bluuebunny/crossref_metadata_2025_split huggingface dataset:
Patterns of herbaceous plant diversity in southeastern Louisiana pine savannas
Authors: Keddy P.A. , Smith L. , Campbell D.R. , Clark M. , Montz G. 
Published: February 2009

AbstractQuestion: How diverse are Louisiana pine savanna plant communities and how is diversity affected by time since burn and removal of a competitively dominant species?Location: Lake Ramsay, southeastern Louisiana, USA.Methods: Species‐area curves were constructed from nine nested quadrats in open savanna differing in time since burn (6, 18 and 30 months). Species frequency was determined for 100 1 ‐m2 quadrats. The dominant gras s, Andropogon virginicus, was removed with herbicide from moist and dry sites to test for possible effects of competition.Results: Slopes of log‐log species‐area relationships were steep (0.195 to 0.379). Time since burn did not affect the richness of herbaceous plants, only woody species. More than half of all species recorded (43/79, 54%) were infrequent (in < 10% of quadrats). After two years, there were no differences in species richness and composition for plots with and without A. virginicus.Conclusions: The high species diversity is typical of other savannas across the coastal plain. The large number of infrequent species indicates that the core‐satellite pattern of species occurrence found in temperate grasslands does not apply to southern pine savannas. The absence of effects due to removal of a dominant may be due to insufficient observation time, or low competition. Most species have traits, such as diminutive life forms, that suggest they are weak competitors for light in the presence of robust matrix grasses and in the absence of fire. Many species in Pinuspalustris savannas are likely either fugitive or peripheral species.
Natural disturbances and the physiognomy of pine savannas: A phenomenological model
Authors: Gilliam Frank S. , Platt William J. , Peet Robert K. 
Published: February 2009

Abstract.Question:The decline of thePinus palustrisecosystems has resulted from anthropogenic influences, such as conversion to pine plantation forestry, agriculture and land development, all of which are closely related to increases in human populations. Other effects, however, have arisen from alterations in disturbance regimes that maintain the structure and function of these ecosystems. How have alterations of the disturbance regime altered the physiognomy of ‘old‐growth’ stands, and what are the implications for ecosystem conservation and restoration?Methods:In contrast to models that emphasize close interactions among the vertically complex strata, we develop a conceptual phenomenological model for the physiognomic structure ofPinus palustrisstands. We relate two natural disturbances (tropical storms and fire) that affect different stages of the life cycle to different aspects of the physiognomic structure. We then compare overstorey stand structure and ground cover composition of two old‐growth longleaf stands near the extremes of different composite disturbance regimes: the Wade Tract (frequent hurricanes and fire) and the Boyd Tract (infrequent hurricanes and long‐term fire exclusion).Results:We predict that tropical storms and fires have different effects on stand physiognomy. Tropical storms are periodic, and sometimes intense, whereas fires are more frequent and less intense. Hurricanes directly influence the overstorey via wind‐caused damage and mortality, and indirectly influence the herb layer by altering the spatial distribution of shading and litter accumulation. Fire exerts direct effects on juvenile stages and indirect effects on the herb layer via fine fuel consumption and selective mortality of potential competitorsof P. palustrisjuveniles. These differences in effects of disturbances can result in widely different physiognomiesfor P. palustrisstands. Finally, some global climate change scenarios have suggested that changes may occur in tropical storm and fire regimes, altering frequency and severity. Such changes may greatly affect pine stands, and ultimately entire pine savanna ecosystems.Conclusions:Our phenomenological model of disturbance regimes inPinus palustrisold‐growth produces very different physiognomies for different disturbances regimes that reflect natural process and human management actions. This model can be used to derive restoration strategies for pine savannas that are linked to reinstitution of important ecological processes rather than specific physiognomic states.
RestoringQuercus pyrenaicaforests using pioneer shrubs as nurse plants
Authors: Castro Jorge , Zamora Regino , Hódar José A. 
Published: February 2009

