Question: The vegetation in a polder after partial tidal restoration does not resemble the targeted salt-marsh vegetation. Is this difference in vegetation due to lack of dispersal or unsuitable abiotic conditions ? What could be done for a better restoration of the site?

Location: Northwestern France.

Methods: Seeds were trapped at the single inlet of the polder with a 200-μm mesh net to estimate inputs of seeds from the bay. In parallel, seed dispersal was studied in the polder by placing Astroturf® seed traps on the surface of the sediment at three different elevations in three distinct areas. Abiotic conditions such as flooding frequency, water table level and soil salinity were monitored.

Results: All but one species from the adjacent salt marshes were trapped at the inlet. Not all of these species were on the seed traps inside the polder. Seed dispersal was not homogeneous in the polder and seed trap content mostly discriminated in function of their elevation. Salinity and water logging at the bottom of the slope were very high compared to tolerance of most halophytes but decreased rapidly higher up the slope.

Conclusions: The development of salt marsh target species is highly restricted by limited hydrochory inside the polder but also by unfavourable soil conditions induced by the actual hydrological regime. Halophytes are excluded at the bottom of the slope by abiotic conditions and out-competed by subhalophytes higher up. In order to restore salt marsh vegetation inside the polder, a larger opening should be induced in order to increase the flooded surface, and diminish water logging and flooding frequencies.

Question: What is the influence of hydrological regime, soils and management on the plant community composition and species richness of Skealoghan turlough (groundwater dependent calcareous wetland).

Location: Skealoghan turlough, County Mayo, Ireland.

Methods: Percentage cover of vascular plants and bryophytes were recorded, and data on hydrological regimes, soils and management were collected. Data were analysed using multivariate statistical techniques.

Results: A total of 69 species of vascular plants and mosses were recorded. Cluster analysis grouped the samples into two separate communities, the Cirsio-Molinietum and the Ranunculo-Potentilletum anserinae plant communities. The plant community composition and species richness followed a main gradient down into the turlough basin, but also varied with microtopography, resulting in a mosaic of vegetation types.

Conclusions: The biodiversity and conservation value of the site is linked to the heterogeneity in its physical environment in which hydrology, soils and grazing management all play critical roles.

Nomenclature: Stace (1997) for vascular plants; Holyoak (2003) for mosses; Goodwillie (1992) for plant communities.

Question: Can GIS and GPS technology be used to quantify the hydrological regime of different plant communities on turloughs (groundwater dependent calcareous wetlands)?

Location: Skealoghan turlough, County Mayo, Ireland.

Methods: Plant communities were mapped and digitised with GIS software and a digital elevation model of the site was constructed from differential GPS data. Together with records of water level fluctuations on the site from May 2001 to May 2004, these data were used to calculate hydrological variables for each plant community. Hierarchical cluster analysis was used to identify groups of plant communities with similar hydrological regimes.

Results: 15 plant communities were mapped at Skealoghan, with the Cirsio-Molinietum and Ranunculo-Potentilletum anserinae being the dominant phytosociological associations. Skealoghan is subject to large temporal and spatial variation in its hydrological regime and fluctuations in water level are intrinsically linked to rainfall. The spatial variation in flooding can be linked to the vegetation zones.

Conclusions: GIS and DGPS technology can be used to quantify the hydrological regime of different plant communities on turloughs. Since the hydrological regime is a major environmental factor controlling the vegetation composition of the site, the maintenance of natural flooding regimes is a vital component for the conservation and management of the diverse vegetation mosaic at Skealoghan turlough.

Nomenclature: Stace (1997) except for Persicaria amphibia which is Polygonum amphibium in Goodwillie (1992) and retained here as it is used in naming the plant communities.

Question: Pollution and eutrophication of surface water is increasingly a problem in agricultural landscapes. Do intact (relatively undisturbed) and degraded forests differ in seasonal nutrient storage and therefore potential to ameliorate nutrient pollution?

Location: United States, Midwestern region.

Methods: We used three sets of paired plots, where intact plots were located close to disturbed woodlands. Herbaceous perennials located in eight 0.25 m² quadrats in the plots were harvested (in spring and mid-summer), dried, separated into above- and below-ground plant parts, and weighed to determine biomass. Nitrogen, phosphorus and potassium content of the plant tissues were then determined, and these data combined with biomass to estimate nutrient storage.

Results: In spring, intact sites had 62% greater above-ground biomass than disturbed sites and 75%greater below-ground biomass. In summer, below-ground biomass of intact plots was still much greater than that of disturbed plots (73 percent), but above-ground biomass was similar. Nutrient tissue concentration generally did not differ, nor did soil nutrient levels. The disturbed sites were largely missing one group of species, the spring ephemerals, and this accounted for the difference in biomass and nutrient storage between sites.

