Question: What is the combined effect of two drivers of local biodiversity changes (presence of a potentially invasive species and seasonal drought) on the performance of seedlings of plants from gypsum habitats under experimental conditions?

Location: A controlled microcosm reconstruction of natural assemblages of gypsum plant communities from central Spain.

Methods: We evaluated the effects of a potentially invasive grass (Lolium rigidum) and water stress on the survival, height growth and biomass of five woody species (Colutea hispanica, Gypsophila struthium, Thymus lacaitae, Lepidium subulatum and Helianthemum squamatum) from semi-arid gypsum ecosystems. Seedlings of the five species were grown with or without the potential invader and under three watering regimes: early stress – simulating an advanced summer, late stress – simulating the characteristic timing of current summer drought and well-watered.

Results: Seedling survival and performance were negatively affected by the presence of the potential invader. Early stress had larger impacts on the gypsum species than late stress. No interactions were found between factors for any of the study variables, and responses to both factors were found to be species-specific.

Conclusions: The lack of interactions between factors indicates that the presence of the potentially invasive grass and water stress had additive effects in our study system. The negative impact of early water stress draws attention to the possible consequences of the advances of summer drought predicted for Mediterranean ecosystems. Finally, the differential responses found for the study species suggest that plant communities will not respond as a unit to global change, leading to significant changes in species composition and dominance.

Nomenclature: Tutin et al. (2001).

Question: What is the relationship of the naturally colonizing vegetation and substrate characteristics in fly ash lagoons?

Location: West lagoon, Deep Bay, a 13-ha coastal lagoon in Hong Kong in subtropical Southeast Asia.

Methods: Vegetation establishment was examined in a coal fly ash lagoon two years after its abandonment to investigate the distribution of vegetation in relationship to the chemical properties of the fly ash in the lagoon. A greenhouse experiment assessed the limits imposed on plant growth in fly ash.

Results: The fly ash was saline, slightly alkaline and very poor in organic matter and nitrogen. Ash from bare and vegetated areas differed significantly in their salinity and extractable concentrations of inorganic nitrogen and various metals. Bare ash had a significantly higher conductivity and extractable sodium, aluminum, manganese, potassium, and lead. In total 11 plant species that belonged to seven families were found growing on the fly ash; all species except the shrub Tamarix chinensis were herbaceous. Using discriminant analysis, the most important factors in distinguishing bare and vegetated ashes were conductivity and sodium. Cluster analysis of bare samples gave two distinct groups, one from the periphery of the lagoon, which had lower sodium, conductivity, organic carbon, potassium and copper, and the other from a second group that contained ashes from the central region of the lagoon. Results of the greenhouse experiment showed that the inhibition of plant growth was significantly correlated with the presence of soluble toxic elements in ash.

Conclusion: Toxicity and salinity seem to be the major limiting factors to plant establishment in fly ash, and these factors must be ameliorated for the successful reclamation of these fly ash lagoons.

Nomenclature: Anon. (2002b).

Questions: 1. Are there differences among species in their preference for coniferous vs. deciduous forest? 2. Are tree and shrub species better colonizers of recent forest stands than herbaceous species? 3. Do colonization patterns of plant species groups depend on tree species composition?

Location: Three deciduous and one coniferous recent forest areas in Brandenburg, NE Germany.

Methods: In 34 and 21 transects in coniferous and deciduous stands, respectively, we studied the occurrence and percentage cover of vascular plants in a total of 150 plots in ancient stands, 315 in recent stands and 55 at the ecotone. Habitat preference, diaspore weight, generative dispersal potential and clonal extension were used to explain mechanisms of local migration. Regression analysis was conducted to test whether migration distance was related to species' life-history traits.

Results: 25 species were significantly associated with ancient stands and ten species were significantly more frequent in recent stands. Tree and shrub species were good colonizers of recent coniferous and deciduous stands. In the coniferous stands, all herbaceous species showed a strong dispersal limitation during colonization, whereas in the deciduous stands generalist species may have survived in the grasslands which were present prior to afforestation.

Conclusions: The fast colonization of recent stands by trees and shrubs can be explained by their effective dispersal via wind and animals. This, and the comparably efficient migration of herbaceous forest specialists into recent coniferous stands, implies that the conversion of coniferous into deciduous stands adjacent to ancient deciduous forests is promising even without planting of trees.

