Question: Is the failure of establishment of rare flood-meadow species in habitat restoration primarily due to seed or microsite limitation? How do sown species respond to artificially created gaps and added litter at two neighbouring sites with similar physical conditions but contrasting vegetation matrix (young arable fallow field vs species-poor meadow sward)?

Location: Upper Rhine valley, southwestern Germany, 85 m a.s.l.

Methods: Seeds of six typical flood-meadow species were sown in four treatment combinations of the factors gap creation and litter addition. Seedling recruitment was monitored for three years.

Results: Five of the six species established successfully at both sites largely irrespective of treatments, indicating seed limitation. Only in the small-seeded Arabis nemorensis, which was revealed to be strictly gap-dependent at the meadow site, could an obvious microsite limitation be shown. The non-significance of gap treatments in all other species at the relatively high productive meadow site is probably due to biomass removal by mowing in early summer. Only at the extremes of the seed size spectrum did the results meet predictions of plant ecological theory, such as the strict gap dependence of small-seeded species in closed swards or the positive to neutral response of large-seeded species to litter layers.

Conclusions: Species identity was revealed to be the major factor influencing differences in recruitment. Due to the lack of a general trend in the response towards treatments the results support conceptual models that describe the interplay of facilitation and interference as a highly dynamic equilibrium, driven by variable abiotic and biotic marginal conditions.

Nomenclature: Wisskirchen & Haeupler (1998).

Questions: What is the effect of the 19th century (pre-industrialization) landscape pattern on the recovery of climax forests in cool-temperate mountain areas dominated by Fagus crenata (Japanese beech)?

Location: Secondary forests on Mt. Daisen, western Japan.

Methods: Vegetation patterns before and after industrialization were obtained from maps drawn in 1898 and 1979. Tree measurements were made in 12 plots in 1997. Correlation between current Fagus crenata dominance and forest edge in the 19th century was analysed using an S-shaped regression curve. Fagus juvenile density was counted in the plots, and distances from each plot to the five nearest mother trees were measured to determine the dispersal kernel.

Results: Secondary grassland covered a substantial area in 1898, whereas forest covered most of the area in 1997. Fagus was dominant in places in the interior forest 100 years ago, and mature Fagus trees were absent in secondary forests that had been grasslands in 1898. The expected number of juveniles decreased to one individual per 100 m² at 43.5 m from the mother tree.

Conclusions: The pre-industrialization landscape greatly affected recovery of Fagus forest. Forests found on the 1898 vegetation map might have acted as refugia for Fagus. The limited dispersal ability of Fagus suggests that it would take many generations (several hundred years) for Fagus forests to recover at the centre of what had been grasslands in the 19th century.

Abbreviation: BA = basal area.

Nomenclature: Satake et al. (1989).

Question: Coastal dune systems are characterized by a natural mosaic that promotes species diversity. This heterogeneity often represents a severe problem for traditional mapping or ground survey techniques. The work presented here proposes to apply a very detailed CORINE land cover map as baseline information for plant community sampling and analysis in a coastal dune landscape.

Location: Molise coast, Central Italy.

Method: We analysed through an error matrix the coherence between land cover classes and vegetation types identified through a field survey. The CORINE land cover map (scale 1 : 5000) of the Molise coast was used with the CORINE legend expanded to a fourth level of detail for natural and semi-natural areas. Vegetation data were collected following a random stratified sampling design using the CORINE land cover classes as strata. An error matrix was used to compare, on a category-by-category basis, the relationship between vegetation types (obtained by cluster analyses of sampling plots) and land cover classes of the same area.

Results: The coincidence between both classification approaches is quite good. Only one land cover class shows a very weak agreement with its corresponding vegetation type; this result was interpreted as being related to human disturbance.

Conclusions: Since it is based on a standard land cover classification, the proposal has a potential for application to most European coastal systems. This method could represent a first step in the environmental planning of coastal systems.

Nomenclature: Pignatti (1982).

Abbreviation: CORINE = Co-ordination on Information of the Environment.

Question: Do soil treatments and addition of seed facilitate rapid vegetation restoration on forest paths excluded from trampling?

Location: Six mesophilic mixed deciduous Querco-Fagetea forests in Flanders, northern Belgium.

