Question: Which are the plant functional groups respondcing most clearly to agricultural disturbances? Which are the relative roles of habitat availability, landscape configuration and agricultural land use intensity in affecting the functional composition and diversity of vascular plants in agricultural landscapes?

Location: 25 agricultural landscape areas in seven European countries.

Methods: We examined the plant species richness and abundance in 4 km × 4 km landscape study sites. The plant functional group classification was derived from the BIOLFLOR database. Factorial decomposition of functional groups was applied.

Results: Natural habitat availability and low land use intensity supported the abundance and richness of perennials, sedges, pteridophytes and high nature quality indicator species. The abundance of clonal species, C and S strategists was also correlated with habitat area. An increasing density of field edges explained a decrease in richness of high nature quality species and an increase in richness of annual graminoids. Intensive agriculture enhanced the richness of annuals and low nature quality species.

Conclusions: Habitat patch availability and habitat quality are the main drivers of functional group composition and plant species richness in European agricultural landscapes. Linear elements do not compensate for the loss of habitats, as they mostly support disturbance tolerant generalist species. In order to conserve vascular plant species diversity in agricultural landscapes, the protection and enlargement of existing patches of (semi-) natural habitats appears to be more effective than relying on the rescue effect of linear elements. This should be done in combination with appropriate agricultural management techniques to limit the effect of agrochemicals to the fields.

Nomenclature: Tutin et al. (2001).

Questions: 1. Do pine seedlings in estuarine environments display discrete or continuous ranges of physiological tolerance to flooding and salinity? 2. What is the tolerance of Pinus taeda and P. serotina to low salinity and varying hydrologic conditions? 3. Are the assumptions for ecological equilibrium met for modeling plant community migration in response to sea-level rise?

Location: Albemarle Peninsula, North Carolina, USA.

Methods: In situ observations were made to quantify natural pine regeneration and grass cover along a salinity stress gradient (from marsh, dying or dead forest, to healthy forest). A full-factorial greenhouse experiment was set up to investigate mortality and carbon allocation of Pinus taeda and P. serotina to low-salinity conditions and two hydrology treatments over 6 months. Treatments consisted of freshwater and two salinity levels (4 ppt and 8 ppt) under either permanently flooded or periodically flushed hydrologic conditions.

Results: Natural pine regeneration was common (5–12 seedlings per m²) in moderate to well-drained soils where salinity concentrations were below ca. 3.5 ppt. Pine regeneration was generally absent in flooded soils, and cumulative mortality was 100% for 4 and 8 ppt salinity levels under flooded conditions in the greenhouse study. Under weekly flushing conditions, mortality was not significantly different between 0 and 4 ppt, confirming field observations. Biomass accumulation was higher for P. taeda, but for both pine species, the root to shoot ratio was suppressed under the 8 ppt drained treatment, reflecting increased below-ground stress.

Conclusions: While Pinus taeda and P. serotina are commonly found in estuarine ecosystems, these species display a range of physiological tolerance to low-salinity conditions. Our results suggest that the rate of forest migration may lag relative to gradual sea-level rise and concomitant alterations in hydrology and salinity. Current bioclimate or landscape simulation models assume discrete thresholds in the range of plant tolerance to stress, especially in coastal environments, and consequently, they may overestimate the rate, extent, and timing of plant community response to sea-level rise.

Nomenclature: Radford et al. (1968).

Questions: How do young sagebrush shrubs (Artemisia rothrockii, Asteraceae) affect soil moisture availability? How do young sagebrush shrubs affect soil nitrogen cycling? How does the resident herb community respond to shrub removal in the early stages of sagebrush encroachment?

Location: Mulkey and Bullfrog Meadows on the Kern Plateau in the Golden Trout Wilderness, Sierra Nevada Mountains, Inyo National Forest, Inyo County, California, USA.

Methods: We removed young encroaching sagebrush shrubs from 3.5 m × 3.5 m plots and compared soil moisture, net mineralization, net nitrification, and herb cover with paired control plots over four growing seasons.