AbstractQuestion:How to improve reforestation success ofQuercus pyrenaica.Location:1800 m a.s.L, southern Spain.Methods:One‐year‐oldQuercus pyrenaicaseedlings were planted using two treatments: (1) bare soil, using a 30‐cm diameter augur bit (conventional technique) and (2) under the canopy of a pioneer shrub,Salvia lavandulifolia, using a 12‐cm diameter augur bit. Survival and growth were monitored for six years. Our hypothesis is that the use of shrubs as nurse plants is an alternative technique of reforestation with higher success than traditional techniques, in which pre‐existing vegetation is usually considered a source of competition. The rationale for the study was that for environments with a dry season, pre‐existing vegetation buffers summer drought stress, ameliorates the water status of seedlings and thus usually increases seedling recruitment.Results:Quercussurvival was 6.3 × higher when planted under individuals of the pioneer shrub as compared to open areas.Quercusseedlings under shrubs also had shoots 1.8 X longer, while the number of shoots per plant did not differ among treatments. The first summer was the period with the highest mortality (49.1% of seedlings). Summer drought was the main cause of mortality.Conclusions:The use of shrubs as nurse plants forQ.pyrenaicareforestation is a viable technique to increase establishment success. The technique could be similarly useful in other environments with a dry period and for otherQuercusspecies. In addition, this technique offers the advantage of following natural succession, thus minimizing the impact in the community.
Transition from P‐ to N‐limited phytoplankton growth in an artificial lake on flooded cutaway peatland in Ireland
Authors: Higgins T. , Colleran E. , Raine R. 
Published: February 2009

AbstractQuestion: Which nutrient limits primary production in a lake created by flooding industrial cutaway peatland?Location: Clongawny Lake (53°10’N, 07°53’W), County Offaly, IrelandMethods: Nutrient concentrations in lake water and the dynamics of phytoplankton populations were monitored over a 38‐month period. The ratio of dissolved inorganic nitrogen to total phosphorus (DIN:TP) and nutrient enrichment bio‐assays were used to investigate temporal changes in nutrient limitation.Results: Primary production in the new lake was phytoplankton‐driven due to the scarcity of recolonizing macrophytes. Phytoplankton growth was initially phosphorus‐limited. The runoff of phosphate fertilizer from an adjacent coniferous forestry plantation raised the TP concentration of lake water 5.5‐fold. Consequently, the biovolume of phytoplankton increased 30‐fold, and chlorophyll‐a concentrations increased eightfold, reaching hyper‐eutrophic levels. A concurrent depletion of nitrogen in lake water reduced the DIN:TP ratio from 17.8 to 0.6, and phytoplankton growth rapidly became nitrogen‐limited. Phytoplankton composition shifted from dinoflagellates to minute, unicellular chlorophytes, with a coincident decline in species diversity. Cyanobacteria did not proliferate, most likely due to the acidic nature of the lake.Conclusions: Results illustrated the vulnerability of newly created cutaway peatland lakes to developing severe phytoplankton blooms and coincident secondary nitrogen limitation in the presence of moderate external phosphorus inputs.
Competition as a factor structuring species zonation in riparian fens ‐ a transplantation experiment
Authors: Kotowski Wiktor , Thörig Werner , van Diggelen Rudy , Wassen Martin Joseph 
Published: February 2009

