bluuebunny/crossref_metadata_2025_split huggingface dataset:
Human disturbance and environmental factors as drivers of long‐term post‐fire regeneration patterns in Mediterranean forests
Authors: Baeza M.J. , Valdecantos A. , Alloza J.A. , Vallejo V.R. 
Published: February 2009

AbstractQuestion: What are the main forces driving natural regeneration in burned mature Mediterranean forests in the medium‐long term and what are the likely successional trajectories of unmanaged vegetation?Location: Valencia Region, eastern Spain.Methods: A wildfire burned 33 000 ha of Pinus halepensis and P. pinaster forest in 1979, and subsequent smaller wildfires took place between 1984 and 1996. The study was designed to sample the range of environmental and disturbance (fire recurrence and land use) conditions. The territory was classified into 17 different geomorphological and fire‐recurrence units. Vegetation cover and floristic composition were measured on a total of 113 plots (1000 m2 each) randomly selected within these units.Results: The results show that 23 years after the fire the regenerated vegetation consists of successional shrublands, and that forest ecosystem resilience can be very low. The vegetation presents a strong correlation with most of the environmental variables, but fire (one or two fires), soil type and land use (in that order) are the main drivers of vegetation composition. Quercus coccifera shrublands persist on limestone soils while diverse types of other shrublands (dominated by seeder species) are found on marl soils.Conclusions: The results of this study indicate that disturbance factors strongly coupled to human activities, such as land use and fire, play a critical role in the current state of vegetation. Fire creates vegetation patches in different successional states while land use and soil type define the different types of shrubland in terms of their specific composition.
Is tree diversity different in the Southern Hemisphere?
Authors: Burns K.C. 
Published: February 2009

AbstractQuestions: Is tree diversity higher in the southern hemisphere? Are latitudinal asymmetries in diversity sensitive to sampling effects?Location: 198 forested locales worldwide.Methods: I re‐analysed the Gentry database, which I augmented with an additional survey from New Zealand. Data were used to test whether latitudinal declines in tree diversity differ between the northern and southern hemispheres. Data were also used to test whether hemispheric asymmetries in diversity are sensitive to sampling effects, or geographic variation in tree densities.Results: Area‐based measurements of species diversity are higher in the southern hemisphere. However, southern forests house denser plant populations. After controlling for geographic variation in tree densities, diversity patterns reverse, indicating tree diversity is higher in the northern hemisphere.Conclusions: Latitudinal changes in tree diversity differ between hemispheres. However, the nature of hemispherical asymmetries in species diversity hinges on how diversity is defined, illustrating how different definitions of diversity can yield strikingly different solutions to common ecological problems.
Endemic regions of the vascular flora of the peninsula of Baja California, Mexico
Authors: Riemann Hugo , Exequiel Ezcurra 
Published: February 2009

AbstractQuestion:Can we recognize areas of high endemism and high endemic richness, using data from collections, and what are the ecological variables that best explain these areas?Location:Peninsula of Baja California, Mexico.Methods:We analysed the distribution of 723 endemic vascular plants species along the peninsula of Baja California and neighbouring islands distributed in 218 cartographic cells 15’ x 20’ in size. By means of a residual analysis, we identified areas of significantly high endemic species richness, and we calculated the degree of endemicity (or rarity) in each cell by giving to each species a weight factor inversely proportional to the land area it covers.Results:Nine regions of high‐endemicity and/or high endemic species richness were found.Discussion and conclusions:The analyses of rarity and endemic species richness showed two contrasting scenarios: High endemicity values in oceanic and sky islands accounts for a high number of species with a restricted distribution, promoted most likely by genetic isolation and high environmental heterogeneity. High endemic richness along the peninsular coast is related to ecotonal transition along vegetation types. After correcting for collection effort (i.e. the number of specimens collected within a cell), we found the phytogeographic region and altitudinal heterogeneity to be the variables that best predicted endemic richness. Both high endemism and high endemic richness have distinct geographic patterns within our study region. The nine endemic regions provide elements for priority definitions in future conservation programs.
Responses of subalpine dwarf‐shrub heath to irrigation and fertilization
Authors: Brancaleoni Lisa , Gualmini Matteo , Tomaselli Marcello , Gerdol Renato 
Published: February 2009

