bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tree regeneration in a New Zealand rain forest influenced by disturbance and drainage interactions
Authors: Urlich Stephen C. , Stewart Glenn H. , Duncan Richard P. , Almond Peter C. 
Published: February 2009

AbstractQuestion:Does canopy tree regeneration response to different large disturbances vary with soil drainage?Location:Old‐growth conifer (Dacrydium and Dacrycarpus)., angiosperm (Nothofagus and Weinmannia) rain forest, Mount Harata, South Island, New Zealand.Methods:Trees were aged (1056 cores) to reconstruct stand history in 20 (0.12–0.2 ha) plots with different underlying drainage. Spatial analyses of an additional 805 tree ages collected from two (0.3—0.7 ha) plots were conducted to detect patchiness for five canopy tree species. Microsite preferences for trees and saplings were determined.Results:There were clear differences in species regeneration patterns on soils with different drainage. Conifer recruitment occurred infrequently in even‐aged patches (> 1000 m2) and only on poorly drained soils. Periodic Nothofagus fusca and N. menziesii recruitment occurred more frequently in different sized canopy openings on all soils. Weinmannia recruitment was more continuous on all soils reflecting their greater relative shade‐tolerance. Distinct periods of recruitment that occurred in the last 400 years matched known large disturbances in the region. These events affected species differently as soil drainage varied. Following earthquakes, both conifers and N. menziesii regenerated on poorly drained soils, while Nothofagus species and Weinmannia regenerated on well‐drained soils. However, Dacrydium failed to regenerate after patchy storm damage in the wetter forest interior; instead faster‐growing N. fusca captured elevated microsites caused by uprooting.Conclusions:Underlying drainage influenced species composition, while variation in the impacts of large disturbance regulated relative species abundances on different soils.
Leaf phenology of three dominant limestone grassland plants matching the disturbance regime
Authors: Kahlert Bettina R. , Ryser Peter , Edwards Peter J. 
Published: February 2009

AbstractQuestion:Does interspecific variation in leaf phenology among grassland species help to explain the differences in species'performance under contrasting disturbance regimes.Location:Merishausen, northern Switzerland.Methods:Seasonal variations in leaf production and mortality were assessed for three species of nutrient‐poor limestone grasslands: Brachypodium pinnatum, Bromus erectus and Salvia pratensis; each of these species tends to become dominant under a contrasting form of management. Their phenological characteristics were compared with their performance in plots differently managed for 21 years: (1) mowing in July; (2) mowing in October; (3) controlled burning in February; and (4) no biomass removal.Results:The species‐specific phenological patterns of leaf production and leaf mortality are associated with the abundance of the three species under the different management regimes. B. erectus, with relatively short‐lived leaves and leaf production late in the season dominates plots mown annually in June; it has almost disappeared from plots with winter burning. B. pinnatum, with production maxima of the long‐lived leaves early in the season, does not tolerate June mowing but is most abundant in plots burnt in winter when the species has no living leaves. S. pratensis, a species with long‐lived leaves but fast senescence of all the leaves in autumn, dominates plots mown in October. In unmown plots, all species are equally abundant.Conclusions:The seasonal pattern of leaf production and mortality strongly influence biomass and nutrient loss due to the management, and the growth that can be realized between the disturbances. A species may become dominant if it ‘fits’into the particular management regime, whereas a mismatch between phenological pattern and disturbance regime leads to its elimination from the community.
Linking microtopography with post‐fire succession in bogs
Authors: Benscoter Brian W. , Kelman Wieder R. , Vitt Dale H. 
Published: February 2009

