bluuebunny/crossref_metadata_2025_split huggingface dataset:
Seedling development of the miombo woodland tree Julbernardia globiflora
Authors: Chidumayo E. N. 
Published: May 2006

Abstract. The development of seedlings of the miombo tree (Julbernardia globiflora) was studied for 28 months (December 1987 ‐ April 1990) at a Zambian grassland site from which fire has been excluded for many years. Germination occurred 10–25 days after seed planting and germination rates under laboratory and field conditions did not differ significantly.Seed germinability after one year of storage declined to 38 %. Leaf production occurred between December and April with peaks in January each year. Leaf fall occurred steadily throughout the dry season but leafless seedlings were first observed in August of each year. All seedlings had shed all their leaves by the end of November during the first year while 10% of the seedlings remained leafy throughout the second year. Annual seedling mortality was about 60 % during the first year and declined to 3 6 % during the second year. Survivorship appeared to stabilise at 3 8 % when seedlings were 5 5 ‐ 5 9 weeks old. Every seedling experienced shoot die‐back during the first hot dry season (September ‐ November) when open‐pan evaporation rates averaged 5–10 mm / day. However, shoot mortality did not necessarily result in plant mortality. Because of recurrent shoot die‐back there was little increase in shoot biomass and height at the end of the second and third growing seasons. Seedlings that survived shoot die‐back sprouted from roots which showed a steady annual accumulation of biomass.Early shoot die‐back in seedlings of Julbernardia globiflora as documented in this study was not causedby fire but most probably by drought and / or nutritional stress.
BOOK REVIEWS
Authors: Snoeijs Pauli 
Published: May 2006

Book reviewed in this issue.Margulis, L., Corliss, J. O., Melkonian, M. & Chapman, D. J. (eds.) 1990. Handbook of Protoctista. The structure, cultivation, habitats and life histories of the eukaryotic micro‐organisms and their descendants exclusive of animals, plants and fungi, xii + 914 pp. Jones and Bartlett Publishers, Boston. ISBN 0–86720–052–9. Price: GBP 195.‐.
Fire regimes and phytomass growth dynamics in a Quercus coccifera garrigue
Authors: Trabaud Louis 
Published: May 2006

AbstractAn experiment was set up in a Quercus coccifera garrigue in southern France to analyze the effect of burning frequency and season on phytomass production. Fire regimes consisted of late spring or early autumn burns, every 6 yr, every 3 yr, or every 2 yr. The experiment started in 1969 and lasted for 19 yr. In May 1981 and May 1987, 10 samples, each 1 m2, were harvested per treatment. Fire frequency had an effect on the quantity of phytomass which was produced: above‐ground phytomass decreased with increasing fire frequency. This was mainly due to the lower biomass of woody plants.In all burning treatments the phytomass of herbs was higher than in the unburned vegetation. Within each burning frequency, the total phytomass of the spring‐burned vegetation was always higher than that of the autumn‐burned community. Generally, the herb phytomass produced was higher in the autumn‐burned plots. There were two fairly distinct phases in the period following fire, each with a different level of annual phytomass production. For the first six years it was about 300 g m−2 yr−1, falling thereafter to about 50 g m−2 yr−1. This and other studies on Q. coccifera garrigue indicate that this community is very resilient with respect to fire, but possesses a low productive capacity and does not show any sign of degeneration up to 30 yr old.
Abundance of trees and grasses in a woodland savanna in relation to environmental factors
Authors: Ben‐Shahar R. 
Published: May 2006

AbstractThe relationships of plant species associations and underlying environmental factors in a woodland savanna in South Africa were investigated. 40 plots were included with 25 tree and 17 grass species dominating the arboreal and ground cover. Correspondence Analysis described the relationships between soil moisture retention, soil nutrients and the abundance of trees and grasses. Dry matter indices represented the accumulated effects of rainfall, fire and grazing of the herbaceous layer. Variations in the abundance of plants corresponded to well‐defined gradients of soil nutrients. The distribution of grass and tree species along the ordination axes indicated that soils with high water retention capacity and high nutrient contents provided a suitable substrate for many of the tree species sampled. However, grass species abundance was high in plots with porous soils and poor nutrient availability.
Nested spatial patterns in seed bank and vegetation of Mediterranean old‐fields
Authors: Lavorel S. , Lebreton J. D. , Debussche M. , Lepart J. 
Published: May 2006

