bluuebunny/crossref_metadata_2025_split huggingface dataset:
Natural disturbance and tree species coexistence in an old‐growth beech ‐ dwarf bamboo forest, southwestern Japan
Authors: Yamamoto Shin‐Ichi , Nishimura Naoyuki , Matsui Kiyoshi 
Published: May 2006

Abstract. The structure and composition of a cool‐temperate old‐growth beech (Fagus crenata) ‐ dwarf bamboo (Sasa spp.) forest, partially affected by landslide disturbance, in the Daisen Forest Reserve of southwestern Japan, were investigated in relation to forest floor and canopy conditions. All stems ≥ 4 cm DBH were mapped on a 4‐ha plot and analyses were made of population structure, spatial distribution and spatial association of major tree species. The dominant species, F. crenata, which had the maximum DBH among the species present, had the highest stem density. However, for other species, larger‐sized species had lower stem density with few smaller stems or saplings, while smaller‐sized species had higher stem density with many smaller stems or saplings. Canopy trees of F. crenata were distributed randomly in the plot, while its stems in the other layers and all other species were distributed patchily. Small patches represent gap‐phase regeneration. Larger patches correlate with landslide disturbance, difference in soil age, or the presence/absence of Sasa. Cluster analysis for spatial associations among species and stems in the different layers revealed that the forest community consists of several groups. One main group was formed on sites not covered with Sasa. This group contained a successional subgroup (from Betula grossa to Acer mono and/or F. crenata) initiated by landslide disturbance and a subgroup of tree species that avoid Sasa. Another group was formed on sites with mature soils covered largely with Sasa. This contained associations of canopy trees of F. crenata and smaller‐sized tree species such as Acanthopanax sciadophylloides and Acer japonicum.It is found that the community of this old‐growth beech forest is largely organized by natural disturbance and heterogeneous conditions of the forest floor (difference in soil age and presence/absence of Sasa). The existence of these different factors and the different responses of species to them largely contribute to the maintenance of tree species diversity in this forest.; Keywords: Cluster analysis; Fagus crenata; Forest dynamics; Gap; Landslide; Spatial pattern.
Patterns of ecological, chorological and taxonomic diversity at both sides of the Strait of Gibraltar
Authors: Ojeda F. , Marañón T. , Arroyo J. 
Published: May 2006

Abstract. Diversity relations in Mediterranean heathlands and the understorey of oak woodlands on sandstone‐derived substrates were studied at both sides of the Strait of Gibraltar. Trends in species composition and cover were analysed by Detrended Correspondence Analysis; the first axis, assumed to reflect a main environmental gradient, was used to analyse the patterns of three aspects of community diversity. Species richness, i.e. number of species along a 100‐m transect, shows a humpbacked trend along the gradient, with the highest values in the understorey of evergreen Quercus suber woodlands, associated with soils of intermediate fertility and moisture status. The number of endemic species is highest in open heathlands, associated with more extreme conditions of acid, infertile soils on exposed ridges. The taxonomic singularity, as measured by the inverse of the average number of species per genus at each site, is highest at the most fertile and moist sites occupied by semideciduous Q. canariensis woodlands.A comparison between northern (Spanish) and southern (Moroccan) sides of the Strait of Gibraltar shows a general concordance of the trends of woody plant communities along the main environmental gradient. However, significant differences of the southern samples are: (1) lack of some differential, habitat‐specific species and greater abundance of widespread generalists; and (2) a general reduction in species diversity, number of endemics and taxonomic singularity. We interpret these differences as affected partly by the smaller extent and fragmentation of sandstone areas in the south, and partly by the higher impact of slashing and grazing there.
Revegetation following experimental disturbance in a boreal old‐growth Picea abies forest
Authors: Rydgren Knut , Hestmark Geir , Økland Rune H. 
Published: May 2006

