We studied the vegetation distribution in eight landscape types distinguished along an altitudinal gradient in the Trans-Himalayan region of Ladakh, India. The point-intercept method was used for vegetation sampling. Six plant communities were distinguished by cluster analysis. Of these 6 communities, three communities were dominated by shrub species. Table lands are the landscape type with the highest species diversity followed by undulating areas and river beds. Most plant species were restricted to one landscape type.

Nomenclature: Kachroo et al. (1977); Polunin & Stainton (1984).

In the southeastern USA, harvest of pine straw sometimes involves mechanical raking of natural Pinus palustris (longleaf pine) communities. Little is known about the effects of raking nor how these effects may vary in time and space. In a two yr experiment, we examined the effects of mechanized raking on Pinus palustris dominated communities (scrub oak, dry savanna, and mesic savanna) by monitoring vegetation at seven spatial scales (0.01-100 m²). We measured floristic similarity and the proportion of species initially present that were gained (i.e. new species) or lost during four sampling periods. Relationships between spatial scale and these community attributes were analyzed using a repeated measures approach and functional response curves. Spatial scale clearly affected observed rates of species loss and floristic similarity; losses declined and floristic similarity increased as scale increased. We relate these patterns to expanding population sizes with scale and our inability to detect species reductions in large populations. Scale had little influence on species gains. The effects of raking did not differ across scales, but raking caused greater mean losses of species and greater mean changes in floristic similarity when mean values were calculated over all scales. Raking also increased the mean rate of species gains in the mesic savanna during one period. Otherwise, interaction effects of community and raking were largely absent from both mean values and response curves. Despite significant short-term effects of raking, changes in species richness were minor.

Nomenclature: Kartesz (1994).

We reconstructed forest development and disturbance events (fire and logging) during the last 1000 yr with tree-ring data, pollen and charcoal analysis from a semi-natural Fagus sylvatica-Picea abies forest (ca. 1 km2) in the hemiboreal zone. According to pollen analysis, Quercus robur together with Pinus sylvestris was abundant in the forest until the turn of the 18th/19th centuries when these species disappeared completely (Quercus) or nearly completely (Pinus) and were replaced by Fagus and Picea. The disappearance of Quercus was corroborated by the remarkable discovery of a single Quercus stump that had been cut in the 18th century and had become overgrown and preserved by a very old Picea. In total 11 fires were dated from 1555 to 1748 from fire scars in several Pinus stumps cut 100 - 200 yr ago. Since the last fire in 1748, no Quercus or Pinus have regenerated in the core of the reserve apart from single pines in neighbouring managed forest (80 yr ago). During the period of documented fires Fagus was protected from fires in a refuge made up of large boulders. Picea colonized the region at the time when the fires ceased 250 yr ago. We hypothesize that most of the fires were probably of human origin because of their patchiness and high frequency compared to the natural background levels of lightning ignitions in the region. On a 300-yr time scale, logging and fire suppression seem to strongly overshadow the effect of climate change on forest composition and dynamics.

Nomenclature: Tutin et al. (1964–1976).

Abbreviation: LID = Lightning Ignition Density.

Seed bank spatial pattern was studied in a secondary forest dominated by Fagus sylvatica and Betula celtiberica in the Urkiola Natural Park (N Spain). Soil samples were taken every 2 m in a regular grid (196 points) and divided into two fractions (0-3 cm and 3-10 cm deep). The viable seed bank was studied by monitoring seedling emergence for ten months. The effect of different factors on seed bank composition and patterning was analysed using constrained ordination as a hypothesis testing tool. Furthermore, the existence of spatial autocorrelation was evaluated by geostatistical analysis. Seed density was high, 7057 seed.m⁻², with a few species dominating. Species composition in the various layers were significantly correlated. The seed bank showed significant spatial structure, which was partially explainable by the spatial structure of the canopy and understorey vegetation. Spatial clumping from 0-8 m was observed in seed bank density and composition, mainly due to the pattern of two abundant taxa Juncus effusus and Ericaceae. The Ericaceae seed bank was related to the spatial distribution of dead stumps of Erica arborea. J. effusus was not present in the above-ground vegetation, which indicates that its seed bank was formed in the past. As expected, the seed bank of this forest reflects its history, which is characterized by complex man-induced perturbations. The seed bank appears to be structured as a consequence of contrasting driving forces such as canopy structure, understorey composition and structural and microhabitat features.

