bluuebunny/crossref_metadata_2025_split huggingface dataset:
Changes in composition and structure of Vitex shrubland in northern China in relation to human disturbance
Authors: Xiao‐bing Dai 
Published: May 2006

AbstractVegetation and biomass in six plots, each with five quadrats, in Vitex shrubland in northern China were related to type and degree of human disturbance. Canonical correspondence analysis of the vegetation and environmental data showed two lines of variation, the first one highly correlated with the degree of disturbance, but the second one appearing within the disturbed plots cannot yet be fully explained. Changes in life‐form spectrum were small, but the geographical spectrum changed under heavy disturbance towards a higher proportion of tropical, subtropical and cosmopolitan species. The number of shrub species also decreased noticeably. The above‐ground biomass of both Vitex and the accompanying species and the total above‐ground biomass of the shrubland was negatively correlated with the intensity of disturbance. The root/stem biomass ratio in Vitex reaches values of over 5 in disturbed plots, but only between 1 and 2 in the protected plots.
A syntaxonomical study of subalpine heathland communities in West European low mountain ranges
Authors: Schaminée J. H. J. , Hennekens S. M. , Thébaud G. 
Published: May 2006

AbstractA survey is presented of the syntaxonomic status and the internal differentiation of the Genisto‐Vaccinion Br.‐Bl. 1926. This alliance comprises subalpine heathland communities of low mountain ranges in western Europe, which are dominated by Vaccinium and other dwarf‐shrub species. The alliance is assigned to the class Nardo‐Callunetea Preising 1949. All available releves were analysed together according to the Braun‐Blanquet approach. The floristic and ecological characteristics of the alliance are given, and the relationship to allied syntaxa is discussed. The Genisto‐Vaccinion is divided into two suballiances, the Phyteumo‐Vaccinenion and the Caricipiluliferae‐Vaccinenion. The Phyteumo‐Vaccinenion is restricted to the upper belt of the subalpine zone, where it includes the major part of the natural climax vegetation. Two associations are distinguished, the Pulsatillo vernalis‐Genistetum Quézel et Rioux 1954 and the Vaccinietum uliginosi‐myrtilli Br.‐Bl. 1926.The Caricipiluliferae‐Vaccinenion is bound to the lower belt of the subalpine zone; mostly, the communities have developed secondarily after cutting of the pre‐existing woodlands, followed by cattle grazing. Within this suballiance, four associations are described, the Alchemillo saxatilis‐Vaccinietum uliginosi Thébaud ex Schaminée et Hennekens 1992, the Allio victorialis‐Vaccinietum Schaminée et Hennekens 1992, the Pulsatillo alpinae‐Vaccinietum Carbiener 1966, and the Leontodonto‐Vaccinietum myrtilli Bartsch et Bartsch 1940. The description of the associations includes an appropriate diagnosis and enumeration of the nomenclatural types.
Correspondence Analysis of species by environmental variable matrices
Authors: Montana Carlos , Greig‐Smith Peter 
Published: May 2006

Abstract. Correspondence Analysis of species by environmental variables matrices is a relatively simple method for handling matrices which include many species and variables. If columns represent species and rows represent the states in which the environmental variables have been divided, each element of the matrix shows the number of releves in which the simultaneous occurrence of that species and that environmental variable state have been recorded. In this paper the use of the method for presence‐absence data is considered.The method is appropriate for studies whose main purpose is to look for broad correlations between groups of environmental variables and groups of species. It is particularly useful for handling heterogeneous data sets including rare species and species‐poor releves, a situation in which Correspondence Analysis and Canonical Correspondence Analysis are frequently complicated by the production of axes explaining the relationship between rare species and species‐poor releves.Examples are presented with artificial data as well as with real data collected in the Mexican portion of the Chihuahuan Desert (Bolsón de Mapimi). It is shown for the Mapimi data that the method is robust to the partition of variables into different numbers of states.
Architecture and development in Fagus japónica ‐ Fagus crenata forest near Mount Takahara, Japan
Authors: Peters R. , Ohkubo T. 
Published: May 2006

