bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stand dynamics of Pinus flexilis‐dominated subalpine forests in the Colorado Front Range
Authors: Rebertus A. J. , Burns B. R. , Veblen T. T. 
Published: May 2006

Population age structure and succession were investigated in subalpine forests in the Colorado Front Range dominated by Pinus flexilis (limber pine). Age, size, and spatial data were collected from three recent burns (<100 yr old), six ca. 240 year‐old post‐fire stands, and two old‐growth stands (individuals > 400 yr old). The sequence of colonization of now extant trees on these post‐fire sites appeared to be consistent: first Pinus flexilis, then Picea engelmannii (Engelmann spruce), and later Abies lasiocarpa (subalpine fir) with a delay between the first Pinus flexilis and Abies of as long as 140 yr. The advantage of Pinus flexilis on post‐burn sites can be attributed to avian seed dispersal and the exceptional drought tolerance of its seedlings. The three recent burns were not extensive, and the delay in establishment of Picea and Abies appeared to be limited by harsh site conditions rather than lack of seed dispersal.Spatial analysis indicated a consistent, although sometimes weak, attraction between Pinus flexilis and Picea and Pinus flexilis and Abies at a scale of 1–4 m, suggesting that Pinus flexilis may facilitate establishment of Picea and Abies seedlings by providing shade or protection from wind. On xeric to slightly xeric sites, Pinus flexilis appeared to form broadly even‐aged, non‐regenerating populations that were gradually being replaced by Picea and Abies. Replacement is proceeding at a faster rate on the least xeric sites (north aspects, valley bottoms) compared to the most xeric sites (south aspects). On the most extreme sites, Pinus flexilis formed all‐aged, self‐maintaining populations with no evidence of replacement by Picea and Abies. In these old‐growth forests with occasional trees aged at > 1300 yr, recruitment is continuous or episodic.
Effects of defoliation on the saplings of a gap‐colonizing neotropical tree
Authors: Núñez‐Farfán Juan , Dirzo Rodolfo 
Published: May 2006

This paper describes a defoliation experiment on saplings of the gap‐colonizing pioneer tree Heliocarpus appendiculatus in the tropical rain forest of Los Tuxtlas (Southeast Mexico). Four levels of defoliation (0, 25, 50, and 75% of the leaf area removed) were applied to naturally established plants in a medium‐sized forest gap. Records were made of growth (height, diameter, and leaf production) and of whole‐plant and leaf survival.Statistical comparisons for all variables showed that plants that had not been defoliated grew better than defoliated ones, but there were no statistically significant differences between the defoliation levels. The risk of death was significantly lower for control plants than for defoliated plants at any level of damage. Leaf survivorship was highly irregular. The most consistent pattern was that the leaves of intact plants always showed higher survivorship, while the most heavily defoliated ones always had the poorest survival. The survivorship pattern of leaves at intermediate defoliation levels was irregular.The results illustrate the lack of a monotonic response to a wide range of defoliation levels, and suggest the potential effect of herbivores as reducers of vegetative growth and survival in pioneer tropical species, and as limiting agents of plant establishment in regenerating forest gaps.
Species turnover and diversity patterns along an evergreen broad‐leaved forest coenocline
Authors: Itow Syuzo 
Published: May 2006