Abbreviations: TVE = Total variance explained.

Nomenclature: Aizpuru et al. (1999).

Dynamics of a Sequoia sempervirens forest in northern California were studied with long-term plot data (1.44 ha) and recent transect data. The study was conducted in an old stand (> 1100 yr) on alluvial flats. Over three decades (1972–2001), changes in the composition and structure of the tree stratum were minor. Sequoia maintained a broad distribution of stem diameters throughout the period. Annual rates of Sequoia mortality (0.0029) and ingrowth (0.0029) were low, reflecting the great longevity of Sequoia and the slow canopy turnover of the study forest. Transect data also indicated a low frequency of canopy gap disturbance (≤ 0.4% of total land area per yr), but gap size was potentially large (> 0.1 ha) and the fraction of area in gaps (ca. 20%) was similar to other temperate forests. Regeneration quadrats sampled along transects, in gap centers, and on logs revealed that Sequoia regeneration is elevated at gap edges. The longevity of Sequoia and its response to gap disturbances ensure that it will remain a dominant species in the study forest.

Nomenclature: Hickman (1993).

This paper is concerned with the vertical distribution of photosynthetic, woody, reproductive and dead organs of Ulex europaeus, the dominant pyrophytic species in most of the shrublands of Galicia (NW Spain). Frequency and weight data for the above-mentioned organs were collected each season for individual plants up to 150 cm tall, in order to quantitatively characterize the vertical organ distribution in this species. The study also deals with regression equations that would allow the prediction of phytomass from easier measurements. Frequency values were recorded using a grid of quadrats situated on the plant's vertical axis, and clipping each individual into vertical layers of 6 cm to obtain phytomass values. The abundance and location of photosynthetic, woody and dead organs varies in the three height classes studied, both regarding frequency and phytomass. A marked decrease in the ratio between photosynthetic and total phytomass is also observed as plant height increases. Significant seasonal differences were recorded only for reproductive organs. A good fit was obtained for several regression equations; total phytomass can be predicted from the largest diameter of the shrub, or organ phytomass from total weight.

Nomenclature: Tutin et al. (1964–1980).

The upland moorlands of Wales are situated on the oceanic fringe of western Europe, and have experienced a long history of pastoral management. Recent vegetation data are analysed to assess the relative contribution of abiotic and anthropogenic factors to variation in habitat composition among the major upland ranges of this region. From a numerical analysis of plant community cover data, recorded from 65 sites covering 260000 ha, a six-cluster site classification emerged with striking biogeographical coherence. Direct gradient analysis and variance partitioning revealed strong correlation between vegetation composition and spatially-structured climatic gradients, in particular temperature, rainfall and oceanicity; differences in bedrock geology appear to have a lesser role. The analysis also indicates a close correlation between habitat variation and anthropogenic parameters, especially grazing intensity, burning frequency, and sulphur and nitrogen deposition levels. At this regional scale, anthropogenic impacts appear to have accentuated, rather than obscured, vegetation patterns which are primarily determined by climate and other abiotic variables. The findings have considerable relevance for conservation planning and also for predictive studies on the consequences of climatic change for the biota of the uplands of southern Britain.

Abbreviations: RDA = Redundancy Analysis.

Nomenclature: Gibbons et al. (1993); Rodwell (1991–2000); Tutin et al. (1964–1980).