Abstract. The architecture and development of forest eco‐units in a mixed Japanese beech forest were studied by means of aerial photographs and belt‐transects. Fagus japónica dominates in this forest because it has the ability to reproduce through root‐collar sprouts. Each individual has a number of stems that reach the canopy. Two eco‐unit types are recognized. Most abundant is the type dominated by multiple‐stem F. japónica individuals (type A). The other type is dominated by other tall tree species, mostly Fagus crenata (type B). The most common cycle of development for type A is mature / stem‐breakage / growing / mature. After stem‐breakage, suppressed sprouts of the same individual replace the broken stem by growing quickly into the canopy. This accounts for the low coverage of patches in the early growing phases and the high coverage in mature phases in the aerial photographs. After uprooting off. japónica or after death of other canopy tree species, a seedling phase will be necessary, during which canopy species establish themselves from seed and F. japónica may establish itself from sprouts. Dwarf bamboo appeared to inhibit the establishment of seedlings but it does not affect the establishment of F. japónica sprouts.It is concluded that the dominance of F. japónica over other tall tree species is the result of F. japónica reproducing by sprouts.
European post‐glacial forests: compositional changes in response to climatic change
Authors: Huntley B. 
Published: May 2006

Abstract. Multivariate analysis of an extensive palyno‐logical database for Europe has enabled reconstruction of broad‐scale vegetation history. Whereas many major features of present vegetation patterns were established early in the Holocene, floristic composition of the forests has changed continuously up to the present day. For example, although ‘mixed deciduous forests’ had reached approximately their present extent in northwest Europe by 8000 B.P., Tilia peaked in abundance in these forests during the middle post glacial, whereas Pinus was most abundant in these forests during the early post‐glacial and Fagus increased in abundance only in recent millennia. Pollen‐climate response surfaces for major pollen taxa show how their distribution and abundance patterns relate to contemporary climate.Past forest‐compositional changes were responses to climatic changes, the nature of which can be inferred from pollen‐climate response surfaces. Post‐glacial climate changes have been different in magnitude and direction in different regions of Europe. For example, in recent millennia the vegetation changes indicate decreasing summer temperatures in northern Europe but increasing summer temperatures in the Mediterranean region. The way in which vegetation responded to past climatic changes gives insight into the likely response of vegetation to future climate changes induced by the ‘greenhouse effect’.
Coastal sand dune vegetation of Tabasco and Campeche, Mexico
Authors: Castillo Silvia , Popma Jean , Moreno‐Casasola Patricia 
Published: May 2006

Abstract. Sand dune vegetation along the coast of the Mexican states of Tabasco and Campeche was sampled by means of 1501 releves and the data were analyzed with classification and ordination programs. 36 community types were distinguished, which were grouped into 10 higher‐order groups. The communities are described in a sequence reflecting the main vegetation zonation. Beach, embryo dune and foredune community groups include 12 community types, the sheltered zone includes 16 types and the fixed dunes 8 types. The ordination results reveal one main vegetation gradient corresponding to the increase in mean distance from the shoreline and elevation, and being covariant with species richness, mean vegetation cover and mean vegetation height.Additional differences are related to the geographical transition between the Gulf and Caribbean coastal vegetation and environmental conditions, mainly type of sand, occurring in the study area. Siliceous sand and a Gulf climate are characteristic for most of Tabasco, and calcareous sand and a Caribbean‐type climate are characteristic for Campeche.Disturbance caused by coconut plantations, cattle grazing and tourism favours the invasion of ruderal species from waste places behind the dunes, which attain local dominance in the dunes described here. Consequently some separate community types had to be distinguished.The distribution of community types is analyzed in the context of the transitions between calcareous and siliceous substrates in the study area.
Species turnover and diversity during early stages of vegetation recovery on the volcano Usu, northern Japan
Authors: Tsuyuzaki Shiro 
Published: May 2006

