bluuebunny/crossref_metadata_2025 huggingface dataset:
Yield and species density of grasslands during restoration management
Authors: Oomes M. J. M.
Published: May 2006

Abstract. The relation between the dry matter production and species density of 27 grasslands with different fertilization histories in the Netherlands was studied. The range in species density was 12–28 species on 150 m2, the average annual dry matter production in 1983–1985 varied between 3.3 and 12.8 ton /ha. The results show an optimum curve and confirm the hump‐backed model proposed by other researchers for a great variety of vegetation types.

It is concluded that a high species density can be expected when the annual dry matter production above a stubble height of 5 cm, is between 4 and 6 ton/ha (ca. 4.6 ‐ 6.0 ton seasonal maximum standing biomass). Species density can be expected to decrease when the dry matter production exceeds values of 6 ‐ 7 ton ha‐1yr‐1 (ca. 6.0 ‐ 6.7 ton seasonal maximum standing biomass). The implications of this relation for grassland restoration, aimed at an increase in species density, are discussed.

The results agree with other grassland data based on the seasonal maximum standing biomass. The difference between annual production estimated by harvesting the biomass after mowing at 5 cm above the soil surface (mostly in two cuts), and the maximum seasonal standing biomass must be taken into account. It is proposed to compare data on the basis of the estimation that 62 ± 5% of the annual yield is harvested at the first cut, and that there is a linear relation between the total standing biomass, y (g/m2), and the biomass harvested above a stubble height of 5 cm, x (g/m2) that could be described by the regression line y = 1.10 x + 189.6 (r = 0.89, p < 0.01, n = 34).
BOOK REVIEWS
Authors: Box Elgene
Published: May 2006

Book reviewed in this issue.

Bohn, U. & Neuhäusl, R. (eds.) 1990. Vegetation and Flora of Temperate Zones. viii+81 pp. SPB Academic Publishing, The Hague. ISBN 90–5103–034–7. Price: USD 16.‐.
Effects of grazing on seedling establishment: the role of seed and safe‐site availability
Authors: Oesterheld Martin , Sala Osvaldo E.
Published: May 2006

Abstract. The first objective of this paper was to assess the effects of grazing on seedling establishment of two species whose relative abundance at the adult stage is affected by grazing in a contrasting fashion. Second, we evaluated the relative importance of seed versus safe‐site availability in explaining the effect of grazing on seedling establishment. We monitored seedling establishment on a grazed area, on two areas which had not been grazed for two and seven years, and on plots which had been experimentally defoliated. The species compared were Dan‐thonia montevidensis, a native perennial grass which dominates both grazed and ungrazed communities, and Leontodón taraxacoides, an invading exotic rosette species from the Compositae family.

Continuous grazing enhanced seedling establishment of both species through its effect on the availability of safe sites. Seed availability accounted for only one, but very important, grazing effect: the lack of response by L. taraxacoides to the defoliation in the seven‐year old exclosure. Its seed supply was depleted by exclusion of grazing and, consequently, its short‐term regeneration capacity after disturbance was lost.
BOOK REVIEWS
Authors: Palmer Michael W.
Published: May 2006

Book reviewed in this issue.

Odum, E. P. 1989. Ecology and our Endangered Life‐Support Systems, x + 283 pp. Sinauer Associates, Inc., Sutherland, MA. ISBN 0–87893–635–1. Price: USD 15.95.
Changes in composition and structure of Vitex shrubland in northern China in relation to human disturbance
Authors: Xiao‐bing Dai
Published: May 2006

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

A survey is presented of the syntaxonomic status and the internal differentiation of the Genisto‐Vaccinion Br.‐Bl. 1926. This alliance comprises subalpine heathland communities of low mountain ranges in western Europe, which are dominated by Vaccinium and other dwarf‐shrub species. The alliance is assigned to the class Nardo‐Callunetea Preising 1949. All available releves were analysed together according to the Braun‐Blanquet approach. The floristic and ecological characteristics of the alliance are given, and the relationship to allied syntaxa is discussed. The Genisto‐Vaccinion is divided into two suballiances, the Phyteumo‐Vaccinenion and the Caricipiluliferae‐Vaccinenion. The Phyteumo‐Vaccinenion is restricted to the upper belt of the subalpine zone, where it includes the major part of the natural climax vegetation. Two associations are distinguished, the Pulsatillo vernalis‐Genistetum Quézel et Rioux 1954 and the Vaccinietum uliginosi‐myrtilli Br.‐Bl. 1926.

