Question: What is the effect of fuel management practices in the recovery capacity of seeder-dominated shrublands?

Location: Ulex parviflorus shrubland localities in Mediterranean regions of eastern Spain.

Methods: We applied prescribed burning and brush-chipping as fuel management techniques in three young and three mature shrublands, and evaluated the effects in the following four years.

Results: Canopy opening by the treatments allowed increasing species richness through the four years of secondary succession. The treatments produced a change in community structure and dominant species, from the woody seeder Ulex parviflorus to the resprouter grass Brachypodium retusum. Vegetation response was conditioned by both shrubland developmental stage and treatment applied. Burning resulted in more severe modification of the ecosystem, increasing bare soil cover. Four years after fuel management in different aged Mediterranean gorse shrublands, vegetation response followed a similar pattern with the exception of the young, brush-chipped shrublands. The treatments applied for controlling Ulex parviflorus were seen to be very effective, with the exception of brush-chipping in young shrublands.

Conclusions: Selective brush-chipping in middle-aged or mature gorse shrublands would combine a drastic reduction in fire hazard with ecosystem conservation and regeneration.

Nomenclature: De Bolòs et al. (1993).

Question: How does the vegetation of boreal forests respond to harvesting and scarification?

Location: 650 m a.s.l., central Sweden (61°38′ N).

Methods: The response of boreal forest vegetation to cutting and scarification was studied in a field trial, which consisted of three treatments plus conventional harvesting as a control in a complete block design with four replicates. The cutting was done 14 years prior to vegetation inventory and scarification and planting were conducted the first or second years after cutting.

Results: The species most abundant at higher cutting intensities were crustose lichens, Cladonia spp., Cladina arbuscula, Polytrichum spp. and pioneer mosses, the grass Deschampsia flexuosa, and the tree Betula pubescens, A few species had substantially lower abundance in treatments with higher cutting intensity, notably Hylocomium splendens and Vaccinium myrtillus. Scarification had a strong effect that was different from the one created by cutting. In scarification treatments, Polytrichum spp. were the only species with high abundance; most species had low abundance, i.e. Barbilophozia lycopodioides, Vaccinium vitis-idaea, Pleurozium schreberi, Carex globularis, Empetrum nigrum, Cladina arbuscula, Sphagnum spp.

Conclusions: Our results elaborate on the details of the well-known effect of cutting on ground-layer flora, and also give support for the profound and long-lasting effect that soil scarification has on forest vegetation.

Nomenclature: T. Karlsson (1998).

Question: Will the predicted climate changes affect species distribution in the Iberian Peninsula?

Location: Iberian Peninsula (Spain and Portugal).

Methods: We modelled current and future tree distributions as a function of climate, using a computational framework that made use of one machine learning technique, the random forest (RF) algorithm. This algorithm provided good predictions of the current distribution of each species, as shown by the area under the corresponding receiver operating characteristics (ROC) curves. Species turnover, richness and the change in distributions over time to 2080 under four Intergovernmental panel on climate change (IPCC) scenarios were calculated using the species map outputs.

Results and Conclusions: The results show a notable reduction in the potential distribution of the studied species under all the IPCC scenarios, particularly so for mountain conifer species such as Pinus sylvestris, P. uncinata and Abies alba. Temperate species, especially Fagus sylvatica and Quercus petraea, were also predicted to suffer a reduction in their range; also submediterranean species, especially Q. pyrenaica, were predicted to undergo notable decline. In contrast, typically Mediterranean species appeared to be generally more capable of migration, and are therefore likely to be less affected.

Nomenclature: Amaral Franco (1990), Govaerts & Avishai (2002) for Quercus pubescens.

Question: Does grazing by large herbivores affect species composition or community-wide variation in plant functional traits?

Location: Dune grasslands at the Belgian coast.

Methods: Plant cover and soil data were collected in 146 plots that were randomly selected at 26 grazed and ungrazed grassland sites. Plant community composition was assessed by Detrended Correspondence Analysis and mean values of plant trait categories were calculated across the plots.