AbstractA nested sampling design was used to describe the spatial patterns for the species richness and composition in the seed bank and vegetation of three Mediterranean old‐fields (1, 7, and 15 yr after the last ploughing). Three scales were examined hierarchically: sampling units within plots of 0.25 m2 for the vegetation and of 0.05 m2 for the seed bank, 100 m2 plots within fields, and fields of 1000 m2. In spite of the strong spatial variation among sampling units, species richness and composition of both seed bank and vegetation showed hierarchically structured patterns of heterogeneity, while each old‐field was a homogeneous entity. These spatial patterns tended to be partially masked when the data were aggregated at the scale of the plot. Such results stress the use of a nested sampling design for studying variation in species richness and taxonomic composition in both vegetation and seed bank. This design, in combination with CCA, also showed that the vegetation showed a coarser grain than the seed bank, probably in relation to seed clumping.
Effects of woodlot isolation on the dispersion of plants with fleshy fruits
Authors: van Ruremonde R. H. A. C. , Kalkhoven J. T. R. 
Published: May 2006

AbstractBy relating species presence, number and density to the perimeter and isolation of small (0.1–2.75 ha) homogeneous woodlots (n = 43), indications were obtained that some fleshy‐fruited species are negatively affected by woodlot isolation. The number of fruit‐bearing herbaceous perennial species increased with woodlot area, probably because of the increasing heterogeneity of the herb layer. The density of individuals of the investigated species were negatively correlated to woodlot area. There were also some indications thatthe presence/absence of species was related to the length of the forest edge (e.g. Hederá helix). Because woodlot area and shape index were strongly correlated, the effects of increased forest area and forest edge were hard to separate.The probability of occurrence of Lonicera periclymenum and the density oí Ilex aquifolium decreased with an increasing degree of isolation of present forest islands. The chance of occurrence of L. periclymenum decreased also with the degree of isolation in the past, measured from topographical maps of about 60 yr ago.The total area of broad‐leaved forest within a radius of 500 m, as well as the distance to the nearest connecting landscape element, seem to be good indicators of woodlot isolation.
A remnant New Zealand carr
Authors: Sykes Martin T. , Wilson J. Bastow , Lee William G. , Allen Ralph B. 
Published: May 2006

AbstractCarr vegetation was once extensive in New Zealand. It can be divided into Cordyline australis I Carex secta carr, comprising an open wood with scattered large herbs and an abundance of Carex species, and podocarp carr, dominated by tall conifers. Both have been almost eliminated by agricultural development. We studied a remnant of Cordyline australis I Carex secta carr in South Island, which graded at one end into salt marsh. Eight communities were recognized, including one pure salt marsh and two more with saline influence. Near the stream that provided moisture and alluvium for the area were herbaceous communities. In the poorly‐drained area away from the stream were communities dominated by shrubs and small trees. The soil environment is similar to that of many European carrs, though generally less organic. A number of the exotic species are also found in European carrs.
Vegetation zonation in dune slacks on the Leba Bar, Polish Baltic Sea coast
Authors: Zoladeski Christopher A. 
Published: May 2006

AbstractVegetation zones in dune slacks on the Leba Bar on the Polish Baltic Sea coast are described. Plant colonization starts on moist sand in eastern ends of slacks, in the wake of receding mobile dunes. Communities on deflation ribs, dominated by psammophytic grasses, sedges and lichens, are structurally simple. Communities in troughs, dominated by species of fresh habitats, become structurally more complex in a western direction and they culminate with thePinus silvestrisforest. The main lines of vegetation variation correlate with groundwa‐ter depth, micro topography, soil profile build‐up and substrate acidification.
Demographic structure of California chaparral in the long‐term absence of fire
Authors: Keeley Jon E. 
Published: May 2006