Conclusions: Relatively undisturbed woodlands in our study had a much greater capacity to store nutrients, and therefore ameliorate nutrient pollution, in early spring. This is significant because spring is also the time of highest potential leaching of nutrients into surface water.

Nomenclature: Anon. (1993 , 2005).

Question: Do specific environmental conditions affect the performance and growth dynamics of one of the most invasive taxa (Carpobrotus aff. acinaciformis) on Mediterranean islands?

Location: Four populations located on Mallorca, Spain.

Methods: We monitored growth rates of main and lateral shoots of this stoloniferous plant for over two years (2002–2003), comparing two habitats (rocky coast vs. coastal dune) and two different light conditions (sun vs. shade). In one population of each habitat type, we estimated electron transport rate and the level of plant stress (maximal photochemical efficiency Fv/Fm) by means of chlorophyll fluorescence.

Results: Main shoots of Carpobrotus grew at similar rates at all sites, regardless habitat type. However, growth rate of lateral shoots was greater in shaded plants than in those exposed to sunlight. Its high phenotypic plasticity, expressed in different allocation patterns in sun and shade individuals, and its clonal growth which promotes the continuous search of available resources, contributed to a good growth and photochemical efficiency of Carpobrotus in the relatively moderate shade of the understories of Mediterranean shrublands and woodlands. Each main shoot of a Carpobrotus clone (which can have several dozens main shoots) grows ca. 40 cm per year, which explains its vigorous habitat colonization capacity.

Conclusion: The highly plastic morphological response to different light regimes of this taxon contributes to a rapid colonization of heterogeneous coastal Mediterranean environments spreading well beyond the open sand dune systems where it has been often reported.

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

Question: What are the consequences of grazing abandonment on the Stipa lessingiana dominated steppe-like grasslands? What is the relative importance of management and environmental factors in causing variation in species composition and abundance in the continuously grazed and abandoned grassland stands?

Location: Transylvanian Lowland, Romania.

Methods: Repeated vegetation mapping of a grassland stand, where grazing was abandoned 35 years ago; re-sampling six grassland stands surveyed 29–57 years ago. For revealing long-term changes in species composition and rank abundance PCoA ordination was applied. The relative importance of management and environmental factors in structuring vegetation were explored by CCA ordination. Diversity, evenness and the relative number and abundance of red-listed species were compared between managed and abandoned stands.

Results: Our results pointed out that grasslands which were formerly grazed and dominated by S. lessingiana, in the longterm absence of grazing, have been transformed into a S. pulcherrima dominated type. Management, probably by creating bare surfaces and preventing litter accumulation, had the strongest effect on the species composition and abundance in the grasslands. Abandoned grassland stands had lower diversity and evenness compared to continuously grazed stands. While at the same time, the relative number of threatened, rare species did not differ between managed and abandoned sites.

Conclusion: Maintaining extensively grazed, as well as unmanaged, Stipa dominated grasslands would be important in order to create various habitat conditions for plant species, especially threatened and rare species, and promote diversity on the landscape scale.

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

Question: What is the role of Stipa tenacissima as a nurse plant of the rare and threatened endemic species Haplophyllumbastetanum?

Location: Semi-arid steppe of the Guadix-Baza basin (SE Spain).

Methods: In the two H. bastetanum populations known, we (1) estimated the number of individuals and (2) analysed the influence of the factors ‘site’ (S1 = Hernán Valle, S2 = Alicún), ‘microhabitat’ (inside and below the canopy of the S. tenacissima tussocks vs. open areas), ‘life stage’ (vegetative, reproductive), ‘aspect’ (N, S, E, W, flat) and ‘damage’ (yes or no), in relation to the distribution of individuals and to the height, number of flowers, number of capsules, and edaphic variables.

Results: The total number of individuals was estimated at 3135. S. tenacissima was found to have a positive and significant effect on the distribution of H. bastetanum, more pronounced in the sample taken at S2 than S1, where 83.8% of the plants were growing in association with S. tenacissima. Similarly, there were more H. bastetanum individuals that became reproductive inside S. tenacissima tussocks than in the open areas, and H. bastetanum individuals had a greater production of flowers and fruits, especially in the sample taken at S1. Organic carbon, nitrogen, and carbon:nitrogen ratio were related to the height and number of flowers and capsules of the plants.

Conclusion: Although new patches were established, with a larger number of individuals, H. bastetanum continues to be Critically Endangered (CR). The results support the hypothesis of the facilitation effect of S. tenacissima on this rare, endemic species. Facilitation of species of interest in conservation is an aspect that has not previously been clearly reported. We propound this important process as a valuable tool for rehabilitation of populations of threatened plant species in conservation biology projects.