AbstractTo study the rate of revegetation during succession on the volcano Usu, northern Japan, vegetation structure and species composition were monitored from 1984 to 1988 in permanent quadrats near the summit of the volcano, which had been almost completely deforested by 1 to 3 m thick volcanic deposits in 1977–78. Analyses of vegetation structure included species richness, species diversity (IT), evenness (J'); year‐to‐year changes were quantified using Community Coefficient (CC), and Percentage Similarity (PS). While species turnover rates fluctuated and vegetation cover gradually increased, species richness, diversity and evenness did not fluctuate much. The diversity parameters showed slightly different levels for three habitat types distinguished. CC values comparing subsequent years with the starting year 1984 suggest only minor changes in qualitative species composition; PS values decreased more rapidly, indicating larger changes in species cover. A few well‐rooted perennial plants were predominant, therefore, PS decline resulted from dominance‐controlled community structure. PS‐value detected not only habitat difference, but also the rate of the volcanic succession, suggesting that PS is most effective to evaluate successional pace.
Population dynamics of coniferous and broad‐leaved trees in a Japanese temperate mixed forest
Authors: Nakashizuka Tohru 
Published: May 2006

AbstractThe growth and survival of coniferous and broad‐leaved trees were followed over a 5‐yr period in a temperate old‐growth mixed forest in Japan, and dynamic features of the forest were studied in relation to the life history of the dominants, the coniferous Abies homolepis and the broad‐leaved Fagus crenata. During this period, the gap formation rate was 31m2 ha−1yr−1, the mortality of trees > 2m high was 1.7%/yr, and the rate of loss in basal area 1.4%/yr. These values were much higher than the recruitment, 0.3%/yr, and the total growth of surviving and new trees, 0.6%/yr, owing to the inhibition of regeneration by understorey dwarf bamboo (Sasa borealis).A transition matrix model based on DBH size classes predicts that the basal area of the forest will decrease by 14% in 50 yr, but that the DBH distribution of trees > 10 cm diameter will change little. Equilibrium DBH distributions assuming recruitment being equal to mortality, were quite different between broad‐leaved and coniferous trees, reflecting different survivorship curves of the two dominants.The composition and structure of the forest may change depending on the pattern and frequency of disturbances, or episodic events, notably the synchronous death of Sasa borealis.
A two‐phase mosaic in a savanna grassland
Authors: Carter A. J. , O'Connor T. G. 
Published: May 2006

AbstractA two‐phase grassland mosaic was described using species association measures and pattern analysis techniques on local frequency data from six transects of contiguous quadrats. One phase consisted of almost mono‐specific patches of Setaria incrassata, which was negatively or not associated with ten common species. The other phase was dominated by Themeda triandra which was positively associated with several species.PQV analyses revealed similar, significant, anisotropic scales of contagion of Setaria and Themeda, with phases alternating over 9 m up‐slope and 4 m along the contour. Setaria was associated with a tree canopy and deeper soils of higher organic carbon content than Themeda, which was negatively associated with tree canopies. Excavation of Setaria rhizomes indicated mean densities of 20.5 putative genets/m2 and 3.6 ramets per genet. Dense clonal growth, seedling recruitment and a competitive exclusion mechanism may contribute to patch maintenance.
Plot size and estimation efficiency in plant community studies
Authors: Kenkel N. C. , Podani J. 
Published: May 2006

We examine the effects of changing plot size on parameter estimation efficiency in multivariate (community‐level) ecological studies, where estimation efficiency is defined in terms relating to the statistical precision of estimates of all variables (e.g. species) in a data set. Three ‘efficiency criteria’ for multivariate estimation are developed, and the relationship between estimation efficiency and plot size examined using three field data sets (deciduous understory, coniferous understory, and mire vegetation) from central Canada.For all three communities, estimation efficiency was found to increase monotonically with increasing plot size. However, relative gains in efficiency at larger plot sizes were offset by substantial increases in sampling effort (enumeration time per plot). Our results indicate that the largest plot size possible, given the constraints of time, should be used for parameter estimation in plant communities. Also, plots that are larger than the mean patch size should be utilized when sampling heterogeneous vegetation.
Overstory vegetation and successional trends of Land Between The Lakes, USA
Authors: Franklin Scott B. , Robertson Philip A. , Fralish James S. , Kettler Stephan M. 
Published: May 2006