Results: Differentiation of plant composition and communitywide plant trait characteristics was largely determined by grazing, soil acidity and their interaction. In ungrazed situations, a clear floristic distinction appears between acidic (non-calcareous) and alkaline (calcareous) grasslands. In grazed situations, these floristic differences largely disappeared, indicating that grazing results in a decrease of natural variation in species composition. At higher soil pH, a larger difference in plant community composition and community-wide plant traits was observed between grazed and ungrazed plots. In ungrazed situations, shifts in plant functional traits along the acidity gradient were observed.

Conclusions: Grazing is responsible for shifts in plant community composition, and hence a decrease in plant diversity among grasslands at opposing acidity conditions in coastal dune grasslands. Therefore, care should be taken when introducing grazing as a system approach for nature conservation in dune grasslands as it may eliminate part of the natural variation in plant diversity along existing abiotic gradients.

Question: How does the dominance of Calamagrostis epigejos influence species turnover of a grassland?

Location: Loess grassland at the foothills of Bükk Mountains, Hungary (47°54′ N, 20°35′ E).

Methods: Presence/absence of vascular plants and different performance attributes of C. epigejos were recorded in a plot-subplot system between 2002 and 2005. Appearance and disappearance rates of grassland species were calculated for pairs of consecutive years. 1. Mean appearance and disappearance rates were compared in grassland plots dominated by C. epigejos and in plots free from this species, based on Monte Carlo randomization. 2. Mean appearance rates were assessed for categories of C. epigejos performance and their confidence intervals were calculated via Monte Carlo randomization. For two performance variables (percentage cover and shoot number) analyses were performed at two spatial scales.

Results: 1. C. epigejos-dominated plots differed from unaffected ones by significantly lower appearance rates. 2. Change in appearance rates was best explained by differences in percentage cover of C. epigejos. Coarse-scale C. epigejos performance had a closer correspondence with appearance rate change than fine-scale performance. Low level C. epigejos performance enhanced appearance rate compared to intact stands, while high level performance decreased it, regardless of the choice of performance measure.

Conclusions: C. epigejos lowers species number by hindering reappearance of species of the original grassland. This is best explained by the increased shading effect at the coarse scale. The marked non-linear initial enhancement in appearance rate, however, can also be taken as an early sign of future species loss.

Nomenclature: Tutin et al. (1964–1993).

Question: What is the most appropriate combination of treatments to reintroduce Nassella pulchra, a perennial bunchgrass, into degraded mediterranean coastal grasslands?

Location: Central coast of California, USA.

Methods: N. pulchra was sown from seeds and transplanted into a degraded grassland in a multi-factorial experiment testing the effects of (1) two grazing intensities (lightly grazed by native mammal species or ungrazed); (2) topsoil removal and (3) reduction of plant neighbours. The experiment was carried out on two types of surrounding vegetation (exotic annual grasses and exotic forbs).

Results: Topsoil removal greatly enhanced establishment from seeds and transplant survival, mainly because it reduced the exotic vegetation and thus reduced competition. While removing neighbours was essential when topsoil was left intact, it had a negative effect on N. pulchra when surrounding species included exotic forbs (Brassica spec. and Asteraceae) at low density (after topsoil removal). Moderate grazing by native mammals (deer, rabbits and gophers) did not affect N. pulchra.

Conclusion: Our results suggest that seeding after topsoil has been removed is a promising method to reintroduce N. pulchra to highly degraded sites where there is little to no native seed bank.

Nomenclature: Hickman 1993.

Question: Do anthropogenic disturbances interact with local environmental factors to increase the abundance and frequency of invasive species, which in turn exerts a negative effect on native biodiversity?

Location: Mature Quercus-Carya and Quercus-Carya-Pinus (oak-hickory-pine) forests in north Mississippi, USA.

Methods: We used partial correlation and factor analysis to investigate relationships between native ground cover plant species richness and composition, percent cover of Lonicera japonica, and local and landscape-level environmental variables and disturbance patterns in mature upland forests. We directly measured vegetation and environmental variables within 34 sampling subplots and quantified the amount of tree cover surrounding our plots using digital color aerial photography.

