bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparing PAR transmission models for forest understorey vegetation
Authors: Stadt Kenneth J. , Lieffers Victor J. 
Published: February 2009

AbstractQuestion: Do Beer's Law models, multi‐layer scattering models, and a semi‐empirical model for predicting PAR transmission through understorey vegetation give comparable results? Do different driving variables (LAI, PLAI and percentage cover) give different results? How do the models vary when fit with species‐specific, species‐average and the ‘default’ parameters recommended in the literature?Location: Upland boreal forests of western North America.Methods: In calibration and validation plots, PAR transmission was measured, total cover visually estimated, and leaf dispersion, PLAI and cover estimated for each species using a point‐frame. Leaf inclination was measured by clinometer. PAR transmission was modelled using empirically‐fit Beer's Law models, a semi‐empirical model based on hemispherical gap fraction and first‐order scattering, and a multi‐layer model allowing multiple scattering. All models were modified to use leaf area index (LAI), vertically projected leaf area index (PLAI), or percentage cover data.Results: The empirical Beer's Law models had the least bias and best precision in predicting PAR transmission. The semi‐empirical model also had little bias and good precision, since the scattering coefficient compensated for problems in the estimation of gap fraction. The multi‐layer model consistently underestimated transmission. There was little benefit in accounting for species separately. LAI and PLAI‐based models were the most precise, but percentage cover models also provided reasonable predictions of PAR transmission.Conclusions: PAR transmission through forest understories can be simply modelled with Beer's Law using one empirical coefficient representing the average understorey species. More complex scattering models are less effective, likely because they fail to account for the complexity of the dispersion of this vegetation layer and its effect on radiation scattering.
Effects of fire on the structure and diversity of a Spartina argentinensis tall grassland
Authors: Feldman Susana R. , Lewis J.P. 
Published: February 2009

AbstractQuestion: What are the effects of fire on the structure and the diversity of a Spartina ar gentinensis tall grassland in the short and medium run. S. argentinensis is the dominant species of tall grasslands on inland marshes of the Chaco‐Pampean region (Argentina), where spontaneous or man‐made fires are very frequent.Location: Federico Wildermuth Reserve (31°57′S; 61°23′W), Province of Santa Fe, Argentina, an area never ploughed that supported cattle until its exclusion in 1988.Methods: Vegetation was surveyed in randomly placed permanent plots using the Braun‐Blanquet cover‐abundance scale. The data were analysed by multivariate methods (PCA and MRPP) for synthesizing information and testing hypotheses.Results: Fire did not have a long‐lasting effect on the tall grassland. There was only a temporarily reduction of cover‐abundance of S. argentinensis which allowed an increase in the number of accompanying species such as Heliotropium curassavicum, Pluchea sagittalis, and Verbena litoralis and of some naturalised or weed species, such as Melilotus alba and Cirsium vulgare, respectively. Fire increased diversity, which remained relatively high for two to three years. Three years after the fire there were no significant differences on the amount of litter accumulated on burned and unburned plots.Conclusion: Fire should be considered an intrinsic part of the dynamics of S. argentinensis tall grassland.
Vegetation and seed bank in a calcareous grassland restored from a Pinus forest
Authors: Bistea E. , Mahy G. 
Published: February 2009

AbstractQuestion: What is the importance of the seed bank in the maintenance of the restoration potential of a 60‐year‐old abandoned calcareous grassland overgrown by Pinus trees?Location: ‘Les Pairées’, province of Luxembourg, Belgium.Methods: The seed bank and the above‐ground vegetation were surveyed in three adjacent stands, previously forming a unique calcareous grassland: a 60‐year‐old Pinus forest, a four‐year‐old clear‐cutting and a typical calcareous grassland. Floristic diversity was compared among stands and between vegetation and seed bank.Results: The species richness of the vegetation and the seed bank was significantly lower in the Pinus forest. More floristic similarities were found between the clear‐cutting and the calcareous grassland. Seed bank was essentially transient, dominated by annual species. Its correspondence with the above‐ground vegetation was weak.Conclusion: Very few calcareous grassland species have persisted in the Pinus stand. Four years after clear‐cutting, the stand was nearing restoration towards a calcareous grassland. Seed longevity in the soil was not the most explicative factor. Dispersal of propagules from adjacent sources was also important.
Pine savanna overstorey influences on ground‐cover biodiversity
Authors: Platt William J. , Carr Susan M. , Reilly Matthew , Fahr Jean 
Published: February 2009