Results: On average throughout the experiment, the difference between removal plots and control plots in soil moisture was small. Removal plots were wetter by 1.3 ± 2.0% at 0–30 cm depth, 2.1 ± 3.1% at 30–60 cm depth and 3.1 ± 5.8% at 60–90 cm depth. By contrast, after four years, net mineralization was 32 ± 26% (mean ± 95% CI) lower in sagebrush removal plots, suggesting that sagebrush encroachment increases rates of N-cycling. Total herb cover was 13.0 ± 6.4% (mean ± 95% CI) higher in plots where young sagebrush shrubs were removed. This difference in cover appeared during the first season in which sagebrush shrubs were removed.

Conclusions: Our results suggest that while young sagebrush shrubs do not contribute substantially to meadow drying, they alter N cycling rates, and may indirectly increase the rate of their own encroachment by competitively reducing resident herbs.

Question: What are the genesis and development of thicket clumps within a savanna landscape at geomorphically different locations and what are the driving forces?

Location: The Kagera Region, in the border area of Rwanda, Uganda and Tanzania.

Methods: The vegetation of 32 dry evergreen thicket clumps and their surrounding savannas have been analysed at different geomorphic locations. At each vegetation plot Na , K , Mg² , Ca² , Al³ , Fe^{2 /3} , H , P, C, N, bulk density and particle size were determined for each soil horizon. The impact of soil and termite mounds on thicket clump dynamics on seasonally waterlogged plains, gentle slopes and stony hillsides were assessed.

Results: Thicket clumps and their surrounding savannas have a distinct structure and floristic composition. They also have distinct soil properties although parent materials are the same. On seasonally waterlogged plains, new thicket clumps can develop on Macrotermitinae mounds; on stony hillsides, Trinervitermes and Macrotermes show a uniform distribution pattern and may initiate the genesis of thicket clumps.

Conclusions: Geomorphology broadly determines the significance and interactions of the main factors affecting site-specific vegetation dynamics. On seasonally waterlogged plains, thicket clumps are restricted to termite mounds. Since intra-species competition dictates a minimal distance between neighbouring Macrotermitinae colonies, thicket clumps do not coalescence. By contrast, on stony hillsides, the vegetation mosaic is highly dynamic and determined by the interplay of several factors. The growth of thicket clumps is mainly a function of the fire regime and the browsing intensity. At the present time, frequent cool, early dry season fires and the near absence of large browsers have favoured the advance and coalescence of thicket clumps and forest patches on stony hillsides.

Nomenclature: Troupin (1978, 1983, 1985, 1988) for grasses and forbs; Beentje (1994) for woody plants; Pearce (1997) for termites.

Question: Are there spatial structures in the composition of plant communities?

Methods: Identification and measurement of spatial structures is a topic of great interest in plant ecology. Univariate measurements of spatial autocorrelation such as Moran's I and Geary's c are widely used, but extensions to the multivariate case (i.e. multi-species) are rare. Here, we propose a multivariate spatial analysis based on Moran's I (MULTISPATI) by introducing a row-sum standardized spatial weight matrix in the statistical triplet notation. This analysis, which is a generalization of Wartenberg's approach to multivariate spatial correlation, would imply a compromise between the relations among many variables (multivariate analysis) and their spatial structure (autocorrelation). MULTISPATI approach is very flexible and can handle various kinds of data (quantitative and/or qualitative data, contingency tables).

A study is presented to illustrate the method using a spatial version of Correspondence Analysis.

Location: Territoire d'Etude et d'Expérimentation de Trois-Fontaines (eastern France).

Results: Ordination of vegetation plots by this spatial analysis is quite robust with reference to rare species and highlights spatial patterns related to soil properties.

Nomenclature: Tutin et al. (2001).

Question: In deciduous-dominated forest landscapes, what are the relative roles of fire weather, climate, human and biophysical landscape characteristics for explaining variation in large fire occurrence and area burned?

Location: The Great Lakes-St. Lawrence forest of Canada.

