bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interpretation of soil δ13C as an indicator of vegetation change in African savannas
Authors: Gillson L. , Waldron S. , Willis K.J. 
Published: February 2009

Abstract:Question:The relationship between carbon‐13 in soil organic matter and C3and C4plant abundance is complicated because of differential productivity, litter fall and decomposition. As a result, applying a mass balance equation to δ13C data from soils cannot be used to infer past C3and C4plant abundance; only the proportion of carbon derived from C3and C4plants can be estimated. In this paper, we compare δ13C of surface soil samples with vegetation data, in order to establish whether the ratio of C3:C4plants (rather than the proportion of carbon from C3and C4plants) can be inferred from soil δ13C.Location:The Tsavo National Park, in southeastern Kenya.Methods:We compare vegetation data with δ13C of organic matter in surface soil samples and derive regression equations relating the δ13C of soil organic matter to C3:C4plant abundance. We use these equations to interpret δ13C data from soil profiles in terms of changes in inferred C3:C4plant ratio. We compare our method of interpretation with that derived from a mass balance approach.Results:There was a statistically significant, linear relationship between the δ13C of organic matter in surface soil samples and the natural logarithm of the ratio of C3:C4plants in the 100m2surrounding the soil sample.Conclusions:We suggest that interpretation of δ13C data from organic matter in soil profiles can be improved by comparing vegetation surveys with δ13C of organic matter in surface soil samples. Our results suggest that past C3plant abundance might be under‐estimated if a mass balance approach is used.
Do different competitive abilities of three fern species explain their different regional abundances?
Authors: Rünk K. , Moora M. , Zobel M. 
Published: February 2009

Abstract:Question: Do different competitive abilities of three fern species explain their different regional abundances?Location: Estonia, Europe.Methods: The factorial pot experiment, in which single individuals of three fern species were grown in natural soil with 0, 2,4, and 8 neighbouring individuals of Deschampsia flexuosa.Results: The response patterns of different biomass fractions and morphological parameters of fern species were similar to each other. The diploid D. expansa was the most vulnerable to competition, while tetraploid D. carthusiana and D. dilatata were more tolerant. D. carthusiana allocated relatively more to below‐ground parts than the other two species and allocation to roots increased when neighbour density increased. For D. expansa and D. dilatata, allocation to below‐ground parts decreased at high neighbour density, while in D. dilatata also the relative length of the stipe increased. Thus, the response of D. carthusiana corresponds to a ‘persistence type’ and that of D. dilatata to a ‘foraging type’.Conclusions: Lower vulnerability of D. carthusiana to competition, compared to D. expansa, may explain the higher regional and local abundance of the former. The rarity of D. dilatata in Estonia, however, could rather be explained by the impact of climatic factors, since this species is near its northeastern distribution limit in Estonia.
Importance of tolerance to herbivory for plant survival in a British grassland
Authors: del‐Val E. , Crawley M.J. 
Published: February 2009

Abstract:Question: Is plant capacity to regrow under different herbivore treatments related to herbivore increaser/decreaser plant status?Location: Grassland in Southeast England (GR 41/944691).Methods: A field experiment was established in order to understand the role of plant tolerance to herbivory in explaining the abundance of nine grassland species previously known as herbivore increasers or decreasers. Tolerance was measured as a plant's capacity to regrow after exposure to herbivores. The experiment was designed to measure the impact of rabbits, molluscs, insects and clipping (artificial damage). Plants were propagated by stolons, exposed to different treatments in the field and then allowed to recover in the greenhouse for a month.Results: Previous studies have stated that plants that are able to persist in a herbivore environment could be tolerant or resistant, in agreement with the later our results showed that rabbit increaser plants were tolerant to herbivory in terms of biomass regrowth. Nonetheless, insect and mollusc increasers did not show any particular pattern related to plant compensation and some decreaser species were intolerant.Conclusions: This study shows that tolerance to herbivory could be an important mechanism for rabbit increaser species survival in grazed ecosystems.
Urban domestic gardens (III): Composition and diversity of lawn floras
Authors: Thompson Ken , Hodgson John G. , Smith Richard M. , Warren Philip H. , Gaston Kevin J. 
Published: February 2009