AbstractQuestion: Our study aimed at testing to what extent water and/or nutrients affect community composition in sub‐alpine heath. We hypothesized that nutrient addition will have an overall positive effect on heath vegetation but water addition will have greater effects and will probably reinforce the effects of fertilization in drier habitat conditions.Location: Monte Rondinaio, northern Apennines, Italy (44°08’ N; 10°35’ E, ca. 1850‐1930 m a.s.l.).Methods: Nutrients and water were added during five growing seasons in two communities (HV community, moister; EV community, drier) and the biomass of all species was estimated non‐destructively by the point‐quadrat method.Results: Total above‐ground biomass increased in both communities with fertilization due to increased graminoid biomass and decreased moss biomass, but was unaffected by irrigation. In the HV community species richness decreased as an effect of fertilization while in the EV community species richness was raised by irrigation.Conclusions: Our study partly supported our hypothesis since water addition had a stronger effect in the drier community. However, this effect was not revealed by changes in above‐ground biomass but rather by differing responses of individual species in the two communities.
Determinants of fine‐scale plant species richness in a deciduous forest of northeastern North America
Authors: Houle G. 
Published: February 2009

AbstractQuestion: What are the determinants of fine‐scale plant species richness (SR)?Location: Île‐aux‐Grues, Québec, Canada.Methods: Elevation, soil organic matter, soil pH, irradiance, tree basal area (BA) and plant SR (herbs, shrubs, and trees) were determined in 100 contiguous 25 m2 quadrats in a deciduous forest. Each variable was analysed for spatial autocorrelation using Moran's I. Path analysis was used to determine the effects of different variables on tree, shrub and herb SR in a hierarchical modelling approach.Results: Most of the variables, except tree BA, PPFD (photo‐synthetic photon flux density) and shrub SR, were positively autocorrelated at a scale of ca. 20 m or less. The path analyses explained ca. ll%‐40% of the variance in plant SR; however, the model for shrub SR was not significant. Tree SR was positively associated, but herb SR was negatively associated with tree BA. Tree SR had a positive influence on shrub SR, but herb SR remained unaffected by tree or shrub SR.Conclusion: The positive association of tree BA and tree SR suggests that the data from the study site correspond to the left (ascending) portion of the SR‐biomass relationship (un‐dersaturated SR). The negative effect of tree BA on herb SR is direct and not mediated through reduced PPFD. High tree BA might cause high resource use, induce high litter production and affect soil properties, all of which might significantly affect herb SR. Several factors not considered here might influence fine‐scale SR, such as interspecific interactions, fine‐scale disturbances and heterogeneity (both spatial and temporal) in resources and abiotic conditions. Within‐site variations of SR might be difficult to model with precision because of the relative importance of stochastic vs deterministic processes at this spatial scale.
Interactive effects of introduced herbivores and post‐flowering die‐off of bamboos in Patagonian Nothofagus forests
Authors: Raffaele Estela , Kitzberger Thomas , Veblen Thomas 
Published: February 2009

AbstractQuestion: In November 2000, Chusquea culeou, a bamboo species dominating Andean forest understories in southern Argentina and Chile, massively flowered and died over a north‐south distance of ca. 120 km. Because bamboo is the major forage for large herbivores in these forests, we examined the interactive influences of the bamboo die‐off and herbivory by introduced cattle on understory and tree regeneration.Location: Lanín National Park, Argentina.Methods: Permanent plots, in and outside livestock exclosures, were installed in a Nothofagus dombeyi forest in patches of flowered and non‐flowered C. culeou. Plots were monitored over four years for changes in understory composition and tree seedling densities and heights.Results: After the C. culeou die‐off, new establishment of N. dombeyi was low, both with and without herbivory. Livestock alone directly increased N. dombeyi seedling mortality through physical damage. However, tree seedling browse ratings and height growth were interactively affected by bamboo flowering and herbivory; unfenced plots in flowered bamboo patches had the shortest seedlings, highest browse ratings, and lowest tree seedling annual growth rates. Understory cover was higher where livestock were excluded, and this effect was intensified in the patches of flowered bamboo. Neither herbivory nor bamboo flowering resulted in major changes in species composition, with the exception of Alstroemeria aurea.Conclusion: Effects of livestock on N. dombeyi regeneration were contingent on flowering of C. culeou. Prior to introduction of livestock, N. dombeyi regeneration was probably successful beneath canopy gaps during windows of opportunity following bamboo die‐off, but now livestock impede tree regeneration. Herbivory during bamboo withering periods also produces more open understories, particularly affecting palatable heliophyllous herb species such as Alstroemeria aurea. The results underscore the importance of assessing herbivore impacts on tree regeneration during relatively short periods of potential tree regeneration immediately following rare bamboo flowering and die‐off.
How reliable is the monitoring of permanent vegetation plots? A test with multiple observers
Authors: Vittoz Pascal , Guisan Antoine 
Published: February 2009