Nomenclature: Wisskirchen & Haeupler (1998).

Background: Senecio aquaticus is an esteemed wetland species, but it is also a poisonous species in grasslands for forage production of various countries (e.g. Great Britain and Central European states), and its further spread onto farmland must be prevented. To reveal links between management practice and the occurrence of S. aquaticus, a survey was carried out on agricultural grassland in the summer of 2005.

Location: The mountain region in the northern and central part of Switzerland.

Methods: Botanical assessments were carried out on management units (parcels) where S. aquaticus occurred and on neighbouring parcels without occurrence. For all parcels, we analysed the soil nutrients and the details of management such as intensity of fertilisation and defoliation frequency.

Results: There was a high risk of S. aquaticus occurrence in parcels with low nitrogen fertilisation, a change of management intensity in the preceding 15 years, high inclination, and gaps in the sward. The change in the vegetation composition caused by altering the management intensity most probably provided gaps in the sward, which were then colonised by S. aquaticus. A novel finding is that, despite its preference for low-nutrient sites, the species was also persistent at sites with a moderate to high management intensity.

Conclusion: A long-term control of S. aquaticus on agricultural grasslands can best be achieved by avoiding sward damage and by promoting dense and stable swards. The management should be adjusted to the local environmental conditions and the requirements of the favourable plant species. This could prevent the spread of S. aquaticus from the protected wetlands onto agricultural grasslands, where the species would threaten animal health.

Nomenclature: Lauber & Wagner (2007).

Questions: How does urbanisation influence soil mineral nitrogen stocks (nitrate and ammonium stocks) and what are the consequences of these modifications on the functional diversity of the herbaceous vegetation (vascular plants) and the seed bank?

Location: Nine study sites were located on an urbanisation gradient in the city of Rennes, France.

Methods: Three urbanisation levels were defined: urban areas (high grey/green ratio,), suburban (medium grey/green ratio) and periurban (low grey/green ratio). For each urbanisation level, nitrates and ammonium stocks were quantified; the herbaceous vegetation was surveyed as well as the soil seed bank (using the seedling emergence method).

Results: Nitrate concentration increased with urbanisation (the nitrate level in urban plots was twice the concentration in periurban ones) whereas the ammonium level was higher in periurban areas than in urban areas. In urban plots, the vegetation and the seed bank were more nitrophilous, whereas the nitrogen requirement was lower for periurban species. The relationship between the seed bank and the above-ground vegetation was not significant.

Conclusions: The higher nitrate concentration in the urban area appeared to be related to higher concentrations of atmospheric pollutants found in this area and lower ammonium levels may be related to the higher temperature in urban areas (leading to higher nitrification rates). The shift in the composition of the seed bank and vegetation appeared to be a consequence of higher nitrate stocks. The dissimilarity between the seed bank and vegetation may be caused by enhanced emergence of nitrophilous species in urban areas.

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

Question: Does the vegetation of restored salt marshes increasingly resemble natural reference communities over time?

Location: The Essex estuaries, southeast England.

Methods: Abandoned reclamations, where coastal defences had been breached in storm events, and current salt marsh recreation schemes were surveyed giving a chronosequence of salt marsh regeneration from 2 to 107 years. The presence, abundance and height of plant species were recorded and comparisons were made with adjacent reference salt marsh communities at equivalent elevations.

Results: Of the 18 paired sites surveyed, 13 regenerated marshes had fewer species than their adjacent reference marsh, three had an equal number and two had more. The plant communities of only two de-embankment sites matched that of the reference community. 0–50 year old sites and 51–100 year old sites had fewer species per quadrat than the 101 year sites and the reference salt marshes. There was a weak relationship between differences in species richness for regenerated and reference marshes and the time since sites were first re-exposed to tidal inundation. Cover values for the invasive and recently evolved Spartina anglica were greater within regenerated than reference marshes.

Conclusions: Salt marsh plants will colonise formerly reclaimed land relatively quickly on resumption of tidal flooding. However, even after 100 years regenerated salt marshes differ in species richness, composition and structure from reference communities.

Nomenclature: Rodwell (2000) for plant communities, Stace (1997) for vascular plants and Hardy & Guiry (2003) for algae.