AbstractQuestion: What is the relative importance of competition and physical factors in restricting the occurrence of different fen species to certain zones of the riparian landscape?Location: Biebrza National Park, NE Poland.Methods: We carried out a two‐season reciprocal transplantation experiment: sod‐blocks were replaced between a low‐productive groundwater‐fed small‐sedge fen and a high‐productive fluviogenous tall‐sedge fen. Five treatments were applied to the transplanted sods: (1) no manipulation; (2) fertilization with NPK to exclude the effect of nutrient limitation; (3) clipping vegetation around the transplant to exclude competition for light; (4) clipping + fertilizing; (5) sods were also transplanted within their own environment.Results: After two seasons, the small‐sedge sods transplanted into the high‐productive zone had a biomass two times lower than that of the control transplants, mainly due to a decrease in small sedges and bryophytes. Tall sedges of the high‐productive zone did not respond significantly to transplantation in the low‐productive zone. Removal of the surrounding vegetation largely enhanced the growth of small sedges and bryophytes and, to a lesser degree, of tall sedges. Fertilization, on the other hand, resulted in increased growth of tall sedges, grasses and non‐graminoid herbs.Conclusion: Species characteristic of low‐productive fen communities are competitively excluded from the high‐productive zone through light competition. In contrast, the performance of tall sedges in the low‐productive zone is lowered by nutrient limitation. In the long run this may lead to a complete disappearance of these species from this zone. We did not find evidence that the physical stress of flooding has a direct effect on the performance and distribution of species. Results from the experiment suggest that productivity gradients and their influence on competition intensity are of primary importance for structuring vegetation patterns in lowland riparian fens.
Restoring prairie pothole wetlands: does the species pool concept offer decision‐making guidance for re‐vegetation?
Authors: Galatowitsch Susan M. 
Published: February 2009

AbstractQuestion: Do regional species pools, landscape isolation or on‐site constraints cause plants from different guilds to vary in their ability to colonize restored wetlands?Location: Iowa, Minnesota, and South Dakota, USA.Methods: Floristic surveys of 41 restored wetlands were made three and 12 years after reflooding to determine changes in local species pools for eight plant guilds. The effect of landscape isolation on colonization efficiency was evaluated for each guild by plotting local species pools against distance to nearby natural wetlands, and the relative importance of dispersal vs. on‐site constraints in limiting colonization was explored by comparing the local species pools of restored and natural wetlands within the region.Results: Of the 517 wetland plant taxa occurring in the region, 50% have established within 12 years. The proportion of the regional species pool represented in local species pools differed among guilds, with sedge‐meadow perennials, emergent perennials and floating/submersed aquatics least represented (33‐36%) and annual guilds most represented (74‐94%). Colonization‐to‐extinction ratios suggest that floating/submersed aquatics have already reached a species equilibrium while sedge‐meadow and emergent perennials are still accumulating species. Increasing distance to nearest wetlands decreased the proportion of the regional species pool present in local pools for all guilds except native annuals and woody plants. The maximum proportion predicted, assuming no distance constraint, was comparable to the lowest‐diversity natural wetlands for most perennial guilds, and also lower than what was achieved in a planted, weeded restoration.Conclusions: A biotic constraints seem to limit the colonization of floating/submersed aquatics into natural or restored wetlands, whereas all other guilds are potentially constrained by dispersal or biotic factors (i.e. competition from invasive species). Using species pools to evaluate restoration progress revealed that immigration potential varies considerably among guilds, that local species richness does not necessarily correspond to immigration limitations, and that some guilds (e.g. sedge‐meadow perennials) will likely benefit more than others from being planted at restoration sites.
Prediction of herbage yield in grassland: How well do Ellenberg N‐values perform?
Authors: Wagner Markus , Kahmen Ansgar , Schlumprecht Helmut , Audorff Volker , Perner Jörg , Buchmann Nina , Weisser Wolfgang W. 
Published: February 2009

AbstractQuestion: How useful are Ellenberg N‐values for predicting the herbage yield of Central European grasslands in comparison to approaches based on ordination scores of plant species composition or on soil parameters?Location: Central Germany (11°00′‐11°37’E, 50°21‐50°34’N, 500–840 m a.s.l.).Methods: Based on data from a field survey in 2001, the following models were constructed for predicting herbage yield in montane Central European grasslands: (1) Linear regression of mean Ellenberg N‐, R‐ and F‐values; (2) Linear regression of ordination scores derived from Non‐metric Multidimensional Scaling (NMDS) of vegetation data; and (3) Multiple linear regression (MLR) of soil variables. Models were evaluated by cross‐validation and validation with additional data collected in 2002.Results: Best predictions were obtained with models based on species composition. Ellenberg N‐values and NMDS scores performed equally well and better than models based on Ellenberg R‐ or F‐values. Predictions based on soil variables were least accurate. When tested with data from 2002, models based on Ellenberg N‐values or on NMDS scores accurately predicted productivity rank order of sites, but not the actual herbage yield of particular sites.Conclusions: Mean Ellenberg N‐values, which are easy to calculate, are as accurate as ordination scores in predicting herbage yield from plant species composition. In contrast, models based on soil variables may be useful for generating hypotheses about the factors limiting herbage yield, but not for prediction. We support the view that Ellenberg N‐values should be called productivity values rather than nitrogen values.
Management of three endangered plant species in dynamic Baltic seashore meadows
Authors: Rautiainen P. , Björnström T. , Niemelä M. , Arvola P. , Degerman A. , Erävuori L. , Siikamäki P. , Markkola A. , Tuomi J. , Hyvärinen M. 
Published: February 2009