We have constructed a phenological model of leaf area index (LAI) of forests based on biological principles of leaf growth. Field data of maximum LAI from 794 plots with mature or nearly mature stand ages over China were used to parameterize and calibrate the model. New measurements of maximum LAI from 16 natural forest sites were used to validate the simulated maximum LAI. The predictions of seasonal LAI patterns were compared with seasonal changes derived from the 1-km satellite AVHRR-NDVI data for nine undisturbed forest sites in eastern China. Then, we used the model to map maximum LAI values for forests in China.

Model results indicated that the PhenLAI model generally predicted maximum LAI well for most forest types, even when maximum LAI is > 6. This suggests an ecological approach to the saturation problem in satellite detection of high forest LAI where the relationship between NDVI and LAI reaches an asymptote near a projected LAI value of 5 or 6. Furthermore, the predictions of seasonal LAI patterns in timing and dynamics were generally consistent with the satellite NDVI changes, except for monsoon forest and rain forest in south China where satellite detection of seasonal variation in leaf area is hardly possible. Compared with average projected LAI measurements of global forests from 809 field plots in literature data, our maximum LAI values were close to the global literature data for most of Chinese forests, but the average area-weighted maximum LAI for all forests of China (6.68 ± 3.85) was higher than the global mean LAI of the 809 field plots (5.55 ± 4.14). We believe that forest LAI in China is commonly > 6, especially in tropical rainforest, subtropical evergreen broad-leaved forest, temperate mixed forest, and boreal/alpine spruce-fir forest where satellite detection of high LAI is hardly possible.

Abbreviations: LAI = Leaf Area Index; NDVI = Normalized Difference Vegetation Index; fPAR = Fraction of incoming Photosynthetically Active Radiation absorbed by plant canopy; WBM = Water balance model.

The relationship between communities of submerged annual macrophytes (predominately Chara spp.) and environmental characteristics is studied in three habitats with different dominant perennial species (Arthrocnemum, Juncus, Scirpus) and areas of bare soil. The distribution of submerged annual macrophytes is significantly dependent on two independent environmental factors: a dominant gradient of flooding/salinity, and a secondary gradient of nutrients related exclusively to the combined abundance of helophytes of the genus Scirpus (S. maritimus and S. litoralis). The results suggest that these emergent helophytes (1) are able to modify water column parameters (such as concentration of nitrates, phosphates, potassium, and bicarbonates) which are important for the communities of submerged macrophytes, and (2) play a fundamental role in the generation of secondary sources of environmental variability which, superimposed on the main gradient of flooding/salinity, favours the appearance of new compositional equilibria in such communities.

The existence of a process of facilitation is discussed by which the emergent helophytes induce changes in nutrient availability that would favour relatively nutrient-demanding charophyte species (such as Chara connivens and Nitella hyalina), altering the established relationships with other coexisting charophytes (such as Chara canescens and C. galioides) that dominate in the absence of the facilitating species. Nevertheless, the increased nutrient concentration associated to the presence of helophytes would not introduce significant changes in the total biomass of submerged aquatic macrophytes.

Abbreviations: SBM = Seasonal biomass maximum; SOM = Soil organic matter; STN = Total nitrogen; STP = Total phosphorus.

Nomenclature: Valdés et al. (1987); Corillion (1961) for Charophytes.

The interdependence of species richness and plant biomass has widely been accepted as a general biodiversity rule. However, there is no information about how relationships are established during colonization and how total biomass is distributed among plants. The main objective of this study was to determine the role of several factors which we have hypothetized as affecting biomass distribution among species in an early old-field community. To test this hypothesis, we conducted an experiment in a deeply ploughed Agropyro-Rumicion crispi community in the Basque Country (Spain). Light, water and soil nitrogen content were factorially manipulated resulting in eight experimental treatments. We also examined several site features, which could potentially influence final biomass distribution: seed bank composition, soil physico-chemical heterogeneity and cover and density of the dominant plant species in the community. A partition hypothesis testing approach using Redundancy Analysis was conducted to determine the fraction of biomass distribution variability assigned to each treatment and site feature. The most important species, in terms of biomass, were Agropyron repens, Sinapis arvensis, Arrhenatherum bulbosum and Picris echioides. As a general conclusion, biomass distribution among species during early secondary succession primarily depends on light availability and nitrogen supply. Several soil variables, such as magnesium, calcium and clay contents, also explain a relevant fraction of the biomass distribution among plant species. On the contrary, we found no effect of seed bank composition on biomass distribution. Finally, the total species number and cover of dominant species such as Sinapis arvensis, may determine final biomass distribution.