Question: The practice of extracting logging residues after clear-cutting for bioenergy purposes is spreading. Logging residues constitute a shelter in clear-cut areas and therefore concerns have been expressed that their removal could make the ground and its vegetation more exposed to extreme microclimatic conditions. We asked whether logging residues and forest edges can protect ground-dwelling forest bryophytes from fatal microclimate events following clear-cutting.

Location: Boreal forests of central Sweden.

Methods: Using transplants of eight forest floor bryophyte species we experimentally analysed the sheltering effect (less solar radiation and less wind) of logging residues and forest edges in seven clear-cut areas. Transplants were placed in two contrasting positions in each area; near a north-facing forest edge and in the centre of the clear-cut area. In each position, half of the transplants were covered by a layer of spruce branches and the other half was left uncovered. We estimated proportion of apparently living shoots (apparent vitality) and measured radial growth of transplants during one growing season.

Results: Position in the clear-cut area, but not cover of spruce branches, clearly influenced radial growth. Vitality scores were higher among transplants covered with branches and the lowest apparent vitality was observed in uncovered transplants in the middle of clear-cut areas. The change in area of apparently living shoots during the course of the experiment (growth minus mortality) was unaffected by branch cover close to the edge but positively affected in the centre of the clear-cut area. In general, the effect of branch cover on bryophytes was higher in the centre of clear-cut areas. Here, climatic measurements showed that branch cover buffers during periods of extreme microclimates.

Conclusions: Extraction of logging residues after clear-felling may reduce the survival of some ground-dwelling forest organisms. The additional sheltering provided by branches was unimportant close to forest edges. We suggest smaller clear-cut areas, green-tree retention and other ways to make logged areas shadier and less windy to mitigate the reduced shelter caused by harvest of logging residues.

Nomenclature: Hallingbäck et al. (2006) for bryophytes and Krok & Almquist (1994) for vascular plants.

Question: Are the seed banks of an isolated subtropical oceanic island capable of naturally regenerating vegetation either with species of the historical forest community or with the existing grassland community after severe damage to the vegetation by goats?

Location: Nakoudojima Island, Bonin Archipelago (Ogasawara Shoto), Japan.

Methods: Soil samples were collected at 0–5 cm and 5–10 cm depths from seven plots in forests, grasslands, artificially matted areas and bare land. Soil seed banks were assessed using the seedling emergence method followed by the hand-sorting of ungerminated seeds. We determined the size and composition of the seed banks in upper soil layers of plots and compared the seed banks to the standing vegetation.

Results: A total of 12 220 seedlings belonging to 42 species from 20 families germinated. Total mean seed density (0–5 cm depth) was low in all plots within forest, grassland, and heavily degraded vegetation types (34.7 ± 8.6 to 693.5 ± 123.6, 58.6 ± 7.8 to107.1 ± 10.0, and 1.1 ± 0.5 to 7.2 ± 2.3 seeds/m², respectively). Forbs and graminoids dominated the seed banks of grassland and forest plots including Cyperus brevifolius, Gnaphalium pensylvanicum, Oxalis corniculata and Solanum nigrum, and these alien species comprised 90% of the density of the seed bank. There was little correlation between seed banks and standing vegetation of the island (Sørensen similarity coefficient values 0.26 to 0.45).

Conclusions: If natural regeneration occurs from the seed bank of the island, future vegetation will not move toward the original forest community, because the seed bank is dominated by non-native herbaceous grassland species. Though isolated, a few forest remnants with low species richness could be an important source for the natural re-establishment of forest on the island; however, seed availability may be limited by either poor dispersal or pollination so that woody species will probably recover very slowly on this goat-impacted island.

Nomenclature: Shimizu (2003a); Toyoda (2003).

Question: We asked how landscape configuration and present management influence plant species richness and abundance of habitat specialists in grasslands in a ‘modern’ (much exploited and transformed) agricultural Swedish landscape.

Location: Selaön, south-eastern Sweden (59°24′ N, 17°10′ E).

Methods: Present and past (150 and 50 years ago) landscape pattern was analysed in a 25 km² area. Species richness was investigated in 63 different grassland patches; grazed and abandoned semi-natural grasslands, and grazed ex-arable fields. Influence of landscape variables; area, past and present grassland connectivity, present management on total species richness, density and abundance of 25 grassland specialists was analysed.