AbstractQuestion:
Arctophila fulva var. pendulina, Primula nutans var. jokelae and Puccinellia phryganodes are threatened early successional species growing in the seashore meadows of the northern Baltic Sea. Patches formed by these species are destined to be replaced by other species during primary succession and in order to persist in the area they have to continuously colonize new areas. We studied whether the displacement of the species could be slowed down and their sexual and/or vegetative reproduction enhanced by management targeted to surrounding vegetation.Location: Bothnian Bay, Baltic Sea, W Finland.Methods: Vegetation surrounding patches of all study species was mown in four successional growing seasons. Moreover, the impact of additional soil turning on creating new favourable growing sites was tested for A. fulva.Results: Deterioration of suitable habitats of A. fulva and P. nutans was markedly slowed down by management and the vegetative and/or sexual reproduction of these species was enhanced. In the case of P. phryganodes, however, no positive response to management was obtained.Conclusions: In order to improve the long‐term persistence of these three species successional vegetation changes should be slowed down and their dispersal and colonization success improved by continuous management of the populations. We further suggest that the colonization of new areas should be aided by transplantations to the non‐vegetated islets, which have recently risen from the sea and cannot be reached by means of dispersal.
Simulating the impacts of southern pine beetle and fire on the dynamics of xerophytic pine landscapes in the southern Appalachians
Authors: Waldron J.D. , Lafon C.W. , Coulson R.N. , Cairns D.M. , Tchakerian M.D. , Birt A. , Klepzig K.D. 
Published: February 2009

AbstractQuestion: Can fire be used to maintain Yellow pine (Pinus subgenus Diploxylon) stands disturbed by periodic outbreaks of southern pine beetle?Location: Southern Appalachian Mountains, USA.Methods: We used LANDIS to model vegetation disturbance and succession on four grids representative of xeric landscapes in the southern Appalachians. Forest dynamics of each landscape were simulated under three disturbance scenarios: southern pine beetle, fire, and southern pine beetle and fire, as well as a no disturbance scenario. We compared trends in the abundance of pine and hardwood functional types as well as individual species.Results: Yellow pine abundance and open woodland conditions were best maintained by a combination of fire and southern pine beetle disturbance on both low elevation sites as well as mid‐elevation ridges & peaks. On mid‐elevation SE‐W facing slopes, pine woodlands were best maintained by fire alone.Conclusions: Our simulations suggest that fire can help maintain open pine woodlands in stands affected by southern pine beetle outbreaks.
Sampling plant functional traits: What proportion of the species need to be measured?
Authors: Pakeman Robin J. , Quested Helen M. 
Published: February 2009

