Françoise Rozé

Resistance of Atlantic Heathlands to trampling in Brittany (France): influence of vegetation type, season and weather conditions.

As a result of the large increase in tourist pressure, trampling has become an important factor in the degradation of natural areas and particularly Atlantic Heathlands. In this study, the resistance of dry and mesophilous heathlands was studied experimentally, under different environmental conditions. The trampling was applied in winter, and in summer in periods of wet and dry weather. The types of heathlands studied appeared to be moderately resistant to trampling. Mesophilous heathlands were on the whole more sensitive to trampling than dry heathlands. The resistance of these communities and of their component species varied greatly in relation to season and weather conditions. For example, Erica ciliaris was more resistant to trampling in summer than in winter, and in summer Erica cinerea was more sensitive to trampling in wet weather than in dry conditions. The analysis of the resistance of species showed that heather species were more sensitive than the rest of the plant cover. These heathers are characteristic species of the heathlands that were studied. The definition of acceptable visitor pressure thresholds must not be based on the index of resistance of the whole community, but on that of the characteristic species, in this case heathers. The aim of visitor pressure management must be to preserve the vegetation structure and not just simply plant cover.

Long-term effects of trampling on Atlantic Heathland in Brittany (France): resilience and tolerance in relation to season and meteorological conditions

Abstract In recent decades, human trampling has become an important factor in the degradation of Atlantic heathlands. In a previous paper we showed that short-term responses of heathland to trampling were dependant on environmental parameters such as season and weather conditions (Gallet, S., Roze, F., 2001b. Resistance of Atlantic Heathlands to trampling in Brittany (France): influence of vegetation type, season and weather conditions. Biological Conservation, 97, 189–198). Here, long term responses of experimental trampling, characterised by the resilience and the tolerance of communities and plants appear also dependant on these parameters. Dry and mesophilous heathlands are more tolerant to trampling in winter than in summer. In the case of mesophilous heathland, this is linked to high plant resilience, especially of Erica ciliaris . In summer, influence of meteorological conditions at the time of trampling depend on the species; indeed wet conditions lead to lower tolerance of Erica cinerea but to higher tolerance of E. ciliaris . Management of tourist pressure on natural or semi-natural sites must take visitors on the more tolerant communities, so it must take into account the variability of tolerance to trampling of the different types of vegetation present and needs to be adaptable to environmental conditions.

Relationships between soil seed bank, vegetation and soil fertility along an urbanisation gradient

ABSTRACT Questions: How does urbanisation influence soil mineral nitrogen stocks (nitrate and ammonium stocks) and what are the consequences of these modifications on the functional diversity of the herbaceous vegetation (vascular plants) and the seed bank? Location: Nine study sites were located on an urbanisation gradient in the city of Rennes, France. Methods: Three urbanisation levels were defined: urban areas (high grey/green ratio,), suburban (medium grey/green ratio) and periurban (low grey/green ratio). For each urbanisation level, nitrates and ammonium stocks were quantified; the herbaceous vegetation was surveyed as well as the soil seed bank (using the seedling emergence method). Results: Nitrate concentration increased with urbanisation (the nitrate level in urban plots was twice the concentration in periurban ones) whereas the ammonium level was higher in periurban areas than in urban areas. In urban plots, the vegetation and the seed bank were more nitrophilous, whereas the nitrogen requirement was lower for periurban species. The relationship between the seed bank and the above-ground vegetation was not significant. Conclusions: The higher nitrate concentration in the urban area appeared to be related to higher concentrations of atmospheric pollutants found in this area and lower ammonium levels may be related to the higher temperature in urban areas (leading to higher nitrification rates). The shift in the composition of the seed bank and vegetation appeared to be a consequence of higher nitrate stocks. The dissimilarity between the seed bank and vegetation may be caused by enhanced emergence of nitrophilous species in urban areas. Nomenclature: Flora Europaea (Tutin et al. 1964–1980).

Conservation of heathland by sheep grazing in Brittany (France): Importance of grazing period on dry and mesophilous heathlands

Abstract Heathlands are characteristic semi-natural ecosystems of western Europe. Nowadays they are threatened because of their lack of agricultural value. Management of the remaining heathland areas necessitates precise knowledge about different management tools that can be used, including grazing. The effects of sheep grazing on dry and mesophilous heathlands of Brittany were studied in relation to grazing season and duration. Management aims were to control shrubs and to maintain the dominance of heathers. The grazing pressures applied here were quite high, about 10–15 sheep ha −1 yr −1 . Erica ciliaris appeared to be very sensitive to grazing at the end of summer. This implicates special care in the management of mesophilous heathland. In dry heathland, Erica cinerea did not show this sensitivity. Control of shrubs was achieved by most grazing regimes which led to a decrease of 11–22 cm in gorse height, except summer grazing which seemed to stimulate their growth.This study underlined the relevance of the use of sheep grazing as a heathland management tool but also the necessity of prior experiments to adapt these operations mainly in terms of grazing period to the type of heathland and the objectives put forward.