Results: Semi-natural grasslands (permanent unfertilised pastures or meadows formed by traditional agricultural methods) had declined from 60% 150 years ago to 5% today. There was a significant decline in species richness and density in abandoned semi-natural grasslands. Total species richness was influenced by present management, size and connectivity to present and past grassland pattern. Landscape variables did not influence species density in grazed semi-natural grassland suggesting that maintained grazing management makes grassland patches independent of landscape context. The abundance of 16 grassland specialists was mainly influenced by management and to some extent also by landscape variables.

Conclusion: Although species richness pattern reflect management and to some extent landscape variables, the response of individual species may be idiosyncratic. The historical signal from past landscapes is weak on present-day species richness in highly transformed, agricultural landscapes. Generalizations of historical legacies on species diversity in grasslands should consider also highly transformed landscapes and not only landscapes with a high amount of diversity hotspots left.

Nomenclature: Lid & Lid (2005).

Question: How distinct is the flora of field boundaries? How does the structure of field boundaries determine the composition of vegetation?

Location: Estonia, six 4 km × 4 km agricultural areas.

Methods: We studied the vegetation of fields and field boundaries using 2 m × 2 m sample plots. We estimated the frequency of species in both habitat types, applied an MRPP test to analyse the vegetation composition of field boundaries with various combinations of landscape features (ditches, roads, tree and bush layers) illustrating this by DCA ordination, and used indicator species analysis to determine the characteristic species of each boundary type.

Results: Ca. 45% of the flora of field boundaries comprised species found on agricultural land. Most typical species in fields – agrotolerants – were also the most common in field boundaries. The vegetation of road verges and grassy boundaries consisted mainly of disturbance-tolerant species. Woody boundaries were characterised by shade-tolerant and nitrophilous species. Ditch banks included species typical of moist habitats and semi-natural grasslands. Few threatened or protected species were observed.

Conclusions: The vegetation composition of field boundaries varied due to the complex effects of landscape structure around and in these boundaries. Plant species in agricultural landscapes can be classified into two broad emergent groups on the basis of their different responses to agricultural disturbances – agrotolerant species and nature-value species. Agrotolerant species are promoted by agriculture, nature-value species include rare weeds and habitat specialists. We suggest that high-nature-value species should prevail in monitoring the effects of land-use intensification on biodiversity rather than total species richness.

Nomenclature: Flora Europaea (Tutin et al. 2001).

Questions: What is the relative role of the bud bank, seed and various species traits in the regeneration of urban plant communities after severe disturbances? Do invasive and exotic species, highly abundant in disturbed communities, regenerate better than native species after disturbance?

Methods: Hand tilling was applied to three urban plant communities with and without additional herbicide treatment to exclude regeneration from the bud bank. Plant traits were determined from the literature and databases. Species responses to the treatments were evaluated with RDA analyses in CANOCO. Linear models were applied to identify traits that could predict the responses of species to disturbance.

Results: The bud bank played a key role in regeneration in the plots without herbicide. In the plots with herbicide treatment, the seed bank was important in re-establishing vegetation after disturbance. Exclusion of the bud bank by using herbicide allowed the establishment of small annuals, whereas biennials and perennials were successful in plots where the bud bank was not inhibited by herbicide. Exotic species with a long residence time in the local flora were successful in plots where regeneration from the bud bank was excluded, whereas species with short residence times or that were invasive were suppressed by both types of disturbance.

Conclusion: In response to various types of disturbance, species with different regeneration strategies (either seeds or bud bank) were promoted. Exotic species were suppressed primarily by disturbance, which suggests that factors other than just regenerative capability contributed to the high abundance of exotics in urban communities.

Nomenclature: Dostál (1989).

Question: Are there effects of long-term deposition of airborne nitrogen and sulphur on the forest floor vegetation from permanent plots collected in 1993 compared to 2005.

Location: Northern limestone Alps in Austria.

Methods: Single species responses were analysed by correlating trends in cover-abundance values, as derived from marginal models, with Ellenberg indicator values. Changes in the species composition of plots were analysed by correlating changes in mean Ellenberg indicator values with the displacement of plots within a multidimensional scaling ordination.

Results: Trends in single species abundance were positively correlated with indicator values of soil pH but were independent of nutrient availability. A general trend towards the homogenisation of vegetation, due to convergent time vectors of the relevés, became obvious. Oligotrophic sites previously situated at the distal ends of ordination axes shifted towards the centre since they were enriched by species preferring mesotrophic conditions. The bulk of plots with intermediate site conditions hardly showed any trends. A concomitant analysis demonstrated that temporal changes in species composition exceed the variation in cover abundance estimates among different field botanists.