AbstractQuestions:Does post‐fire plant succession in boreal bogs vary microtopographically and are successional patterns reproducible among similar microtopographic features? Does succession preserve microtopography post‐fire?Location:Boreal bog peatlands near Sinkhole Lake and Athabasca, Alberta, Canada.Methods:We assessed microtopographic variation in post‐fire plant community succession through stratigraphic macrofossil analysis of bog soil cores collected from high (hummock) and low (hollow) positions. We conducted vegetation surveys and collected soil cores from ten hummocks and hollows in each bog. Pre‐fire microtopographic status was inferred based on floral composition and compared to current microtopography.Results:Hollow vegetation was more variable than hummocks, both in present composition and post‐fire succession. The successional trajectory of current hummocks was relatively uniform, showing relatively rapid shifts to Sphagnum fuscum dominance, but varied greatly in hollows. Hollows, although compositionally variable, were typically perpetuated following fire, while hummocks had an approximately equal chance of being perpetuated or becoming hollows.Conclusions:Greater compositional variability at lower microtopographic positions, both spatially and temporally, is most likely due to the ability of hollows to support a wider range of species and greater susceptibility to severe disturbance. Likewise, spatial variability in fire severity appears to be responsible for perpetuation or change in microtopographic status, favouring the creation of hollows over maintenance of hummocks.
Relationships between gap makers and gap fillers in an Arkansas floodplain forest
Authors: King Sammy L. , Antrobus Terry J. 
Published: February 2009

AbstractQuestion:In floodplain forests, does frequent flooding allow for self‐replacement of shade‐intolerant tree species or do small canopy gap openings lead to replacement by shade‐tolerant tree species?Location:Cache River, Arkansas, US; 55 m a.s.l.Methods:The species, diameter‐at‐breast height, and elevation of primary gap‐maker trees were determined for new gaps from 1995–1998. The size and species of gap‐filler trees were identified and placed into three classes: definitive, edge, or interior. Transition probabilities were determined.Results:The dominant shade‐intolerant species Quercus texana is being replaced primarily by the more shade‐tolerant A. rubrum var. drummondii, Fraxinus spp. and Ulmus americana. Only 20 of 2767 gap fillers were Q. texana. Replacement probabilities are not constant across elevations, however, as the least shade‐tolerant of the three most common species of definitive gap fillers, Fraxinus spp., occurred at lower elevations than A. rubrum var. drummondii, and U. americana.Conclusions:The contention that frequent flooding would allow for self‐replacement of shade‐intolerant species was only partially supported. The small canopy gaps undoubtedly influenced canopy replacement processes.
Stratified resampling of phytosociological databases: some strategies for obtaining more representative data sets for classification studies
Authors: Knollová Ilona , Chytrý Milan , Tichý Lubomír , Hájek Ondřej 
Published: February 2009

AbstractQuestion:The heterogeneous origin of the data in large phytosociological databases may seriously influence the results of their analysis. Therefore we propose some strategies for stratified resampling of such databases, which may improve the representativeness of the data. We also explore the effects of different resampling options on vegetation classification.Methods:We used 6050 plot samples (relevés) of mesic grasslands from the Czech Republic. We stratified this database using (1) geographical stratification in a grid; (2) habitat stratification created by an overlay of digital maps in GIS; (3) habitat stratification with strata defined by traditional phytosociological associations; (4) habitat stratification by numerical classification and (5) habitat stratification by Ellenberg indicator values. Each time we resampled the database, taking equal numbers of relevés per stratum. We then carried out cluster analyses for the resampled data sets and compared the resulting classifications using a newly developed procedure.Results:Random resampling of the initial data set and geographically stratified resampling resulted in similar classifications. By contrast, classifications of the resampled data sets that were based on habitat stratifications (2–5) differed from each other and from the initial data set. Stratification 2 resulted in classifications that strongly reflected environmental factors with a coarse grain of spatial heterogeneity (e.g. macroclimate), whereas stratification 5 resulted in classifications emphasizing fine‐grained factors (e.g. soil nutrient status). Stratification 3 led to the most deviating results, possibly due to the subjective nature of the traditional phytosociological classifications.Conclusions:Stratified resampling may increase the representativeness of phytosociological data sets, but different types of stratification may result in different classifications. No single resampling strategy is optimal or superior: the appropriate stratification method must be selected according to the objectives of specific studies.
Development of the cultural landscape in the forest‐grassland transition in southern Alberta controlled by topographic variables
Authors: Simonson J.T. , Johnson E.A. 
Published: February 2009