The Caricipiluliferae‐Vaccinenion is bound to the lower belt of the subalpine zone; mostly, the communities have developed secondarily after cutting of the pre‐existing woodlands, followed by cattle grazing. Within this suballiance, four associations are described, the Alchemillo saxatilis‐Vaccinietum uliginosi Thébaud ex Schaminée et Hennekens 1992, the Allio victorialis‐Vaccinietum Schaminée et Hennekens 1992, the Pulsatillo alpinae‐Vaccinietum Carbiener 1966, and the Leontodonto‐Vaccinietum myrtilli Bartsch et Bartsch 1940. The description of the associations includes an appropriate diagnosis and enumeration of the nomenclatural types.
Correspondence Analysis of species by environmental variable matrices
Authors: Montana Carlos , Greig‐Smith Peter
Published: May 2006

Abstract. Correspondence Analysis of species by environmental variables matrices is a relatively simple method for handling matrices which include many species and variables. If columns represent species and rows represent the states in which the environmental variables have been divided, each element of the matrix shows the number of releves in which the simultaneous occurrence of that species and that environmental variable state have been recorded. In this paper the use of the method for presence‐absence data is considered.

The method is appropriate for studies whose main purpose is to look for broad correlations between groups of environmental variables and groups of species. It is particularly useful for handling heterogeneous data sets including rare species and species‐poor releves, a situation in which Correspondence Analysis and Canonical Correspondence Analysis are frequently complicated by the production of axes explaining the relationship between rare species and species‐poor releves.

Examples are presented with artificial data as well as with real data collected in the Mexican portion of the Chihuahuan Desert (Bolsón de Mapimi). It is shown for the Mapimi data that the method is robust to the partition of variables into different numbers of states.
Architecture and development in Fagus japónica ‐ Fagus crenata forest near Mount Takahara, Japan
Authors: Peters R. , Ohkubo T.
Published: May 2006

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

It is concluded that the dominance of F. japónica over other tall tree species is the result of F. japónica reproducing by sprouts.
European post‐glacial forests: compositional changes in response to climatic change
Authors: Huntley B.
Published: May 2006

Abstract. Multivariate analysis of an extensive palyno‐logical database for Europe has enabled reconstruction of broad‐scale vegetation history. Whereas many major features of present vegetation patterns were established early in the Holocene, floristic composition of the forests has changed continuously up to the present day. For example, although ‘mixed deciduous forests’ had reached approximately their present extent in northwest Europe by 8000 B.P., Tilia peaked in abundance in these forests during the middle post glacial, whereas Pinus was most abundant in these forests during the early post‐glacial and Fagus increased in abundance only in recent millennia. Pollen‐climate response surfaces for major pollen taxa show how their distribution and abundance patterns relate to contemporary climate.

Past forest‐compositional changes were responses to climatic changes, the nature of which can be inferred from pollen‐climate response surfaces. Post‐glacial climate changes have been different in magnitude and direction in different regions of Europe. For example, in recent millennia the vegetation changes indicate decreasing summer temperatures in northern Europe but increasing summer temperatures in the Mediterranean region. The way in which vegetation responded to past climatic changes gives insight into the likely response of vegetation to future climate changes induced by the ‘greenhouse effect’.
Effects of variable precipitation on the structure and diversity of a California salt marsh community
Authors: Callaway Ragan M. , Sabraw Craig S.
Published: May 2006

Abstract. We measured the effects of annual variation in climate and experimentally augmented rainfall on patterns of distribution and above‐ground productivity in annual plant communities at Carpinteria Salt Marsh in central California. In the driest year, Hutchinsia procumbens was codominant throughout much of the upper marsh; however, Hutchinsia was very rare or not present in the wetter years. Conversely, Juncus bufonius was common in the wettest year and absent in the driest year. Elevational distributions of other annual species also differed among years with different total precipitation. In 1989–1990, an exceptionally dry season, supplemental water decreased soil salinity, increased above‐ground productivity of annuals, and caused significant changes in spatial patterns and relative density. In the lowest zone, Hutchinsia occurred only in watered plots and supplemental water increased the density of Spergularia marina. At intermediate elevations Lasthenia glabrata occurred only in watered plots and supplemental water increased the density of Spergularia, Hutchinsia, and Parapholis incurva. At upper elevations, Juncus occurred only in watered plots, and Lasthenia was the only species that increased significantly in density with watering. Unlike natural shifts in species abundance, no species declined significantly in cover in any zone in the watered treatment. Although climatic variation has complex affects on annual plant communities, our experiments isolated important affects of total annual rainfall on the structure of annual plant communities that were similar to those that occurred with natural variation in rainfall. We conclude that variation in total annual precipitation promotes dynamic community composition and spatial distributions among years, and thus increases overall species diversity in the salt marsh.
Testing scale dependent assumptions in regional ecosystem simulations
Authors: White Joseph D. , Running Steven W.
Published: May 2006