Abstract133 stands from the uplands of Land Between The Lakes (LBL) were sampled. Stand data were ordinated to identify clinal patterns in the overstory vegetation. A coeno‐cline, accounting for 52% of the species variance, was developed from the first ordination axis. Classification of stands identified nine dominance types: Pinus echinata‐Quercus spp., Q. prinus, Q. prinus‐Q. alba, Q. stellata‐Q. alba, Q. velutina‐Q. alba, Q. alba, Q. alba‐Q. rubra, Acer saccharum‐Q. alba‐Fagus grandifolia sadF. grandifolia‐A. saccharum.Compositionally‐stable (climax) and unstable (successional) stands were analyzed separately. Trajectories of unstable stands include the succession of P. echinata to Quercus‐dominated communities on xeric sites and of Quercus types to more mesophytic communities (e.g. A. saccharum and F. grandifolia) onmesic sites. These shifts indicate the nature of the future climax overstory composition at LBL.The first axis DCCA ordination for climax stands accounted for 45% of the vegetation variance. Factor Analysis identified two significant suites of variables related to vegetation: soil chemistry/soil moisture and soil texture. Specific variables related to variation in the climax vegetation include soil pH, calcium and magnesium, effective soil depth, available water capacity, percent rock in the soil, slope position, aspect, elevation and distance to the opposing slope.Modal positions of species along the direct gradient ordination were similar in rank order to those derived from the indirect gradient ordination of all stands. The latter ordination represents the present forest vegetation pattern at LBL. Climax stands showed a shift in modes of Quercus spp. toward the xeric end of the gradient and increases in habitat width of mesophytic species. Following a reduction in disturbance, species appear to adjust to changes in competition and available habitat. That is, the dimensions of realized niches (i.e. habitat widths) change with succession. The climax vegetation at LBL appears to show centrifugal organization.
Forest development in canopy gaps in old‐growth beech (Nothofagus) forests, New Zealand
Authors: Stewart Glenn H. , Rose Alan B. , Veblen Thomas T. 
Published: May 2006

Abstract. Tree size and age structures, treefall and canopy gap characteristics, and regeneration responses to treefalls were compared for three stands of old‐growth beech (Nothofagus) forest dominated by N. fusca and N. menziesii on the South Island, New Zealand. Treefall gaps (up to 1000 m2) were most often caused by standing trees killed by drought and/or insect attack, or by trees snapped by wind. The causes of gap formation and the size and age distributions of treefall gaps varied between localities because of spatial and temporal differences in the histories of disturbance. At Fergies Bush where drought‐related dieback had produced many large gaps with standing dead trees, gaps were generally young. Conversely, at Station Creek, small, old gaps formed by bolesnap dominated the disturbance regime. At Rough Creek, gaps of all ages and sizes were found along with an almost complete fern cover, and abundant shrubs and occasional subcanopy hardwood trees.Although overall patterns of regeneration were unrelated to differences in gap size, the relative abundance of N. fusca and N. menziesii varied between localities according to the seemingly minor differences in forest structure and disturbance history described above. Interpretations of regeneration response to gap parameters, therefore, need to account for differences in disturbance history between sites. Differences in the disturbance history between localities will also influence rates of gap closure, and because closure rates are used to estimate forest turnover times, meaningful comparisons of disturbance regimes for different forest types can only be made if this intersite variability is addressed.
On the use of three performance measures for fitting species response curves
Authors: Ferrer‐Castán Dolores , Calvo José F. , Esteve‐Selma Miguel A. , Torres‐Martínez Antonio , Ramírez‐Díaz Luis 
Published: May 2006

Abstract. Quantitative response surfaces obtained from three performance measures, density, cover and volume, are compared, using as an example the spatial distribution of Periploca angustifolia (Asclepiadaceae) in SE Spain. Generalized linear models are used to examine relationships between these species performance measures and complex gradients of aspect, slope angle and altitude.All three performance measures showed a skewed response to the environmental gradients, unlike the Gaussian responses commonly assumed in vegetation theory; skewness increased as the number of dimensions of the performance measures increased. Certain asymmetries between the responses are discussed in terms of competition, and problems related to the use of complex gradients are considered.
Long‐term after effects of fertilization on above‐ground phytomass and species diversity in calcareous grassland
Authors: Willems J.H , van Nieuwstadt M.G.L 
Published: May 2006