Abbreviations: DCA = Detrended Correspondence Analysis; GLM = General Linear Model; MANOVA = Multiple Analysis of Variance; PAR = Photosynthetically Active Radiation; RDA = Redundancy Analysis; TVE = Total Variation Explained; uSD = units of Standard Deviation.

Nomenclature: Castroviejo et al. (1986–2002); for species not included in this work: Tutin et al. (1964–1980).

Carex curvula is a dominant sedge of European alpine tundra, exhibiting two morphological forms: C. curvula ssp. curvula (Ccc) and C. curvula ssp. rosae (Ccr). In this paper, we attempt to explore whether Ccc and Ccr are ecotypes or vicariant forms and whether between- and within-regional distribution patterns can be explained by variations in the amount of available habitats and/or by changes in niche attributes. The study area covered three bioclimatically distinct regions of the southwestern Alps in which local abundances of Ccc and Ccr strongly differ.

The realized niche of both forms was investigated by a direct gradient analysis performed on an extensive floristic and environmental data set. We found no evidence of niche overlap between Ccc and Ccr as their distribution curves differ strongly along disturbance, mesotopography and soil acidity gradients. We investigated the effect of region on the structure of local scale variables tables. Highly concordant patterns among regions were found, except that optimal habitat conditions for Ccc were infrequent in the southernmost regions. We compared the ecological behaviour of range centre and range margin populations of each form. We found a narrower ecological amplitude for Ccr in the northern part of its range, whereas for Ccc the niche breadth of range-margin populations was not reduced compared to range centre populations. At its southern range limit, Ccc mostly occupies ecologically marginal habitats.

We conclude that Ccc and Ccr represent ecotypes, not vicariant forms. Finally, we suggest that habitat availability, resulting from the interplay of regional-scale and local-scale variables, satisfactorily explains the distributional patterns of Carex curvula ecotypes in the southwestern Alps.

Abbreviations: CCA = Canonical Correspondence Analysis; Ccc = Carex curvula ssp. curvula; Ccr = Carex curvula ssp. rosae; OMI = Outlying Mean Index; PCA = Principal Component Analysis; RDA = Redundancy Analysis.

Nomenclature: Tutin et al. 1964–1980.

Relationships between seed deposition, size of soil seed banks and some of the environmental factors affecting them were assessed for Calluna vulgaris throughout its altitudinal range (150-960 m a.s.l.) in eastern Scotland. Seed rain was assessed using pitfall traps, collected every 5-10 wk for 3 yr; germinability was determined by laboratory incubation. Seed bank size was estimated, once only, by counting seedlings emerging from soil cores kept for 50 wk in a glasshouse.

Seed deposition varied annually, was related to parent plant cover but always declined with altitude, falling sharply above 600 m a.s.l. Seed bank size was more closely correlated with the proportion of organic matter in the soil than with the amount of seed rain. Seed bank sizes declined gradually with altitude but did not differ significantly between four altitudinal zones. The mean density of buried seeds was less than half the mean annual seed rain at sites below 300 m a.s.l. but was over 200 × greater than annual seed rain above 800 m, suggesting that seeds buried at high altitudes remain viable for much longer than those at lower altitudes.

Nomenclature: Stace (1997).