Methods: We characterized the recent (1959–1999) regime of large (≥ 200 ha) fires in 26 deciduous-dominated landscapes and analysed these data in an information-theoretic framework to compare six hypotheses that related fire occurrence and area burned to fire weather severity, climate normals, population and road densities, and enduring landscape characteristics such as surficial deposits and large lakes.

Results: 392 large fires burned 833 698 ha during the study period, annually burning on average 0.07% ± 0.42% of forested area in each landscape. Fire activity was strongly seasonal, with most fires and area burned occurring in May and June. A combination of antecedent-winter precipitation, fire season precipitation deficit/surplus and percent of landscape covered by well-drained surficial deposits best explained fire occurrence and area burned. Fire occurrence varied only as a function of fire weather and climate variables, whereas area burned was also explained by percent cover of aspen and pine stands, human population density and two enduring characteristics: percent cover of large water bodies and glaciofluvial deposits.

Conclusion: Understanding the relative role of these variables may help design adaptation strategies for forecasted increases in fire weather severity by allowing (1) prioritization of landscapes according to enduring characteristics and (2) management of their composition so that substantially increased fire activity would be necessary to transform landscape structure and composition.

Question: What is the relative importance of environmental gradients and surface microtopography (variation in vertical level within sampling units) for fine-scale plant species richness in Picea abies swamp forests?

Location: 11 swamp forests in SE Norway.

Methods: We recorded species richness (number of species of vascular plants, mosses, Sphagnum and hepatics), depth to water table, soil base status and vertical range (microtopographic relief) in 2400 microplots, (each 1/16 m²), in 150 1-m² plots in the 11 swamp forests. Relationships between species richness and environmental predictors were modelled by GLMM.

Results: Moss and hepatic species richness increased with increasing microtopographic relief, most strongly for wet acid sites, in which similar trends were also found for Sphagnum. Relief was a poor predictor of vascular plant species richness.

Conclusions: Microtopographic relief is a good predictor of local species richness in Picea abies swamp forests, partly because larger vertical variability means higher within-plot habitat diversity with respect to the wet-dry gradient, and partly because qualitatively new microhabitats associated with steep slopes are added in drier sites. The relationship between species richness and microtopographic relief is context dependent, differing in complex ways among species groups and among sites with different environmental conditions.

Question: Do coexisting plant life forms differ in overall phenology, leaf traits and patterns of leaf litterfall?

Location: Patagonian Monte, Chubut Province, Argentina.

Methods: We assessed phenology, traits of green and senesced leaves and the pattern of leaf litterfall in 12 species of coexisting life forms (perennial grasses, deciduous shrubs, evergreen shrubs).

Results: We did not identify differences in phenology, leaf traits and patterns of leaf litterfall among life forms but these attributes contrasted among species. Independent of the life form, the maintenance of green leaves or vegetative growth during the dry season was mostly associated with leaves with high leaf mass per area (LMA) and high concentration of secondary compounds. Low LMA species produced low litterfall mass with low concentration of secondary compounds, and high N concentration. High LMA species produced the largest mass of leaf litterfall. Accordingly, species were distributed along two main dimensions of ecological variation, the dimension secondary compounds in leaves - length and timing of the vegetative growth period (SC – VGP) and the dimension leaf mass per area - leaf litterfall mass (LMA – LLM).

Conclusions: Phenology, leaf traits and leaf litterfall varied among species and overlapped among life forms. The two dimensions of ecological variation among species (SC – VGP, LMA – LLM) represent distinct combinations of plant traits or strategies related to resource acquisition and drought tolerance which are reflected in the patterns of leaf litterfall.

Nomenclature: Correa (1971, 1978, 1984, 1988, 1999).

Question: In stressful abiotic environments positive plant interaction is expected to be a frequent and an important process driving community composition and structure. In the high Andes in central Chile, the cushion plant Azorella madreporica dominates plant communities and appears to benefit the assemblage of species that grows within it. However, there are also many other species that grow outside this nurse cushion plant, which may or may not interact with this species. What is the prevailing type of spatial associations among the plant species that are not growing inside the nurse plant? What is the type of interactions between cushion plants and those species growing outside them?