Abstract. Demographic structure of 12 chaparral sites unburned for 56 to 120 years was investigated. All sites were dominated by vigorous shrub populations and, although there was colonization by seedlings of woodland tree species in several stands, successional replacement of chaparral was not imminent. Although successional changes in community composition were evident, there was no indication of a decline in species diversity. Non‐sprouting species of Ceanothus suffered the greatest mortality at most, but not all, sites. Sprouting shrubs, such as Quercus and Heteromeles had very little mortality, even in stands more than a century old. All postfire resprouting species had multiple stems of different ages indicating these shrubs were capable of continuously regenerating their canopy from basal sprouts. Ceanothus populations were highly clumped and there was a significant correlation across all sites between variance/mean ratio and percentage mortality. As Ceanothus populations thinned, they became less clumped. In mixed chaparral stands, Quercus and Heteromeles were significantly taller than associated Ceanothus shrubs and overtopped the Ceanothus; at two sites, the density of live Quercus per plot was correlated with the density of dead Ceanothus. Thus, mortality of Ceanothus stems is likely related to both intra and interspecific interations.Seedling recruitment was observed for most shrub species that regenerate after fire by resprouting; seedling and sapling densities ranging from 1000–36 500 ha‐1 were recorded for Quercus dumosa, Rhamnus crocea, Prunus ilicifolia, Heteromeles arbutifolia and Cercocarpus betuloides. For all but the last species, seedlings and saplings were most abundant beneath the canopy cover and not in gaps. Across all sites, recruitment was significantly correlated with depth and bio‐mass of the litter layer. Cercocarpus betuloides was present in several stands, but seedling establishment was found only in one very open, disturbed stand. Regardless of stand age, taxa such as Adenostoma, Arctostaphylos and Ceanothus, which recruit seedlings after fire, had no significant seedling production.
The relationship between the seed bank and species composition of plant communities in two British salt marshes
Authors: Ungar Irwin A. , Woodell S. R. J. 
Published: May 2006

AbstractThe composition of the seed bank was compared with that of the above‐ground vegetation in two British salt marshes. Vegetation and seed banks were sampled in autumn and spring. There was a relatively low correlation between seed bank and vegetation in most perennial‐dominated zones. Percentage annual plant cover was significantly positively correlated to percentage similarity value between vegetation and seed bank. Cluster analysis indicated that the zones dominated by annuals and by Suaeda vera on the ungrazed Nod Marsh in Norfolk formed groups between seed bank and vegetation, whereas on the Llanrhidian Marsh in Wales the seed bank of four of the six zones formed a group.
Ecology of a paramo cushion mire
Authors: Bosnian A.F. , van der Molen P.C. , Young R. , Cleef A.M. 
Published: May 2006

Abstract. The vegetation ecology of a paramo cushion mire was studied along four transects. Six local vegetation types were distinguished. Two types are called cushion bogs; one is dominated by Oreobolus cleefii and the other by Plantago rigida. Types 3 and 4 are mire vegetation dominated by bryophytes; one is characterised by Sphagnum sparsum, Breutelia sp. and Campylopus cucullatifolius, the other one is dominated by Lophozia subinflata with Cortaderia sericantha. Vegetation type 5 is dominated by submerged Sphagnum cyclophyllum; type 6 refers to aquatic vegetation with only Equisetum bogotense and algae.The relation between the first four vegetation types and edaphical and hydrological gradients is analysed by means of Canonical Correspondence Analysis (CCA). From the results of CCA it can be concluded that the occurrence of the Oreobolus cleefii type is restricted to areas with a thinner peat layer, a wider distance surface‐anaerobic zone and water table‐anaerobic zone, a higher NO2 concentration and a lower pH. The occurrence of the Plantago rigida type is restricted to a situation with a lower electrical conductivity of the ground water, a lower NO3 and PO4 concentration, and a higher Fe concentration. The occurrence of the Sphagnum type is restricted to places with a higher conductivity of the ground water, a higher NO3 and PO4 concentration, and a lower Fe concentration. The occurrence of the Lophozia subinflata with Cortaderia sericantha type is restricted to a situation with a lower K and Al concentration.
BOOK REVIEWS
Authors: Thompson Philip A. 
Published: May 2006

