relationship of host tree diameter and host tree identity on single tree vine species richness was investigated by GLM modelling. Partial redundancy analyses were used to partition the variation in vine species composition on two sources: environmental factors and tree species identity.

Results: Single tree vine richness increased with increasing host tree DBH and differed significantly among host species. For climbing vines, the ratio of variation in subplot presence explained by tree species and by environmental variables was ca. 4:1 (in the most disturbed logged plots slightly lower), for free standing vines this ratio varied from 1:2 in the most disturbed logged plots to 9:1 in reserve plots, while a ratio of ca. 1:1 was found for all plots analysed together.

Conclusion: Different tree species have different probabilities of being infested by vines. Vines see both the forest and the trees; the environment is more important in earlier developmental stages, properties of individual trees become more important from the time vines start to climb.
Predicting future community composition from random soil seed bank sampling – evidence from a drained lake bottom
Authors: Bossuyt Beatrijs , Van Wichelen Jeroen , Hoffmann Maurice
Published: February 2009

Questions: What is the accuracy and reliability of the commonly used random soil sampling methodology for predicting seedling density, species richness and composition of the emerging seedling community?

Location: Lake Kraenepoel, western Belgium.

Methods: We compared density, species composition and observed and rarefactioned species richness of the seedling community emerging on a soft water lake bed exposed after drainage with the seedling community germinating in the laboratory from random soil samples in the same plots.

Results: Seedling density did not differ between the two methods and there was a significant correlation between seedling density on the exposed lake bed and in the soil samples. This indicates that future seedling density can be reliably predicted based on soil sampling, in particular for the most abundant species. The most frequently occurring and abundant species among the seedlings in the soil samples were also the most frequent and abundant species germinating on the exposed lake bed. In contrast, species richness was much higher on the exposed lake bed than in the soil samples, and this difference was still significant for annual species after correction for differences in sampling intensity by rarefaction. We found no correlation between the number of species retrieved by the two methods. Although seedlings of rare and target species emerged on the lake bed, random soil sampling clearly failed to detect seeds of most of these species.

Conclusions: Random soil sampling at a commonly used intensity and using the standard germination conditions can accurately predict future total seedling density and the density of the most abundant species. However, the method is not reliable for predicting the probability of establishment of populations of uncommon species. When executing a seed bank study, sampling intensity and germination conditions need to be adapted to the nature and the level of detail of the research question to be answered.
Trait‐divergence assembly rules have been demonstrated: Limiting similarity lives! A reply to Grime
Authors: Wilson J. Bastow
Published: February 2009

The recent Forum contribution by Grime (2006) contrasts the MacArthur/Diamond assembly‐rule approach to studying plant communities with the study of environmental trait gradients. Both are valid and useful. In doing so, Grime declares that the assembly rules model, in which negative interactions between plants act with limiting similarity to cause local trait divergence, is “not supported by empirical study of plant communities”. This is, he says, the agony of community ecology. I show that there is now abundant evidence for assembly rules, and no agony.
Excerpta Botanica ‐a valuable bibliographical source for vegetation science
Authors: Goodall David W.
Published: February 2009

Attention is drawn to a source citing some 90000 papers in vegetation science and related fields published before 1995. A subject index is provided.
Long‐term datasets: From descriptive to predictive data using ecoinformatics
Authors: Bekker Renée M. , van der Maarel Eddy , Bruelheide Helge , Woods Kerry
Published: February 2009

This Special Feature includes contributions on data‐processing of large ecological datasets under the heading ecoinformatics. Herewith the latter term is now al so established in the Journal of Vegetation Science. Ecoinfomatics is introduced as a rapid growing field within community ecology which is generating exciting new developments in ecology and in particular vegetation ecology. In our field, ecoinformatics deals with the understanding of patterns of species distributions at local and regional scales, and on the assemblages of species in relation to their properties, the local environment and their distribution in the region. Community ecology using ecoinformatics is related to bioinformatics, community ecology, biogeography and macroecology.

We make clear how ecoinformatics in vegetation science and particularly the IAVS Working Group on Ecoinformatics has developed from the work of the old Working Group for Data Processing which was active during the 1970s and 1980s. Recent developments, including the creation of TURBOVEG and Syn Bio Sys in Europa and VEGBANK in the USA, form a direct link with these pioneer activities, both scientifically and personally.

The contributions collected in this Special Feature present examples of seco‐infeveral types of the use of databases and the application of programmes and models. The main types are the study of long‐term vegetation dynamics in different cases of primary and secondary succession and the understanding of successional developments in terms of species traits.

Among the future developments of great significance we mention the use of a variety of different large datasets for the study of the distribution and ecology and conservation of rare and threatened species.
Local above‐ground persistence of vascular plants: Life‐history trade‐offs and environmental constraints
Authors: Ozinga Wim A. , Hennekens Stephan M. , Schaminée Joop H.J. , Smits Nina A.C. , Bekker Renée M. , Römermann Christine , Klimeš Leoš , Bakker Jan P. , van Groenendael Jan M.
Published: February 2009

Questions: 1. Which plant traits and habitat characteristics best explain local above‐ground persistence of vascular plant species and 2. Is there a trade‐off between local above‐ground persistence and the ability for seed dispersal and below‐ground persistence in the soil seed bank?