Direct gradient analysis was applied to the evergreen broad‐leaved forest coenocline in the Tatera Forest Reserve, Japan. 10 quadrats of 0.1 ‐0.05 ha were laid out from 140 m to 560 m above sea level at intervals of 25–70 m. Gradient analysis revealed that distributions of many species terminated or started at ca. 400 m. Community similarity, calculated in Percentage Similarity (PS) and Community Coefficient (CC), changed abruptly below and above the 400 m contour, suggesting a change of vegetation structure at this altitude, which was also clear from population distributions.The spatial turnover rate of species along the altitudinal gradient was calculated in two ways: as the Average turnover rate along the whole range of the gradient, and as the Zone turnover rate at individual altitudes. The overall rates calculated for five categories of populations: DBH > 10 cm, DBH >3 cm, all woody species, herb‐layer, and total vegetation, were‐ 0.0011 to‐ 0.0021 for PS, and ‐ 0.0009 to‐ 0.0019 for CC. The calculated rates (PS basis) indicate that a 95% change in species composition is reached at 1120 to 620 m altitude. Similarly, the rates ‐0.0009 to ‐ 0.0019 (CC) correspond to 1410 ‐ 680 m. The altitudinal range expected here for a 95% change agrees with the actual elevation of forest zonation in northwestern Kyushu. The average rate of both PS and CC in the herb‐layer population was 1.56 times higher than the rate in the woody species population, showing a more rapid change in herb‐layer population than in the woody ones along the gradient.The Zone turnover rates were higher at the 370–440 m belt than those below and above the belt. This coincided with the interchanging pattern in population distributions and the abrupt change in similarity at about 400 m above sea level. This may be due to the change in environmental conditions such as physiography and air humidity. In the diversity measurements, the species density per 100 m2 showed a gradual increase in the DBH >3 cm population but a constant level in the DBH >10 cm population along the whole range of the forest coenocline studied, while index values of S(100) and Shannon's H showed decreasing trends in the same gradient with a few exceptionally high and low values.
Succession of mycorrhizal fungi in stands of Pinus sylvestris in the Netherlands
Authors: Termorshuizen A. J. 
Published: May 2006

The mycorrhizal mycoflora was investigated in 35 stands of Pinus sylvestris in three types of young (4‐13 yr) and three of old (50‐80 yr) stands in the Netherlands, differing in number of rotations and soil type. A plot of 1050 m2 (30 m x 35 m) within each stand was searched for carpophores during the autumns of 1986 and 1987. 10 soil samples per plot were taken in October 1987 in order to assess the mycorrhizal status of the tree roots. The composition of mycorrhizal mycoflora in the different plots was subjected to TWINSPAN cluster analysis and Detrended Correspondence Analysis.Plot groupings generated by these analyses largely parallelled the stand types, indicating that each stand type has its own mycoflora. Differences in myco‐floristic composition between stand types were parallelled by differences in the composition of green vegetation. The young stand types had 3.5–27 x more carpophores and 1.4–6.8 x more species than two of the old stand types One old stand type was intermediate. Considerable differences in species composition between the young stand types were observed. It is concluded that the succession of mycorrhizal fungi is not primarily influenced by ageing of the trees, but rather by changes in the soil.The results were compared with data on changes in the occurrence of fruiting species of mycorrhizal fungi in the Netherlands during this century. It appeared that species which have declined according to these data were more frequent in the young plots than in the old plots. However, these species are reported to be frequent in old stands of P. sylvestris in Estonia and Finland. It is argued that this difference is related to the high nitrogen deposition in the Netherlands.
The effect of salinity on the reproduction of coastal submerged macrophytes in experimental communities
Authors: Bonis Anne , Grillas Patrick , van Wijck Carla , Lepart Jacques 
Published: May 2006

AbstractThe effects of salinity on the reproduction of coastal submerged macrophyte species were studied on samples of communities from six seasonal marshes in two outdoor experiments performed in autumn and in spring. The submerged macrophyte communities were submitted to five different salinity levels (0, 1, 2, 4 and 6 g/1 Cl−1). In a companion paper (Grillas, van Wijck & Bonis 1993) three groups of species were distinguished on the basis of their biomass production over the salinity range 0 to 6 g/1 Cl−1: (1) glycophytes (non‐salt‐tolerant species), (2) salt‐tolerant species and (3) halo‐phytes. This part of the study describes the impact of salinity on the reproduction of the individual species during the two experiments.The species differ in their capacity to reproduce in the autumn; only Zannichelliapedunculata and Tolypella hispánica were able to produce fruits in that season. For all species reproduction was greater in spring and strongly correlated with biomass, except for Chara canescens. Differences in reproductive effort over the salinity range amplified the halophytic nature of Ruppia marítima and Chara canescens and the intolerance of Callitriche truncata and Chara contraria. For the other species, reproductive effort did not differ significantly over the salinity range.Regarding the effect of salinity on biomass and reproductive effort of individual species, there were large differences in the total weight of propagules produced at the community level and in the relative contribution of individual species. The resulting quantitative changes in the species composition of the seed bank could affect the structure of the communities by their effects on the establishment and survival of species populations.
Plant communities of the Stirling Range, Western Australia
Authors: Pignatti Erika , Pignatti Sandro , Lucchese Fernando 
Published: May 2006

