A regional vegetation survey of the temperate grassy woodlands (temperate savanna) in Australia was designed to assess the effects of clearing and grazing on the composition of vegetation remnants and the adjacent pasture matrix. Vegetation was sampled across a range of habitats using 77 0.1024-ha quadrats; the relative abundance of species was recorded. Classification analysis clustered the sites into three main groups that corresponded to intensity of grazing/clearing followed by groups based on underlying lithology (basalt, metasediment, granites). Using Canonical Correspondence Analysis, exogenous disturbance and environmental variables were related to the relative abundance of species; grazing intensity had the highest eigenvalue (0.27) followed by tree canopy cover (0.25), lithology (0.18), altitude (0.17) and slope (0.10). Based on two-dimensional ordination scores, six species response groups were defined relating to intensity of pastoralism and nutrient status of the landscape. Abundance and dominance of native shrubs, sub-shrubs, twiners and geophytes were strongly associated with areas of less-intense pastoralism on low-nutrient soils. The strongest effects on species richness were grazing followed by canopy cover. Continuously grazed sites had lower native species richness across all growth forms except native grasses. There was no indication that intermediate grazing intensities enhanced forb richness as a result of competitive release. Species richness for all native plants was lowest where trees were absent especially under grazed conditions. Canopy cover in ungrazed sites appeared to promote the co-existence of shrubs with the herbaceous layer. Predicted declines in forb richness in treeless, ungrazed, sites were not detected. The lack of a disturbance-mediated enhancement of the herbaceous layer was attributed to habitat heterogeneity at 0.1 ha sampling scale.

Nomenclature: Harden 1990–1993.

Bischofia javanica is an invasive tree of the Bonin Islands in the western Pacific, Japan. This species has aggressive growth, competitively replacing native trees in the natural forest of the islands. The aim of this study was to examine seed and seedling factors which might confer an advantage to the establishment of Bischofia over native trees. During a 5-yr period we compared the demographic parameters of early life history of Bischofia and Elaeocarpus photiniaefolius, a native canopy dominant, in actively invaded forests. Predation of Elaeocarpus seeds by in troduced rodents was much higher before (27.9–32.9%) and after (41.3–100%) dispersal of seeds than that of B. javanica. Most Elaeocarpus seeds lost viability ca. 6 mo after burial in forest soil while some seeds of Bischofia remained viable for more than 2 yr. Seedling survival in the first 2 yr was much higher in Bischofia (16%) than in Elaeocarpus (1.3%). The high persistence of Bischofia in the shade, coupled to its rapid acclimation to high light levels, is an unusual combination because in forest tree species there is generally a trade-off between seedling survival in the shade and response to canopy opening. Compared with a native canopy dominant, greater seed longevity, lower seed predation by introduced rodents, longer fruiting periods and the ability to form seedling banks under closed canopy appear to have contributed to the invasive success of Bischofia on the Bonin Islands.

Nomenclature: Satake et al. (1989).

The vegetation of central Arizona is a mosaic of four vegetation types: chaparral, chaparral grassland, woodland, and woodland grassland. We analysed ten environmental variables, three disturbance variables, and five disturbance indicators to answer the question: What is the relative importance of environment and disturbance in explaining the vegetation pattern of our study area? We found that chaparral, chaparral grassland, and woodland are differentiated primarily by environmental factors and have high stability in the landscape. In contrast, woodland grassland is differentiated primarily by disturbance and is likely an early-successional stage of woodlands. Although other researchers have indicated that semi-arid vegetation is generally unstable, the vegetation of central Arizona is composed of two systems: those with a more stable landscape position determined primarily by environmental factors and those with a less stable landscape position determined primarily by disturbance factors.

Nomenclature: Kearney & Peebles (1960) and McDougall (1973).

Abbreviations: A = Grazing allotment size and chance corrected within-agreement; C = Number of permitted domestic grazing animals; CCA = Canonical Correspondence Analysis; DCA = Detrended Correspondence Analysis; MRPP = Multi-Response Permutation Procedure; NMS = Non-Metric Multi-dimensional Scaling; S = Fire size class; T = Grazing period; W = Probability that fire burned a stand or a conversion event took place.

