Guy Pautou

Universal primers for amplification of three non-coding regions of chloroplast DNA.

Six primers for the amplification of three non-coding regions of chloroplast DNA via the polymerase chain reaction (PCR) have been designed. In order to find out whether these primers were universal, we used them in an attempt to amplify DNA from various plant species. The primers worked for most species tested including algae, bryophytes, pteridophytes, gymnosperms and angiosperms. The fact that they amplify chloroplast DNA non-coding regions over a wide taxonomic range means that these primers may be used to study the population biology (in supplying markers) and evolution (inter- and probably intraspecific phylogenies) of plants.

Historical influence of man on the riparian dynamics of a fluvial landscape

Mans influence, over the last three centuries, has gradually influenced the dynamics of forest cover along the valley of the Garonne, a seventh order river in Southern France. The vegetation cover of the floodplain depends on topographical levels which govern the frequency and duration of submergence during flooding. Along the valley, forest patches vary from a continuous ribbon of riparian wood along the river to a mosaic of groves towards the upland terraces. In the floodplain, the forest dynamics are influenced by floods, appear to be reversible, and are subject to dominant allogenic processes. On the contrary, forest dynamics on the terraces, which are not influenced by floods, are irreversible and subjected to dominant autogenic processes. Since the end of the 17th century, the structure of riparian woods has been modified by navigation and agriculture leading to a fragmentation of forest cover in the floodplain. Modern agriculture and urbanization have accentuated these tendencies by modifying the hydrologic regime of the river. These historical changes result in a fragmentation of forest cover and a substitution of species in the riparian zone, the forest dynamics being still reversible in the floodplain.

Success in the demographic expansion of Fraxinus excelsior L.

This review examines the ecological traits and ecophysiological characteristics of the common ash (Fraxinus excelsior L.) that help to explain the current spread of ash communities in Europe. As a consequence of anthropogenic disturbance, the common ash has experienced new environmental conditions and the frequency of the species has fluctuated over space and time. Owing to its ubiquity, over the last few decades the common ash has been greatly favoured in areas abandoned by agriculture and also along impounded rivers. F. excelsior is a mesophilic species that usually thrives on alluvial soils and can also survive the strong water deficit on hillslopes. Drought tolerance in ash trees is related to stomatal regulation, a decrease in osmotic potential and also an increase in the elastic modulus ε. Malic acid plays a central role in drought tolerance, first as one of the major solutes involved in osmotic adjustment, and second as an effector for stomatal regulation through a drought-induced increase in its xylem concentration.

Initial repercussions and hydroelectric developments in the French upper rhone valley: A lesson for predictive scenarios propositions

The authors demonstrate the difficulties inherent in predicting vegetation changes in floodplains affected by hydroelectric developments. The results are based on phytoecological studies in the Rhone River valley between Geneva and Lyon. The study is based in a 200-km stretch of river where the floodplain can attain 10 km in width. Vegetation is described for the area prior to the construction of four dams and compared with the situations 8 yr later. Research methods include systematic sampling of geomorphological, soils, and floristic factors; collection of a data base of spatial information; and large-scale vegetation mapping.

Phenology, growth and ecophysiological characteristics of Fallopia sachalinensis

Fallopia (Polygonum) sachalinensis (Polygonaceae) is native to the Far East from where it was introduced into Europe and Northern America. It has only recently appeared on the large alluvial plains of alpine rivers, while it has formed monospecific stands in many habitats. In this study, we investi- gated some of the biological characteristics of this species in order to predict its invasiveness under the specific environmen- tal conditions of alpine alluvia. When compared to other plants which tend to monopolize space, F. sachalinensis appears to have a life cycle characterized by an early seasonal develop- ment. It exhibits a high growth rate - ca. 4 to 5 cm/day, and its productivity is associated with intrinsic characteristics of the species: abundant leaf cover, the appearance of branches when the leaves reach an optimal size on the main stem, and favourable leaf orientation to capture high light intensity. Another morphological characteristic is the presence of a large medullary air cell containing a liquid rich in mineral salts which can be used by the plant when the demand for evaporation increases. Clonal spread associated with an ex- traordinarily high rate of proliferation of below-ground or- gans, and mechanisms for adaptation to adverse conditions are biological traits rendering F. sachalinensis an invader in alluvial plains along alpine rivers. There is a risk that such species experience a demographic explosion in the geographi- cal region under study.

Succession modeling of river floodplain landscapes

Abstract The spatial organization of ecological units that constitute river floodplains was modeled using a recent image synthesis method. The model combined a purely spatial process, the stochastic pyramid, with analytical descriptions of ecological successions observed on each landform of the fluvial landscape. Because the stochastic pyramid is a generator of non-homogeneous, anisotropic, multicolored and random patterns, based on concepts of mosaics, it could be articulated with a series of diagrams which related the seral successional states to the spatial configuration of ecological units. Modeling was performed in two steps. A priori probabilities were determined to transpose theoretical diagrams onto a processing image containing only the channel network of a real map; then after a random draw, a randomly textured image was obtained, this image was then transformed by the controlled stochastic pyramid in order to create a partition of wider regions without texture. As a result of this transformation, each colored pixel tended to expand and to incorporate its neighboring pixels that were randomly deleted. The model simulates various ecological maps of the same floodplain with both deterministic (fluvial network and ecological successions) and stochastic components (decimation and expansion rules).

New merging method of multispectral and panchromatic SPOT images for vegetation mapping

The French satellite SPOT is carrying two high resolution sensors. The first supplies 10-m panchromatic (0.51-0.73) data; the second supplies multispectral 20-m data (XS1 in the blue band 0.50 - 0.59, XS2 in the green band 0.61 - 0.69, XS3 in the near infra-red band 0.79 - 0.90). The multispectral and panchromatic merging processes are becoming current procedures for studying land covers and particularly for vegetation mapping which needs a good spatial resolution and a good spectral resolution respectively. The usually applied merging methods are more or less altering radiometric values of the original XS data. Original information is modified and, consequently, photointerpretation procedures are becoming awkward or really impossible so a new merging method has been performed. Thanks to the combined panchromatic image, this method is simulating 10-m images while conserving spectral properties of original XS 20-m images. This method uses two tools coming from the signal processing field and based on solid mathematical procedures: the multiresolution analysis and the wavelet transform. The results issued from this merging method are really promising. Analyses and thematic processings (i. e. production of thematic colour composite images) carried out from that high resolution data, have exhibited a significant improvement of imagery added to a great potential concerning vegetation mapping of the floodplains.