Abstract. We present a Regional Ecosystem Simulation System (RESSys) which uses satellite data to define vegetation properties, topographic and soil data to define site characteristics, and a climate generator program to build a topographically sensitive microclimate map. We use a 150‐km2 mountainous forested watershed in Glacier National Park to test the consequences of modeling various ecosystems processes using different versions of RESSys with increasing simplification of the landscape: (1) spatial scaling generated using 30 m x 30 m Landsat Thematic Mapper data versus 1 km x 1 km Advanced Very High Resolution Radiometer data for vegetation definition; (2) modeling hydrologic dynamics produced by using a topographic routing model versus a simple soil ‘bucket’ model; (3) variable landscape partitioning based on patterns of topographic complexity; and (4) representation of annual net primary productivity (ANPP) using an absorbed photosynthetic active radiation (APAR) model. We evaluate results of these simulations by comparison with average values and areal distributions of photosynthesis, evapotranspiration, hydrologic outflow, and ANPP. Our primary goal is to test whether areal average flux of carbon and water can be scaled linearly over a complex landscape. We found that daily photosynthesis could be predictably estimated between modeling scales with correlation coefficients ranging between 0.89 to 0.99. ANPP was highly correlated among the modeling scales with maximum differences between ANPP prediction of ca. 0.5Mg C ha‐1 yr‐1. Evapotranspiration was similarly predictable between scales but was influenced by differences associated with hydrologic modeling. Hydrologic outflow was not highly correlated between different modeling scales as a function of the different hydrologic models used at different scales.
Distribution and conservation status of coastal sage scrub in southwestern California
Authors: Davis Frank W. , Stine Peter A. , Stoms David M.
Published: May 2006

Abstract.A landscape‐based characterization of vegetation has been developed for southwestern California using satellite imagery, air photos, existing vegetation maps, and field data. Distribution maps of nine dominant coastal scrub species and 13 species assemblages that were identified by divisive information analysis have been analyzed to quantify spatial patterns of species co‐occurrence. Three general distribution patterns are identified that suggest the Diegan, Ventaran and Riversidian Associations identified by other workers. Vegetation data have also been related to land ownership and management to assess the conservation status of upland plant communities. A large proportion of the mapped distribution of species and vegetation types is on private land, and several taxa show less than 4 % of mapped distribution in nature reserves. The analysis highlights the need to extend current conservation planning efforts into the northern part of the region to encompass areas whereSalvia leucophyllais a frequent community dominant.
Coastal sand dune vegetation of Tabasco and Campeche, Mexico
Authors: Castillo Silvia , Popma Jean , Moreno‐Casasola Patricia
Published: May 2006

Abstract. Sand dune vegetation along the coast of the Mexican states of Tabasco and Campeche was sampled by means of 1501 releves and the data were analyzed with classification and ordination programs. 36 community types were distinguished, which were grouped into 10 higher‐order groups. The communities are described in a sequence reflecting the main vegetation zonation. Beach, embryo dune and foredune community groups include 12 community types, the sheltered zone includes 16 types and the fixed dunes 8 types. The ordination results reveal one main vegetation gradient corresponding to the increase in mean distance from the shoreline and elevation, and being covariant with species richness, mean vegetation cover and mean vegetation height.

Additional differences are related to the geographical transition between the Gulf and Caribbean coastal vegetation and environmental conditions, mainly type of sand, occurring in the study area. Siliceous sand and a Gulf climate are characteristic for most of Tabasco, and calcareous sand and a Caribbean‐type climate are characteristic for Campeche.

Disturbance caused by coconut plantations, cattle grazing and tourism favours the invasion of ruderal species from waste places behind the dunes, which attain local dominance in the dunes described here. Consequently some separate community types had to be distinguished.

The distribution of community types is analyzed in the context of the transitions between calcareous and siliceous substrates in the study area.
Species turnover and diversity during early stages of vegetation recovery on the volcano Usu, northern Japan
Authors: Tsuyuzaki Shiro
Published: May 2006

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

The growth and survival of coniferous and broad‐leaved trees were followed over a 5‐yr period in a temperate old‐growth mixed forest in Japan, and dynamic features of the forest were studied in relation to the life history of the dominants, the coniferous Abies homolepis and the broad‐leaved Fagus crenata. During this period, the gap formation rate was 31m2 ha−1yr−1, the mortality of trees > 2m high was 1.7%/yr, and the rate of loss in basal area 1.4%/yr. These values were much higher than the recruitment, 0.3%/yr, and the total growth of surviving and new trees, 0.6%/yr, owing to the inhibition of regeneration by understorey dwarf bamboo (Sasa borealis).

