bluuebunny/crossref_metadata_2025_split huggingface dataset:
Deterministic versus Individualistic community structure: a test from invasion by Nothofagus menziesii in southern New Zealand
Authors: Wilson J.Bastow , Allen Ralph B. 
Published: May 2006

Abstract. The Clements' Deterministic model of plant communities implies that a change in one species, especially a change in the physiognomic dominant, would have profound effects on the remainder of the community. Gleason's Individualistic model suggests there would be little effect.These alternative models are tested by examining the forest composition on both sides of a boundary along which the tree Nothofagus menziesii is slowly invading.Classification of forest composition, excluding N. menziesii, gave little evidence of an effect of N. menziesii on the lower strata: understorey vegetation types were distributed across the boundary. Some differences were found at individual sites, but these were often inconsistent between sites.Ordination, also excluding N. menziesii, similarly showed that none of the first three understorey axes reflected any effect of N. menziesii. The fourth axis was correlated with the presence of N. menziesii, but only when canopy trees were included. It is concluded that specific composition of the canopy in these montane New Zealand evergreen forests has little effect on the understorey, supporting Gleason's Individualistic concept of the community.
Disturbance and forest dynamics along a transect from Andean rain forest to Patagonian shrubland
Authors: Veblen Thomas T. , Kitzberger Thomas , Lara Antonio 
Published: May 2006

Abstract. At ca. 40° S in northern Patagonia, Andean rain forests are replaced eastwards by woodlands and shrublands and eventually by steppe. Along this gradient we examined stand dynamics by analyzing tree population age structures and tree growth patterns. We also examined spatial and temporal characteristics of disturbance regimes by dating disturbances and mapping stands of differing disturbance history. From west to east, the ecological importance of earthquake‐related disturbance decreases, whereas that of fire, logging, and livestock increases. Abrupt changes in rates of tree growth correspond with earthquakes in 1837, 1939 and 1960. In the mesic western forests earthquakes can result in massive new tree establishment on landslide‐affected sites and increased rates of treefall.Fire, however, is the more pervasive disturbance over most of the gradient and creates extensive even‐aged patches dominated by the regionally dominant trees, Nothofagus and Austrocedrus. Although some lightning‐ignited and aboriginal‐set fires occurred in these forests prior to European settlement, much of the present forest structure may be attributed to the massive burning associated with European settlement of this area near the turn of the present century. In contrast to the settlement‐related increase in fire frequency in the western forested district, at the woodland/steppe ecotone the demise of the native American population resulted in a decrease in fire frequency. Heavy browsing and grazing following fire can seriously impede post‐fire tree regeneration. These preliminary results document the important influences of varying disturbance regimes along a major environmental gradient in creating landscape‐scale vegetation patterns.
Inferences for life history strategies of Artemisia tridentata subspecies
Authors: Bonham C. D. , Cottrell T. R. , Mitchell J. E. 
Published: May 2006

AbstractCommunities dominated by Artemisia tridentata ssp. tridentata, A. tridentata ssp. wyomingensis, and A. tridentata ssp. vaseyana, found in the Piceance Basin of western Colorado, were evaluated for life history strategy. Species cover data were analyzed using Grime's (1984) triangular model. Then a canonical analysis was conducted to obtain an ordination of relative species cover. Results from these two analyses were then used to infer strategy differences among life histories of subspecies, based on the respective plant community associates. These differences were found to be consistent with the divergent evolution assumed to have occurred in this species. The primary ordination axis was interpreted as an elevation‐moisture gradient. Further analysis of soil data by factor analysis also separated the three Artemisia subspecies along a soil texture gradient.
Classification, species richness, and environmental relations of monsoon rain forest in northern Australia
Authors: Russell‐Smith Jeremy 
Published: May 2006

AbstractA floristic classification for monsoon rain forest vegetation in the Northern Territory, Australia, is derived based on comprehensive floristic inventory and environmental data. Allied aims include relating the floristic classification to Australia‐wide structural and floristic schema, documenting species richness, and exploring site‐environmental relations. TWINSPAN classification and complementary DCA analysis of a data set comprising 1219 sites x 55 9 rain forest taxa yielded 16 floristic assemblages. A diagnostic floristic key to these groups is presented. Eight groups describe rain forests associated with sites of perennial moisture; eight groups are associated with seasonally dry landforms. The structural typology of Australian rain forests is found wanting when applied to relatively simple monsoon rain forest communities. Rain forest patches are mostly less than 5 ha in size; maximum species richness is ca. 135 species per patch. Two major environmental gradients are identified through indirect gradient analysis: a primary latitudinal‐moisture gradient and a subsidiary topographic‐drainage gradient. Given the demonstrated tolerance of monsoon rain forest to a broad range of environmental conditions, the question remains: why is this vegetation type so restricted in occurrence in northern Australia?
Hydro‐ecological analysis of the fen system Lieper Posse, eastern Germany
Authors: Van Diggelen R. , Grootjans A. P. , Kemmers R. H. , Kooijman A. M. , Succow M. , De Vries N. P. J. , Van Wirdum G. 
Published: May 2006