Abstract. We studied revegetation patterns after experimental fine‐scale disturbance (e.g. uprooting) in an old‐growth Picea abies forest in southeastern Norway. An experimental severity gradient was established by manipulation of the depth of soil disturbance; two types of disturbed areas were used. Species recovery was recorded in the disturbed patches in three successive years after disturbance. The cover of vascular plants and, even more so the cover of bryophytes and lichens, recovered slowly after disturbance. The least severe treatments (removal of vegetation and removal of vegetation and the litter layer) was followed by the fastest recovery. The mean number of vascular plant species was usually higher three years after disturbance than before disturbance, while the opposite was true for bryophytes. Several vascular plant species that were abundant in intact forest floor vegetation (Vaccinium myrtillus, V. vitis‐idaea and Deschampsia flexuosa) recovered during a three‐year period primarily by resprouting from intact rhizomes and clonal in‐growth. Other important recovery mechanisms included germination from a soil‐buried propagule bank (e.g. Luzula pilosa, Plagiothecium laetum agg., Pohlia nutans and Polytrichum spp.) and dispersal of propagules into the disturbed patches (e.g. Betula pubescens and Picea abies). Microsite limitation seemed to occur in several species that were abundant in the soil propagule bank (e.g. the ferns Athyrium filix‐femina, Gymnocarpium dryopteris and Phegopteris connectilis) but which did not appear in disturbed patches.Disturbance severity influenced revegetation patterns, recorded both as trajectories of vegetation composition in a DCA ordination space and as change in floristic dissimilarity. The length of the successional path (compositional change measured in β‐diversity units) increased with increasing disturbance severity, and was also influenced by the area of the disturbed patch and the distance to intact vegetation. The rate of succession depended on the method by which it was measured; decreasing year by year in floristic space, while first decreasing and then increasing in ordination space. The reason for this difference is explained.
Influence of edaphic factors on the spatial structure of inland halophytic communities: a case study in China
Authors: Pan Daiyuan , Bouchard André , Legendre Pierre , Domon Gérald 
Published: May 2006

Abstract. In order to understand the influence of edaphic factors on the spatial structure of inland halophytic plant communities, a 2.6 km2 study site, located on the lower fringe of the alluvial fan of the Hutubi River, in an arid region of China, was sampled and mapped. 105 patches were found to be homogeneous in species composition. Plant species and their coverage were recorded in each patch. 45 patches were randomly selected for the measurement of edaphic variables. A map with quadrat locations and boundaries of patches was digitized into a GIS and related to the vegetation and edaphic data matrices. CCA was used to evaluate the relative importance of edaphic factors in explaining the variation of the species assemblages and to identify the ecological preferences of species. The spatial structure of the communities and the main edaphic factors were analyzed using correlograms, Mantel correlograms and clustering under constraint of spatial contiguity.Gradient analysis showed that there are two distinct vegetation gradients in the study area, one of which is determined mainly by soil moisture (determined by depth to the water table), and the other by soil salinity (determined by electrical conductivity and hydrolytic alkalinity of the first soil layer). However, spatial analyses showed that at the sampling scale the halophytic communities in the study area are structured along one main spatial gradient determined by the water table level. Similar spatial autocorrelation structures between the factors related to the first soil layer and the communities, given our sampling scale, could not be detected. Our results suggest that the relative importance of the effects of different edaphic factors on the spatial structure of halophytic communities is scale‐dependent. The partitioning of species variation indicates that in addition to edaphic factors, other factors, such as biotic interactions, may play an important role in structuring these communities.
Epiphytic lichen diversity in old‐growth and managedPicea abiesstands in southern Finland
Authors: Kuusinen M. , Siitonen J. 
Published: May 2006

Abstract.Epiphytic and epixylic lichens were surveyed on 15 1‐ha plots in maturePiceaabies‐dominated boreal forests in southern Finland. The sample plots were classified into three groups according to the age of the dominant tree stand and recent signs of cutting: (1) early mature managed, ‘EM’ (95 ‐109 yr), (2) late mature managed, ‘LM’ (126 ‐ 145 yr) and (3) old‐growth, ‘OG’ (129 ‐ 198 yr). Two data sets on epiphytic and epixylic lichens were recorded from each plot: (1) species on basal trunks and branches ofPicea abiesand (2) species on all available woody substrates, including basal parts of all tree species, saplings, snags, logs and stumps.142 epiphytic and epixylic lichen species were found, of which 83 (58%) occurred onP. abies. Mean total numbers of species per sample plot were 69 in EM, 78 in LM and 88 in OG plots, species number onP. abieswere 47, 56, and 54 respectively. The LM plots had lower species numbers than OG plots, mainly due to the lack of oldPopulus tremulatrees, but they had higher species number than the EM plots mainly due to the higher age ofPicea abies. Differences in species composition, both within and between the three groups, were small. The results suggest that the epiphytic and epixylic lichen diversity in a managed stand can be increased by prolonging the rotation of the stand to >120 yr and by increasing the diversity of habitats in the stand.
Tree‐shrub interactions in a subtropical savanna parkland: competition or facilitation?
Authors: Barnes Paul W. , Archer Steve 
Published: May 2006