A transition matrix model based on DBH size classes predicts that the basal area of the forest will decrease by 14% in 50 yr, but that the DBH distribution of trees > 10 cm diameter will change little. Equilibrium DBH distributions assuming recruitment being equal to mortality, were quite different between broad‐leaved and coniferous trees, reflecting different survivorship curves of the two dominants.

The composition and structure of the forest may change depending on the pattern and frequency of disturbances, or episodic events, notably the synchronous death of Sasa borealis.
A two‐phase mosaic in a savanna grassland
Authors: Carter A. J. , O'Connor T. G.
Published: May 2006

A two‐phase grassland mosaic was described using species association measures and pattern analysis techniques on local frequency data from six transects of contiguous quadrats. One phase consisted of almost mono‐specific patches of Setaria incrassata, which was negatively or not associated with ten common species. The other phase was dominated by Themeda triandra which was positively associated with several species.

PQV analyses revealed similar, significant, anisotropic scales of contagion of Setaria and Themeda, with phases alternating over 9 m up‐slope and 4 m along the contour. Setaria was associated with a tree canopy and deeper soils of higher organic carbon content than Themeda, which was negatively associated with tree canopies. Excavation of Setaria rhizomes indicated mean densities of 20.5 putative genets/m2 and 3.6 ramets per genet. Dense clonal growth, seedling recruitment and a competitive exclusion mechanism may contribute to patch maintenance.
Community structure in montane grasslands of central Argentina in relation to land use
Authors: Díaz Sandra , Acosta Alicia , Cabido Marcelo
Published: May 2006

Abstract. We compared the responses of natural montane grasslands in central Argentina to two land‐use patterns: cultivation ‐ high intensity, low frequency, and short history of disturbance ‐ and livestock raising ‐ low intensity, high frequency and long history of disturbance. We analysed species composition, richness, and architectural traits in seven neighbouring sites under different land use. There were sharp floristic discontinuities between post‐agricultural stages, whereas only minor shifts occurred among different grazing situations. Unlike cultivation, grazing did not produce significant differences in species richness and allowed very slight invasion by exotics. In post‐cultivation situations, architectural differences were accounted for by species composition. In the case of different grazing intensities, they were mainly explained by morphological differences among populations of the same dominants. In view of the historical information and current ideas, we suggest that the differential responses to both land uses can be explained not only by the different frequencies and intensities of disturbance they represent, but also by their contrasting histories in the area. Accordingly, herbivory by ungulates should not be considered as a disturbance in these montane grasslands.
Application of multifractals to the analysis of vegetation pattern
Authors: Scheuring István , Riedi Rudolf H.
Published: May 2006

Abstract. A method of characterizing the geometry and statistical nature of vegetation patterns and for studying their fractal dimension is proposed. The method utilizes the concept of multifractals, and is especially suited to the description of complex patterns. The properties of multifractals and their role in detecting the scale of vegetation patterns are explained. We suggest an extension of the term multifractal for use in landscape ecology and coenology connected with patterns of many different kinds of points. Relationships between information‐statistical functions and the fractal dimensions introduced are shown. A computer‐simulated example demonstrates the use of statistical functions and illustrates its applicability in vegetation science.
Annual nutrient budget for an alpine grassland in the Garhwal Himalaya
Authors: Sundriyal R. C. , Joshi A. P.
Published: May 2006

Abstract. N, P and K dynamics were investigated in grazed and ungrazed alpine forb and grassy meadows in the Garhwal Himalaya. The growth forms examined were dwarf shrubs, forbs and graminoides. N, P and K contents were determined for various plant components and soil. The contribution of plant parts to the total vegetation capital of N, P and K was 20–33% (live shoot), 6–8% (dead shoot), 2–3% (litter) and 56–71% (root) in ungrazed plots, and 16–27, 6–7, 1–2, and 64–76% respectively in grazed plots. Grazing removed between 41–69% of total uptake of nutrients from the grassland. In protected areas, however, 65 to 81% of all nutrients were retained by the vegetation. This retention of nutrients is due to translocation to roots and rhizomes and is considered beneficial during grazing as it aids resprouting of the vegetation.
Plot size and estimation efficiency in plant community studies
Authors: Kenkel N. C. , Podani J.
Published: May 2006

We examine the effects of changing plot size on parameter estimation efficiency in multivariate (community‐level) ecological studies, where estimation efficiency is defined in terms relating to the statistical precision of estimates of all variables (e.g. species) in a data set. Three ‘efficiency criteria’ for multivariate estimation are developed, and the relationship between estimation efficiency and plot size examined using three field data sets (deciduous understory, coniferous understory, and mire vegetation) from central Canada.