Abstract. Long‐term after effects on species number and productivity in calcareous grassland were analyzed after cessation of fertilization. Three series of permanent plots were monitored yearly from 1971 to 1993. These series differed in duration of fertilization and in fertilizer composition, notably the amount of nitrogen and phosphorus.Yearly above‐ground production decreased in all series after fertilization had been stopped, however at different speeds. The grass/forb ratio also decreased, while species number and Shannon index of diversity (H') increased. In the series where fertilizer treatment was stopped in 1967 (1968‐series), productivity and grass/forb ratio decreased equally as in the plots where fertilization with a high nitrogen content was stopped in 1979 (80/Npk‐series). However, species number in the plots of the 80/Npk‐series increased faster than in the 1968‐series. This was probably the result of a higher number of species present in the seed rain from the surrounding vegetation in the period after 1980 than from after 1968.In the plots receiving a high amount of phosphorus (80/nPk series), the productivity decreased more slowly than in the high nitrogen plots (80/Npk‐series). At approximately the same total production level, the grass/forb ratio remained higher for another five‐year period in the 80/nPk‐series. Species number and the Shannon index of diversity increased more slowly in the 80/nPk‐series than in the 80/Npk‐series. Over a given range of productivity, changes in species number and Shannon index correlated better with the grass/forb ratio than with total above‐ground phytomass. Therefore, restoration of species‐rich grassland should not only be focused on lowering the yearly production, but also on reducing the grass component of the vegetation.
Plant functional types and ecosystem function in Mediterranean shrubland
Authors: Díaz Barradas M.C. , Zunzunegui M. , Tirado R. , Ain‐Lhout F. , García Novo F. 
Published: May 2006

Abstract. This study attempts to identify Plant Functional Types (PFTs) within the scrub vegetation of the stabilized sand dunes of the Doñana National Park (southwestern Spain) and to explore possible links with ecosystem function. Two 10‐km long transects were sampled along a gradient of water table depth from elevated and dry dunes to a border area close to the salt marsh.A matrix of cover values for 20 woody species × 58 plots and a matrix of 24 morphological and physiological traits × 20 species were analysed by means of DCA and TWINSPAN to identify the main vegetation types and PFTs. In order to know the predominant plant traits, the matrix of 20 species × 58 plots was multiplied by the 24 traits × 20 species matrix. The resulting 24 traits × 58 plots matrix was analysed by means of DCA.The main vegetation types coincide with the previous descriptions of the Park with Juniperus phoenicea woodland and xerophytic species dominating the top of the dunes and hygrophytic species with isolated Quercus suber trees in the depressions. Previous classifications of Mediterranean woody plants resulted in two main PFTs. The present analysis confirmed these two groups: maquis versus garrigue, but added four new groups. The analysis of the traits × plots matrix revealed that the main trend of variation is related to the water table gradient, while the traits related to the species of mature plant communities had little weight in the analysis because these communities are restricted to isolated patches.
Fire, canopy cover and seedling dynamics in Mediterranean shrubland of northeastern Spain
Authors: Lloret Francisco 
Published: May 2006

Abstract. Seedling establishment and survival of the main woody species of early‐successional shrubland in northeastern Spain were studied from 1992 to 1995 with emphasis on the importance of vegetation cover (existence of open areas and the situation beneath the plant canopy) and microhabitat (occurrence of stones, litter and bare soil). In the absence of fire, vegetation cover (measured at a scale of 30cm × 30 cm) was not correlated with seedling emergence of most species, nor with growth and survival of seedlings up to one year old. Seedlings older than one year showed a similar pattern: their density was not significantly different in both kinds of habitats. The emergence of seedlings was mainly associated with the presence of mature plants – which can provide seeds – and with the absence of unsuitable microhabitats (large stones, deep litter and bare soil).In April 1994 a wildfire burned the study area. This enabled a study of the pattern of post‐fire establishment. After the wildfire, seedling emergence of several species increased and most species produced seedlings with higher survival and growth rates than in the period before the fire. Pre‐fire cover, however, did not show significant effects on post‐fire seedling dynamics in most cases.