Nomenclature: Castroviejo (1986–2003); Valdés et al. (1987).

Question: Are the biophysical conditions of abandoned limestone quarry floors and natural alvars sufficiently similar to each other for alvars to be used as a model for quarry floor restoration?

Location: Ontario, Canada.

Methods: We measured plant species frequency and environmental and soil variables in 13 abandoned limestone quarries and used ANOVA to compare them with data previously collected from seven natural alvars. We used multivariate ordinations on the quarry floor data alone and on the combined quarry floor and alvar data to determine how plant community structure was controlled by the abiotic environment in both habitats.

Results: Except for higher levels of many nutrients, the physical characteristics were similar between quarry floors and alvars. 246 plant species were found on quarry floors as compared to 283 on alvars, with 79 species in common between the two habitat types. While quarry floors supported fewer bryophytes and more exotic vascular plants compared with alvars, five alvar endemics and 24 characteristic alvar species were found to grow there. The age of the site, nutrient levels, and presence of standing water and bare rock were important factors influencing species composition in both habitats.

Conclusions: Through natural revegetation alone, the abandoned quarry floors surveyed in this study have already taken on many physical and vegetation characteristics of natural alvars. This makes alvars very suitable as the restoration goal for abandoned limestone quarries.

Nomenclature: Newmaster et al. (1998).

Question: How do habitat edges and trampling affect mesic (Myrtillus type) understorey vegetation in fragmented urban forests, and what are the relative strengths and spatial extent of these effects?

Location: The city of Helsinki, southern Finland.

Methods: Vegetation sample plots were placed at different distances from the forest edge. At each distance we selected plots on, next to and away from paths of different levels of wear, and the covers and frequencies of plant species were sampled. We used generalized linear mixed models and ordination techniques to test our hypotheses.

Results: The effect of the edge penetrated up to 50 m into the forest interior. Only light effects of trampling were found in seemingly untrampled areas, in addition to the direct effects of trampling on the paths. Both trampling and edge effects changed the forest understorey species composition. Trampling changed plant species composition locally on paths, and provided opportunities for new species to establish in previously unbroken forest vegetation. Urban forest edges were characterised by species better adapted to sunny, warm and dry conditions. These species, such as grasses, replaced more sensitive forest species, such as dwarf shrubs and mosses. We observed a large number of light demanding deciduous trees at the edges, which may be one of the factors increasing soil fertility and consequently promoting the high abundance of fast growing species, such as grasses and herbs related to more fertile site types.

Conclusions: We recommend that urban forest fragments left within urban development should be at least 2–3 ha in size and that the shape of the patch and the number of potential recreational users should be taken into account when preserving true forest understorey vegetation from the effects of edges and trampling.

Nomenclature: Hämet-Ahti et al. (1998) for vascular plants, Koponen (1994) for mosses, Ahti (1989) for lichens.

Questions: What vegetational changes does a boreal rich fen (alkaline fen) undergo during a time period of 24 years after drainage? How is plant species richness affected, and what are the changes in composition of ecological groups of species? Is it possible to recover parts of the original flora by rewetting the rich fen? Which are the initial vegetation changes in the flora after rewetting? What are the major challenges for restoration of rich fen flora after rewetting?

Location: Eastern central Sweden, southern boreal vegetational zone. Previously rich fen site, drained for forestry purposes during 1978-1979. The site was hydrologically restored (rewetted) in 2002.

Method: Annual vegetation survey in permanent plots during a period of 28 years.

Results: There were three successional stages in the vegetational changes. In the first stage there was a rapid (< 5 years) loss of rich fen bryophytes. The second step was an increase of sedges and early successional bryophytes, which was followed by an increase of a few emerging dominants, such as Molinia caerulea, Betula pubescens and Sphagnum spp. After rewetting, there are indications of vegetation recovery, albeit at slow rates. Depending on, for instance, initial species composition different routes of vegetation change were observed in the flora after drainage, although after 24 years, species composition became more homogenous and dominated by a few species with high cover.

Conclusion: Major changes have occurred after changes in the hydrology (drainage and rewetting) with a severe impact on the biodiversity among vascular plants and bryophytes. Several rich fen bryophytes respond quickly to the changes in water level (in contrast to vascular plants). The recovery after rewetting towards the original rich fen vegetation is slow, as delayed by substrate degradation, dispersal limitation and presence of dominant species.

Nomenclature: Karlsson (2002) for vascular plants; Hallingbäck et al. (2006) for bryophytes.

Question: How do differing social and economic systems affect the dynamics and trajectory of land cover / land use change on similar, neighbouring ecosystems in a time span when an economic industrialization program was enforced?