For all three communities, estimation efficiency was found to increase monotonically with increasing plot size. However, relative gains in efficiency at larger plot sizes were offset by substantial increases in sampling effort (enumeration time per plot). Our results indicate that the largest plot size possible, given the constraints of time, should be used for parameter estimation in plant communities. Also, plots that are larger than the mean patch size should be utilized when sampling heterogeneous vegetation.
Overstory vegetation and successional trends of Land Between The Lakes, USA
Authors: Franklin Scott B. , Robertson Philip A. , Fralish James S. , Kettler Stephan M.
Published: May 2006

133 stands from the uplands of Land Between The Lakes (LBL) were sampled. Stand data were ordinated to identify clinal patterns in the overstory vegetation. A coeno‐cline, accounting for 52% of the species variance, was developed from the first ordination axis. Classification of stands identified nine dominance types: Pinus echinata‐Quercus spp., Q. prinus, Q. prinus‐Q. alba, Q. stellata‐Q. alba, Q. velutina‐Q. alba, Q. alba, Q. alba‐Q. rubra, Acer saccharum‐Q. alba‐Fagus grandifolia sadF. grandifolia‐A. saccharum.

Compositionally‐stable (climax) and unstable (successional) stands were analyzed separately. Trajectories of unstable stands include the succession of P. echinata to Quercus‐dominated communities on xeric sites and of Quercus types to more mesophytic communities (e.g. A. saccharum and F. grandifolia) onmesic sites. These shifts indicate the nature of the future climax overstory composition at LBL.

The first axis DCCA ordination for climax stands accounted for 45% of the vegetation variance. Factor Analysis identified two significant suites of variables related to vegetation: soil chemistry/soil moisture and soil texture. Specific variables related to variation in the climax vegetation include soil pH, calcium and magnesium, effective soil depth, available water capacity, percent rock in the soil, slope position, aspect, elevation and distance to the opposing slope.

Modal positions of species along the direct gradient ordination were similar in rank order to those derived from the indirect gradient ordination of all stands. The latter ordination represents the present forest vegetation pattern at LBL. Climax stands showed a shift in modes of Quercus spp. toward the xeric end of the gradient and increases in habitat width of mesophytic species. Following a reduction in disturbance, species appear to adjust to changes in competition and available habitat. That is, the dimensions of realized niches (i.e. habitat widths) change with succession. The climax vegetation at LBL appears to show centrifugal organization.
Gas exchange and resource‐use patterns along a Mediterranean successional gradient
Authors: De Lillis M. , Federici F. M.
Published: May 2006

Abstract. Gas exchange, leaf‐nitrogen concentration and water potential were measured in early and late spring in early successional herbaceous plants occurring after cutting and after fire, and in mature woody species from the Mediterranean climax community Quercetum ilicis in central Italy. Net photosynthesis peaked in early spring in all species studied when values for temperature and light were lower but leaf‐nitrogen content was higher as compared to late spring, suggesting that nitrogen more than energy input controlled photosynt‐hetic rates. Herbaceous pioneer species occurring after cutting showed higher field photo synthetic capacity than evergreen climax trees and shrubs. By contrast, net photosynthesis of herbaceous species occurring in a persistent stage after fire, was in the same range as that of climax trees. This evidence suggests that carbon‐gaining appears to be partly related to the dynamic stage of succession and not solely to the growth form.
Generalized additive models in plant ecology
Authors: Yee Thomas W. , Mitchell Neil D.
Published: May 2006

Abstract. Generalized additive models (GAMs) are a non‐parametric extension of generalized linear models (GLMs). They are introduced here as an exploratory tool in the analysis of species distributions with respect to climate. An important result is that the long‐debated question of whether a response curve, in one dimension, is actually symmetric and bell‐shaped or not, can be tested using GAMs. GAMs and GLMs are discussed and are illustrated by three examples using binary data. A grey‐scale plot of one of the fits is constructed to indicate which areas on a map seem climatically suitable for that species. This is useful for species introductions. Further applications are mentioned.
Forest development in canopy gaps in old‐growth beech (Nothofagus) forests, New Zealand
Authors: Stewart Glenn H. , Rose Alan B. , Veblen Thomas T.
Published: May 2006