Locations: 845 long‐term permanent plots in terrestrial habitats across the Netherlands.

Methods: We analysed the local above‐ground persistence of vascular plants in permanent plots (monitored once a year for ca. 16 year) with respect to functional traits and habitat preferences using survival statistics (Kaplan‐Meier analysis and Cox’ regression). These methods account for censored data and are rarely used in vegetation ecology.

Results: Local above‐ground persistence is determined by both functional traits (especially the ability to form long‐lived clonal connections) and habitat preferences (especially nutrient requirements). Above‐ground persistence is negatively related to the ability for dispersal by wind and to the ability to accumulate a long‐term persistent soil seed bank (‘dispersal through time’) and is positively related to the ability for dispersal by water.

Conclusions: Most species have a half‐life expectation over 15 years, which may contribute to time lags after changes in habitat quality or ‐configuration (‘extinction debt’). There is evidence for a trade‐off relationship between local above‐ground persistence and below‐ground seed persistence, while the relationship with dispersal in space is vector specific. The rate of species turnover increases with productivity.
Groupings of life‐history traits are associated with distribution of forest plant species in a fragmented landscape
Authors: Endels Patrick , Adriaens Dries , Bekker Renée M. , Knevel Irma C. , Decocq Guillaume , Hermy Martin
Published: February 2009

Questions: 1. Do relationships among forest plant traits correspond to dispersability‐persistence trade‐offs or other inter‐trait correlations found in the literature? 2. Do species groups delineated by trait similarity, differ in occurrence in ancient vs. new forests or isolated vs more continuous forest patches? 3. Are these patterns consistent for different forest types?

Location: Central Belgium, near Leuven.

Methods: We investigate the distributions of a large set of plant traits and combinations among all forest species occurring in patches with varying forest continuity and isolation. Through calculation of Gower's similarity index and subsequent clustering,‘emergent’ species groups are delineated. Then, the relative occurrence of these different groups in forest patches of different age and size, sustaining different forest types (alluvial vs. Quercion), and having different isolation status is compared through multivariate GLM analysis.

Results: Correlations among several life history traits point towards trade‐offs of dispersability and fecundity vs. longevity. We distinguished three species groups: 1= mainly shrubs or climbers with fleshy or wind dispersed fruits and high dispersal potential; 2 = dominated by small, mainly vegetatively reproducing herbs; 3 = with spring flowering herbs with large seeds and mainly unassisted dispersal. Relative occurrence of these groups was significantly affected by forest age, area, isolation and forest type. Separate analyses for alluvial and Quercion forests indicated that the relative importance of these factors may differ, depending on forest type and species group. Both forest continuity and isolation are important in restricting the relative occurrence of forest species in alluvial forests, whatever their group membership. In Quercion forests forest patch area was the primary determinant of relative occurrence of species groups.

Conclusions: It is very important to preserve the actual forest area including the spatial setting and the dispersal infrastructure within the landscape. Next, forest connectivity may be restored, but it is inherently a long process.
Predicting tree death for Fagus sylvatica and Abies alba using permanent plot data
Authors: Wunder Jan , Reineking Björn , Matter Jean‐François , Bigler Christof , Bugmann Harald
Published: February 2009

Question:How well can mortality probabilities of deciduous trees(Fagus sylvatica)and conifers(Abies alba)be predicted using permanent plot data that describe growth patterns, tree species, tree size and site conditions?

Location:Fagusforests in the montane belt of the Jura folds (Switzerland).

Method:Permanent plot data were used to develop and validate logistic regression models predicting survival probabilities of individual trees. Backward model selection led to a reduced model containing the growth‐related variable ‘relative basal area increment’ (growth‐dependent mortality) and variables not directly reflecting growth such as species, size and site (growth‐independent mortality).

Results:The growth‐mortality relationship was the same for both species (growth‐dependent mortality). However, species, site and tree size also influenced mortality probabilities (growth‐independent mortality). The predicted survival probabilities of the final model were well calibrated, and the model showed an excellent discriminatory power (area under the receiver operating characteristic curve = 0.896).

Conclusion:Mortality probabilities ofFagus sylvaticaandAbies albacan be predicted with high discriminatory power using a well calibrated logistic regression model. Extending this case study to a larger number of tree species and sites could provide species‐ and site‐specific tree mortality models that allow for more realistic projections of forest succession.
The RAINFOR database: monitoring forest biomass and dynamics
Authors: Peacock J. , Baker T.R. , Lewis S.L. , Lopez‐Gonzalez G. , Phillips O.L.
Published: February 2009

Problem: Data from over 100 permanent sample plots which have been studied for 10–20 years need a suitable system for storage which allows simple data manipulation and retrieval for analysis.