AbstractQuestion: Understanding functional change in vegetation and how it might impact on vegetation change and ecosystem function entails measuring plant traits and attributes in situ. However, it is not realistically possible to sample every species for every trait, hence we need to address the consequences of not sampling all species.Location: Nine arable and grassland sites from the machair of the Western Isles, UK and twenty grassland and woodland sites from Nynäs Nature Reserve, southern Sweden.Methods: The effects of progressively reducing the proportion of species used to estimate the weighted mean of a range of continuous and qualitative traits were assessed.Results: Relative abundance and species traits were related, and hence there is a cost in accuracy in reducing the number of species sampled in estimating the weighted mean for the vegetation. This cost was higher for qualitative traits than quantitative ones.Conclusion: The analysis suggested that for the quantitative traits a minimum of those species that make up at least 80% of the vegetation should be sampled if traits do not vary greatly between species. If this variability is high and the trait is likely to be correlated to abundance then greater effort in sampling species for traits is required. Qualitative information on the rarer species should still be entered into the analysis if it can be accessed in any way, even if quantitative information for that species is unavailable.
Long‐term effectiveness of sowing high and low diversity seed mixtures to enhance plant community development on ex‐arable fields
Authors: Lepŝ Jan , Doleẑal Jiri , Bezemer T. Martijn , Brown Valerie K. , Hedlund Katarina , Igual Arroyo Mariano , Jörgensen Helene Bracht , Lawson Clare S. , Mortimer Simon R. , Peix Geldart Alvaro , Rodríguez Barrueco Claudino , Santa Regina Ignacio , Ŝmilauer Petr , van der Putten Wim H. 
Published: February 2009

AbstractQuestions: How is succession on ex‐arable land affected by sowing high and low diversity mixtures of grassland species as compared to natural succession? How long do effects persist?Location: Experimental plots installed in the Czech Republic, The Netherlands, Spain, Sweden and the United Kingdom.Methods: The experiment was established on ex‐arable land, with five blocks, each containing three 10 m × 10 m experimental plots: natural colonization, a low‐ (four species) and high‐diversity (15 species) seed mixture. Species composition and biomass was followed for eight years.Results: The sown plants considerably affected the whole successional pathway and the effects persisted during the whole eight year period. Whilst the proportion of sown species (characterized by their cover) increased during the study period, the number of sown species started to decrease from the third season onwards. Sowing caused suppression of natural colonizing species, and the sown plots had more biomass. These effects were on average larger in the high diversity mixtures. However, the low diversity replicate sown with the mixture that produced the largest biomass or largest suppression of natural colonizers fell within the range recorded at the five replicates of the high diversity plots. The natural colonization plots usually had the highest total species richness and lowest productivity at the end of the observation period.Conclusions: The effect of sowing demonstrated dispersal limitation as a factor controlling the rate of early secondary succession. Diversity was important primarily for its‘insurance effect’: the high diversity mixtures were always able to compensate for the failure of some species.
Spatial distribution patterns of Rhynchostegium megapolitanum at the landscape scale ‐ an expanding species?
Authors: Zechmeister Harald G. , Moser Dietmar , Milasowszky Norbert 
Published: February 2009

AbstractQuestion: Is Rhynchostegium megapolitanum an expanding species?Location: Viennese Basin (120‐220 m a.s.1.), Austria.Methods: 121 dry grasslands, were investigated for the occurrence of R. megapolitanum. Nineteen environmental variables at 50 randomly selected sites, species composition at sites with and without R. megapolitanum and the spatial patterns of distribution of the species at the landscape scale were analysed. We compared actual distribution data of three rare species (Didymodon acutus, Pleurochaete squarrosa R. megapolitanum) and a common one (Brachythecium rutabulum) with the distribution obtained by vouchers that were collected between 1860 and 1940 in the investigated area. We calculated a GIS based model pattern and compared it with the actual distribution.Results:
R. megapolitanum was detected in 28 of these sites, almost 50 % of its populations produced sporophytes. We found significant differences between sites with and without R. megapolitanum with regard to grassland size, the percentage of silt and of sand in the soil. There were fewer occurrences of historic herbarium vouchers of R. megapolitanum than our current field survey discovered. The GIS based analyses of distribution patterns at the landscape scale showed a clustering of sites in which R. megapolitanum was present or absent. Simulations with a spatially realistic expansion model showed high similarities to the actual distribution of the species.Conclusions: All these analyses suggest that R. megapolitanum has been expanding in the investigated area. A significant increase in temperature and nitrogen deposition within the last hundred years might be the underlying cause for the species' spread.