Facilitation by dispersal occurs if the nurse plant acts as a focus which is actively selected by seed dispersers and enhances the fitness of the facilitated plant. Sex-biased facilitation may be produced if seed dispersers tend to concentrate the seeds under female, fruit-bearing plants of dioecious species more often than under conspecific males. Juniperus sabina is a dioecious shrub with a prostrate growth form from Mediterranean high mountains that modifies many microhabitat characteristics related to seedling establishment and survival. Soil water availability, maximum soil temperature in summer, organic matter and total nitrogen content, were different on open ground as compared with beneath J. sabina shrubs, irrespective of its sex. Other studied characteristics such as soil bulk density and soil compaction after rain did not differ between the microhabitats considered. Some species, such as Juniperus communis, Pinus nigra, Helleborus foetidus and Euphorbia nicaeensis, are spatially associated to J. sabina shrubs, strongly suggesting a facilitative role. The anemochorous P. nigra and myrmechorous H. foetidus and E. nicaeensis did not associate preferentially to any sex of J. sabina. Only J. communis, an endozoochorous species sharing the same bird dispersers as J. sabina, presented a female-biased spatial association with the nurse plant. Seed dispersal mediated by birds attracted by the fruit-rewarding females of J. sabinaexplains the sex-biased spatial pattern of Juniperus communis.

Nomenclature: Mateo & Crespo (1998).

Abbreviation: PAR = Photosynthetically active radiation.

In order to test for cumulative effects of fire on Paspalum quadrifarium-dominated grasslands (‘pajonal’), we analysed the impact of single and repeated fires on the community structure and post-fire recovery of canopy after a final, simultaneous fire event. Nine plots were defined within a homogeneous pajonal stand, and treatments of low (LF), medium (MF) and high frequency (HF) of fire were defined by the application of one, two or four cold-season burns, respectively, along a 6-yr period. Both burned and unburned plots were exposed to grazing by cattle during the summer following the first and the third years of that period. High cattle preference for burned sites conditioned fire temperature and vegetation responses to the following burning events. Cumulative effects between successive burning events were observed for the cover of basal area of the dominant and other sprouting species, the cover and thickness of the litter layer, the seed bank size of the principal recruiter species, and the floristic composition. While light interception by the canopy was positively related to fire frequency during the early growth season, further growth of P. quadrifarium determined a greater light interception in LF than in MF and HF. These patterns of light interception were associated with a faster occupation of the inter-tussock areas by opportunistic species in plots subjected to frequent fires (HF and MF) than in plots with low fire frequency (LF), and a more lasting regrowth of P. quadrifarium in the LF plot than in the HF ones. High fire frequencies reduced the dominance of P. quadrifarium. Percent of species classified as subordinated graminoids or forbs did not vary among treatments. However, the abundance of different forb species was differentially favoured by contrasting frequencies of fire, describing some coarse relationships between their specific responses and their dispersal strategies.

Nomenclature: Cabrera & Zardini (1978); Bertiller & León (1975).

Abbreviations: HF = High burning frequency; LF = Low burning frequency; MF = Medium burning frequency; PAR = Photosynthetically Active Radiation; TED = Tiller Effective Density; TIR = Tiller Increment Ratio; T_max = Maximum temperature at ground level during fire.

A large number of plots (306) were sampled for floristic data and variables of soil nutrient availability in a wide range of forest conditions in the Vosges mountains (NE France). Half of the data were used to model species presence/absence as a function of nutritional variables using two numerical methods: parametric logistic regression and non-parametric Kernel estimation. Species responses were established for calcium, aluminium, Ca : Al ratio, base saturation, pH and C : N measured in the upper soil horizon. The other half were used to predict these variables with vegetation with three approaches: maximum likelihood, indicator values and ecological groups.