Methods: A relational database linking tree records, taxonomic nomenclature and corresponding environmental data has been built in MS Access as part of the RAINFOR project.

Conclusion: The database allows flexible and long‐term use of a large amount of data: more than 100 tree plots across Amazonia, incorporating over 80 000 records of individual trees and over 300 000 total records of tree diameter measurements from successive censuses. The database is designed to enable linkages to existing soil, floristic or plant‐trait databases. This database will be a useful tool for exploring the impact of environmental factors on forest structure and dynamics at local to continental scales, and long term changes in forest ecology. As an early example of its potential, we explore the impact of different methodological assumptions on estimates of tropical forest biomass and carbon storage.
Leaf green‐up in a semi‐arid African savanna ‐separating tree and grass responses to environmental cues
Authors: Archibald S. , Scholes R.J.
Published: February 2009

Question: Can satellite time series be used to identify tree and grass green‐up dates in a semi‐arid savanna system, and are there predictable environmental cues for green‐up for each life form?

Location: Acacia nigrescens /Combretum apiculatum savanna, Kruger National Park, South Africa (25° S, 31° E).

Methods: Remotely‐sensed data from the MODIS sensor were used to provide a five year record of greenness (NDVI) between 2000 and 2005. The seasonal and inter‐annual patterns of leaf display of trees and grasses were described, using additional ecological information to separate the greening signal of each life form from the satellite time series. Linking this data to daily meteorological and soil moisture data allowed the cues responsible for leaf flush in trees and grasses to be identified and a predictive model of savanna leaf‐out was developed. This was tested on a 22‐year NDVI dataset from the Advanced Very High Resolution Radiometer.

A day length cue for tree green‐up predicted 86% of the green‐ups with an accuracy better than one month. A soil moisture and day length cue for grass green‐up predicted 73% of the green‐ups with an accuracy better than a month, and 82% within 45 days. This accuracy could be improved if the temporal resolution of the satellite data was shortened from the current two weeks.

Conclusions: The data show that at a landscape scale savanna trees have a less variable phenological cycle (within and between years) than grasses. Realistic biophysical models of savanna systems need to take this into account. Using climatic data to predict these dynamics is a feasible approach.
Vegetation shifts towards wetter site conditions on oceanic ombrotrophic bogs in southwestern Sweden
Authors: Gunnarsson Urban , Flodin Lars‐Åke
Published: February 2009

Question: Is ombrotrophic bog vegetation in an oceanic region of southwestern Sweden changing in the same direction over a five year period (1999 ‐ 2004) as northwest European bogs in the last 50 years, i.e. towards drier and more eutrophic vegetation?

Location: The province of Halland, southwestern Sweden.

Methods: Changes in species composition were monitored in 750 permanently marked plots in 25 ombrotrophic bogs from 1999 to 2004. Changes in species occurrences and richness were analysed and a multivariate statistical method (DCA) was used to analyse vegetation changes.

Results: The species composition changed towards wetter rather than drier conditions, which is unlike the general pattern of vegetation change on bogs in northwestern Europe. Species typical of wetter site conditions including most Sphagnum species increased in abundance on the bogs until 2004. The total number of species per plot increased, mostly due to the increased species richness of Sphagnum species. Nitrogen‐demanding (eutrophic) species increased in occurrence.

Conclusions: Ombrotrophic bog vegetation in an oceanic region in Sweden became wetter and was resilient to short‐term climatic shifts, after three years of below normal precipitation followed by several years with normal precipitation levels. Shifts towards more nitrogen demanding species were rapid in this region where the deposition levels have been high for several decades.
Bayesian classification of vegetation types with Gaussian mixture density fitting to indicator values
Authors: Witte Jan‐Philip M. , Wójcik Rafał B. , Torfs Paul J.J.F. , de Haan Martin W.H. , Hennekens Stephan
Published: February 2009

Question:Is it possible to mathematically classify relevés into vegetation types on the basis of their average indicator values, including the uncertainty of the classification?

Location:The Netherlands.

Method:A large relevé database was used to develop a method for predicting vegetation types based on indicator values. First, each relevé was classified into a phytosociological association on the basis of its species composition. Additionally, mean indicator values for moisture, nutrients and acidity were computed for each relevé. Thus, the position of each classified relevé was obtained in a three‐dimensional space of indicator values. Fitting the data to so called Gaussian Mixture Models yielded densities of associations as a function of indicator values. Finally, these density functions were used to predict the Bayesian occurrence probabilities of associations for known indicator values. Validation of predictions was performed by using a randomly chosen half of the database for the calibration of densities and the other half for the validation of predicted associations.

Results and Conclusions:With indicator values, most reléves were classified correctly into vegetation types at the association level. This was shown using confusion matrices that relate (1) the number of relevés classified into associations based on species composition to (2) those based on indicator values. Misclassified relevés belonged to ecologically similar associations. The method seems very suitable for predictive vegetation models.