AbstractQuestion:How has the terrain, namely elevation, slope and aspect, controlled the cultural modification of the forest‐grassland transition in southern Alberta?Location:The aspen parkland region of the Rocky Mountains foothills southwest of Calgary, Alberta, Canada.Methods:Dominion Land Survey data, historical maps and a DEM (digital elevation model) were used to determine which decision rules settlers used to plough native grassland and parkland at the turn of the last century. Comparative measurements between historical and current vegetation patterns and GIS techniques were used to explore relationships between terrain, land use and the modification of the landscape.Results:Grassland at lower elevations, aspen parkland at mid elevations and closed forest at higher elevations dominated the pre‐settlement forest‐grassland transition. Elevation, hillslope angle and aspect affected which parts of the landscape were cleared and ploughed for agriculture or left in their natural state. Clearing and ploughing occurred mostly on gentle hill‐slopes (≤ 6°). At higher elevations with fewer gentle hillslopes clearing and ploughing were limited. Ca. 90% of the original vegetation at lower elevations has been cleared or ploughed, compared to ca. 30% at higher elevations. Almost all of the grassland at lower elevations has been converted to cropland. In the mid‐elevation parkland 48% of the tree cover and > 72% of the native grass have been converted to domesticated grass and cropland. Tree cover has expanded at the expense of grass on steep hillslopes and in ravines that presumably were burned frequently by wildfires in pre‐settlement times. At higher elevations, the closed forest has remained more or less intact.Conclusions:Terrain structure has controlled the arrangement of suitable agricultural land and consequently determined the current vegetation patterns in the forest‐grassland transition zone in southern Alberta. Tree invasion into grass has been minimal, and has been restricted to hilly topography or wet areas, even though the parkland has expanded somewhat in its distribution. Any effect the cessation of wildfires may have had on aspen expansion has been overshadowed by agriculture, which has converted vast areas of native grassland and aspen parkland to farmland. Thus, along this forest‐grassland transition, the strong elevation, slope and aspect have maintained some of the regional variation in vegetation.
Rao's quadratic entropy as a measure of functional diversity based on multiple traits
Authors: Botta‐Dukát Zoltán 
Published: February 2009

AbstractQuestion:Is Rao's quadratic entropy a suitable measure of functional diversity if several traits are considered?Methods:It is checked whether Rao's quadratic entropy (FDQ) satisfies a priori criteria suggested by Mason et al. A real data set is used to show that there are often zeros in abundance distributions which maximize functional diversity.Results and Conclusion:FDQ fulfils all a priori criteria and it surpasses other proposed indices, because it includes species abundances and more than one trait. Therefore, it seems to be an improvement compared to measures of functional diversity that are currently available. An unexpected property of FDQ is that its value may decrease if species richness increases. The reason is that functional diversity is influenced by both species‐abundance based diversity and differences among species. Introduction of a new species into the community increases the species‐abundance based diversity, while it may decrease the average dissimilarity among species.
Trends in the upward shift of alpine plants
Authors: Walther Gian‐Reto , Beißner Sascha , Burga Conradin A. 
Published: February 2009

AbstractQuestions:The 1990s were the warmest decade since the beginning of climate measurements. Based on almost 100 years of monitoring in the Swiss Alps, we asked (1) whether the extraordinary warm climatic conditions of the 1990s are reflected in the floristic composition of Alpine summit vegetation and, if so, (2) what the magnitude and rate of species change has been over the last few decades compared to the documented increase in species richness within the first 80 years of the 20th century.Location:Ten high mountain summits of the Bernina area in the southeastern Swiss Alps.Methods:Resurvey of the floristic composition of the uppermost altitudinal 10 m of these summits, applying the same methodology of former two surveys (1905 and 1985) and recording the presence of all vascular plant species.Results:Whereas the continued increase in plant species richness of high alpine summit vegetation is confirmed, our results also suggest an acceleration of the trend in the upward shift of alpine plants.Conclusion:Vegetation change in the southeastern Swiss Alps has accelerated since 1985, consistent with a climate change explanation.
Small‐scale guild proportions and niche complementarity in a Caucasian subalpine hay meadow
Authors: Kikvidze Zaal , Khetsuriani Liana , Kikodze David 
Published: February 2009