More than 80 % of the 122 studied species showed a significant response to one or more nutrition factors. Species often had optima for maxima or minima of the studied values. For each variable, species were more frequent in conditions with good nutrition and/or low toxicity: maximum values were most frequent for Ca, Ca : Al, base saturation, pH and minimum values were most frequent for Al and C : N. For all variables, optima estimated by logistic regression were well correlated with those estimated by kernel estimation: R² > 0.9.

Mean differences between measured values and predictions by vegetation were ca. 2.6 meq for Ca, 1.2 for log Ca, 3.1 meq for Al, 1.8 for log Al, 30 for Ca : Al, 2.1 for log Ca : Al, 0.21 for base saturation, 0.7 for pH and 5.7 for C : N. The quality of prediction as measured by R² between predicted and measured values varied from 0.60 to 0.14. The quality of prediction decreases from soil base saturation to aluminium according to the next order: base saturation > log Ca : Al > log Ca > Ca > C : N > pH > log Al > Al > Ca : Al. Maximum likelihood and ecological groups methods of prediction were more efficient than the indicator values method.

Abbreviations: BS = Base Saturation; EG = ecological group; IV = Indicator value; KE = Kernel estimation; LR = Logistic regression; ML = Maximum Likelihood; RMSE = Root mean square error.

Nomenclature: Tutin et al. (1976, 1977).

Nutrient conservation in vegetation affects rates of litter decomposition and soil nutrient availability. Although resorption has been traditionally considered one of the most important plant strategies to conserve nutrients in temperate forests, long leaf life-span and low nutrient requirements have been postulated as better indicators. We aimed at identifying nutrient conservation strategies within characteristic functional groups of NW Patagonian forests on Andisols. We analysed C-, N-, P-, K- and lignin-concentrations in mature and senescent leaves of ten native woody species within the functional groups: broad-leaved deciduous species, broad-leaved evergreens and conifers. We also examined mycorrhizal associations in all species. Nutrient concentration in mature leaves and N- resorption were higher in broad-leaved deciduous species than in the other two functional groups. Conifers had low mature leaf nutrient concentrations, low N-resorption and high lignin/N ratios in senescent leaves. P- and K-resorptions did not differ among functional groups. Broad-leaved evergreens exhibited a species-dependent response. Nitrogen in mature leaves was positively correlated with both N resorption and soil N-fertility. Despite the high P-retention capacity of Andisols, N appeared to be the more limiting nutrient, with most species being proficient in resorbing N but not P. The presence of endomycorrhizae in all conifers and the broad-leaved evergreen Maytenus boaria, ectomycorrhizae in all Nothofagus species (four deciduous, one evergreen), and cluster roots in the broad-leaved evergreen Lomatia hirsuta, would be possibly explaining why P is less limiting than N in these forests.

Nomenclature: Zuloaga & Morone (1996, 1999).

As part of a larger survey of biodiversity in gardens in Sheffield, UK, we examined the composition and diversity of the flora in two 1-m² quadrats in each of 60 gardens, and compared this with floristic data from semi-natural habitats in central England and derelict urban land in Birmingham, UK. Garden quadrats contained more than twice as many taxa as those from any other habitat type. Ca. 33 % of garden plants were natives and 67 % aliens, mainly from Europe and Asia. A higher proportion of garden aliens originated from Asia and New Zealand than in the UK alien flora as a whole; 18 of the 20 most frequent plants in garden quadrats were natives, mostly common weeds. Garden quadrats showed no evidence of ‘nestedness’, i.e. a tendency for scarce species to be confined to the highest diversity quadrats. Conversely, species in all semi-natural and derelict land data sets were significantly nested. Compared to a range of semi-natural habitats, species richness of garden quadrats was intermediate, and strikingly similar to the richness of derelict land quadrats. Although species accumulation curves for all other habitats showed signs of saturation at 120 quadrats, gardens did not. Correlations between Sørensen similarity index and physical distance were insignificant for all habitat types, i.e. there was little evidence that physical distance played any part in structuring the composition of the quadrats in any of the data sets. However, garden quadrats were much less similar to each other than quadrats from semi-natural habitats or derelict land.

Nomenclature: Stace (1997); Wright (1984).