AbstractQuestion:Does the overstorey of pine savannas influence plant species biodiversity in the ground cover?Location:Camp Whispering Pines (30°41’N; 90°29’W), eastern Louisiana (USA).Methods:We used ecologically sensitive restoration logging to remove patches ofPinus palustris(longleaf pine) in a second‐growth loess plainPinus palustrissavanna managed using frequent lightning season fires. Five years later, we measured numbers of vascular plant species and transmitted light in replicated 100‐m2plots. Treatments involved three different overstorey conditions: no overstorey for 5 years, no overstorey for several decades, and overstorey pines present for decades.Results:Both recent and long‐term openings contained, on average, about 100 vascular plant species per 100 m2, 20% more than in similar‐sized areas beneath overstorey trees. Responses varied with life form; more herbaceous species occurred in recent and older overstorey openings than beneath overstorey trees. Total numbers of all species and of less abundant forb species were positively and linearly related to light transmitted to ground level. Those species responding to openings in the overstorey and positively associated with increased transmitted light levels were monocarpic and shortlived perennial forb and grass species with a seed bank in the soil. In addition, community structure, as reflected in species composition and abundances, appeared to vary with canopy condition.Conclusions:Restoration involving ecologically sensitive removal of patches of overstorey pines in frequently burned pine savannas should benefit the ground cover and increase plant species biodiversity as a result of increased abundance of seed bank species.
Conservation management of Pinus palustris ecosystems from a landscape perspective
Authors: Kirkman L. Katherine , Mitchell Robert J. 
Published: February 2009

AbstractQuestion: Do case studies from silvicultural and restoration studies and applied conservation management in second‐growth Pinus palustris stands provide unique insights for conservation models?Methods: A review of management paradigms that conserve the high biological diversity and rare species, drawn from characteristics in both second‐growth and old‐growth stands, is presented for fire‐maintained Pinus palustris (longleaf pine) forests.Results: A common assumption that old‐growth stands provide the primary information for the development of conservation management strategies de‐emphasizes lessons learned from second‐growth and restoration studies. Primary conservation management goals for the Pinus palustris ecosystem include the perpetual regeneration of the fire‐maintained forest and conservation of the characteristically high biological diversity and rare species. Several attributes, such as a sustained population of Picoides borealis (red‐cockaded woodpecker), Aristida stricta (wiregrass)‐dominated ground cover, and undisturbed upland‐wetland ecotones, can predict a diverse and ecologically functional ecosystem. Such indicators are linked to critical structural and functional features of the system and reflect previous land management histories that suggest sustainable approaches.Conclusions: A traditional definition of ‘old‐growth’ relying on overstorey may be limited in describing important features of healthy, diverse Pinus palustris ecosystems. Some characteristics are significantly more important for maintenance of diversity than age of the trees and these features may be present in old‐ or second‐growth forests. We advocate that the management history, structural characteristics and landscape context of stands that harbour desirable conservation attributes (red‐cockaded woodpeckers, wiregrass, gopher tortoises and undisturbed upland‐wetland ecotones) can be used as indicators to identify important conservation and forest management principles.
Modelling responses of pine savannas to climate change and large‐scale disturbance
Authors: Beckage Brian , Gross Louis J. , Platt William J. 
Published: February 2009

AbstractGlobal warming can potentially influence ecological communities through altered disturbance regimes in addition to increased temperatures. We investigate the response of pine savannas in the southeastern United States to global warming using a simple Lotka‐Volterra competition model together with predicted changes to fire and hurricane disturbance regimes with global climate change. In the southeastern United States, decreased frequency of both fires and hurricanes with global warming will shift pine savannas toward a forested state. A CO2 fertilization effect that increases the growth rate of tree populations will also push southeastern landscapes from open savannas towards closed forests. Transient dynamics associated with climate driven changes in vegetation will last on the order of decades to a century. In our model, the sensitivity of savannas to relative changes in the frequency of fire versus hurricanes is linearly dependent on the growth rate and mortality of trees in fire and hurricane disturbances.
Importance of sediment deposition and denitrification for nutrient retention in floodplain wetlands
Authors: Olde Venterink Harry , Vermaat Jan E. , Pronk Mario , Wiegman Frank , van der Lee Guda E.M. , van den Hoorn Martin W. , Higler L.W.G. (Bert) , Verhoeven Jos T.A. 
Published: February 2009