Abstract. Tree size and age structures, treefall and canopy gap characteristics, and regeneration responses to treefalls were compared for three stands of old‐growth beech (Nothofagus) forest dominated by N. fusca and N. menziesii on the South Island, New Zealand. Treefall gaps (up to 1000 m2) were most often caused by standing trees killed by drought and/or insect attack, or by trees snapped by wind. The causes of gap formation and the size and age distributions of treefall gaps varied between localities because of spatial and temporal differences in the histories of disturbance. At Fergies Bush where drought‐related dieback had produced many large gaps with standing dead trees, gaps were generally young. Conversely, at Station Creek, small, old gaps formed by bolesnap dominated the disturbance regime. At Rough Creek, gaps of all ages and sizes were found along with an almost complete fern cover, and abundant shrubs and occasional subcanopy hardwood trees.

Although overall patterns of regeneration were unrelated to differences in gap size, the relative abundance of N. fusca and N. menziesii varied between localities according to the seemingly minor differences in forest structure and disturbance history described above. Interpretations of regeneration response to gap parameters, therefore, need to account for differences in disturbance history between sites. Differences in the disturbance history between localities will also influence rates of gap closure, and because closure rates are used to estimate forest turnover times, meaningful comparisons of disturbance regimes for different forest types can only be made if this intersite variability is addressed.
Climate and the distribution of Fallopia japonica: use of an introduced species to test the predictive capacity of response surfaces
Authors: Beerling David J. , Huntley Brian , Bailey John P.
Published: May 2006

Abstract. The relationship between present climate and the distribution in Europe of the aggressively invasive exotic Fallopia japonica is described by fitting a response surface based on three bioclimatic variables: mean temperature of the coldest month, the annual temperature sum > 5 °C, and the ratio of actual to potential evapotranspiration. The close fit between the observed and simulated distributions suggests that the species' European distribution is climatically determined. The response surface also provides a simulation of the extent of the area of native distribution of F. japonica in Southeast Asia that is generally accurate, confirming the robustness of the static correlative model upon which it is based. Simulations of the potential distribution of F. japonica under two alternative 2 x CO2 climate change scenarios indicate the likelihood of considerable spread into higher latitudes and possible eventual exclusion of the species from central Europe. However, despite the robustness of the response surface with present‐day climate, the reliability of these simulations as forecasts is likely to be limited because no account is taken of the direct effects of CO2 and their interaction with the species' physiological responses to climate. Similarly, no account is taken of the potential impact of interactions with ‘new’ species as ecosystems change in composition in response to climate change. Nevertheless, the simulations indicate both the possible magnitude of the impacts of forecast climate changes and the regions that may be susceptible to invasion by F. japonica.
Old‐field successional dynamics on the Inland Pampa, Argentina
Authors: Omacini M. , Chaneton E.J. , León R.J.C. , Batista W.B.
Published: May 2006

Abstract. The first 10 yr of old‐field successional dynamics on the Argentine Inland Pampa were studied on a series of adjacent plots established consecutively between 1978 and 1989. We examined differences in species abundance patterns among plots in order to detect the spatial and temporal variability of succession. Perennial grasses steadily increased in cover and replaced the dominant annual species after 5 yr. Pioneer dicots persisted in older seral stages with 20 — 23 species/plot. Overall, exotic species (mostly the grasses Lolium multiflorum and Cynodon dactylon) contributed much to the plant cover in these communities. Native grasses comprised 45 % of total cover at years 7 — 10 of succession, but occurred with less than 7 species/plot. Substantial variation was found in the successional pathway, which reflected the particular sequence from annual forbs to short‐lived and perennial grasses in the various plots. The course of succession was apparently influenced by a 2‐yr period of unusually high rainfall. Deyeuxia viridiflavescens, a native perennial grass virtually absent before the wet period, spread over the study area and dominated seral communities for 3 yr, irrespective of plot age. Climatic conditions thus affected the successional turnover of life forms by increasing the rate of colonization by perennial grasses. We further point out the constraints imposed on secondary succession by the life histories of ‘available’ species.
On the use of three performance measures for fitting species response curves
Authors: Ferrer‐Castán Dolores , Calvo José F. , Esteve‐Selma Miguel A. , Torres‐Martínez Antonio , Ramírez‐Díaz Luis
Published: May 2006

Abstract. Quantitative response surfaces obtained from three performance measures, density, cover and volume, are compared, using as an example the spatial distribution of Periploca angustifolia (Asclepiadaceae) in SE Spain. Generalized linear models are used to examine relationships between these species performance measures and complex gradients of aspect, slope angle and altitude.

