F. Romane

Forest management and plant species diversity in chestnut stands of three Mediterranean areas

Over many centuries, chestnut fruits had an important role as food, while chestnut wood was used for local purposes. Today sweet chestnut stands are very common around the western Mediterranean Basin, and it is necessary to analyze the dynamic of plant species diversity in different chestnut stand types (groves and coppices) to guide management strategies that will allow the conservation of biodiversity. Our objective was to analyze consequences on plant species diversity of various management strategies in chestnut stands of three Mediterranean areas, Salamanca (Spain), the Cevennes (France), and Etna volcano (Italy). We found that plant species diversity is different according to management types; it is higher in groves than in coppice stands. We also demonstrated that Castanea sativa cultivated groves were characterized by small heliophillous therophytes. C. sativa abandoned groves, mixed C. sativa-Quercus pyrenaica coppice stands, Q. pyrenaica coppice stands, and young C. sativa coppice stands were characterized by hemicryptophytes with anemochorous dispersal mode and chamaephytes. Medium and old C. sativa coppice stands (that differ by the shoot age) were characterized by phanerophytes with zoochorous dispersal mode. Human perturbations maintain a quite high level of species diversity. In contrast, the abandonment of chestnut stands leads to homogeneous vegetation with decreasing diversity. One solution could be to maintain a landscape mosaic constituted of diverse chestnut stands modified by human activities (groves, cultivated or abandoned, and coppice stands). This could enhance regional plant diversity.

Impact of soil surface disturbances on functional group diversity after clear-cutting in Aleppo pine (Pinus halepensis) forests in southern France

Abstract The objective of this study was to analyze soil surface disturbances resulting from logging tractors, of different types (skidder and forwarder), used for clear-cutting in natural Aleppo pine forests and their consequences on plant species and functional group diversity. Results indicate that shallow disturbances (litter left in place or removed) were more frequent than deep disturbances (topsoil removed, subsoil exposed, rut exposed) regardless of the logging tractor used. The forests with previously cultivated terraces were the least disturbed. Moreover, with the aid of a functional group analysis we distinguished four plant species response groups to soil surface disturbance types. The mosaic created by these groups after clear-cutting and log removal probably contributes to a rapid auto-regeneration of a mixed plant community similar to that existing just prior to the clear-cutting.

Dynamics of holm oak (Quercus ilex L.) coppices after clearcutting in southern France

Holm oak (Quercus ilex L.) forest is one of the most widespread biocoenoses in the southern part of France. Until recently, clearcutting of wood for domestic use was carried out every 20 years or so in these coppice stands. In order to study coppice stand dynamics after cutting this paper presents results of observations of some items describing the vegetation structure, the floral composition, and the life cycles in a holm oak coppice stand during a six year period after clearcutting. One of the questions addressed in this study was whether these coppice stands reach a ‘steady’ state based on auto-succession, or if they continue to change. The results of the floristic changes after cutting suggest that the model of auto-succession best fits with the vegetation dynamics, even if changes in the density and life cycles of herbaceous species still exist six years after clearcutting.

Local characterization of vegetation through growth forms: Mediterranean Quercus ilex coppice as an example

Growth forms are considered from two viewpoints: a descriptive and a functional one. Mono-character growth forms and their biological spectra were used to test whether they can characterize certain underlying processes in Quercus ilex coppice in southern France. Correspondence analysis of 35 mono-character growth forms of 203 described taxa shows that location of renewal buds is a good integrating indicator of plant adaptations to the environment. Two of these characters (renewal bud location, i.e. Raunkiaers main life forms, and leaf consistency) appear to vary significantly along a gradient of increasing environmental constraints, especially climatic ones.

Essai de synthèse sur la dynamique actuelle des châtaigneraies cévenoles et ses conséquences sur la diversité végétale

Abstract The present vegetation of the Cévennes mountains (southern France) dominated by sweet chestnut (Castanea sativa) is an outcome of an uninterrupted and frequently intense human influence existing since millennia. It is very different from the deciduous Downy oak (Quercus pubescens) forest which occupied the area at the end of the last glaciation, during a period when climate was quite similar to present day conditions in this subhumid, mid-altitude Mediterranean climate bioregion. Since human impact has been drastically decreasing for the last half century, but especially in recent years, possible vegetation trends can be envisioned for this formerly chestnut-dominated vegetation built on steep slopes and terraces. Based on experimental results in seed germination studies as well as on analysis of plant species diversity trends, we propose some possible trajectories and eventual ‘threshold crossings’ for the vegetation and landscapes of a region suffering rural exodus and agricultural abandonment. All new changes and trajectories have to be modelled taking into account a series of new constraints.