Book reviewed in this issue.Dafni, A. 1992. Pollination Ecology: A Practical Approach. xiv + 250 pp. Oxford University Press, Oxford, U.K. Cloth: ISBN 0–19–963299–5. Price: USD 56.95. Paper: ISBN 0–19–963298–7. Price: USD 39.95.
BOOK REVIEWS
Authors: Denslow Julie S. 
Published: May 2006

Book reviewed in this issue.Holm‐Nielsen, L. B., Nielsen, I. S. & Balslev, H. (eds.) 1989. Tropical Forests: Botanical Dynamics, Speciation and Diversity, xv + 380 pp. Academic Press, London. ISBN 0–12–323550–6. Price: USD 49.50.
Floristic classification and ecology of tundra vegetation of the Taymyr Peninsula, northern Siberia
Authors: Matveyeva Nadezhda V. 
Published: May 2006

Abstract. A first systematic description is presented of tundra plant communities of the Taymyr Peninsula, northern Siberia, using the floristic approach of the Braun‐Blanquet School. Five associations are described: 1. Carici arctisibiricae‐Hylocomietum alaskanii, the main‘zonal’association, widely spread on ‘plakor’, i.e. flat or slightly sloping well‐drained sites in the tundra zone, but absent in the polar desert zone. 2. Meesio triquetris‐Caricetum stantis, typical for mire depressions throughout the tundra zone. 3. Poo arcticae‐Dupontietum fisheri, found in the northern part of the typical tundra subzone on western Taymyr. 4. Gymnomitrio‐Phippsietum concinnae and 5. Deschampsio‐Cerastietum regelii, which occur on snowbeds with various snow duration. Within several of these associations vicariants are described.These syntaxa are only the first to be described for the Taymyr area. A complete description is still under way.
Primary succession of Hawaiian montane rain forest on a chronosequence of eight lava flows
Authors: Kitayama Kanehiro , Mueller‐Dombois Dieter , Vitousek Peter M. 
Published: May 2006

Abstract. The primary‐successional sere of a Hawaiian montane rain forest was inferred from an age sequence of eight closely located ‘a’ ā flows (clinker type lava); 8, 50, 140, ca. 300, ca. 400, ca. 1400, ca. 3000 and ca. 9000 yr, on a windward slope of Mauna Loa, Hawaii.All study sites (0.2 ha each) were at 1120 — 1250 m a.s.l. with 4000 mm mean annual rainfall. The 400‐yr, 1400‐yr, and 9000‐yr flows had younger volcanic ash deposits, while the others were pure lava. Comparisons of tree size and foliar nutrients suggested that ash increased the availability of nitrogen, and subsequently standing biomass. An Unweighted Pair Group Cluster Analysis on the samples (flows) using quantitative vascular species composition revealed that clusters were correlated with age regardless of the substrate types (pure lava vs. ash), and an indirect ordination on the samples suggested that the sequence of sample scores along axis 1 was perfectly correlated with the age sequence. Although ash deposits increased biomass, they did not affect the sequence of the successional sere. Both pubescent and glabrous varieties of Metrosideros polymorpha (Myrtaceae) dominated upper canopy layers on all flows ≥ 50 yr and ≤ 1400 yr, but the pubescent variety was replaced by the glabrous on the flows ≥ 3000 yr. Lower layers were dominated initially by a matted fern, Dicranopteris linearis, up to 300 yr, and subsequently by tree ferns, Cibotium spp., to 9000 yr. The cover of Cibotium declined slightly after 3000 yr, while other native herb and shrub species increased. A ‘climax’ stage in the conventional sense was apparently not reached on the observed age gradient, because the sere changed continuously in biomass and species; this divergent successional phenomenon may be unique to Hawaii where the flora is naturally impoverished and disharmonic due to its geographic isolation in contrast to more diverse and harmonic floras in continents.
Parallel Analysis: a method for determining significant principal components
Authors: Franklin Scott B. , Gibson David J. , Robertson Philip A. , Pohlmann John T. , Fralish James S. 
Published: May 2006