All three performance measures showed a skewed response to the environmental gradients, unlike the Gaussian responses commonly assumed in vegetation theory; skewness increased as the number of dimensions of the performance measures increased. Certain asymmetries between the responses are discussed in terms of competition, and problems related to the use of complex gradients are considered.
Grazing in remnant woodland vegetation: changes in species composition and life form groups
Authors: Pettit Neil E. , Froend Raymond H. , Ladd Phillip G.
Published: May 2006

Abstract. Grazing by domestic livestock in native woodlands can have major effects on ecosystem functioning by the removal of plant species that form important functional groups. This paper documents the changes in floristics in a large group of remnants of native woodland left after agricultural clearing in southwestern Australia. Species richness and diversity were significantly reduced in remnants and the proportion of exotic species increased. Detrended Correspondence Analysis (DCA) was used to identify floristic and environmental patterns among plots and identified two distinct groups based on grazing intensity. This indicated that the significance of the relationship between grazing effects and DCA floristic axes was greater than edaphic characteristics that normally influence floristic patterns. Floristic characteristics of sites that were influencing the position of plots on the ordination diagram included proportion of exotic species and proportion of native perennial shrubs and herbs. Numbers of species of native shrubs and perennial herbs were significantly reduced in grazed plots and numbers of exotic annual grasses and herbs were significantly higher. Other life form groups such as native perennial grasses and geophytes were not significantly affected by grazing. Reproductive strategies of perennial species showed a significant decrease in numbers of resprouters and a significant increase in numbers of facultative seeder/sprouters. Exclosure plots showed increases in number and cover of perennial shrubs and herbs after three years whereas number and cover of exotic species did not change. Time series DCA showed that the floristic composition of exclosure plots in grazed sites became closer to that of the ungrazed sites.
On the concept of vegetation class in phytosociology
Authors: Pignatti S. , Oberdorfer E. , Schaminée J.H.J. , Westhoff V.
Published: May 2006

Abstract. The vegetation class is generally accepted as the highest category in vegetation taxonomy. Vegetation classes, following the tradition, are defined mainly on the basis of character species. However, these are sometimes relatively rare and not always really representative of the ecological conditions of plant communities included in the class. In the present study the possibilities are discussed for a more comprehensive definition of the class, including spatial structure and environmental characteristics of the vegetation and the geographical distribution of character species. These include criteria with practical value, in particular for the understanding of vegetation in tropical areas. Some cases of well‐known vegetation classes are discussed; in most of them the ranges of single character species and the range of the class as a whole largely coincide.
Long‐term after effects of fertilization on above‐ground phytomass and species diversity in calcareous grassland
Authors: Willems J.H , van Nieuwstadt M.G.L
Published: May 2006

Abstract. Long‐term after effects on species number and productivity in calcareous grassland were analyzed after cessation of fertilization. Three series of permanent plots were monitored yearly from 1971 to 1993. These series differed in duration of fertilization and in fertilizer composition, notably the amount of nitrogen and phosphorus.

Yearly above‐ground production decreased in all series after fertilization had been stopped, however at different speeds. The grass/forb ratio also decreased, while species number and Shannon index of diversity (H') increased. In the series where fertilizer treatment was stopped in 1967 (1968‐series), productivity and grass/forb ratio decreased equally as in the plots where fertilization with a high nitrogen content was stopped in 1979 (80/Npk‐series). However, species number in the plots of the 80/Npk‐series increased faster than in the 1968‐series. This was probably the result of a higher number of species present in the seed rain from the surrounding vegetation in the period after 1980 than from after 1968.

In the plots receiving a high amount of phosphorus (80/nPk series), the productivity decreased more slowly than in the high nitrogen plots (80/Npk‐series). At approximately the same total production level, the grass/forb ratio remained higher for another five‐year period in the 80/nPk‐series. Species number and the Shannon index of diversity increased more slowly in the 80/nPk‐series than in the 80/Npk‐series. Over a given range of productivity, changes in species number and Shannon index correlated better with the grass/forb ratio than with total above‐ground phytomass. Therefore, restoration of species‐rich grassland should not only be focused on lowering the yearly production, but also on reducing the grass component of the vegetation.
Establishment of Picea abies seedlings in a central European mountain grassland: an experimental study
Authors: Prach K. , Lepš J. , Michálek J.
Published: May 2006