Location: Tijuana River watershed, located on the border between Baja California, Mexico and California, United States.

Methods: We quantified land use changes between 1970 and 1994 in the Tijuana River watershed. Using aerial photographs and geographic information systems, we elaborated land-cover/use maps and calculated transition probability matrices to describe natural land-cover changes at the landscape level on both sides of the border.

Results: Land cover / land use transitions are mainly driven by urban development on both sides of the border, but exhibit different patterns in each country. The processes seem to be more complex in the Mexican part of the basin, where itinerant land use may revert induced grasslands and rain-fed agriculture into natural communities, than on the US side, where the transition pathways are few and unidirectional.

Conclusions: Despite the need for an integrated planning and management of binational basins and shared water resources, in practice, these goals may be hampered by different economic and social factors triggering land use change within each country.

Question: How are plant communities of the Flooding Pampa grasslands spatially distributed? How do canopy dynamics of the different communities vary among seasons and years?

Location: Buenos Aires province, Argentina.

Methods: We characterized the distribution of communities through a supervised classification based on four Landsat 5 TM images. We sampled species composition of 200 sites, with 130 of them corresponding to natural communities. Of the sampling areas 60% were used to classify, and the remaining areas to assess classification accuracy. We characterized the seasonal and interannual variability of canopy dynamics using NDVI (Normalized Difference Vegetation Index) data provided by MODIS /Terra images.

Results: Overall accuracy of the classification was satisfactory. The resulting maps showed a landscape formed by a matrix of extended lowlands with small patches of mesophytic and humid mesophytic meadows. The October scene (near the peak of productivity) was particularly important in discriminating among communities. The seasonal pattern of NDVI differed among communities and years. Mesophytic meadows had the highest NDVI mean and the lowest interannual coefficient of variation, halophytic steppes had the lowest mean, and vegetated ponds were the most variable.

Conclusions: These grasslands have a fine-grained heterogeneity at the landscape scale. Each plant community has distinct seasonal and interannual canopy dynamics. These two features of grassland structure and functioning represent key information for rangeland management that may be obtained through a combination of minor field sampling and remote sensing.

Question: Does the seed density of invasive species affect establishment by native species in a bare ground context (following invasive species control efforts), and is it possible to promote transition to a native species dominated state by manipulating sowing density of the native community?

Location: Experimental wetland basin in Chanhassen, Minnesota, USA.

Methods: A mesocosm experiment investigated the influence of Phalaris arundinacea (invasive species) propagule pressure on establishment of native wet meadow species in the context of a newly restored wetland. Mesocosms were sown with P. arundinacea (0, 10, 50, 100, or 500 seeds/m²) and a mix of native species (3000 or 15000 seeds/m²).

Results: When planted at densities > 100 seeds/m², P. arundinacea increased suppression of native species. Also, high native seed density suppressed P. arundinacea biomass production. This effect was more pronounced when P. arundinacea seed density was high (> 100 seeds/m²), but high native seed density (15000 seeds/m²) did not suppress recruitment of P. arundinacea from seed.

Conclusions: The transition from post-control bare ground (a common result of efforts to control invasive species) to native species establishment depends on both native species and invader seed density. These results suggest that a threshold of P. arundinacea propagule pressure exists, beyond which transition to a native community is less likely without management intervention. P. arundinacea can establish in the presence of a newly developing native plant community, even at very low densities of P. arundinacea seed. Invader control (following initial site clearing efforts) is essential to native species establishment.

Nomenclature: Gleason & Cronquist (1991).

Question: Spatial prediction of plant populations is essential for conservation management. This is especially true for rare and/or threatened endemic species, for which knowledge of determinants of distribution is necessary to mitigate threats and counteract decline. We therefore ask if the distribution of an endemic species can be accurately predicted by georeferenced environmental variables or, if anthropogenic variables also need to be taken into account.

Location: Alps, Hautes-Alpes, France.

Methods: Potential distribution area and abundance of Eryngium spinalba were predicted with logistic regression and ordinal logistic regression, respectively, in a 57-km² watershed.

Results: Aspect, global solar radiation in March, elevation and grazing pressure were the main predictors of the probability of occurrence of Eryngium spinalba. Taking into account the persistence of agro-pastoral activities by diachronic analysis (Napoleonic cadastral map and orthorectified photographs) improved predictions from the model and the level of spatial concordance with independent surveys.

Conclusions: Niche modelling improved our understanding of the distribution of this threatened species which, in the context of land abandonment, is diminishing as a result of the decline of its favoured habitats. The key role of pastoral activities and historic continuity for its distribution and persistence was clearly demonstrated.

Nomenclature: Kerguélen & Brisse (1994).