Abstract. Numerous ecological studies use Principal Components Analysis (PCA) for exploratory analysis and data reduction. Determination of the number of components to retain is the most crucial problem confronting the researcher when using PCA. An incorrect choice may lead to the underextraction of components, but commonly results in overextraction. Of several methods proposed to determine the significance of principal components, Parallel Analysis (PA) has proven consistently accurate in determining the threshold for significant components, variable loadings, and analytical statistics when decomposing a correlation matrix. In this procedure, eigenvalues from a data set prior to rotation are compared with those from a matrix of random values of the same dimensionality (p variables and n samples). PCA eigenvalues from the data greater than PA eigenvalues from the corresponding random data can be retained. All components with eigenvalues below this threshold value should be considered spurious. We illustrate Parallel Analysis on an environmental data set.We reviewed all articles utilizing PCA or Factor Analysis (FA) from 1987 to 1993 from Ecology, Ecological Monographs, Journal of Vegetation Science and Journal of Ecology. Analyses were first separated into those PCA which decomposed a correlation matrix and those PCA which decomposed a covariance matrix. Parallel Analysis (PA) was applied for each PCA/FA found in the literature. Of 39 analy ses (in 22 articles), 29 (74.4 %) considered no threshold rule, presumably retaining interpretable components. According to the PA results, 26 (66.7 %) overextracted components. This overextraction may have resulted in potentially misleading interpretation of spurious components. It is suggested that the routine use of PA in multivariate ordination will increase confidence in the results and reduce the subjective interpretation of supposedly objective methods.
Changes in Mediterranean plant succession: old‐fields revisited
Authors: Debussche Max , Escarré José , Lepart Jacques , Houssard Claudie , Lavorel Sandra 
Published: May 2006

Abstract. Old‐field plots used for a study of succession in Mediterranean France were revisited after 12–14 yr. Our aims were: (1) to verify if predicted patterns of species richness, turnover and composition are confirmed; (2) to compare the development in disturbed plots with that in undisturbed ones; (3) to discuss the impact of management changes.In undisturbed plots species richness and turnover decreased with successional age. Floristic composition changed in a way consistent with the predicted successional development in most plots. Therophytes decreased and phanerophytes increased; anemochorous species decreased and endozoochorous species increased, as expected. In plots disturbed since the first analysis richness decreased with successional age, but generally remained higher than in undisturbed plots. Floristic composition, species turnover and an increase in therophytes indicated changes towards younger successional stages. Thus, disturbance changed succession but not much. This is probably linked with the regeneration abilities typical of mediterranean species, e.g. resprouting. At the landscape scale, richness did not change and species turnover was low.The plots studied were situated in two distinct locations. One had not been disturbed between the two observation periods, while the other is a mosaic of undisturbed and disturbed sites. Observations fitted predictions much more closely at the undisturbed location.We conclude that permanent plot studies are powerful in identifying successional trends and can also provide additional insights into the effects of disturbance some of the mechanisms underlying the dynamics of diversity.
Vegetation heterogeneity and diversity in flat and mountain landscapes of Patagonia (Argentina)
Authors: Jobbágy Esteban G. , Paruelo José M. , León Rolando J.C. 
Published: May 2006

Abstract. We studied floristic and diversity patterns and their environmental controls in two landscapes of contrasting topography in the Patagonian steppe. The analyses were focused on the effects of water availability gradients and landscape configuration on plant species distribution and coexistence.Floristic variation was investigated using Correspondence Analysis. The relationship between floristic and environmental variation was analyzed using Canonical Correspondence Analysis and correlation tests. We explored diversity patterns by relating spatial distance to floristic dissimilarities. The floristic gradient was determined by shrub and grass species and was related to precipitation in the flat area, and to precipitation, elevation and potential radiation in the mountain area. Site species richness increased with water availability in both areas. Mean site species richness and species turnover in space was higher in the mountain than in the flat area. Landscape species richness and floristic gradients were more concentrated in the mountain than in the flat area. In contrast to shrubs and grasses, forb species distributions were uncoordinated and probably independent of any environmental gradient. Our results suggest (1) that landscape configuration affects species composition and diversity through its direct effect on abiotic environmental heterogeneity, and (2) that the environmental controls of the community composition vary depending on the plant functional type considered.