Abstract:Question: How do lawn floras compare with those of semi‐natural grasslands? Are the compositions of lawn floras determined by local, within‐garden factors (e.g. lawn management and size) or by regional factors (e.g. climate and location)? Are lawn floras nested (like semi‐natural grasslands) or not (like cultivated parts of gardens)? Are there gradients of species composition within lawns?Location: Sheffield, UK.Methods: We examined the composition of the floras of entire lawns and of two 1‐m2 lawn quadrats in 52 gardens.Results: A total of 159 species of vascular plants was recorded, 60 of them only once. Most lawn species were forbs, but most lawn cover consisted of grasses. Lawn species were predominantly natives. Bigger lawns had more species, but richness was not closely linked to other environmental or management variables. Composition of lawn floras varied with altitude, with woodland and wetland plants more common in the higher west of the city, and weeds of waste ground in the east. The species‐area curve derived from 1‐m2 lawn quadrats was very similar to that of semi‐natural grasslands. Lawn quadrats were significantly nested, with rarer species mostly confined to more species‐rich quadrats. Trampling‐tolerant Poa annua was more abundant in the part of the lawn nearer the house.Conclusions: In most respects, lawns behaved much more like semi‐natural grasslands than like cultivated flower beds and borders. Species composition of lawns is strongly influenced by local climate. Most lawns show an internal gradient of composition, linked to a gradient of intensity of use.
Nutrient limitation and nutrient‐driven shifts in plant species composition in a species‐rich fen meadow
Authors: van der Hoek Dick , van Mierlo Anita J.E.M. , van Groenendael Jan M. 
Published: February 2009

Abstract:Question: We studied the development and persistence of the effects of nutrient pulses on biomass production and species composition in a fen meadow.Location: Nature reserve, central Netherlands, 5 m a.s.l.Methods: Single pulse fertilization with N and P in a factorial design on an undrained central and a drained margin site in a species‐rich fen meadow (Cirsio dissecti‐Molinietum). Biomass production and species composition were monitored during four years.Results: At the central site, N addition boosted biomass production, but only during one year. The species composition was not changed. P fertilization increased the biomass production and changed the species composition from a vegetation dominated by Carex panicea to a grassland community with abundant Holcus lanatus, but not before the second year. At the margin site, P fertilization changed the species composition in a similar way, but biomass production was not increased. N fertilization had no effect. At both sites the P induced shift in species composition persisted for four years although the P effect declined during the experiment.Conclusions: The biomass responses show that N was limiting in the central site. Another nutrient, besides N and P (probably K) must have been limiting in the marginal site. The fast decline of the N effect on biomass is ascribed to increased denitrification and biomass removal. The delay in the P effect on biomass and species composition and the persistence of the P effect on species composition are ascribed to fast immobilisation and subsequent slow release of fertilizer P in the peat soil. Recurrence of the P pulses is expected to cause permanent changes in species composition.
Structural complexity and land‐surface energy exchange along a gradient from arctic tundra to boreal forest
Authors: Thompson C. , Beringer J. , Chapin F.S. , McGuire A.D. 
Published: February 2009

Abstract:Question: Current climate changes in the Alaskan Arctic, which are characterized by increases in temperature and length of growing season, could alter vegetation structure, especially through increases in shrub cover or the movement of treeline. These changes in vegetation structure have consequences for the climate system. What is the relationship between structural complexity and partitioning of surface energy along a gradient from tundra through shrub tundra to closed canopy forest?Location: Arctic tundra‐boreal forest transition in the Alaskan Arctic.Methods: Along this gradient of increasing canopy complexity, we measured key vegetation characteristics, including community composition, biomass, cover, height, leaf area index and stem area index. We relate these vegetation characteristics to albedo and the partitioning of net radiation into ground, latent, and sensible heating fluxes.Results: Canopy complexity increased along the sequence from tundra to forest due to the addition of new plant functional types. This led to non‐linear changes in biomass, cover, and height in the understory. The increased canopy complexity resulted in reduced ground heat fluxes, relatively conserved latent heat fluxes and increased sensible heat fluxes. The localized warming associated with increased sensible heating over more complex canopies may amplify regional warming, causing further vegetation change in the Alaskan Arctic.
Seed bank assembly follows vegetation succession in dune slacks
Authors: Bossuyt Beatrijs , Hermy Martin 
Published: February 2009

Abstract:Question: Is the seed bank in dune slacks during the whole successional range mainly composed of early successional species or does it vary according to the changing vegetation?Location: Belgium, western part of the coast.Methods: We investigated the soil seed bank composition using a seedling germination method in a chronosequence of 20 dune slacks, ranging in age from five to 55 yr.Results: Both seed density and species richness in the seed bank were very low in the first successional stages and increased with age, mainly as a result of increasing seed production. The similarity between seed bank and vegetation was higher in older slacks. A comparison of characteristics between seed bank and vegetation showed that the seed bank was, to a large extent, composed of later successional species. Occurrence patterns of individual species also showed that seeds become incorporated in the soil after the species has established in the vegetation.Conclusion: The seed bank is not likely to be the driving force for successional changes in the vegetation, and successional changes rely on dispersal. Some early successional species persist in the seed bank, but generally only in low numbers. The results also confirm that most typical dune slack species do not form persistent seeds, so that re‐establishment from the seed bank is not to be expected when the species has disappeared from the vegetation.
Biomass distribution of two subalpine dwarf‐shrubs in relation to soil moisture and nutrient content
Authors: Gerdol Renato , Anfodillo Tommaso , Gualmini Matteo , Cannone Nicoletta , Bragazza Luca , Brancaleoni Lisa 
Published: February 2009