Methods for coupling two data sets (species composition and environmental variables for example) are well known and often used in ecology. All these methods require that variables of the two data sets have been recorded at the same sample stations. But if the two data sets arise from different sample schemes, sample locations can be different. In this case, scientists usually transform one data set to conform with the other one that is chosen as a reference. This inevitably leads to some loss of information. We propose a new ordination method, named spatial-RLQ analysis, for coupling two data sets with different spatial sample techniques. Spatial-RLQ analysis is an extension of co-inertia analysis and is based on neighbourhood graph theory and classical RLQ analysis. This analysis finds linear combinations of variables of the two data sets which maximize the spatial cross-covariance. This provides a co-ordination of the two data sets according to their spatial relationships. A vegetation study concerning the forest of Chizé (western France) is presented to illustrate the method.

Abbreviations: CA = Correspondence analysis; CCA = Canonical Correspondence Analysis; GIS = Geographic Information System; GSVD = Generalized singular value decomposition; PCA = Principal Component Analysis; RDA = Redundancy analysis.

Nomenclature: Rameau et al. (1989).

The wet to moist bryophyte-dominated vegetation of Sassendalen, Svalbard, was classified into seven communities. These communities were grouped into (1) Cardamino nymanii-Saxifragion foliolosae marsh; (2) Caricion stantis fen; (3) Luzulion nivalis snowbed – including manured vegetation corresponding to moss tundras. All communities have a basically arctic distribution. Marshes are developed in habitats with a water table above the bryophyte vegetation surface and fens on sites with a water table level high above the permafrost but below the bryophyte surface. Moss tundras normally have no standing water table, but in Sassendalen they have a low water table due to their development on less steep slopes than in their normal habitat near bird cliffs.

CCA confirms that the standing water level is the prime differentiating factor between the alliances, while aspect favourability and permafrost depth differentiate between the fen communities and temporary desiccation is important for the Catoscopium nigritum community. Carex subspathacea is a characteristic fen species in the absence of other Carex species dominating elsewhere in the Arctic. Arctic marshes are linked to an extremely cold environment. They have a very low species diversity with a few species dominating; Arctophila fulva, Pseudocalliergon trifarium, Scorpidium scorpioides and Warnstorfia tundrae are character species. Moss tundra as defined here appears to be restricted to Svalbard and, probably, neighbouring Novaya Zemlya. This may be due to the absence of rodents and the high seabird density, which is related to the mild sea currents reaching further to the north here and which implies manuring of surrounding ecosystems. Manuring in a very cold environment produces moss carpets with a thin active layer and accumulation of thick peat layers without a standing water level. In Sassendalen the role of arctic seabirds is replaced by Svalbard reindeer which are non-migratory and are concentrated to favourable grazing areas where their manuring effect is intense. Their long-term manuring effect probably explains the occurrence of moss tundras in this weakly rolling landscape where seabird colonies are absent.

Nomenclature: Elvebakk & Prestrud (1996) for species; Elvebakk (1994) for syntaxa.

This paper explores whether plant breeding system and pollination specialization influence the reproductive response of plants to habitat fragmentation. It is meaningful for conservation to predict a plant species' extinction risk. We found 25 studies in the literature assessing the effects of habitat fragmentation on either pollination or reproductive success of 46 plant species to answer the following questions: 1. Are pollination and reproductive success of self-incompatible species more likely to decline with habitat fragmentation than the pollination and reproductive success of self-compatible species? Although most of the species showed statistically significant negative effects, the pollination and reproduction of self-incompatible species were as likely to decline with fragmentation as those of self-compatible species. 2. Are pollination and reproductive success of specialist plants more affected than the pollination and reproduction of generalist plants? Comparisons of fragmentation-related changes in pollination and reproductive success between specialists and generalists do not support the hypothesis that specialization in pollination increases the risk of plant extinction. 3. Can self-incompatible species offset their expected higher vulnerability to fragmentation by being, on average, more pollination generalist than self-compatible species? In a larger data set on 260 species, we did not find significant differences in either the mean number or frequency distribution of numbers of flower-visiting species or orders between self-compatible and self-incompatible species. Our review suggests that no generalizations can be made on susceptibility to fragmentation based on compatibility system and pollination specialization.