AbstractQuestion:Monocot and dicot perennial herbaceous species can be considered two a priori guilds, which interact in regularly mown grasslands. Complementary resource use in space is important for diversity and productivity of perennial herbaceous communities, yet small‐scale spatial patterns of guilds and niche complementarity have rarely been linked explicitly. We ask: 1. Do guild interactions in our community generate small‐scale patterns such as guild proportionality? 2. Do these patterns coincide with overyielding of guilds, that is, can small‐scale spatial patterns of guilds be experimentally linked to niche complementarity?Location:Georgia, central Caucasian mountains.Methods:We sampled randomly placed small quadrats and used presence‐absence data to measure small‐scale spatial patterns within plots. We experimentally tested overyielding of monocots and dicots grown separately and in mixtures.Results:We found measurable small‐scale pattern of guilds in our community: monocots and dicots showed significant guild proportionality. However, variance deficit in the number of species per small quadrat was stronger in monocots than in dicots. Experiments found considerable overyielding, which was unaffected by water stress.Conclusions:Coincidence of measurable small‐scale arrangements of guilds with robust overyielding indicates that spatial arrangement is an important manifestation of niche complementarity. Stronger variance deficit of monocot species at small scale suggests that monocots compete with each other more strongly and, as a consequence, are more regularly dispersed at small spatial scale. Conversely, morphologically more diverse and more plastic dicots may more easily fit within the neighbourhood patchwork created by monocots.
Can competitive ability predict structure in experimental plant communities?
Authors: Fraser Lauchlan H. , Keddy Paul A. 
Published: February 2009

AbstractQuestion:Two questions were posed: 1. Can an independent measure of relative competitive ability be used to predict the abundance of species in mixtures? 2. Is the success of those predictions affected by low fertility (stress simulation) or clipping (disturbance simulation)?Location:Greenhouse at Carleton University, Ottawa, Canada.Methods:We collected adult plant ramets of 11 species from the field and transplanted one ramet of each species into 56 containers of 60 L. We applied a 4 × 2 factorial combination of fertilization (none, full nutrients except N, full nutrients except P, full nutrients) and clipping (no clipping, clipping to 10 cm above soil) with seven replicates of each treatment. After two growing seasons the above‐ and below‐ground biomass of each species was determined.Results:Regression analyses uncovered a significant positive relationship between plant biomass (measured in this study) and relative competitive ability (as measured in an independent study) under all experimental conditions. Both the mean slope and meanR2were lowest in treatments with low nutrients and highest in the full nutrient treatment (irrespective of clipping).Conclusions:Our results show that (1) at high fertility, relative competitive ability can generally predict the abundance of species in experimental plant communities, and (2) the intensity of competition (inferred from the magnitude of the slope orR2) increased with increasing nutrient supply, particularly nitrogen.
Variation in seed buoyancy of species in wetland ecosystems with different flooding dynamics
Authors: van den Broek Tom , van Diggelen Rudy , Bobbink Roland 
Published: February 2009

AbstractQuestion:Do species from communities with different flooding dynamics differ in seed buoyancy? Is there a trade‐off between seed buoyancy and seed longevity?Methods:Seeds of 55 freshwater wetland species were collected and related to communities along the hydrological gradient, ranging from constantly flooded reed beds, through tall herb fens and rich fens, to rarely flooded wet meadows. Species were experimentally tested for seed buoyancy over 210 days in standing water and moving water. Seed longevity for each species was calculated.Results:Community occurrence along the hydrologic gradient was mirrored by seed buoyancy. Seed buoyancy was highest for species of almost permanently inundated reed beds and lowest for species of rarely inundated wet meadows. The seed buoyancy characteristics of species of reed beds were best adapted to hydrological dynamic conditions mimicked by the treatment moving water and were the most independent of the flow rate of the water. A high percentage of the species used had a transient seed bank. Together with high buoyancy in many species, this suggests a trade‐off between dispersal capacity and seed persistence.Conclusions:In freshwater wetlands with rather stable water levels, many species lack a persistent seed bank and depend on dispersal for colonization of new habitats. Seed buoyancy enhances aquatic seed dispersal, and can be of great importance in both vegetation dynamics and restoration. In wetlands that are inundated for a long period during the year and with a water level above soil surface, higher seed buoyancy enhances the possibility for hydrochory.
Demographic and life‐history correlates for Amazonian trees
Authors: Nascimento Henrique E.M. , Laurance William F. , Condit Richard , Laurance Susan G. , D'Angelo Sammya , Andrade Ana C. 
Published: February 2009