Abstract. Prosopis glandulosa var. glandulosa has played a central role in the encroachment of woody plants in southern Texas, grasslands and savannas by acting as a nurse plant for various shrubs that establish in its understory. To test for continued facilitation of established understory shrubs by Prosopis and to determine if established shrubs compete with the Prosopis nucleus, selective removal experiments were conducted and monitored over a 2–5 yr period. Short‐term (1–3 days) and long‐term (2 yr) growth and physiological activities (midday net photosynthesis and leaf/shoot water potential) of two common understory shrubs, Zanthoxylum fagara and Berberis trifoliolata, growing with Prosopis, were generally comparable to those of individuals occurring in clusters where Prosopis was removed. Shrubs growing with an intact Prosopis occasionally showed significantly higher leaf‐[N] and pre‐dawn water potentials than those in clusters lacking a live Prosopis, especially under drought conditions; however, these differences did not translate into greater midday leaf gas exchange or shoot growth. By comparison, removal of understory shrubs elicited large increases in Prosopis net photosynthesis, annual trunk growth in each of the 5 yr monitored, and seed pod production in three of the four years monitored. Seven of 26 Prosopis plants in experimental clusters with an intact understory died over a 5‐yr period, compared to only two of the 26 plants in clusters with the cleared understory.Results indicate that (1) the founding overstory Prosopis plant may continue to facilitate understory shrubs following their establishment, but these beneficial effects appear to be small and transitory, and (2) the understory shrubs have a pronounced negative effect on Prosopis, such that competition between overstory and understory woody plants is strongly asymmetrical. These findings suggest that understory shrubs will likely persist despite changes in microclimate and soils (potentially) that occur after the Prosopis plant, which facilitated their ingress or establishment, has died. Soil resource depletion by shallow‐rooted understory shrubs appears to be a primary factor contributing to the demise of the deeply rooted, overstory Prosopis plants, especially on upland sites with duplex soils where below‐ground competition is accentuated.
Predicting competitive interactions between pioneer plant species by using plant traits
Authors: Rösch H. , Van Rooyen M.W. , Theron G.K. 
Published: May 2006

Abstract. A competitive effect hierarchy for 15 Namaqualand pioneer plant species was established by using the mean mass of the phytometer (Dimorphotheca sinuata) when grown in combination with itself and 14 other species. There were no clear groupings of species in the hierarchy. This competitive hierarchy (gradient) indicated which species are strong competitors (resulting in a low phytometer mass) with D. sinuata and which species are weak competitors (resulting in a high phytometer mass).Each plant species has a certain combination of plant traits which determines its life history strategy and competitive ability. Regressions of various plant traits (measured on plants grown singly) against phytometer biomass indicated which traits were significantly correlated. The traits, most being size‐related, were: maximum shoot mass, total mass, stem mass, reproductive mass, leaf area, stem allocation, specific leaf area (SLA), vegetative height × diameter, leaf area ratio (LAR); and mean number of days to flower initiation. A forward stepwise multiple regression of the significant traits was used to determine an equation to predict competitive effect.
Effects of prescribed fire on the composition of woody plant communities in southeastern Texas
Authors: Liu Changxiang , Harcombe Paul A. , Knox Robert G. 
Published: May 2006

Abstract. The response to prescribed burning of plant communities ranging from dry to wet habitats was monitored using permanent plots sampled from 1989 to 1993. Temporal controls for fire effects were provided by matched sets of plots protected from fire by newly constructed fire breaks. Changes in species composition were studied by ordination of strata of trees (> 5 cm DBH), small trees (2–5 cm DBH), large saplings (1–2 cm DBH), and small saplings and seedlings (50–140 cm tall). Results show that changes occurred largely in the small tree stratum, in which xeric species increased in importance. Although there were changes in sapling and seedling strata, no clear direction of change was recognized. Fire had little effect on the tree stratum.Of the seven community types under study, three types, sandhill, upland pine, and upperslope pine‐oak, were most strongly affected, as indicated by post‐fire change in positions of samples representing these communities in ordination space and reduction in understory species abundance. Samples representing the other four mesic and wet communities showed little or no change in their positions.These short‐term results indicate that changes in vegetation resulting from fire were small and were mostly restricted to the dry types in which possible compositional change is expected to occur. This differential effect of fire suggests that the influence of fire is secondary to that of topographical and soil gradients in determining vegetation pattern under current fire regimes. Fire seems to reinforce an overall vegetation gradient controlled by soil in southeastern Texas.
Facilitation by nurse shrubs of resprouting behavior in a post‐fire shrubland in northern Patagonia, Argentina
Authors: Raffaele Estela , Veblen Thomas T. 
Published: May 2006