Methods: Enclosures on paths were excluded from trampling by fencing. In a full factorial design, plots were subjected to seeding, soil scarification, addition of organic material and inoculum. The following two years, seedling establishment and growth were sampled during spring and summer. Soil treatments and seeding effect was tested and seedling occurrence was analysed in relation to species' origin.

Results: Spontaneous revegetation was significant in all plots since fencing. Throughout the observation period seedling cover and height continued to increase. Seeding had an overall effect on seedling density, cover and height. Some soil treatment interactions significantly enhance revegetation, although each individual soil treatment had no significant effect. Regardless of the seeded individuals, invading species mostly originated from the surrounding area and the seed bank.

Conclusion: The preliminary results of this experiment imply that seeding is the only treatment which has a positive effect on revegetation success in all circumstances, provided that the exclusion from trampling is effective.

Nomenclature: Lambinon et al. (1998).

Question: Is the vegetation of meadow and mountain steppes distinct from the ground vegetation of light taiga forests in the transitional zone between these biomes?

Location: Western Khentey Mountains, northern Mongolia.

Methods: Vegetation was recorded from 100-m² plots from all dominant types of light taiga forest and dry grassland. Distinctness of ground vegetation was studied with Detrended Correspondence Analysis (DCA).

Results: Ground vegetation in the light taiga was significantly different from the herbal vegetation of meadow and mountain steppes. Clear separation was only absent for the Carex amgunensis meadow steppes that occur in a narrow strip along the forest edge and are partly shaded by trees. Forest and steppe communities followed a moisture gradient according to the DCA ordination with light taiga forests at the moistest sites and steppe communities at the driest sites. Ulmus pumila open woodlands diverged from this pattern, because of their close spatial and phytosociological relationship to mountain steppes.

Conclusions: The present results do not support the assumption that grasslands in Mongolia's transitional zone between forest and steppe would generally resemble the ground vegetation of light taiga forests. This contradicts a published hypothesis stating that the vegetation of meadow and mountain steppes would not clearly differ from ground vegetation of light taiga forests in the forest-steppe transitional zone of Mongolia.

Nomenclature: Gubanov (1996).

Question: Do tree species, with different litter qualities, affect the within-forest distribution of forest understorey species on intermediate to base-rich soils? Since habitat loss and fragmentation have caused ancient forest species to decline, those species are the main focus of this study.

Location: Three ancient forests, along a soil gradient from acidification-sensitive to base-rich, were studied: Limbrichterbosch and Savelsbos in The Netherlands and Holtkrat in Denmark.

Methods: Canopy and soil surveys along transects generated data for Redundancy Analysis on tree - humus relationships. We analysed the distribution of forest plant species with Canonical Correspondence Analysis. The explanatory factors were soil characteristics (pH, organic matter, loam content and thickness of the humus layers), external crown projection, groundwater and canopy data. We further analysed the relationship between forest species and humus characteristics with Spearman correlations.

Results: Tree species have a significant impact on humus characteristics through the nature of their litter. Humus characteristics significantly explain the distribution of forest understorey species. The pH of the first 25 cm mineral soil and the thickness of the F- (fermentation) layer are the primary factors affecting the distribution of ancient forest species.

Conclusion: This study indicates that the species composition of the forest canopy affects the distribution of forest understorey species. Ancient forest species are more abundant and frequent underneath trees with base-rich litter. On acidification-sensitive soils these relationships were stronger than on more base-rich, loamy soils.

Abbreviations: Ah = Soil horizon consisting of mineral soil with a high organic matter content; CEC = Cation exchange capacity; F = Fermenting litter (layer); Ah = Humus-rich mineral soil (layer); L = Litter (layer); RDA = Redundancy analysis.

Question: What is the importance of the seed bank in the maintenance of the restoration potential of a 60-year-old abandoned calcareous grassland overgrown by Pinus trees?

Location: ‘Les Pairées’, province of Luxembourg, Belgium.

Methods: The seed bank and the above-ground vegetation were surveyed in three adjacent stands, previously forming a unique calcareous grassland: a 60-year-old Pinus forest, a four-year-old clear-cutting and a typical calcareous grassland. Floristic diversity was compared among stands and between vegetation and seed bank.