AbstractQuestions:Which demographic and life‐history differences are found among 95 sympatric tree species? Are there correlations among demographic parameters within this assemblage?Location:Central Amazonian rain forest.Methods:Using long‐term data from 24 1–ha permanent plots, eight characteristics were estimated for each species: wood density, annual mortality rate, annual recruitment rate, mean stem diameter, maximum stem diameter, mean stem‐growth rate, maximum stem‐growth rate, population density.Results:An ordination analysis revealed that tree characteristics varied along two major axes of variation, the major gradient expressing light requirements and successional status, and the second gradient related to tree size. Along these gradients, four relatively discrete tree guilds could be distinguished: fast‐growing pioneer species, shade‐tolerant sub‐canopy species, canopy trees, and emergent species. Pioneers were uncommon and most trees were canopy or emergent species, which frequently had low mortality and recruitment. Wood density was negatively associated with tree mortality, recruitment, and growth rates when all species were considered. Growth rates varied markedly among and within species, with pioneers exhibiting far faster and less variable growth rates than did the other species. Slow growth in subcanopy species relative to canopy and emergent trees was not a simple consequence of mean tree size, but apparently resulted from physiological constraints imposed by low‐light and other conditions in the forest understorey.Conclusions:Trees of Amazonian rain forests could be classified with some success into four relatively distinctive guilds. However, several demographic and life‐history traits, such as those that distinguish early and late successional species, probably vary along a continuum, rather than being naturally grouped into relatively discrete categories.
Reproduction of dipterocarps during low intensity masting events in a Bornean rain forest
Authors: Maycock Colin R. , Thewlis Richard N. , Ghazoul Jaboury , Nilus Reuben , Burslem David F.R.P. 
Published: February 2009

AbstractQuestion:The evolution of general flowering and mast fruiting of dipterocarps in tropical rain forest has been explained by different mechanisms. We studied whether the abundance of flowering conspecifics influences the recruitment success of tropical forest trees in Borneo.Location:Sepilok Forest Reserve, Sabah, Malaysia.Method:We examined the recruitment success of 17 species ofDipterocarpaceaein a 640–ha sample area over two flowering events in 2001–2002 using seed traps and quadrats. Seed predation experiments were used to investigate if post‐dispersal seed survival was density‐dependent.Results:We found a negative relationship between the percentage of flowers abscised per individual and the number of flowering conspecifics and a positive relationship between the percent of flowering trees that produced viable seeds and the number of flowering conspecifics. However, we found no evidence of decreasing pre‐ and post‐dispersal predation with increasing numbers of flowering conspecifics. High levels of flower abscission, and pre‐ and post‐dispersal seed mortality, resulted in near‐complete recruitment failure of most species, with only three species successfully recruiting in only one year. One of these,Parashorea tomentella, satiated seed predators over a large area, whileHopea beccarianaandShorea multifloraonly recruited in small isolated clumps. Seed predation experiments suggest that post‐dispersal seed survival was positively density‐dependent in the short‐term.Conclusions:Increased density of flowering conspecifics may contribute to increased likelihood of successful cross‐pollination during low intensity flowering events and, in some cases, to enhanced probability of short‐term seed and seedling survival. Both processes may contribute to the evolution of mast fruiting and general flowering in Southeast Asian lowland dipterocarp forests.