Results: Simple bivariate correlations revealed that high species richness and a high proportion of herbs were associated with low Lonicera japonica cover, moist and sandy uncompacted soils, low disturbance in the surrounding landscape, and periodic prescribed burning. Partial correlations and factor analysis showed that once we accounted for the environmental factors, L. japonica cover was the least important predictor of composition and among the least important predictors of species richness. Hence, much of the negative correlation between native species diversity and this invasive species was explained by soil texture and local and landscape-level land-use practices.

Conclusions: We conclude that negative correlations between the abundance of invasive species and native plant diversity can occur in landscapes with a gradient of human disturbance, regardless of whether there is any negative effect of invasive species on native species.

Nomenclature: Radford et al. (1968).

Questions: What are the relative roles of abiotic and grazing management factors on plant community distribution in landscapes? How are livestock type and stocking rate related to changes in vegetation structure and composition?

Location: Sub-alpine grasslands in the central and eastern Pyrenees.

Methods: Multivariate analysis and variance partitioning methods were used to evaluate the relative roles of environmental factors in structuring vegetation composition and diversity patterns in three surveys on differently managed grasslands.

Results: Vegetation composition within a region was affected by environmental factors hierarchically, changing first according to abiotic factors and then to grazing management. At landscape scales, abiotic factors explained two-fold more variation in vegetation composition than grazing factors. Within landscape units, cattle grazing increased vegetation heterogeneity at landscape and patch scales, while sheep grazing favoured the presence of a specific set of species with high conservation value. Species composition was highly responsive to management variables compared to diversity components.

Conclusions: The combination of sheep and cattle grazing at various stocking rates is an effective tool to preserve the diversity of plant species and communities within a region with a long tradition of livestock management, through the scaling up of effects by local processes occurring in patches at smaller scales.

Nomenclature: Tutin et al. (1964–1980); Bolòs et al. (1993).

Questions: Could the seed bank increase biodiversity during restoration of abandoned, species-poor, formerly cultivated vegetation? Is it possible to identify how climate, soil and former and present management and vegetation affected the seed bank?

Location: The study sites were eight abandoned grasslands, four in Orkdal, central Norway and four in Gaular, western Norway.

Methods: 144 seed bank samples were collected from three depths. Each sample was sown and placed in a greenhouse. After three months, the trays were dried and stored at 4°C in a dry place for two months. This was repeated twice.

Results: There was a separation of the two regions along the first DCA axis in both the seed bank and in the vegetation analysis and also a clear separation of the seed bank from the vegetation along the second axis. These results are caused by differences in former management as well as temperature, precipitation and soil type between Gaular and Orkdal. We found more annuals, short-lived species and species demanding light open conditions in the seed bank than in the vegetation probably because these species have the capacity for producing persistent seeds. Most of the species found only in the seed bank were found in very few samples and with few individuals.

Conclusion: These results suggest that it may be difficult to increase vegetation biodiversity through restoration of grasslands such as those investigated if the natural soil seed bank is the main seed source.

Nomenclature: Lid & Lid (1994).

Question: Interacting disturbance effects from Dendroctonus frontalis outbreaks and wildfire are thought to maintain Pinus spp. composition in the southeastern U.S. Our objective was to assess forest composition, structure, and succession following the interaction of two frequently occurring disturbance events in southern Pinus spp. forests: cut-and-leave suppression, a commonly used means for managing D. frontalis outbreaks, and wildfire.

Location: Western Gulf Coastal Plain, Louisiana, USA.

Method: Pinus taeda stands with cut-and-leave suppression and subsequent wildfire were compared to stands undisturbed by D. frontalis but with the same wildfire events twenty years after Pinus spp. mortality. The woody plant community was assessed in three different size classes and used to predict future forest types with the Forest Vegetation Simulator (50 years).