A previous study of the spatial patterns of Borassus aethiopum (a humid savanna palm tree) led to the following predictions: H1. Trees and termite mounds positively influence all developmental stages; H2. There is intense competition between B. aethiopum juveniles; H3. Juvenile and seedling survival and growth rates are higher away from mother plants; H4. Mound positive effect overwhelms the effect of intra-specific competition for very young B. aethiopum individuals, the reverse applies to older, non-reproductive individuals. To test for these hypotheses the potential positive and negative neighbourhood effects were analysed. Progression of seedlings into the juvenile stage and juvenile growth were analysed through logistic regression models including the effects of four neighbourhood indices designed to model the respective influence of B. aethiopum juveniles and adults, trees and termite mounds. Statistical results explain the observed spatial pattern and reveal two main neighbourhood effects that influence both B. aethiopum juveniles and seedlings: a positive effect of mounds due to the fact that they constitute nutrient-rich soil patches, and a negative effect of juveniles due to intraspecific competition. Seedlings would be mostly affected by the mound positive effect, whereas juveniles would be mostly affected by competition.

Abbreviations: EL-seedling = Entire-leafed seedling; H = Height. LN = Leaf number, LNI = leaf number increment, PFI = Practical fit index; SL-seedling = Slit-leafed seedling

Scaevola plumieri is an important pioneer on many tropical and subtropical sand dunes, forming a large perennial subterranean plant with only the tips of the branches emerging above accreting sand. In South Africa it is the dominant pioneer on sandy beaches along the east coast, less abundant on the south coast and absent from the southwest and west coasts. Transpiration rates (E) of S. plumieri are predictably related to atmospheric vapour pressure deficit under a wide range of conditions and can therefore be predicted from measurement of ambient temperature and relative humidity. Scaling measurements of E at the leaf level to the canopy level has been demonstrated previously. Using a geographic information system, digital maps of regional climatic variables were used to calculate digital maps of potential transpiration from mean monthly temperature and relative humidity values, effectively scaling canopy level transpiration rates to a regional level. Monthly potential transpiration was subtracted from the monthly median rainfall to produce a map of mean monthly water balance. Seasonal growth was correlated with seasonal water balance. Localities along the coast with water deficits in summer corresponded with the recorded absence of S. plumieri, which grows and reproduces most actively in the summer months. This suggests that reduced water availability during the summer growth period limits the distribution of S. plumieri along the southwest coast, where water deficits develop in summer. Temperature is also important in limiting the distribution of S. plumieri on the southwest coast of South Africa through its effects on the growth and phenology of the plant.

Nomenclature: Dyer (1967).

Abbreviations: E = Transpiration; ISSR = Inter Simple Sequence Repeat; LAI = Leaf area index; RH = Relative humidity; SVP = Saturation vapour pressure; VPD = Vapour pressure deficit.

The effects of selective logging on tree diversity, changes in tree species composition and plant functional types were studied with the use of seven permanent plots in virgin and in logged forest. All plots were located in a lowland dipterocarp rain forest in East Kalimantan on the island of Borneo. Just after logging and during the following 20 yr tree diversity measured as Fishers' α was not significantly affected in logged forest plots. Temporal shifts in tree species composition were analysed with Principal Component Analysis (PCA). Logged forest plots had much larger changes over time than virgin forest plots. In the smallest diameter class, some logged forest plots showed a distinct trajectory in PCA space compared to virgin forest plots, while in larger diameter classes movement of logged plots in PCA space was random. This suggests that there is no pre-determined community to which logged forest plots tend to shift when recovering from logging. We found a significant negative correlation between diameter increments and the species-specific wood densities of tree species. Species-specific wood density and potential tree height were used to assign species to five PFTs. As expected, logging increased the fraction of softwood stems in small diameter classes. In the largest diameter classes (≥ 50 cm DBH) a strong decrease of softwood emergent stems was found in logged forest plots. After more than 20 yr no recruitment was found of softwood emergent stems in selectively logged forest.

Nomenclature: Sidiyasa et al. (1999); Anon. (1955–1994).