AbstractThe Stirling Range is a mountain system of Proterozoic origin in the southern part of Western Australia, reaching an altitude of 1000 m; it consists of acid rocks and has a mediterranean climate with a rainfall of 500 ‐ 550 mm/yr. It is the only extensive mountain system of this portion of the continent and presents a rich endemic flora. The vegetation of the area was investigated from 1984 to 1992; 68 phytosoci‐ological releves, ecological observations and extensive floris‐tic collections were made. On the basis of multivariate analysis eight communities have been distinguished: Eucalyptus woodland, mallee, evergreen shrubland (plain, mountain and slope), and herbaceous communities of wet sands, springs and rocks. The Stirling Range is the only area in the south of Western Australia where vegetation belts can be recognised.
BOOK REVIEWS
Authors: Hunt E. Raymond 
Published: May 2006

Book reviewed in this issue.Solomon, A. M. & Shugart, H. H. (eds.) 1993. Vegetation Dynamics & Global Change. xii+338 pp. Chapman & Hall, New York, London. (cloth) ISBN 0–412–03671–1. Price: USD 65.‐. (paper) ISBN 0–412–03681–9. Price: USD 29.95.
Simulated dynamics of succession in a North American subtropical Prosopis savanna
Authors: Scanlan J. C. , Archer Steve 
Published: May 2006

Abstract. A transition matrix model was used to explore the dynamics, rate and potential extent of changes in landscape vegetation patterns on a southern Texas Prosopis savanna. Transitions between seven vegetation classes were determined for the periods 1941–1960 and 1960–1983 on aerial photographs of three sites. During these periods, the sites were heavily grazed by cattle and were fire‐free. Vegetation states assessed in grids of 20 m x 20 m cells superimposed on photographs ranged from grass‐dominated to woody plant‐dominated. The 1941–1960 period (denoted DRY) was characterized by prolonged drought, whereas annual rainfall during the 1960–1983 period (denoted WET) was typically normal to above‐normal. The 1941 landscape consisted of herbaceous zones (6% of cells), woodland (50% of cells) and savanna parkland (44% of cells with grass/woody plant mixtures). The woodland state was the most stable, with probabilities of no change being 0.970 and 0.873 in WET and DRY periods, respectively. The herbaceous state was least stable, with corresponding values of 0.074 and 0.353.Past and future landscape structure was modelled by randomly selecting DRY or WET transitions at 20 year time steps. The model was run under a series of rainfall scenarios where the probability of selecting the WET transition matrix (P[WET]) ranged from 0 (DRY always chosen) to 1 (WET always chosen). Historical records indicate P[WET] has approximated 0.3 to 0.4 in the region. The rate of succession to states of greater woody cover increased as P[WET] increased. Forward simulations based on P[WET] > 0.2 suggest the present landscape is unstable and will develop into a closed‐canopy woodland within the next 180 years, assuming the processes operating between 1941 and 1983 continue (e.g. grazing by cattle and lack of fire). Reverse simulations concur with historical observations and projections derived from woody plant growth rates in other studies and suggest that 200 to 300 yr BP these landscapes contained a substantially greater proportion of cells dominated by grassland or grassland with scattered woody plants (43 to 74%) than was present in 1983 (19%). Based upon elapsed time between predicted past and future steady states, succession from open savanna to closed‐canopy woodland may occur in ca. 400 to 500 yr for P(WET) ≥ 0.33. Arresting or reversing the projected trend may require changes in climate and/or changes in livestock grazing and land management practices.The approaches employed in this study illustrate how time series maps, aerial photographs and satellite imagery can be analyzed and used to interpret, project and reconstruct local and regional changes in ecosystem structure. Difficulties and limitations associated with the use of Markov chains to model succession are identified and discussed.
High species richness in an Estonian wooded meadow
Authors: Kull Kalevi , Zobel Martin 
Published: May 2006