Conclusions: N deposition can lead to a homogenisation of forest floor vegetation. Larger limestone areas with diverse soil conditions, such as the Northern limestone Alps in Austria, as a whole are thus negatively affected by airborne N deposition. Nevertheless, the vegetation was at least as strongly affected by an increase of basiphilous species as a result of decreasing S deposition.

Nomenclature: Adler et al. (1994).

Question: Does aspect affect hydroseeding success and the development of vegetation during early vegetation establishment on the steep slopes of coal wastes during the reclamation process?

Location: Open-pit coal mine near Villanueva de la Peña, northern Spain.

Methods: In the first year after hydroseeding, we monitored the dynamics of hydroseeded species in three permanent plots of 20 m² on north- and south-facing slopes every two months. Soil properties and weather conditions were also monitored.

Results: Aspect was related to total plant cover during early revegetation, and south-facing slopes had the lowest cover. Aspect also influenced the early dynamics of hydroseeded grasses and legumes establishing on these slopes. Grass cover was greater on the north slope throughout the study, but differences in plant cover between north and south slopes appeared later for the legumes. Aspect also affected the relative contribution of both of grasses and legumes to the total plant cover, with grasses dominant on both northern and southern slopes, except during the summer on the southern slope. The species with the greatest difference in cover between the north- and south-facing slopes were Festuca spp., Lolium perenne and Trifolium repens.

Conclusion: In coal mine reclamation areas of Mediterranean climates, differences in the development of hydroseeded species depended on the slope of the coal mine reclamation areas, and this information is of importance to managers in selecting species for use in reclamation.

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

Questions: Does the increased atmospheric deposition of nitrogen, which can have major effects on the established vegetation of nutrient-poor habitats, also impact germination from the soil seed bank?

Location: Coastal dune slacks at Newborough Warren, Wales, UK.

Methods: The effects of nitrogen addition (15 kg.ha⁻¹.a⁻¹) on seed germination from the soil seed bank were investigated using the seedling emergence method between September 2004 and February 2005.

Results: More seedlings emerged from fertilised samples than unfertilised controls. Most species showed enhanced germination after fertilisation with nitrogen, with seedling numbers statistically significantly greater in nitrogen addition samples in a quarter of species abundant enough for analysis. Species that responded positively to fertilisation were species with low Ellenberg indicator values indicative of infertile sites.

Conclusions: Most species showed increased germination after fertilisation with nitrogen, including early successional species normally growing in nutrient-poor conditions. This suggests that the increased atmospheric deposition of nitrogen probably not only impacts on established vegetation, but also has the potential to alter seed bank dynamics.

Nomenclature: Stace (1997).

Questions: How well do GIS-derived categorical variables (e.g., vegetation, soils, geology, elevation, geography, and physiography) separate plots based on community composition? How does the ability to distinguish plots by community composition vary with spatial scale, specifically number of patch types, patch size and spatial correlation? Both these questions bear on the effective use of stratifying variables in landscape ecology.

Location: Arctic tundra; Bering Land Bridge National Preserve, northwestern Alaska, USA.

Methods: We evaluated the strength of numerous alternative stratifying variables using the multi-response permutation procedure (MRPP). We also created groups based on lichen community composition, using cluster analyses, and evaluated the relationship between these groups and groupings within categorical variables using Mantel tests. Each test represents different measures of community separation, which were then evaluated with respect to each variable's spatial characteristics.

Results: We found each categorical variable derived from GIS separated lichen communities to some degree. Separation success ranged from strong (Alaska Subsections) to weak (Watersheds and Reindeer Ownership). Lichen community groups derived from cluster analysis demonstrated statistically significant relationships with 13 of the 17 categorical variables. Partialling out effects of spatial distance had little effect on these relationships.

Conclusions: Greater number of patch types and larger average patch sizes contribute to optimal success in separating lichen communities; geographic distance did not appear to significantly alter separation success. Group distinctiveness or strength increased with more patch types or groups. Alternatively, congruence between lichen community types derived from cluster analysis and the 17 categorical variables was inversely related to patch size and spatial correlation.