Results: P. taeda is the most abundant (> 50%) species of saw- and poletimber-sizes following cut-and-leave suppression with wildfire and in stands only with fire. Using canonical correspondence analysis, vegetation assemblages were primarily explained by slope position and elevation (7.6% variation explained). Fire intensity and stand age also accounted for variance in the ordination (4.4% and 3.1%, respectively). Dominant and co-dominant P. taeda forest types were predicted by the model to be the most abundant forest types in each disturbance regime. In addition, new regeneration represents high hazard for future mortality from D. frontalis.

Conclusion: Our study demonstrates that cut-and-leave suppression with additional wildfire disturbance maintains P. taeda composition, and does not alter forest composition differently from stands receiving only wildfire. As a result, predicted Pinus spp. basal area under both disturbances is great enough to facilitate future bark beetle disturbance.

Nomenclature: USDA NRCS (Anon. 2005).

Question: Can landscape quality be evaluated and compared with a single numerical value using vegetation maps?

Location: Northern Apennines (Italy), ca. 44° N, 10–11° E.

Methods: Seven phytosociological vegetation maps (1 : 25 000), which correspond to man's different impact on mountain landscapes, were considered. Syntaxa were classified into five degrees of naturalness: urbanized, agricultural, semi-natural, sub-natural, and natural. Vegetation maps showing naturalness were derived in a vectorial GIS. The degrees of naturalness were ordered according to increasing naturalness. If c_i is the cumulative relative value of every mapped area of the degrees of naturalness, the sum of these cumulative values A = Σ c_i is is a measure of vegetation artificiality. Its maximum value is A_max = n – 1. The Index of Vegetation Naturalness IVN = 1 - A / A_max, ranging from 0 to 1. Our IVN is an extension of the ILC by Pizzolotto & Brandmayr (1996) due to the ordinal character of the vegetation classification into degrees of naturalness. The maps of vegetation naturalness were also analysed by two known metrics for the evaluation of landscape quality: TECI (Total Edge Contrast Index) and MSI (Mean Shape Index).

Results: The case studies show that IVN is linearly correlated with decreasing area of urbanized and agricultural vegetation types as well as with increasing area of the highest degree of naturalness.

Conclusions: IVN can be joined with the TECI for the evaluation of naturalness of landscapes. TECI can supply additional information about the importance of landscape ecotones. Our case studies suggest that an urbanized landscape should correspond to IVN values lower than 0.20. A natural landscape will have IVN values higher than 0.80.

Nomenclature: Oberdorfer (1994) for plant communities, except for mixed oak woods (Ubaldi 1993).

Questions: How do changes in forest management, i.e. in disturbance type and frequency, influence species diversity, abundance and composition of the seed bank? How does the relationship between seed bank and vegetation change? What are the implications for seed bank dynamics?

Location: An ancient Quercus petraea - Carpinus betulus forest in conversion from coppice-with-standards to regular Quercus high forest near Montargis, France.

Methods: Seed bank and vegetation were sampled in six replicated stand types, forming a chronosequence along the conversion pathway. The stand types represented mid-successional stages of stands in transition from coppice-with-standards (to high forest (16 plots) and early- and mid-successional high forest stands (32 plots).

Results: Seed bank density and species richness decreased with time since last disturbance. Adjusting for seed density effects obscured species richness differences between stand types, but species of later seres were nested subsets of earlier seres, implying concomitant shifts in species richness and composition with time since disturbance. Later seres were characterized by species with low seed weight and high seed longevity. Seed banks of early seres were more similar to vegetation than to later seres.

Conclusions: Abandonment of the coppice-with-standards regime altered the seed bank characteristics, as well as its relationship with vegetation. Longer management cycles under high forest yield impoverished seed banks. For their persistence, seed bank species will increasingly rely on management of permanently open areas in the forest landscape. Thus, revegetation at the beginning of new high-forest cycles may increasingly depend on inflow from seed sources.

Nomenclature: Lambinon et al. (1998).

Question: Can dissimilarity measures of individual plots be used to forecast the driving factors among various anthropogenic disturbances influencing understorey successional changes?

Location: Yambulla State Forest, south-eastern Australia (37°14′ S, 149°38′ E).