Abbreviations:GRH = Gap-phase Regeneration Hypothesis; IDH = Intermediate Disturbance Hypothesis; LLOG = Low-intensity logging; MLOG = Moderate-intensity logging.

The allometric relationships of trees in temperate and tropical forests are relatively well known, but not those of woody shrubs or transitional (shrub/tree) life forms. We explored the transition of Prosopis glandulosa var. torreyana from tree to shrub along a semi-arid topographic sequence comprising of six landforms (hillslope, footslope, upper and lower bajada, playa and dune) with varying soil texture and water availability. In each landform, we measured P. glandulosa shoot pre-dawn water potentials (Ψ) in one ‘dry’ and one ‘wet’ year. We also measured plant height, widest basal stem diameter, crown area and number of basal branches. Total basal stem area was calculated. We used simple (Model II linear regression) and expanded (incorporating an asymptote to height or crown area) allometry models to compare height with widest basal stem diameter and crown area with total basal stem area. There were significant correlations between maximum plant size and inter-year Ψ means suggesting that soil water availability decreased down the topographical sequence. The height asymptote was statistically significant in all landforms and lower toward finer-textured soils. On the other hand, crown area was a linear function of total basal stem area and was also site specific. Our results suggest that more basal branches are produced as plant height decreases in more stressful environments, effectively increasing crown area with a minimum investment in supporting tissues. The polymorphic characteristics of Prosopis may partly explain their occurrence in many arid and semi-arid environments.

Nomenclature: Correll & Johnston (1970); for families: Anon. (1998).

Diversity-biomass relationships are frequently reported to be hump-shaped over space at a given time. However, it is not yet clear how diversity and biomass change simultaneously and how they are related to each other over time (e.g. in succession) at one locality. This study develops a temporal model based on the projected changes of various community variables in a generalized terrestrial environment after fire and uses post-fire succession data on Santa Monica Mountains of southern California and other published succession data to examine the temporal diversity-biomass relationships. The results indicate that in the early stages of succession, both diversity and biomass increase and a positive relationship appears, while in the late stages of succession, biomass continued to increase but diversity usually declines; thus a negative relationship may be observed. When the scales of measurement become sufficiently large so that the measured diversity and biomass cross various stages of succession, a ‘hump-shaped’ relationship can emerge. The diversity-biomass relationship appears to be concordant in space and time when appropriate scales are used. Formerly proposed explanations for spatial patterns may well apply to the temporal patterns (particularly colonization, facilitation and competitive exclusion).

Pattern of native vegetation, distribution of alien species and variation of environmental parameters were studied in mountain grasslands in a lithologically homogeneous Córdoba mountain range in Central Argentina. CCA showed that altitude was the most important factor determining the compositional variation of the vegetation, with soil nutrient status and stoniness as additional factors. Short-grass communities, associated with the driest habitats on plateaus, showed higher small-scale native species richness than wet-turf communities in valleys and tall-grass communities on slopes. Species richness was negatively correlated with soil parameters that indicate nutrient status and water availability. Also, there was a negative correlation between soil Ca- and Mg-content and richness. High native species richness coincided with high alien species richness. When smaller units – community types – were considered, it became evident that within short-grass vegetation, the three most species-rich community types contained significant numbers of alien species, while the other two did not. Even within one community type, the same quadrats that contained the highest number of native species, were also characterized by the highest numbers of alien species. Evidently, the same mechanism was responsible for high richness of both native and alien species. Alien species were distinguished by a greater proportion of annuals and prostrate stoloniferous plants, by lower palatability and by smaller proportion of zoochory.

DCA ordination of quadrats on the basis of plant traits as attributes resulted in a clear distinction of three main vegetation types. Short-grass vegetation was distinguished by a predomination of late flowering species, tall-grass vegetation by the presence of high herbaceous plants and bushes, and wet-turf vegetation by the presence of plants with storage organs, the lack of hairy leaves, and by a high proportion of cryptophytes. Quadrats with and without alien species were distinguished as well, indicating that the occurrence of aliens may be dependent on plant traits in a particular patch of a community.

Nomenclature: Cantero & Bianco (1986).