Location: Molina River basin (33°20′ S, 70°16′ W, 3600 m a.s.l.), in the Andes of central Chile, ca. 50 km east of Santiago.

Methods: Two accurate mapping plots of individual plants of different species were located at two summits (Franciscano and Tres Puntas sites). The spatial distributions and associations between species growing outside cushions and within cushions at each site were estimated by point-pattern analyses using the univariate and bivariate transformations of Ripley's K-functions.

Results: We found both positive and, especially, negative spatial associations (8 out of 12 species in Franciscano site) between A. madreporica cushions and plants growing outside them. However, most of the species showed positive spatial associations among them. The variation in spatial association was site-specific and also depended on the type of plants involved. Adesmia spp., the second most abundant non-cushion species, displayed negative associations with cushions and positive associations with other species growing outside cushions.

Conclusions: Our study suggests very complex interactions among species, which ranged from positive to negative, and are also affected by abiotic environmental conditions.

Question: Is post-fire, medium-term vegetation dynamics determined by land-use or fire history prior to fire?

Location: South-facing slope in the Gallinera valley, Alicante province, eastern Spain.

Methods: After mapping the land-use and fire history of the study site using photo-interpretation, we sampled vegetation structure on a set of plots representing the most frequent land-use and fire history combinations on an area burned six years before sampling. We studied the effects of land-use history, comparing the one-fire land-use trajectories. We analysed the effects of fire history; comparing one- and two-fire plots for both previously cropped and uncropped areas.

Results: Most variables were not significantly different between the earliest abandoned plots (abandoned at least 38 years before the fire) and the uncropped plots. On the most recently abandoned plots (abandoned between one and four years before the fire), the therophyte richness and the ratio of seeder:resprouter richness were significantly greatest. Different fire recurrences did not determine different post-fire vegetation on either the uncropped or the early abandoned plots (all dominated by fire-recruited seeder shrubs). The most recently abandoned plots had a lower resilience to fire.

Conclusions: Land-use history and recent pre-fire land use, in particular, determined the post-fire vegetation in the medium term. The vegetation composition converged during secondary succession among land-use histories. Increasing fire recurrence had a small effect on mature plant communities, due to the combination of life-history traits determining the response to fire of the dominant species.

Nomenclature: de Bolòs et al. (1990) for vascular plants, except for Quercus ilex ssp. ballota.

Question: The prominent role of wind dispersal in alpine habitats has been recognized early but has rarely been quantified. The aim of this study is to compare wind dispersal under alpine and lowland conditions and to analyse whether differences are caused by species traits, e.g. terminal velocity of seeds (V_term) or weather conditions.

Location and Methods: We characterized wind dispersal potential of >1100 Central European species using measured V_term. To quantify the habitat effect on wind dispersal, we measured meteorological key-parameters and simulated dispersal distance spectra of nine selected species under typical alpine conditions (foreland of the Scaletta-glacier, Switzerland) and typical lowland conditions (grassland in Bad Lippspringe, Germany).

Results: Lowland species had higher V_term compared to alpine species. However, this difference is absent when only species of species of open habitats are concerned. The meteorological measurements showed that the alpine habitat was mainly characterized by higher frequency and strength of updrafts. The simulations showed that under alpine conditions long distance dispersal occurred much more frequent.

Conclusions: More than 50 % of the alpine species have a fair chance to be dispersed by wind over long distances, while this proportion is less than 25 % for species from open habitats in the lowland. The more prominent role of wind dispersal in alpine habitats is mainly a result of differences in environmental conditions, namely more intense vertical turbulence in the alpine habitat, and does not result from prominent differences in plant traits, namely V_term, between alpine and lowland species.

Nomenclature: Wisskirchen & Haeupler (1998).