Methods: Assessments of understorey vegetation communities were taken prior to anthropogenic disturbances and at three subsequent time periods representing a period of 15 years post-disturbance. Dissimilarities were calculated from the original assessment and modelled in a Bayesian framework to examine the influence of logging, number of prescribed burns and time.

Results: All sites underwent significant changes over time independently of the imposed management regimes. Logging resulted in an immediate change in vegetation assemblage which decreased in the subsequent assessments. The number of prescribed fires brought greater change in the shrub vegetation assemblages, but less change in the ground species vegetation assemblages.

Conclusions: The anthropogenic disturbances did have some role in the changes of vegetation assemblages but these were minimal. The ongoing changes appear to be a natural response to the last wildfire, which passed through the study area in 1973 (13 years prior to the study). Forest management practices should consider the influence of wildfire succession when planning for the conservation of biodiversity.

Question: How does agricultural land usage affect plant species diversity in semi-natural buffer strips at multiple scales?

Location: Lepsämä River watershed, Nurmijärvi, Southern Finland.

Methods: Species diversity indicators included both richness and evenness. Plant communities in buffer strips were surveyed in 29 sampling sites. Using ArcGIS Desktop 9.0 (ArcInfo) and Fragstats 3.3 for GIS analysis, the landscape composition around each sampling site was characterized by seven parameters in square sectors at five scales: 4, 36, 100, 196, and 324 ha. For each scale, Principle Component Analysis was used to examine the importance of each structural metric to diversity indicators using multiple regression and other simple analyses.

Results: For all but the smallest scales (4 ha), two structural metrics including the diversity of land cover types and percentage of arable land were positively and negatively correlated with species richness, respectively. Both metrics had the highest correlation coefficients for species richness at the second largest scale (196 ha). The density of arable field edges between the fields was the only metric that correlated with species evenness for all scales, which had highest predictive power at the second smallest scale (36 ha).

Conclusions: Species richness and evenness of buffer strips had scale-dependent relationships to land use in agricultural ecosystems. The results of this study indicated that species richness depends on the pattern of arable land use at large scales, which may relate to the regional species pool. Meanwhile, species evenness depended on the level of field edge density at small scales, which relates to how the nearby farmland was divided by the edges (e.g. many small-scale fields with high edge density or a few big-scale fields with low edge density). This implies that it is important to manage the biodiversity of buffer strips within a landscape context at multiple scales.

Nomenclature: Hämet-Ahti et al. 1998.

Question: What are the long-term implications of former fertilisation for the ecological restoration of calcareous grasslands?

Location: Gerendal, Limburg, The Netherlands.

Methods: In 1970, ten permanent plots were established in just abandoned agricultural calcareous grassland under a regime of annual mowing in August. From 1971 to 1979, two different fertiliser treatments were applied twice a year to a subset of the plots (artificial fertiliser with different proportions of nitrogen and phosphorus). The vegetation of the plots was recorded yearly and vegetation biomass samples were taken for peak standing crop and total amounts of nitrogen, phosphorus and potassium. Species composition and floristic diversity were analysed over the research period (1970–2006) and between the treatments, including the use of multivariate techniques (Detrended Correspondence Analysis).

Results: In terms of species number, there is a clear optimum 10 to 20 years after fertilisation has been terminated. Afterwards, there is a slow decrease; no new species appear and species of more nutrient-rich conditions gradually disappear. For the fertilised plots that received a relatively high proportion of N, effects are found only in the first years, whereas, for the plots that received a relatively high proportion of P, long-term after-effects are found in species composition, peak standing crop, total amounts of phosphorus in biomass, and in soil phosphorus data.

Conclusions: The effect of artificial fertiliser with a large amount of nitrogen disappears in less than ten years when mown in August, including removal of the hay. This is a promising result for restoration of N-enriched calcareous grasslands, as the applied dose of nitrogen in this experiment largely exceeds the extra input of nitrogen via atmospheric deposition. Application of fertiliser with a large amount of phosphorus, however, has effects even more than 25 years after the last addition. There are no prospects that this effect will become reduced in the near future under the current mowing management.

Nomenclature: van der Meijden (2005) for vascular plant species and Schamineé et al. (1996) for plant communities.