Abstract:Question: Do soil water content and/or soil nitrogen (N) content and/or soil phosphorus (P) content affect the biomass of Vaccinium myrtillus and V. vitis‐idaea in a sub‐alpine heath?Location: Dolomites, northern Italy, 1800 m a.s.l.Methods: We determined above‐ground and below‐ground biomass of the shrubs at three sites, each on a different substrate type. At each site, we determined soil N‐ and P‐contents. We also determined leaf water potential (Psi;1), N‐ and P‐concentrations in plant tissues and litter, as well as δ13C and δ15N in mature leaves.Results: V. myrtillus biomass was highest at the silicate site, V. vitis‐idaea biomass was highest at the carbonate site. Both shrubs had low biomass at the peat site, possibly due to a toxic effect of waterlogging in wet soils. For both species, pre‐dawn Psi;1 indicated optimal hydration and midday Psi;1 did not show any sign of water stress. Water use efficiency (WUE) did not differ among sites for any species. Whole‐plant nutrient concentrations showed that, with increasing biomass, N was diluted in V. myrtillus tissues while P was diluted in V. vitis‐idaea tissues. Foliar N‐concentration was higher overall for V. myrtillus. Foliar P‐concentration in V. myrtillus peaked at the silicate site. Foliar N : P ratios suggested that V. myrtillus was primarily P‐limited and V. vitis‐idaea primarily N‐limited.Conclusions: Water content affected the distribution of the two shrubs in a similar way, higher P‐availability in the soil enhanced V. myrtillus rather than V. vitis‐idaea.
Palm distribution patterns in Amazonian rainforests: What is the role of topographic variation?
Authors: Vormisto Jaana , Tuomisto Hanna , Oksanen Jari 
Published: February 2009

Abstract:Question:Are soil properties and topographic variation related with palm (Arecaceae) species composition and distribution patterns? If so, are species distribution patterns consistent across sites?Location:100–200 m a.s.l, non‐inundated Amazonian rainforest, NE Peru.Methods:One 0.65‐ha line transect divided into 5 m by 5 m subunits was inventoried for all palm individuals at each site. Soil samples were collected, and topography was measured.Results:A total of 56 palm taxa were recorded. Floristic similarity among transects clearly corresponded with similarity in soil cation content when species abundances were taken into account, but less so when only presence‐absence data were used. Taxon‐wise distribution analyses were done for the 37 most abundant palm taxa. Quite a few of these taxa proved not to be randomly distributed along the transects, but instead were clearly more abundant in some topographic positions than in others. However, the consistency of the distribution patterns across study sites proved to be rather low, and many of the palm taxa showed different distribution patterns at different sites.Conclusions:The ambiguity in distribution patterns across study sites may partly be due to the complexity of topography as a measure of ecological conditions, and the probability that it is related to the variation in different environmental variables at different sites.
How doesReynoutriainvasion fit the various theories of invasibility?
Authors: Bímová Kateřina , Mandák Bohumil , Kašparová Ivana 
Published: February 2009

Abstract:Questions:1. How does species richness of recipient communities affectReynoutriainvasion? 2. How doesReynoutriainvasion change host community structure? 3. Are there any differences in habitat preferences among three closely relatedReynoutriataxa? 4. How does the genetic structure ofReynoutriapopulations change along the course of a river?Location:River Jizera basin, north Bohemia, Czech Republic.Methods:Nine 0.25 km2plots were chosen along the river. Within each plot all main habitat types were determined and sampled using the Braun‐Blanquet scale to determine the invasibility of various communities. The patches invaded byReynoutriataxa and surroundingReynoutria‐freevegetation in the same habitat type were sampled as relevé pairs to compare the composition of invaded and non‐invaded vegetation. In addition, to characterize the genetic structure ofReynoutriapopulations along the river, 30 samples from different clones were collected.Results and conclusions:1. The species richness of communities has no influence on the success ofReynoutriainvasion in the area studied. The combination of environmental conditions and propagule spread is more important to the invasion success than the number of species in the host community. 2.Reynoutriainvasion greatly reduces species diversity. 3.R. japonicainvaded more habitat types thanR. sachalinensisandR.×bohemica. The hybridR.×bohemicaoutcompetes the parental taxa at sites where both taxa co‐occur. 4. Isozyme analysis revealed phenotype variability in the hybrid in contrast to the parental taxa. Different hybrid phenotypes are distributed randomly on the middle and lower reaches of the River Jizera; one of them dominates and the other three occur occasionally. This pattern supports the hypothesis that sexual reproduction occasionally occurs withinReynoutriataxa.
Population responses of Ulex shrubs to fire in a lowland heath community
Authors: Stokes K.E. , Allchin A.E. , Bullock J.M. , Watkinson A.R. 
Published: February 2009