Question: The quantification of functional traits in natural communities can be difficult (e.g. root traits, RGR). Can functional traits measured on pot grown plants be reliably applied to natural communities? Alternatively, can below-ground plant traits be predicted from above-ground traits?

Location: Southeastern Australia.

Methods: We compared 17 shoot, root and whole-plant morphological traits measured on 14 plant species in a native grassland community to those measured under two different pot conditions: unfertilised and fertilised.

Results: The majority of trait values for pot grown plants differed to plants in the field, however, species ranking remained consistent for most leaf traits between the field and the two pot growing conditions. In contrast, species ranking was not consistent for most whole plant traits when comparing field plants to fertilised pot grown plants, providing a caution against the tendency to grow plants in controlled conditions at ‘optimal’ (high) resource levels. Moderate to strong correlations were found between below-ground and above-ground plant traits, including between root dry matter content and leaf dry matter content, and between specific root area and specific leaf area.

Conclusions: The utility of pot grown plants to quantify traits for field plants is highly dependent on the selection of the growing conditions in the controlled environment. The consistency we observed between above-ground and below-ground trait strategies suggests that below-ground traits may be predictable based on above-ground traits, reducing the need to quantify root traits on cultured plants.

Nomenclature: Harden (1996); Linder (1997).

Questions: 1. Is there a trade-off between gap dependency and shade tolerance in each of the life-history stages of three closely related, coexisting species, Acer amoenum (Aa), A. mono (Am) and A. rufinerve (Ar)? 2. If not, what differences in life-history traits contribute to the coexistence of these non-pioneer species?

Location: Ogawa Forest Reserve, a remnant (98 ha), species-rich, temperate deciduous forest in central Japan (36°56′ N, 140°35′ E, 600 - 660 m a.s.l.).

Methods: We estimated the demographic parameters (survival, growth rate and fecundity) by stage of each species growing in gaps and under closed canopy through observations of a 6-ha permanent plot over 12 years. Population dynamics were analysed with stage-based matrix models including gap dynamics.

Results: All of the species showed high seedling and sapling survival rates under closed canopies. However, demographic parameters for each growth stage in gaps and under closed canopies revealed inter-specific differences and ontogenetic shifts. The trade-off between survival in the shade and growth in gaps was detected only at the small sapling stage (height < 30 cm), and Ar had the highest growth rate both in the shade and in the gaps at most life stages.

Conclusions: Inter-specific differences and ontogenetic shifts in light requirements with life-form differences may contribute to the coexistence of the Acer species in old-growth forests, with Aa considered a long-lived sub-canopy tree, Am a long-lived canopy tree, and Ar a short-lived, ‘gap-phase’ sub-canopy tree.

Nomenclature: Satake et al. (1989).

Questions: Which environmental and management factors determine plant species composition in semi-natural grasslands within a local study area? Are vegetation and explanatory factors scale-dependent?

Location: Semi-natural grasslands in Lærdal, Sogn og Fjordane County, western Norway.

Methods: We recorded plant species composition and explanatory variables in six grassland sites using a hierarchically nested sampling design with three levels: plots randomly placed within blocks selected within sites. We evaluated vegetation-environment relationships at all three levels by means of DCA ordination and split-plot GLM analyses.

Results: The most important complex gradient determining variation in grassland species composition showed a broad-scale relationship with management. Soil moisture conditions were related to vegetation variation on block scale, whereas element concentrations in the soil were significantly related to variation in species composition on all spatial scales. Our results show that vegetation-environment relationships are dependent on the scale of observation. We suggest that scale-related (and therefore methodological) issues may explain the wide range of vegetation-environment relationships reported in the literature, for semi-natural grassland in particular but also for other ecosystems.

Conclusions: Interpretation of the variation in species composition of semi-natural grasslands requires consideration of the spatial scales on which important environmental variables vary.

Nomenclature: Lid & Lid (1994) except for Betula pubescens agg. (which includes B. pubescens and B. verrucosa) and Hieracium spp. (which includes all Hieracium species except H.umbellatum).