The Lieper Posse is a calcareous, ground water‐fed fen system, situated in the end‐moraine area of northeastern Germany. Nowadays the fen is partly drained and the vegetation adversely affected; hence regeneration measures are considered. Here we report a pilot survey of the actual vegetation cover in relation to the hydrological conditions of the system.The vegetation in the central part of the fen system can be assigned to the Caricetum lasiocarpae, with small areas of Eleocharitetum quinqueflorae. The southern part of the system includes a Ledo‐Pinetum sylvestris bog. Along the edges eutrophic forest types are present.Peat analysis revealed that the system started as an open lake and subsequently changed into a rheophilous mire, ‘percolating mire’. The southern bog has only recently come into being. Hydrological investigations showed that the original mineral‐rich ground water had to a large extent been replaced by acid rainwater; this is likely due to the construction of a ditch before 1850. The effects of this drainage on hydrological conditions and some aspects of soil fertility are discussed. Possible consequences for the restoration of calciphilous vegetation types are being considered. It is concluded that the vegetation development is predictable only to a limited extent, which is mainly due to a lack of knowledge on hysteresis effects in both vegetation and soil.
A simulated map of the potential natural forest vegetation of Switzerland
Authors: Brzeziecki B. , Kienast F. , Wildi O. 
Published: May 2006

AbstractUsing empirical data (ca. 7500 phytosociological releves), a simple, probabilistic ‘vegetation‐site’ model was developed, to simulate geographical distribution of 71 forest community types, representing the potential natural vegetation (PNV) of Switzerland. The model was interfaced to a geographic information system (GIS) and used to generate a numerical vegetation map, on the basis of digital maps of 12 environmental variables including climatic conditions (temperature and precipitation), topography (elevation, slope, aspect), and soil parameters (soil pH and physical soil parameters). The predicted distribution of forest communities was compared with several vegetation maps, prepared for some subregions of Switzerland by means of traditional field methods. Similarity ranged from 50 to 80 %, depending on the community type, level of vegetational hierarchy and the geographical region. The current resolution and accuracy of the simulated vegetation map allows us to study the vegetational patterns on the level of the entire country or its major geographical and climatic regions. The simulated vegetation map is potentially an important tool in ecological risk assessment studies concerning the possible impacts of climate change on the ecological potential of forest sites and biological diversity of forest communities.
Environmental relations of the bryophytic and vascular components of a talus slope plant community
Authors: Cox Janet E. , Larson Douglas W. 
Published: May 2006

AbstractThe environmental factors correlating with community structure of vegetation on talus slopes of the 785 km long Niagara Escarpment, southern Ontario, Canada, were studied using canonical correspondence and regression analysis. The bryophytes and higher vascular plants were analysed separately to see if their responses were similar or different. Both vascular plants and bryophytes responded similarly to the environmental variables that were measured. For both vegetation components, location from north to south explained most of the variance. When species richness was plotted against location for the complete vegetation and for the two components separately, the results showed that vascular plant species richness decreased with increasing latitude, while bryophyte richness increased. The magnitude of both of these trends was slight but consistent with the hypothesis that available environmental energy governs a significant amount of the variance in species richness. Since separate components of the talus vegetation were shown to respond differently to the same environmental variable, groups of taxa should not be excluded from community level studies without a consideration of the possible consequences of this bias.
Experimental analysis of patch dynamics in tallgrass prairie plant communities
Authors: Glenn Susan M. , Collins Scott L. 
Published: May 2006

Abstract. Previous research has indicated that patch structure at small spatial scales (<100m2) in tallgrass prairies was defined by a diverse array of infrequent species because dominant species occurred in all samples at this scale. Also, patch structure was not significantly different from that derived from random species associations. Based on these results, we hypothesized that remo val of a dominant species would have no effect on patch structure in these prairies. We tested this hypothesis by removing a dominant grass, Schizachyrium scoparium (Poaceae), from half of each of four 10 m × 10 m study blocks, and comparing differences in patch structure between control and removal halves before and after removal. The minimum resolution in our study was 1 m2. Patches of similar species composition were defined by cluster analysis of presence/absence data and cover data. Patch sizes ranged from 1 to 34 m2.Following the removal of S. scoparium there was an overall increase in the number of species in the removal half of each block compared to pre‐treatment levels. However, the number of patch types and number of spatially mapped groups, based on presence/absence or cover data, did not change between control and removal plots after the removal of S. scoparium. This supports the hypothesis that removal of a large, dominant species would have no effect on patch structure at this scale of resolution in these prairies. Thus, patch structure, as defined here, is an emergent property in these grasslands that is not predictable from changes in species composition. This property of stochastic patch structure results from interactions of processes operating at scales both larger and smaller than our scale of resolution. Stochastic models may provide a reasonable approach to modelling small‐scale patch dynamics in tallgrass prairie communities.
BOOK REVIEWS
Authors: Burrows Colin J. 
Published: May 2006