Abstract. The nurse‐plant syndrome is a widely recognized example of positive (facilitative) influences of plant species on the establishment and growth of other species. Most studies of the nurse‐plant syndrome have been on species that reproduce mainly from seed rather than vegetatively. In this study, we experimentally compared the influences of two species of nurse shrubs, Schinus patagonicus and Berberis buxifolia, on the survival and growth of vegetatively reproducing herbaceous and woody plants in a post‐fire shrubland in northern Patagonia, Argentina. The vegetation beneath shrubs was removed by clipping and, in a paired‐sample design, one half of the canopy of each shrub was removed. We determined species richness, counted number of resprouts, and measured photon flux density and soil moisture beneath cut and uncut halves of each shrubs.Abundances of resprouts were several times greater beneath the uncut vs. the cut shrubs, as was the mean number of species. Thus, shrubs have a strong facilitating influence as measured by resprout densities and the number of species. Numbers of resprouts and of species were twice as high beneath Schinus as beneath Berberis, implying important differences in the facilitative effects of the two shrubs species. Microsites beneath Schinus were characterized by lower and more heterogeneous light levels but by greater soil moisture. Even though the reproductive mode in this post‐fire shrubland is overwhelmingly vegetative, facilitation by nurse shrubs is important and differentially effective for different species of nurse shrubs.
Size‐structure dynamics of two conifers in relation to understorey dwarf bamboo: A simulation study
Authors: Takahashi Koichi , Kohyama Takashi 
Published: May 2006

Abstract. Size‐structure dynamics and co‐existence of the conifers Abies sachalinensis and Picea glehnii in subalpine forests in Japan, in relation to the understorey dwarf bamboo Sasa, were examined using a simulation model. This model explicitly incorporated recruitment rate, size growth rate and mortality. Recruitment and growth rates were assumed to be suppressed by the cumulative basal area of taller trees and the density of Sasa. As for the one‐sided crowding effect, two types of model were examined. The total basal area of the two species suppresses the growth and recruitment rates in an additive model, while the basal area of each species has a separate effect included in a specific model. Two types of recruitment process were examined, i.e. open and closed systems; recruitment rates of open and closed systems are independent of, and proportional to, the basal area of the same species within the plot, respectively. Parameters were estimated from data of plot censuses for four years. The parameters of the specific model showed that recruitment and size growth rates were more suppressed by the same species than the other species. Recruitment of A. sachalinensis was more sensitive to suppression by Sasa compared with P. glehnii. The stationary size structure of the two species, generated from both the models with the open system, fitted well to the observed size structures across various Sasa densities. A. sachalinensis and P. glehnii dominated at lower and higher densities of Sasa, respectively. However, the closed‐system simulation showed that the stable co‐existence of the two species with a good fit to the observed size structure occurred only in the specific model.These results suggest that within‐species interference, which is more severe than between‐species interference, is important for the co‐existence of the two species and that the relative dominance of the two species readily explained the differential responses to Sasa abundance.
Phytogeographical and community similarities of alpine tundras of Changbaishan Summit, China, and Indian Peaks, USA
Authors: Qian Hong , White Peter S. , Klinka Karel , Chourmouzis Christine 
Published: May 2006

Abstract. We compared the diversity, phytogeography, and plant communities in two mid‐latitude alpine tundras with comparable aerial and elevational extents: Changbaishan Summit in eastern Asia and Indian Peaks in western North America. Despite wide separation, the two areas shared 72 species. In all, 43% of the species on Changbaishan Summit are also distributed in the alpine zones of western North America, while 22% of the species on Indian Peaks are also distributed in the alpine zones of eastern Asia. Almost all the shared species also occur in the Beringian region. Phytogeographical profiles of species and genera showed that 69% of species and over 90% of genera in both alpine tundras belong to the three phytogeographical categories: cosmopolitan, circumpolar, and Asian‐North American. We attributed the current floristic relationship between these widely separated areas to the periodic past land connection between the two continents during the Tertiary and Pleistocene. Indian Peaks has a closer floristic relationship with the Arctic tundra than does Changbaishan Summit. Indian Peaks also has 45% higher species richness and lower vegetation cover than Changbaishan Summit.Plant communities from the two areas were completely separated in the two‐way indicator species analysis and non‐metric multidimensional scaling on floristic data at both species and generic levels, whereas ordination of communities by soil data produced a greater overlap. The plant communities on Changbaishan Summit in general have lower alpha diversity, higher beta diversity (lower between‐community floristic similarity), and more rare species than does Indian Peaks. Mosaic diversity does not differ in the two alpine tundras, although the analysis suggests that Changbaishan Summit communities are more widely spaced on gradients than the Indian Peaks communities.