AbstractQuestions: Various floodplain communities may differ in their relative abilities to influence water quality through nutrient retention and denitrification. Our main questions were: (1) what is the importance of sediment deposition and denitrification for plant productivity and nutrient retention in floodplains; (2) will rehabilitation of natural floodplain communities (semi‐natural grassland, reedbed, woodland, pond) from agricultural grassland affect nutrient retention?Location: Floodplains of two Rhine distributaries (rivers Ussel and Waal), The Netherlands.Methods: Net sedimentation was measured using mats, denitrification in soil cores by acetylene inhibition and bio‐mass production by clipping above‐ground vegetation in winter and summer.Results: Sediment deposition was a major source of N and P in all floodplain communities. Highest deposition rates were found where water velocity was reduced by vegetation structure (reedbeds) or by a drop in surface elevation (pond). Sediment deposition was not higher in woodlands than in grassland types. Denitrification rates were low in winter but significantly higher in summer. Highest denitrification rates were found in an agricultural grassland (winter and summer) and in the ponds (summer). Plant productivity and nutrient uptake were high in reedbeds, intermediate in agricultural grasslands, ponds and semi‐natural grasslands and very low in woodlands (only understorey). All wetlands were N‐limited, which could be explained by low N:P ratios in sediment.Conclusions: Considering Rhine water quality: only substantial P‐retention is expected because, relative to the annual nutrient loads in the river, the floodplains are important sinks for P, but much less for N. Rehabilitation of agricultural grasslands into ponds or reedbeds will probably be more beneficial for downstream water quality (lower P‐concentrations) than into woodlands or semi‐natural grasslands.
Fen‐meadow succession in relation to spatial and temporal differences in hydrological and soil conditions
Authors: van der Hoek D. , Sýkora K.V. 
Published: February 2009

AbstractQuestion: In fen meadows with Junco‐Molinion plant communities, falling groundwater levels may not lead to a boosted above‐ground biomass production if limitation of nutrients persists. Instead, depending on drainage intensity and micro‐topography, acidification may trigger a shift into drier and more nutrient‐poor plant communities.Location: Nature reserve, central Netherlands, 5 m a.s.l.Methods: Long‐term study (1988‐1997) in a fen meadow along a gradient in drainage intensity at different scales.Results: Above‐ground biomass increased only slightly over ten years, despite a lower summer groundwater table. The accountable factors were probably a limited availability of nutrients (K in the higher well‐drained plots, P in the intermediate plots and N in the lower hardly drained plots), plus removal of hay.Junco‐Molinion species increased in dry sites and Parvo‐caricetea species increased in wet sites, presumably primarily because of soil acidification occurring when rainwater becomes more influential than base‐rich groundwater. The extent of the shift in species composition depends primarily on the drainage intensity and secondarily on microtopography. Local hydrological measures have largely failed to restore wetter and more basic‐rich conditions.Conclusions: Acidification and nutrient removal, leaching and immobilization resulted in the succession towards Junco‐Molinion at the cost of Calthion palustris elements. Lower in the gradient this change was reduced by the presence of buffered groundwater in slightly drained sites. To conserve the typical plant communities of the Junco‐Molinion to Calthion gradient in the long term, further acidification must be prevented, for example by inundation with base‐rich surface water.
Higher acidification rates in fens with phosphorus enrichment
Authors: Kooijman A.M. , Paulissen M.P.C.P. 
Published: February 2009

AbstractQuestion: Why is bryophyte succession in eutrophicated fens faster than in natural fens?Location: Mineral‐rich fens in The Netherlands and NW Europe.Methods: Literature review on the ecology of four bryophyte species in various successional types as observed in Dutch fens.Results: Bryophyte succession in eutrophicated fens from the brown moss Calliergonella cuspidata to Sphagnum squarrosum is much faster than in natural fens with species shifts from Scorpidium scorpioides to Sphagnum subnitens. Under P‐poor conditions, the brown moss stage is stabilized as long as mineral‐rich water is supplied. This is because S. scorpioides is tolerant of rainwater, is a strong competitor and can counteract acidification to some extent while S. subnitens is intolerant to groundwater and has low growth rates and low acidification capacity. In contrast, the Sphagnum stage is stable after rapid succession from rich‐fen mosses under P‐rich conditions. Calliergonella cuspidata has suboptimal growth in rainwater, possibly due to ammonium toxicity, while the high growth rates of S. squarrosum in nutrient‐rich and highly acidic groundwater allow early establishment and rapid expansion.Conclusions: If measures to improve fen base status occur in environments of increased nutrient (P) availability, the management may not lead to the desired restoration of brown moss stages, but instead to rapid acidification by S. squarrosum.
Seed dispersal in fens
Authors: Middleton Beth , van Diggelen Rudy , Jensen Kai 
Published: February 2009

AbstractQuestion: How does seed dispersal reduce fen isolation and contribute to biodiversity?Location: European and North American fens.Methods: This paper reviews the literature on seed dispersal to fens.Results: Landscape fragmentation may reduce dispersal opportunities thereby isolating fens and reducing genetic exchange. Species in fragmented wetlands may have lower reproductive success, which can lead to biodiversity loss. While fens may have always been relatively isolated from each other, they have become increasingly fragmented in modern times within agricultural and urban landscapes in both Europe and North America. Dispersal by water, animals and wind has been hampered by changes related to development in landscapes surrounding fens. Because the seeds of certain species are long‐lived in the seed bank, frequent episodes of dispersal are not always necessary to maintain the biodiversity of fens. However, of particular concern to restoration is that some dominant species, such as the tussock sedge Carex stricta, may not disperse readily between fens.Conclusions: Knowledge of seed dispersal can be used to maintain and restore the biodiversity of fens in fragmented landscapes. Given that development has fragmented landscapes and that this situation is not likely to change, the dispersal of seeds might be enhanced by moving hay or cattle from fens to damaged sites, or by reestablishing lost hydrological connections.
Sphagnum establishment on bare peat: The importance of climatic variability and Sphagnum species richness
Authors: Chirino C. , Campeau S. , Rochefort L. 
Published: February 2009