Sustainable management of fixed dunes: example of a pilot site in Brittany (France)

The sand-dunes of Quiberon was chosen as a pilot site to investigate experimentation in conservatory management. Sand burial is necessary to conserve the semi-fixed dune which is a transitory dynamic stage. In the fixed dune, low disturbances benefit the vegetation diversity while heavy ones create serious injury. An opening of the milieu can restore very fast but a naked substrate is difficult to heal. The deposition of gorse branches is then efficient to facilitate the restoration. The fixed dune biodiversity is linked to human activities. Disturbances, natural or not, may be used as management tools.

Ecological study of pine forest clearings along the French Atlantic sand dunes: perspectives of restoration.

The 18th century afforestation campaign carried out in western France to fix sand dunes has left only a small surface of non-forested dunes. As dune plantations have only a small conservation value, it would be of great interest to restore grey dunes. But, for the moment, there is no proof that pine felling would lead to grey dunes. So, a study has been carried out on pine forest clearings along the French Atlantic shoreline. Floral and ecological data were carried out and analysed with two statistical tools, CA (canonical analysis) and CCA (canonical correspondence analysis). The clearings appear very different from one bank of the Gironde river to the other. South of the river, the clearing vegetation develops on acid soils and possess some thermophilous species. North of the river, the clearings are composed mostly of species growing best on calcareous soils. Apart from geographical variations, clearings showed two patterns of response: development of closed thickets and tall heathlands; or an open vegetation similar to growing heathlands and grasslands. The cover, the height, the floral richness per strata as well as pedological characteristics are the parameters which explain the best floristic composition of pine clearings. The vigour of pine forests and the degree of exposure to coastal influences determine whether close or open vegetation develops. Where there is an open vegetation, restoration of grey dunes may be possible. In the other case, alternative solutions, such as the restoration of dune woodlands or dune heath, may provide best conservation values.

A Study of the Dynamics of the Seed Banks in a Complex Dune System, with the Aim of Restoration

Abstract To assess the possibility of restoring the original plant community of grey dune from a pine plantation, a synchronic study of the seed banks of three habitats, the grey dune, the pine plantation, and a clearing, was conducted at Quiberon (France). Five stations were selected: a Grey dune, Pine plantation 1, Pine plantation 2, Clearing 1, and Clearing 2. In contrast to the pine plantations, clearing 1, subject to heavy human disturbance, had a great similarity between its seed banks and its established vegetation. The larger clearing (C2) tend to resemble the grey dune, whereas the other was dominated by ruderal species. The analysis of the seed banks demonstrated differences between the clearings and the pine plantations from which they were derived. The potential vegetation of the clearings was closer to that of the grey dune and had a larger number of species with a short life cycle than the pine plantations. The seed banks of the pine plantations were not similar to that of the grey dune, but also differed from that of closed vegetation. This study suggested that it may not be possible to obtain a short term restoration of a grey dune after just clear felling only with the help of seed banks. On the other hand, seed dissemination could facilitate a restoration in a larger time scale as for clearings.

Etude des successions après abandon des pratiques culturales en Bretagne

Summary Our study is concerning with plant succession in neglected fields and grasslands, using diachronic and synchronic analysis. It is aiming to build dynamic series and to characterize the ecological parameters during these successions. Two spatial scales and two temporal scales is used: on one hand, the bocage landscape scale for long term analysis and on the other hand the parcel scale for short term studies on permanent plots and on permanent lines. Dynamic processes occur very rapidly, using two strategies: by marginal growth from the hedges and by patch growth into the parcel. Various succession scenarios have been observed. They are depending on the parcel history (particularly its original state before abandonment) and also on the biotic environment of the parcel. Most of the plant succession theories can be applied to recolonization of neglected lands.

Réponses d'une lande atlantique au piétinement expérimental

Abstract Trampling responses of an Atlantic heathland dominated by furzes were experimentally determined. They concerned two levels of biological systems: the vegetal community level (community scale) and the species level (intracommunity scale). Two trampling experiments were conducted: the first one was carried out in summer and the second one in winter. Heathland was trampled over 4 months, at differents intensities: 10, 30 and 90 persons a day. Whether trampling was conducted in the summer or in the winter, immediate responses of heathland (community scale) were similar: resistance of this vegetal community did not vary with the trampling season. Responses also showed that there is no linear relationship between vegetation degradation and trampling intensity. Deferred vegetation responses were similar, but within the community heathland (intracommunity scale) responses of a taxonomic group can depend on the trampling season. For example, resilience of furzes trampled in winter was greater than resilience of furzes trampled in summer. All these results should be considered in order to establish management orientations of trampled heathlands.