Abstract. A wooded meadow at Laelatu in western Estonia was found to be very rich in vascular plants. The maximum number of species found was 25 in a 10 cm x 10 cm plot, 42 in a 20 cm x 20 cm plot and 63 in a 1 m2 plot.Species richness is related to the management history of the site. The highest richness was found in sites with the most regular long‐term mowing. Species density was lower in the case of fertilization or temporary cessation of mowing.The richest community had an LAI of 2.8 and an above‐ground dry biomass of 175 g/m2. With increasing height of the herb layer the number of species decreases. Small disturbances cause a remarkable decrease in species density.
Modelling potential impacts of climate change on the spatial distribution of zonal forest communities in Switzerland
Authors: Brzeziecki B. , Kienast F. , Wildi O. 
Published: May 2006

Abstract. A spatially explicit, climate‐sensitive vegetation model is presented to simulate both present and future distribution of potential natural vegetation types in Switzerland at the level of zonal forest communities. The model has two versions: (1) a ‘basic’ version using geographical region, aspect, bedrock (represented by soil pH), and elevation, and (2) a ‘climate‐sensitive’ version obtained by replacing elevation (complex environmental gradient) with temperature (climatic factor). Version 2 is used to predict vegetation response under different (today's and projected) climatic conditions.Two regional climate scenarios are applied: (1) assuming an annual mean temperature increase of 1.1 — 1.4 °C, and (2) assuming an increase of 2.2 — 2.75 °C. Both scenarios result in significant changes of the spatial vegetation patterns as compared with today's climatic conditions. In scenario 1, ca. 33 % of the sample points remain unchanged in terms of the simulated zonal forest community; in scenario 2, virtually all sample points change. The most noticeable changes occur on the Swiss Plateau with Carpinion forests (zonal vegetation of present colline belt) expanding to areas that are occupied today by submontane and low‐montane Fagus forests.To estimate the reliability of the simulation, quantitative (comparison with field mapping) and qualitative (comparison with climate types in the Alpine region) tests are performed and the main limitations of the approach are evaluated.
Comparison of different methods for diversity ordering
Authors: Tóthmérész Béla 
Published: May 2006

Abstract. The measurement of diversity, one of the most important concepts in present‐day ecology, can be improved by methods of diversity ordering which have recently been developed. This ordering is achieved by a D(α) diversity index family. Indices of this family show varying sensitivities to the rare and abundant species as the scale parameter, α, changes. The aim of this paper is to review and assess 12 methods of diversity ordering and discuss their relationships in detail. Two of the methods are new to the ecological literature.The diversity ordering methods are compared as to their effectiveness in graphically displaying the differences of community structure and demonstrating the (non‐)comparability of communities. Small, medium and large data sets were used to evaluate the methods. A small artificial data set (five to seven species) and a large semi‐artificial data set (31 — 141 species) are used in this paper.The results suggest that Rényi's diversity index family and Logarithmic dominance ordering are the most useful methods for diversity ordering of communities of all sizes. Right‐tailsum diversity ordering performs well for small communities.
Implementation of a hierarchical global vegetation classification in ecosystem function models
Authors: Nemani Ramakrishna , Running Steven W. 
Published: May 2006