AbstractQuestion: What is the relative ability of four species of Sphagnum (S. fuscum, S. rubellum, S. magellanicum and S. angustifolium) to establish on bare peat substratum in the field when re‐introduced as single or multi‐species re‐introductions and in relation to interannual variations in climate?Location: Continental southeastern Canada.Methods: Diaspores (fragments) of four Sphagnum species alone or in combination were re‐introduced onto residual peat surfaces and were monitored to follow the development of the moss carpet over four growing seasons. In order to compare results under a variety of climatic conditions, this whole experimental setting was repeated four times (trials), with a four‐year follow‐up for each trial.Conclusions: The establishment rate of the moss carpet varied among years, in response to climatic variations between growing seasons. The relative success of different moss species and combinations of species, however, did not vary within or between trials. Thus, the species and combinations of species resulting in the highest short‐term or long‐term establishment rates remained the same for all trials, independent of the climatic conditions at the time of re‐introduction. Our results showed no link between the number of species in the diaspore mixture and successful establishment of the moss carpet. Yet successful regeneration was clearly influenced by the identity of species chosen for re‐introduction. S. fuscum, alone or in combination, was the species found to lead to the most extensive development of the moss carpet under the current test conditions.
Spatial heterogeneity in the determinants of woody plant invasion of lowland heath
Authors: Manning Peter , Putwain Philip D. , Webb Nigel R. 
Published: February 2009

AbstractQuestions: 1. What is the scale and extent of spatial variability in factors affecting Betula invasion of heaths? 2. How much effect does each factor have on within‐patch patterns of invasion? 3. How can this understanding aid in managing Betula invasions?Location: Lowland heath of southern England.Methods: Determinants of Betula (both B. pubescens and B. pendula) invasion: biomass density, necromass density, mean vegetation height, P‐availability, soil water content and total Betula seed bank density, were measured at two sites on a 5‐ha sampling grid. Spatial pattern was assessed using geostatistics. Contributions of each determinant to within‐site heterogeneity in predicted Betula seedling densities were estimated by varying variables over their full and interquartile ranges in a statistical model derived from experimental data.Results: Salient spatial trends were revealed: strong autocorrelation over distances of < 50 m for soil factors and more extensive autocorrelation (0 to > 150 m) in vegetation variables and Betula seed bank densities. The latter resulted in single across‐site gradients, the former small, distinct patches. All patterns were overlain with variance that was present at distances of < 17.6 m. Variables displaying spatial pattern also accounted for within‐site heterogeneity in predicted Betula seedling densities but their relative contribution to this varied between sites.Conclusions: Identifiable spatial autocorrelation in factors controlling patch‐scale invasion patterns allows managers to target invasion prone patches, potentially reducing management intensities. Furthermore, management effort may be optimised by spatially de‐coupling Betula seed from safe‐sites. This plan may adaptable to the management of other weeds and open‐land ecosystems.
Using life‐history traits to achieve a functional classification of habitats
Authors: Hérault Bruno , Honnay Olivier 
Published: February 2009

AbstractQuestion: To establish a habitat classification based on functional group co‐occurrence that may help the drawing up of conservation plans.Location: Riverine forest fragments in the Grand‐duché de Luxembourg, Europe.Methods: Forest fragments were surveyed for their abundance of vascular plants. These were clustered into emergent groups according to 14 life‐traits related to plant dispersal, establishment and persistence. Forest fragments were classified according to similar distribution of the identified emergent groups. Environmental factors were related to the emergent group richness in each forest type using generalized linear models.Results: Contrary to former species centred classifications, only two groups of forests, each with clearly different emergent group composition and conservation requirements, were detected: (1) swamp forests characterized by anemogamous perennials, annuals and hydrochorous perennials and (2) moist forests characterized by barochorous perennials, small geophytes and zoochorous phanerophytes. From a conservation point of view, priority should be given to large swamp forest with intact flooding regimes. This is in accordance with the high wind and water dispersal capacities of their typical emergent groups. For the moist forests, conservation priorities should be high forest connectivity and historical continuity since dispersal and establishment of their characteristic emergent groups are highly limited.Conclusions: The described methodology, situated at an intermediate integration level between the individual species and whole community descriptors, takes advantage of both conservation plans built for single species and the synthetic power of broad ecological measures.