Pollen signals of ground flora in managed woodlands

This paper explores the vegetation signals contained in the non-arboreal pollen and spore (NAPS) components of pollen assemblages from Tauber traps placed in woodlands subject to rotational cutting (coppicing) in lowland England. Sets of three Tauber traps were placed in compartments of different ages at multiple locations within each woodland for 1 year, and pollen assemblages recorded along with a vegetation survey using a modified pin-frame method in an area of 10 m radius around each trap array. Cluster analysis suggests that, as expected, the ground layer vegetation broadly reflects the different environmental conditions in the three woods, with the main subdivisions within woods apparently driven by changes in ground cover between the early and late stages of the coppice cycle. Non-arboreal pollen and spores (NAPS) assemblages group according to woodland of origin, with subdivisions which relate to pollen abundance but lack a simple relationship with years since cutting. Indices of Association between NAPS records and plant presence in the area around each array were calculated using presence–absence data for multiple distances of vegetation survey. All values tend towards an asymptote, which is interpreted as implying an effective source area for the single taxon presence–absence indicator values of ground flora taxa in coppiced woodlands on the order of a 10 m radius. Only four taxa, Poaceae, Ranunculus acris-type, Cyperaceae, and Scilla-type, have an Index of Association (A) greater than 0.5, implying that the presence of pollen can be interpreted in terms of the local presence of the relevant plant taxon with some confidence. Estimates of Pollen Productivity relative to Poaceae are presented for five taxa: Apiaceae, Asteraceae (Cardueae), Cyperaceae, Mercurialis perennis, and Scilla-type. Years since cutting does affect the ground vegetation and NAPS assemblage trapped in these woods, but that the effect is more clearly seen at an assemblage level in the vegetation than in the pollen assemblages. The interpretative significance of NAPS taxa does not seem to be in providing information about the local conditions around the sampling point, but in reflecting the ground flora of the wider woodland

Modern pollen-vegetation relationships in the Champsaur valley (French Alps) and their potential in the interpretation of fossil pollen records of past cultural landscapes

This study is an attempt to evaluate the relationships between the vegetation and the modem pollen rain as a contribution to palaeoecological research. Pollen analysis of surface moss polsters and floristic records has been undertaken for 51 sampling points distributed all over the study area (Champsaur valley, Hautes-Alpes, France), within different vegetation and land-use types and along a west-east altitudinal transect, ranging from 870 to 2200 in a.s.l. The pollen and vegetation data were analysed independently using numerical methods (clustering and correspondence analysis) to investigate how vegetation is reflected in pollen assemblages. There was a good agreement between classifications and ordinations of the two data-sets and a pollen-analytical separation of different types of human activities was found despite the major gradients related to altitude and soil moisture. Both the AP/NAP ratio and the major pollen type percentage ranges given for each vegetation type were however very wide because of the typical fine-scale mosaic of the landscape in this region. Detailed comparisons of the two data-sets showed consistent differences between vegetation and pollen assemblages. Misclassifications of some modem pollen spectra were mainly attributed to differential pollen representation between species, but also to the effect of various land-use practices on flowering and pollination of herbaceous plant taxa. Moreover these differences, as well as discrepancies with earlier published data from lowlands of southern France and other parts of western Europe, are promoted by complex pollen dispersal which characterizes mountain environments. Although an overlap of characteristics thus exists between pollen assemblages, we were able to recognize specific features and indicator pollen taxa have been identified for each natural, semi-natural and human-induced vegetation type. (c) 2005 Elsevier B.V All rights reserved

Dynamique du peuplement et activités agro-pastorales durant l’âge du Bronze dans les massifs du haut Champsaur et de l’Argentiérois

Des programmes de recherche pluridisciplinaires sur l’occupation du sol et le pastoralisme de la Préhistoire au Moyen Âge dans le sud du massif alpin sont menés, depuis 1998, sur les massifs du Haut Champsaur, de Freissinières et de l’Argentièrois (Hautes-Alpes). Des dix phases d’occupation et d'activité agropastorale mises en évidence (prospections pédestres et fouilles), entre 1600 et 2700 m d’altitude, trois se distinguent: la fin du Néolithique, l’âge du Bronze et la période médiévale. Au travers des premières données archéologiques et environnementales, cet article présente, depuis le milieu du IIIe millénaire au début du Ier millénaire, les grandes caractéristiques de l’occupation du sol mais aussi l’originalité et l’importance de l’activité humaine dans cette zone alpine. La fin du Néolithique et l’âge du Bronze correspondent à une multiplication des gisements archéologiques marquant de façon évidente une rupture dans la gestion de l'espace montagnard. Les paysages sont largement façonnés par les activités humaines et l’entretien des terres cultivées, des prairies et des alpages, paraît continu. À la lumière des données de terrain, l’une des évolutions qui apparaît sur les sites d’altitude durant cette période concerne l’apparition de structures pastorales bâties entre 2 067 et 2 303 m d’altitude (datation 14C).Since 1998, two multi-disciplinary research programmes have been running in the southern French Alps. Concentrating on the Haut Champsaur, Freissinières and the Argentières area, they study the settlement and economy from the prehistoric periods through to the middle ages. Ten phases of activity between 1 600 and 2 700 m have been identified as a result of prospection and excavation. However, three major phases of activity (often agro-pastoral in nature) stand out : the end of the Neolithic, the Bronze Age and the Medieval period. Integrating both archaeological and environmental evidence, this article presents the development of an original and intensely exploited landscape between the middle of the third millennium through to the beginning of the first millennium BC. The end of the Neolithic and the Bronze Age are characterised by an important increase in the number of sites that represent a change in the exploitation of the mountain zone. The landscape is affected by human activities that comprise the use of cultivated zones and the development of alpine pastures. One important development during this period is the appearance of pastoral structures between 2 067 and 2 303 m all dated by 14C

A palaeoecological perspective for the conservation and restoration of wetland plant communities in the central French Alps, with particular emphasis on alder carr vegetation

Wetland conservation and management are generally only based on present-day studies, without integrating historical considerations. However, wetlands contain palaeoecological archives that can provide accurate records of their own history. Our study aims at reconciling this paradox in the central French Alps, by reconstructing the past wetland diversity/richness and the controls of Holocene hydroseral dynamics, and by discussing on this historical basis their conservation, management and restoration. Previously published data, complemented by the palaeoecological study of a sedge mire, reveal three main stages in the regional hydroseral succession: initial aquatic plant communities (Nymphaea alba, Nuphar cf. lutea, Menyanthes trifoliata), carrs (Alnus glutinosa/incana, Salix spp., Thelypteris palustris), then sedge meadows (Cyperaceae, Poaceae, Lythrum salicaria…). This dynamic comprises (1) a classical evolution from open water bodies to treed wet communities, controlled by the relationships between sedimentation processes and climate, and (2) an unexpected return to herbaceous wet habitats mainly triggered by Subatlantic human-induced managements. Such recent changes induced in the studied region the decline of Alnus cf. glutinosa, the disappearance of Thelypteris palustris, and the extinction of the carr communities they constituted. The historically-based assessment of community naturalness and resilience appears critical for defining conservation priorities, refining management actions, and identifying baseline conditions for restoration initiatives. The main implications of our results are to reinforce conservation measures on the less impacted habitats and to increase the diversity/richness of isolated lowlandmires, notably by restoring alder communities in some of them