Abstract. We propose an alternative approach for the currently used biogeographic global vegetation classifications. A hierarchical vegetation classification system is proposed for consistent and routine monitoring of global vegetation. Global vegetation is first defined into six classes based on plant canopy structure and dynamics observable by remote sensing from satellites. Additional biome variability is then represented through a remote sensing derived leaf area index map, and direct climate data sets driving an ecosystem model to compute and map net primary production and evapotranspiration. Simulation results from an ecosystem function model suggest that the six canopy structure‐based classes are sufficient to represent global variability in these parameters, provided the spatio‐temporal variations in Leaf Area Index and climate are characterized accurately.If a bioclimatically based classification is needed for other purposes, our six class approach can be expanded to a possible 21 classes using archived climatic zones. For example, tropical, subtropical, temperate and boreal labels are defined by absolute minimum temperature. Further separation in each class is possible through changes in water availability defined by precipitation and/or soils. The resulting vegetation classes correspond to many of the existing, conventional global vegetation schemes, yet retain the measure of actual vegetation possible because remote sensing first defines the six biome classes in our classification.Vegetation classifications are no longer an end product but a source of initializing data for global ecosystem function models. Remote sensing with biosphere models directly calculates the ecological functions previously inferred from vegetation classifications, but with higher spatial and temporal accuracy.
Ecosystem responses to changes in plant functional type composition: An example from the Patagonian steppe
Authors: Aguiar Martín R. , Paruelo José M. , Sala Osvaldo E. , Lauenroth William K. 
Published: May 2006

Abstract. Grass cover along a grazing intensity gradient in Patagonia decreases, whereas bare soil and shrub cover increases. Our objective was to study the effect of a change in the dominant plant functional type on soil water balance, primary production, herbivore biomass, roughness, and albedo. Using a soil water balance model, we found increases in evaporation and deep drainage, and a decrease in total transpiration along the grazing intensity gradient. Above‐ground primary production, estimated from transpiration, decreased along the grazing intensity gradient because shrubs did not fully compensate for the decrease in grass production. Using a statistical model, we calculated herbivore biomass from estimates of above‐ground primary production. Estimated herbivore biomass was lowest in the shrub‐dominated extreme of the grazing gradient. Roughness increased from the grass‐dominated to the shrub‐dominated community. Albedo had a maximum at an intermediate position along the gradient.Our results suggest that changes in plant functional type composition, independent of changes in biomass, affect ecosystem functioning and the exchange of energy and material with the atmosphere. Grasses and shrubs proved to be appropriate plant functional types to link structure and function of ecosystems.
Impact of grazing and atmospheric nitrogen deposition on the vegetation of dry coastal dune grasslands
Authors: ten Harkel Matthijs J. , van der Meulen Frank 
Published: May 2006

Abstract. A five‐year experimental study was carried out to examine the combined effects of grazing and atmospheric nitrogen deposition on the vegetation of three dry dune grasslands: one short species‐rich, one short species‐poor, and one predominated by tall graminoids.Additional fertilization with nitrogen had no significant effect, neither in grazed nor in non‐grazed plots. Exclusion of grazing by rabbits resulted in an increase in the frequency of perennial graminoids and a decrease in the frequency of annual graminoids and herbs. Nevertheless, species diversity remained the same in the species‐rich grassland. During the experiment, the above‐ground biomass increased in all nongrazed plots and the amount of bare soil and mosses decreased.The vegetation changes occurred mainly within one year after the exclusion of grazing. An exception is the grass‐dominated site where the amount of Calamagrostis epigejos increased gradually from ca. 20 % in the first two years to about 50 % in the fourth and fifth year.Grazing by rabbits seems essential to prevent graminoids to become predominant in the dry dunes. If graminoids are dominant, grazing by horses can be an appropriate method to restore the original grassland vegetation. After six months of grazing by horses the grass‐dominated site showed a decrease of the frequency of perennial graminoids, from 95 % to 80 %, and an increase of the frequency of perennial herbs, from 2.5 % to between 13 and 20 %.