Book reviewed in this issue.John A. Matthews. 1992. The Ecology of Recently Deglaciated Terrain. A Geoecological Approach to Glacier Forelands and Primary Succession. xvii + 386 pp. ISBN 0–521–36109–5. Cambridge University Press, Cambridge. Price: USD 120.‐.
Functional types of trees in temperate and boreal forests: classification and testing
Authors: Bugmann Harald 
Published: May 2006

Abstract. Impacts of climatic change on ecosystems over large areas cannot usually be assessed on a species basis. The definition of plant functional types (PFTs) may make this task feasible, but its potential and limitations need to be evaluated carefully by quantitative tests. This paper presents such a method for testing a hypothesis about PFTs.A deductive approach is used to elaborate a functional classification of temperate and boreal trees based on their response to climatic change and their feedbacks to the climate system using four attributes: (1) evergreen/deciduous; (2) cold tolerance; (3) drought tolerance; (4) shade tolerance. These attributes are combined to yield six PFTs.The classification is tested by implementing the six PFTs in the forest gap model ForClim, and the behaviour of the PFT‐based model is compared to species‐based simulation results in Europe and in eastern North America.The six PFTs provide an accurate description of both the physiognomy and the composition of European forests in both transient and equilibrium phases. Under the IPCC ‘Business‐ As‐Usual’ scenario of climatic change for southern and central Europe, some differences in the forest composition are simulated, pointing at the need of testing PFT schemes not only under current, but also under hypothesized future climates.For eastern North America it was necessary to estimate the parameters characterizing the six PFTs anew. When this was done, the PFT‐based simulation yielded results paralleling those of the species‐based model closely.The potential and limitations of the present classification are discussed. It is concluded that deficiencies in current gap models, but probably also different evolutionary pathways in North America as compared to Europe, are responsible for the different parameterizations on the two continents.
Assessing the response of plant functional types to climatic change in tropical forests
Authors: Condit Richard , Hubbell Stephen P. , Foster Robin B. 
Published: May 2006

Abstract. We propose and test a classification of plant functional types for tropical trees based on demography, growth form, phenology, and moisture requirements, using data from a 50‐ha forest dynamics plot in Panama. Correlations among demographic variables for individual species ‐ mortality, growth, and the tendency to colonize light gaps ‐ were strong, and a single principal component (PC) accounted for a large fraction of the demographic variability. Most species ‐ shade‐tolerants ‐ were clustered at the low end of the PC axis (low growth, low mortality), while the rest were continuously distributed over a wide range. Three demographic guilds could be defined from scores on this axis: we call these pioneer, building phase, and shade‐tolerant trees, following earlier terminology.Leaf lifetime correlated negatively with the demographic axis, and there was a weak relationship between demography and moisture‐preference: no species with high demographic scores also had high moisture requirements. There was no significant relationship between deciduousness and the demographic axis, but deciduousness was negatively correlated with leaf lifetime and moisture index. Altogether, 11 different combinations of demographic variables, deciduousness, moisture needs, and growth form (canopy vs. understory species) were identified.We evaluated how these functional types changed in abundance between 1982 and 1995. Because of a recent run of dry years and long dry seasons, we predicted that deciduous species, canopy species, pioneers, and drought‐tolerant species would be increasing at the expense of their counterparts. Only one aspect of this prediction was borne out: moisture‐ demanding species declined sharply in abundance relative to drought‐tolerant species. Neither deciduousness nor growth form was associated with population change, and pioneer species declined in abundance more often than shade‐tolerants. The overall structure of the forest ‐ the density of deciduous, pioneer, and understory species ‐ did not change much, but the decline of the moisture‐demanding guild indicates that a change in composition is preceding a structural change.
Effects of forest soil desiccation on the growth of Eucalyptus regnans F. Muell. seedlings
Authors: Ashton D.H. , Kelliher K.J. 
Published: May 2006