AbstractQuestions: A multiple plot design was developed for permanent vegetation plots. How reliable are the different methods used in this design and which changes can we measure?Location: Alpine meadows (2430 m a.s.l.) in the Swiss Alps.Methods: Four inventories were obtained from 40 m2 plots: four subplots (0.4 m2) with a list of species, two 10m transects with the point method (50 points on each), one subplot (4m2) with a list of species and visual cover estimates as a percentage and the complete plot (40 m2) with a list of species and visual estimates in classes. This design was tested by five to seven experienced botanists in three plots.Results: Whatever the sampling size, only 45‐63% of the species were seen by all the observers. However, the majority of the overlooked species had cover < 0.1%. Pairs of observers overlooked 10‐20% less species than single observers. The point method was the best method for cover estimate, but it took much longer than visual cover estimates, and 100 points allowed for the monitoring of only a very limited number of species. The visual estimate as a percentage was more precise than classes. Working in pairs did not improve the estimates, but one botanist repeating the survey is more reliable than a succession of different observers.Conclusion: Lists of species are insufficient for monitoring. It is necessary to add cover estimates to allow for subsequent interpretations in spite of the overlooked species. The choice of the method depends on the available resources: the point method is time consuming but gives precise data for a limited number of species, while visual estimates are quick but allow for recording only large changes in cover. Constant pairs of observers improve the reliability of the records.
Does invasion by an alien plant species affect the soil seed bank?
Authors: Vilà Montserrat , Gimeno Isabel 
Published: February 2009

AbstractQuestions: How does invasion affect old‐field seed bank species richness, composition and density? How consistent are these effects across sites? Does the soil seed bank match vegetation structure in old‐fields?Location: Menorca, Balearic Islands, Spain, western Mediterranean basin.Methods: We monitored seed germination in soils from old‐fields that were both uninvaded and invaded (legacy effect) by the annual geophyte Oxalis pes‐caprae. We also added O. pes‐caprae bulbs to uninvaded soils to test O. pes‐caprae interference with seedling emergence (competitive effect). We compared species composition in the seed bank with that of the vegetation.Results: Species richness in the seed bank and in the vegetation was not significantly different between invaded and uninvaded areas. Uninvaded areas did not have larger seed banks than invaded areas. More seedlings, especially of geophytes, emerged when O. pes‐caprae bulbs were added to the soil. Species similarity between invaded and uninvaded areas was higher in the seed bank (74%) than in the vegetation (49%). Differences in species composition were as important as differences among sites. The degree of species similarity between the seed bank and the vegetation was very low (17%).Conclusions: Despite invasion by O. pes‐caprae not affecting species richness, the variation in the seed bank species composition in invaded and uninvaded areas, and the differences between the seed bank and the mature vegetation, highlights that even if the invader could be eradicated the vegetation could not be restored back to the exact composition as found in uninvaded areas.
Vegetation change from chronic stress events: Detection of the effects of tide gate removal and long‐term drought on a tidal marsh
Authors: Wetzel Paul R. , Kitchens Wiley M. 
Published: February 2009

AbstractQuestion: Chronic stress events are defined as disturbance events that exceed the lifespan of the dominant plant species, fluctuate in intensity and lack abruptness or physical destruction of biomass. Can the effects of chronic stress events be measured on vegetation communities? Did two chronic stress events, the removal of a tide gate and a four year drought, cause a temporary or permanent shift in the vegetation communities of a tidal marsh?Location: Tidal marsh in southeastern United States.Methods: Change in species composition and dominance and community change on a landscape level salinity gradient were measured between time periods ranging from four months to seven years to construct a statistical baseline reference community at freshwater, oligohaline, and mesohaline sections of a tidal marsh. Statistical shifts in the plant community were defined as changes in the plant community that fell outside of the defined baseline reference community.Results: Plant community changes outside of the reference community occurred in 13 out of 378 community comparisons. Removal of the tide gate had a greater effect on interstitial salinity levels than the drought and was most intense in the oligohaline marsh, where between 20 to 45% of the freshwa‐ter/oligohaline community types permanently converted to oligohaline community types. However, community shifts in the freshwater and oligohaline marsh induced by the drought were temporary, lasting from 1 to 3+ years. Neither chronic stress event permanently altered the mesohaline plant communities.Conclusion: The effects of chronic stress events could be detected; an extended historical record of vegetation change (18 years) was necessary to identify community shifts outside of a reference condition of the community and to determine if those shifts were permanent or temporary.
Use of the ecological information system SynBioSys for the analysis of large datasets
Authors: Schaminée Joop H.J. , Hennekens Stephan M. , Ozinga Wim A. 
Published: February 2009