Abstract. Secondary meadows in the Krušné hory mountains, central Europe, are not colonized by woody species, although they have been abandoned for half a century and are surrounded by Picea abies (Norway spruce) forests. The causes of inhibition of establishment of Norway spruce seedlings in the meadows were tested experimentally. The experiment was started in a masting year to ensure sufficient seed input. Four treatments (vegetation cut; vegetation cut and litter removed; all above‐ground biomass and topsoil removed; control) were combined in a factorial design. The effect of browsing, mainly by deer, was assessed by fencing half of the experimental plots. Seedling establishment differed among treatments (all pair‐wise differences were significant) but was independent of fencing. In contrast, seedling survival was influenced both by the treatment and fencing. At the end of the second year, only the plots with all biomass and organic topsoil removed supported viable populations of spruce seedlings. Dense herb cover and a thick layer of slowly decaying litter are considered the main factors inhibiting the establishment of woody species.
Estimation of tree replacement patterns in an AppalachianPicea‐Abiesforest
Authors: Busing R.T.
Published: May 2006

Abstract.Patterns of tree species replacement in aPicea‐Abiesforest, determined by several different methods, are compared and the methods are assessed. Methods are grouped as either understory‐based or gap‐based estimates of replacement. The understory‐based methods characterize canopy‐understory interactions with spatial statistics, sapling density measurement, sapling frequency measurement, and successor sapling identification beneath live canopy trees. The gap‐based methods include sapling density measurement, sapling frequency measurement, and successor sapling identification in tree‐fall gaps. Methods except those based on frequency indicate a strong trend of replacement of all canopy species byAbies. Understory‐based methods may underestimate canopy recruitment of intolerant trees, while gap‐based methods relying on sapling density or frequency may overestimate recruitment of intolerant trees. Estimates based on the selection of successor saplings in the understory or in gaps are reliable. Gap successor estimates consider the process of gap capture and are useful in analyses of forest dynamics.
Development of secondary pine forests after pine wilt disease in western Japan
Authors: Fujihara Michiro
Published: May 2006

Abstract. The development of secondary Pinus densiflora (Japanese red pine) forests after pine wilt disease was studied through phytosociological analysis, estimation of forest structure before disease and size‐structure, tree ring and stem analyses. Following the end of the disease, the growth of previously suppressed small oak trees was accelerated. This is quite different from the development of forests following fire, which starts with the establishment of pine seedlings. Pine wilt disease shifted the dominance of secondary forests from Pinus densiflora to Quercus serrata oak forest. In pine forests, disturbance by fire is important for forest maintenance. In contrast, disturbance by pine wilt disease leads to an acceleration of succession from pine forest to oak forest.
Ordinal response regression models in ecology
Authors: Guisan Antoine , Harrell Frank E.
Published: May 2006

Abstract.Although ordinal data are not rare in ecology, ecological studies have, until now, seriously neglected the use of specific ordinal regression models. Here, we present three models – theProportional Odds, theContinuation Ratioand theStereotypemodels – that can be successfully applied to ordinal data. Their differences and respective fields of application are discussed. Finally, as an example of application, PO models are used to predict spatial abundance of plant species in a Geographical Information System. It shows that ordinal models give as good a result as binary logistic models for predicting presence‐absence, but are additionally able to predict abundance satisfactorily.
Variation in vegetation and seed bank in a Chilean semi‐arid community affected by ENSO 1997
Authors: Gutiérrez J.R. , Arancio G. , Jaksic F.M.
Published: May 2006

Abstract. We followed plant cover and soil seed density of shrubs and herbs in two markedly contrasting years with regard to annual rainfall in two opposite‐facing slopes (mesic vs xeric) and an intervening, relatively wet, ravine of a typical creek in semi‐arid Chile. During the ENSO year 1997 cover of ephemerals increased in all three sites; 43% vs 8% on the xeric slope 75% vs 26% on the mesic slope and 57% vs 32% in the ravine. The number of species was almost three times higher on the xeric slope (27 vs 10 species), increased by 47% on the mesic slope (28 vs 19) and by 14% in the ravine (24 vs 21). Cover of shrubs plus perennial grasses increased from 52% in 1996 to 59% in 1997 on the xeric slope, but no significant cover changes were found on the mesic slope or the ravine. On the xeric slope peak density of seeds was 4500/m2 in 1996, while during the ENSO year it was 24000/m2. On the mesic slope equivalent values were 3000 and 17000 seeds/m2 while in the ravine figures were 8500 and 27000 seeds/m2. The strong responses of ephemerals and seed bank to the ENSO‐driven wet year of 1997 demonstrate the importance of this phenomenon in replenishing, recovering and probably maintaining ephemeral vegetation in this region.