Results: The species richness of the vegetation and the seed bank was significantly lower in the Pinus forest. More floristic similarities were found between the clear-cutting and the calcareous grassland. Seed bank was essentially transient, dominated by annual species. Its correspondence with the above-ground vegetation was weak.

Conclusion: Very few calcareous grassland species have persisted in the Pinus stand. Four years after clear-cutting, the stand was nearing restoration towards a calcareous grassland. Seed longevity in the soil was not the most explicative factor. Dispersal of propagules from adjacent sources was also important.

Nomenclature: Lambinon et al. (1992).

Questions: How does recreational disturbance (human trampling) affect soil characteristics, the performance of the understorey vegetation, and the density and species composition of the soil seed bank in Fagus sylvatica forests?

Location: Suburban forests near Basel, northwestern Switzerland.

Methods: We compared various soil characteristics and the performance of the understorey vegetation in six beech forest areas frequently disturbed by recreational activities with those in six undisturbed control areas, in spring 2003. In the same forest areas, the soil seed bank was investigated using the seedling emergence method. Samples were obtained from soil cores in January 2003.

Results: We found substantial changes in soil compaction, above-ground vegetation and in the soil seed bank due to recreational activities. In frequently visited areas, soil compaction was enhanced which caused a decrease in cover, height and species richness of both herb and shrub layers. Compared with control areas, the number of trampling-tolerant species of the seed bank was significantly higher in disturbed areas, and total species richness tended to be higher in disturbed than in control areas. Furthermore, the similarity in species composition between the above-ground vegetation and seed bank was significant lower in disturbed than in control areas.

Conclusions: The intensive use of suburban forests for recreational activities, mainly picnicking, affects the vegetation of natural beech forests. Our study indicates that a restoration of degraded forest areas from the soil seed bank would result in a substantial change of the vegetation composition.

Nomenclature: Binz (1990) for plant species; Moor (1963) and Burnand & Hasspacher (1999) for forest communities.

Question: Can prescribed winter burning compensate atmospheric nutrient loads for dry heathlands? What effects does prescribed burning have on nutrient balances, particularly as regards the limiting nutrients N and P?

Location: Lueneburg Heath, NW Germany.

Methods: In two burning experiments (in 10/15 year old Calluna-stands) nutrient balances (for N, Ca, K, Mg, P) were calculated by analysing nutrient inputs (atmospheric deposition, ash deposition), nutrient stores (above-ground biomass, organic horizon) and nutrient outputs (biomass combustion, leaching).

Results: Atmospheric nutrient deposition amounted to 22.8 kg.ha⁻¹.a⁻¹ for N and < 0.5 kg.ha⁻¹.a⁻¹ for P. Nutrient stores in the above-ground biomass were 95/197 kg.ha⁻¹ for N and 5/13 kg.ha⁻¹ for P (first/second experiment, respectively). From these stores 90/53% (for N) and 25/14% (for P) were removed by burning. Effects of leaching on nutrient balances were low. In the first two years after burning, leaching rates of N increased by about 4/6 kg.ha⁻¹, whereas leaching rates of P did not change significantly. Input/output-ratios showed that prescribed burning leads to positive nutrient balances for N, Ca and Mg in the long term. For example, the amounts of N removed by prescribed burning are equivalent to ca. five years of atmospheric inputs. Applied in ten-year cycles, this measure alone cannot prevent N accumulation in the long term.

Conclusion: Regarding 10/15 year old Calluna-heaths, we assume that prescribed burning cannot compensate for atmospheric N inputs, thus making long-term changes in the nutritional state inevitable. Therefore, prescribed burning should be applied in combination with high-intensity management measures.

Abbreviation: TEP = Theoretical Effective Period.

Questions: What is the variability in abundance of lichens on grassland soil between and within fields after prescribed fire? Is post-fire lichen abundance an effect of pre-fire population size?

Location: Cedar Creek Natural History Area, Minnesota, USA.

Methods: Lichen abundance, estimated as ground cover and dominated by Cladonia spp., was mapped in plots in two fields before prescribed burning on 06.10.2003 and 15.10.2003 for the first time since abandonment in the 1950s. The plots were resurveyed one year post-fire.