AbstractThe rapid developments in computer techniques and the availability of large datasets open new perspectives for vegetation analysis aiming at better understanding of the ecology and functioning of ecosystems and underlying mechanisms. Information systems prove to be helpful tools in this new field. Such information systems may integrate different biological levels, viz. species, community and landscape. They incorporate a GIS platform for the visualization of the various layers of information, enabling the analysis of patterns and processes which relate the individual levels. An example of a newly developed information system is SynBioSys Europe, an initiative of the European Vegetation Survey (EVS). For the individual levels of the system, specific sources are available, notably national and regional Turboveg databases for the community level and data from the recently published European Map of Natural Vegetation for the landscape level. The structure of the system and its underlying databases allow user‐defined queries. With regard to its application, such information systems may play a vital role in European nature planning, such as the implementation the EU‐program Natura 2000. To illustrate the scope and perspectives of the program, some examples from The Netherlands are presented. They are dealing with long‐term changes in grassland ecosystems, including shifts in distribution, floristic composition, and ecological indicator values.
Scale sensitivity of synthetic long‐term vegetation time series derived through overlay of short‐term field records
Authors: Wildi Otto , Schütz Martin 
Published: February 2009

AbstractQuestions: Is change in cover of dominant species driving the velocity of succession or is it species turnover (1)? Is the length of the time‐step chosen in sampling affecting our recognition of the long‐term rate of change (2)1Location: 74 permanent plots located in the Swiss National Park, SE Switzerland, ca. 1900 m a.s.l.Methods: We superimpose several time‐series from permanent plots to one single series solely based on compositional dissimilarity. As shown earlier (Wildi & Schütz 2000) this results in a synthetic series covering about 400 to 650 yr length. Continuous power transformation of cover‐percentage scores is used to test if the dominance or the presence‐absence of species is governing secondary succession from pasture to forest. The effect of time step length is tested by sub‐samples of the time series.Results: Altering the weight of presence‐absence versus dominance of species affects the emerging time frame, while altering time step length is uncritical. Where species turnover is fast, different performance scales yield similar results. When cover change in dominant species prevails, the solutions vary considerably. Ordinations reveal that the synthetic time series seek for shortest paths of the temporal pattern whereas in the real system longer lasting alternatives exist.Conclusions: Superimposing time series differs from the classical space‐for‐time substitution approach. It is a computation‐based method to investigate temporal patterns of hundreds of years fitting between direct monitoring (usually limited to decades) and the analysis of proxy‐data (for time spans of thousands of years and more).
Limits to convergence of vegetation during early primary succession
Authors: del Moral R. 
Published: February 2009

AbstractQuestions: Primary succession, measured by changes in species composition, is slow, usually forcing a chronose‐quence approach. A unique data set is used to explore spatial and temporal changes in vegetation structure after a 1980 volcanic eruption. On the basis of data from a transect of 20 permanent plots with an altitudinal range of 250 m sampled through 2005, two questions are asked: Do changes along the transect recapitulate succession? Do plots converge to similar composition over time?Location: A ridge between 1218 and 1468 m on Mount St. Helens, Washington, USA.Methods: Repeat sampling of plots for species cover along a 1‐km transect. Floristic changes were characterized by techniques including DCA, clustering and similarity.Results: Species richness and cover increased with time at rates that decreased with increasing elevation. The establishment of Lupinus lepidus accelerated the rate of succession and may control its trajectory. Diversity (H) at first increased with richness, then declined as dominance hierarchies developed. Primary succession was characterized by overlapping phases of species assembly (richness), vegetation maturation (diversity peaks, cover expands) and inhibition (diversity declines). Each plot passed through several community classes, but by 2005, only four classes persisted. Succession trajectories (measured by DCA) became shorter with elevation. Similarity between groups of plots defined by their classification in 2005 did not increase with time. Similarity within plot groups converged slightly at the lower elevations. Despite similarities between temporal and spatial trends in composition, trajectories of higher plots do not recapitulate those of lower plots, apparently because Lupinus was not an early colonist. Any vegetation convergence has been limited to plots that are in close proximity.
A database application for long‐term ecological field experiments
Authors: Le Due M.G. , Yang L. , Marrs R.H. 
Published: February 2009

AbstractProblem: A series of long‐term field experiments is described, with particular reference to monitoring and quality control. This paper addresses problems in data‐management of particular importance for long‐term studies, including data manipulation, archiving, quality assessment, and flexible retrieval for analysisMethod: The problems were addressed using a purpose‐built database system, using commercial software and running under Microsoft Windows.Conclusion: The database system brings many advantages compared to available software, including significantly improved quality checking and access. The query system allows for easy access to data sets thus improving the efficiency of analysis. Quality assessments of the initial dataset demonstrated that the database system can also provide general insight into types and magnitudes of error in data‐sets. Finally, the system can be generalised to include data from a number of different projects, thus simplifying data manipulation for meta‐analysis.