Abstract. The growth rate of Eucalyptus regnans seedlings in their first year can be much increased if the soil is first dried and then rewetted. The ratio of growth on predried soil to growth on undried soil (the Growth Ratio or GR) reaches a maximum at air‐dryness (pF 6.0–6.4). In E. regnans forest soil, GR is greatest in humus‐rich topsoil and declines with depth. The effect of air‐drying persists for several months after rewetting when soil is stored under glasshouse conditions. It is largely unaffected by repeated drying and wetting, by the rate of drying or by the season of collection. The mixing of dried and undried soil or the placement of a layer of dried soil above undried soil produces an enhancement of growth proportional to the amount of dried soil added. Firing of a litter layer above soil at wilting point increases subsequent seedling growth to that in air‐dried soil. The addition of ash from a litter fire to undried soil produces an increase in growth approximately equal to that caused by air‐dryingThe drying effect is most pronounced in soils from mature E. regnans forest and nearby brackenland and is less in dense younger forest, frost‐hollow grasslands and old grassy gaps in the mature forest. The effect is restored by the inoculation of E. regnans mycorrhizal roots from both dried and undried soil. The effect varies along an gradient from 500 to 1500 m a.s.l. and is a maximum in the wet E. regnans climatic zone and a minimum in zones or local aspects where forests are normally subject to frequent drying. The stimulatory effect on seedling growth in soils of the E. regnans zone may have an effect on the outcome of competition during regeneration in large gaps. Part of the growth responses previously ascribed to the ‘ash‐bed’ effect may be due to the desiccation effect in these soils.
Permanent plots as tools for plant community ecology
Authors: Herben Tomáš 
Published: May 2006

Abstract. Permanent plots provide information on spatio‐temporal patterns in plant communities, which could be analyzed to yield correlated changes in pairs of species and information on species replacements in space. The potential use of permanent plots to study underlying processes of interspecific interactions (namely competition) is discussed. Two examples (one simulated, using a cellular automaton model, and one from a removal experiment in grasslands) are used to demonstrate that this use is not straightforward, since (1) radically different underlying mechanisms (symmetric founder control with little competitive replacement vs. asymmetric dominance control strongly structured by competition) may produce very similar spatio‐temporal patterns; and (2) topology of species replacements in space may be very different from the competitive hierarchy as determined by the removal experiment.Permanent plot data can be used to study interspecific interactions in the following ways: (1) if there is additional information to decide which of the potential underlying models is acceptable, permanent plot data may enable further articulation of the model, such as estimation of the model parameters; this approach is similar to that used in many other plant ecology fields (fine scale patterns, chronosequences, plant size distribution and dynamics); (2) data from permanent plots constrain the number of feasible underlying models; (3) permanent plot data provide verification of predictions of experimental studies; in this respect, they are much superior to non‐repeated studies of pattern.
Influence of overstory composition on understory colonization by native species in plantations on a degraded tropical site
Authors: Parrotta John A. 
Published: May 2006

Abstract. Patterns of understory colonization by native and naturalized trees and shrubs were evaluated in 4.5‐year‐old plantations of three exotic tree species, Casuarina equisetifolia, Eucalyptus robusta, and Leucaena leucocephala, on a degraded coastal grassland site with reference to overstory composition and understory environmental conditions. 19 secondary forest species were established in the plantation understories (with a total area of 0.52 ha), while no natural regeneration occurred in unplanted, though protected, control areas. The majority of these species (90 %) and the total seedling population (97 %) were zoochorous, indicating the importance of frugivorous bats and particularly birds as facilitators of secondary forest species colonization. Understory species richness and seedling densities were affected significantly by overstory composition, the most abundant regeneration occurring beneath Leucaena and least under Casuarina. Understory colonization rates within mixed‐species stands were intermediate between those of single‐species stands of the trees comprising their overstories. Significant negative correlations were found between understory species richness and seedling density, and forest floor depth and dry mass, especially for small‐seeded ornithochorous species. Higher colonization rates near the peripheries of plantation plots relative to plot interiors were due in part to roosting site preferences by frugivores, particularly bats.The study results indicate that overstory species selection can exert a significant influence on subsequent patterns of colonization by secondary forest species and is an important consideration in the design of plantations for ‘catalyzing’ succession on deforested, degraded sites.
Soil nutrient fluxes and vegetation changes on molehills
Authors: Canals Rosa‐Maria , Sebastià Maria‐Teresa 
Published: May 2006

Abstract. The hypothesis that mole burrowing activity alters soil nutrient fluxes and that, as a response to the new conditions, a specialized guild of species develops on the molehills, was tested in an area located in the southwestern Spanish Pyrenees, on a spectrum of montane grassland communities that varies from xeric to temporally waterlogged.Evidence for an association between disturbance and nutrient availability was reported for nitrogen. Mole‐disturbed soils had elevated amounts of inorganic nitrogen compared to soils in surrounding pastures. At the first stages of mound revegetation, changes in nitrate flushes and in species competitive relationships following disturbance appeared to facilitate the establishment of ruderal and non‐mycorrhizal species. The diversity of the whole grassland was enhanced by the existence of these sets of species, abundant on mounds and rarer in the pasture. However, the difference was mainly quantitative, as exclusive colonizers of molehills were not found.