Results: Post-fire cover of Cladonia spp. varied strongly between the fields, most likely due to different weather conditions between the burn events, which resulted in different fire intensities, one of low and one of high intensity. In the field that experienced the low intensity fire, post-fire cover of Cladonia spp. was still relatively high, and showed a positive relationship with pre-fire cover, while no such relationship was found after the high intensity fire. In that field Cladonia spp. experienced high mortality rates irrespective of pre-fire cover.

Conclusions: This study provides an example of how species response to disturbance can be a function of population size, but that this relationship can be non-linear; lichens in grassland can survive a low intensity fire proportionally to pre-fire population size, but experience high mortality rates above a fire intensity threshold. The applications of these results are that fire intensity matters to species response to prescribed fire, and that the persistence of climax lichen communities and biodiversity in the study system needs a broad range of fire intervals.

Nomenclature: Esslinger (1997).

Abbreviation: CCNHA = Cedar Creek Natural History Area.

Question: What are the effects of shallow flooding on boreal peatlands on vegetation composition and size of carbon pools in the living and dead vegetation?

Location: Lake 979, Experimental Lakes Area, northwestern Ontario, Canada.

Methods: A boreal basin peatland complex with treed bog, open bog, and open water was experimentally flooded by raising water level ca. 1.3 m. Vegetation and above-ground biomass were compared between pre-flood conditions and those nine years after flooding. Peat accumulation since flooding was also quantified.

Results: Flooding caused almost all trees to die, leading to a net loss of 86% of the above-ground living plant biomass after nine years of the flooding. Floating up of peat was rapid in the central part of the basin, and the floating peat mats were characterized by newly established open bog community. Wetland types were diversified from bog into open bog, fen, and marsh, accompanied with great species turnover. Floating open bog community accumulated the greatest amount of peat since flooding.

Conclusions: This study shows that shallow flooding of bog vegetation can lead to quick re-establishment of open bog vegetation upon the floating up of peat mats as well as changes to more diverse vegetation over decadal time spans. We estimate that the carbon pools in 2002 in living and dead plant biomass since 1992 are comparable to what they were in the above-ground biomass in 1992. Flooding caused an initial net decrease in carbon stores, but carbon in the pre-flood living plant biomass was replaced by both carbon in dead biomass of the pre-flood vegetation and newly sequestered carbon in new peat growth and post-flood living plant biomass. Possible vegetation change toward bog-dominated system could lead to increasing rate of new peat growth, which could affect future carbon sink/source strength of the system.

Nomenclature: Scoggan (1978a, b, 1979) for vascular plants except for Vaccinium oxycoccus (VanderKloet 1983) and Rhododendron groenlandicum (Kron & Judd 1990); Anderson et al. (1990) for mosses except for Sphagnum (Anderson 1990).

Question: Can combined sod cutting and liming successfully restore species composition of degraded wet heaths?

Location: The Netherlands.

Methods: The effects of sod cutting with or without liming on plant species composition were studied in two degraded wet heath areas. Seeds and seedlings of Arnica montana were put out in the treated plots to test the suitability of the restored soil conditions. In addition, seed banks of both degraded areas were studied.

Results: Germination, growth and survival of Arnica montana were significantly greater after sod cutting and liming compared to sod cutting alone. At the end of the four-year study period, the number of endangered wet heath species was significantly greater in the sod-cut plots than in the untreated vegetation. Acid-tolerant species were especially positively affected. Additional liming only slightly increased the total number of species over the two-year study period and the number of endangered species did not increase. Viable seeds of most of the endangered species were absent in the seed banks of both areas.

Conclusions: Sod cutting is sufficient for the return of acid-tolerant, endangered wet heath species of early successional stages, because their seeds are still present in the seed bank. In contrast, acid-sensitive species likely depend on combined sod cutting and liming, as they need the weakly buffered soil conditions created by these restoration measures. However, successful restoration of formerly species-rich wet heaths is limited significantly by the absence of seeds of the target species in the seed banks. Therefore, re-introduction of wet heath target species in areas with limited seed availability should be seriously considered.

Abbreviations: HO = Havelte-Oost heathland; LP = Leem-putten nature reserve.

Nomenclature: Nomenclature follows Schaminée et al. (1995) and Schwertz et al. (1996) for plant communities, and van der Meijden (2002) for vascular plants.