Abstract:Question: How does the frequency of heathland fire events affect population growth rates of two woody shrub species, Ulex gallii and U. minor?Location: Dry heathland on the south coast of England, UK.Methods: The population dynamics of U. gallii and U. minor were modelled at each phase of the heathland cycle — pioneer, building, mature and degenerate — using periodic matrix products to investigate the response to different fire regimes.Results: Population growth rates of both Ulex species declined under annual burning. Initially, as the time between burns increased, population growth rate increased for both species. Maximum population growth rates for each Ulex species were achieved under a 16‐yr fire return interval. Fire return intervals > 16 yr resulted in declining population growth rates.Conclusions: A species‐specific critical fire frequency can be predicted, the minimum fire return intervals permitting persistence were 4 yr for U. minor and 3 yr for U. gallii. These patterns are similar to those reported for a range of woody plant species within savanna environments.
Pathways of stand development in ageing Pinus sylvestris forests
Authors: Kint Vincent , Mohren G.M.J. , Geudens Guy , de Wulf Robert , Lust Noël 
Published: February 2009

Abstract:Question: What are the main pathways of long‐term stand development in forest ecosystems on oligotrophic and acidic sandy soils?Location: Nine forest reserves at different locations in The Netherlands; all ageing Pinus sylvestris forests that are no longer managed and where massive regeneration of broad‐leaved species is often reported.Methods: Agglomerative cluster analysis was used to define structural classes from forest reserve data. Sequences of structural classes, representing different trajectories of stand development, were constructed with the aid of a process based gap model.Results: Four main pathways of stand development could be distinguished. Three pathways are linked to gap dynamics, and lead towards dominance of Betula, Quercus or Fagus. They differ in light availability for regeneration and/or seed tree availability. The fourth pathway comprises of development patterns after major disturbances.Conclusions: The new methodological approach, combining the empirical strength of forest reserve data with the predictive ability of a process based model, made it possible to detail and quantify insights into structure and dynamics of forests on poor sandy soils. Some factors not included in the study can substantially influence pathways, especially those where Quercus and Fagus potentially play an important role.
Why should we constrain stress and limitation? Why conceptual terms deserve broad definitions
Authors: Weiher Evan 
Published: February 2009

Abstract:In his recent essay, Ch. Körner (2003) suggested that we need to clarify and narrow the meaning of limitation and stress. Current definitions and usage of these terms are not in any great need of revision. Limiting the use of ‘stress’ to only extreme situations is inappropriate because sometimes stress is indeed weak. What is needed is to use the terms within a comparative framework, a framework based on comparisons along gradients and among taxa. Recent studies on the factors controlling diversity have used such a comparative framework, and have increased our understanding of the relative roles of various types of stress. Redefining and narrowing general terms that relate to common processes would limit our ability to make comparisons and generalizations, and this should be avoided.
Why we should conserve ‘limiting factors’, at least sometimes!
Authors: Marrs R.H. 
Published: February 2009

Abstract:Körner's recent paper provided an excellent initial discussion of the term ‘limitation’ in ecology. I accept most of his arguments but would argue that there are some circumstances in applied ecology where the concept of limitation can be useful; these are (1) where there is a deficiency of a factor that prevents growth, and (2) where there is a need to manage an ecosystem so that a limitation is enforced.
Community‐level changes in Australian subalpine vegetation following invasion by the non‐native shrub Cytisus scoparius
Authors: Wearne Lynise J. , Morgan John W. 
Published: February 2009

Abstract:Question: What are the changes associated with the recent invasion by the non‐native legume, Cytisus scoparius?Location: Subalpine vegetation (1500 m a.s.l.) in Australia.Methods: We used multivariate techniques and regression analyses to assess vegetation and environmental changes across six study sites. Vegetation and environmental variables were investigated at three different stages of invasion: (1) recent invasion (8–10 yr), (2) mature invasion (15–16 yr) and (3) long‐term invasion (25 yr).Results: Substantial changes in floristic composition and species richness were evident after 15 yr and these changes became more pronounced after 25 yr. Changes due to invasion were associated with a dramatic loss of native species or a reduction in their abundance. No ‘new species’ were evident under invaded stands. Forbs were most affected by the establishment of C. scoparius, although all growth forms responded negatively. Dense canopy shading and an increasingly dense, homogeneous litter layer in the understorey as a result of C. scoparius were strong environmental drivers of vegetation change. Greenhouse studies confirmed the importance of these processes on the germination and growth of two native species.Conclusions: This study highlights the potential for C. scoparius to alter both vegetation and environmental processes in the subalpine region.