Didier Alard

Towards sustainable land use: identifying and managing the conflicts between human activities and biodiversity conservation in Europe

Conflicts between biodiversity conservation and human activities are becoming increasingly apparent in all European landscapes. The intensification of agricultural and silvicultural practices, land abandonment and other land uses such as recreation and hunting are all potential threats to biodiversity that can lead to conflicts between stakeholder livelihoods and biodiversity conservation. To address the global decline in biodiversity there is, therefore, a need to identify the drivers responsible for conflicts between human activities and the conservation of European biodiversity and to promote the management of these conflicts. Here, the drivers of biodiversity conflicts are analysed in a European context for five habitat types: agricultural landscapes, forests, grasslands, uplands and freshwater habitats. A multi- disciplinary approach to conflict management is described, with active stakeholder involvement at every stage of conflict identification and management as well as a range of other approaches including stakeholder dialogue and education, consumer education, improvement of political and legislative frameworks, financial incentives, and planning infrastructure.

Nitrogen deposition threatens species richness of grasslands across Europe.

Evidence from an international survey in the Atlantic biogeographic region of Europe indicates that chronic nitrogen deposition is reducing plant species richness in acid grasslands. Across the deposition gradient in this region (2-44 kg N ha(-1) yr(-1)) species richness showed a curvilinear response, with greatest reductions in species richness when deposition increased from low levels. This has important implications for conservation policies, suggesting that to protect the most sensitive grasslands resources should be focussed where deposition is currently low. Soil pH is also an important driver of species richness indicating that the acidifying effect of nitrogen deposition may be contributing to species richness reductions. The results of this survey suggest that the impacts of nitrogen deposition can be observed over a large geographical range.

Permanent seed banks in chalk grassland under various management regimes: their role in the restoration of species-rich plant communities

A survey was carried out on four stands of a chalk grassland (open, intensively grazed, tall and scrub) in order to monitor the permanent soil seed bank under various management regimes responsible for the decline of the ecological interest of this ecosystem. There was no real similarity between the seed banks and the associated vegetation, except in the intensively grazed stand. When vegetation changes, seed banks appear to be quite stable and are mostly dominated by three species (Centaurium erythraea, Origanum vulgare, Hypericum perforatum). The seed bank seems to be quite useless in order to restore a species-rich community after both grazing intensification or abandonment. Because recolonization processes are the critical factor, the management of species-rich grassland has to be designed with a view to preserving a given plant community as well as to improving dispersion processes from a source to target areas.

Relationship between plant and soil microbial communities along a successional gradient in a chalk grassland in north-western France

Plant and microbial communities were compared through their structure and their functions in a chalk grassland in north-western France. Multivariate statistical analyses allowed us to establish floristic patterns and to identify four stages of succession from short grasslands to early stages of forest. In each stage, several measurements were made on vegetation (floristic data, biomass weight and lignin content), on soil (total carbon, soluble organic carbon, total nitrogen, polysaccharides and phenols contents, lignin content in litter) and on soil microbial communities (microbial biomass, functional structure assessed by using BIOLOG analysis, genetic structure of bacterial and fungal communities assessed by using Amplified Ribosomal DNA Restriction Analysis (ARDRA) for 16S and 18S rDNA: ARDRA 16S and 18S). Although the organic matter resources that support soil microbial communities are larger in older stages of plant succession (high plant and litter biomass and nitrogen content in plant leaves in forest stages), results show that biomass and potential level of enzymatic activity of microbial communities are negatively correlated with the presence of shrubs and positively associated with grassland habitats. These microbiological variables also present complex interactions with other factors and are positively correlated with soil humidity, soil soluble carbon and polysaccharides contents and negatively correlated with the presence of lignin in plant biomass and litter. The results show out that microbial communities are independent from the successional gradient of vegetation, in terms of functional (BIOLOG analysis) and genetic structure (ARDRA 16S and 18S). This study provides a first step in understanding the link between the biodiversity (number and type of plant species, genetic structure of microbial community) and function (biomass production, enzymatic catabolism) in chalk grassland ecosystems.

Diversity of plant assemblages in managed temperate forests: a case study in Normandy (France)

Abstract We investigate the patterns of variation of plant community diversity along a silvicultural cycle in a managed beech forest. A statistical model of the silvicultural cycle is constructed in order to identify: (i) the relationships between species and environmental factors, and (ii) species assemblages occurring along the successional gradient. We measure six diversity indices accounting for the structural (species richness (SR), Shannon index, evenness index), the functional (factorial diversity, FD) and the compositional dimension (similarity index within and between records) of biodiversity. We compare their patterns of variation along the succession in order to understand the different information provided by each index. The model reveals that species assemblages occurring in regeneration stands have the highest SR along the cycle. Species coexistence in these assemblages appears to be based on non-equilibrium mechanisms. On the other hand, mature stands with closed canopy seem to host the more organised communities reflecting true coexistence based on equilibrium mechanisms. We discuss the indicative values of the different diversity measures and their interest for the development of sustainable forest management. We advocate that conservation priorities should thus be defined in reference to the processes controlling biodiversity and to the taxonomic groups responding to these processes.

The impact of nitrogen deposition on acid grasslands in the Atlantic region of Europe

A survey of 153 acid grasslands from the Atlantic biogeographic region of Europe indicates that chronic nitrogen deposition is changing plant species composition and soil and plant-tissue chemistry. Across the deposition gradient (2-44 kg N ha(-1) yr(-1)) grass richness as a proportion of total species richness increased whereas forb richness decreased. Soil C:N ratio increased, but soil extractable nitrate and ammonium concentrations did not show any relationship with nitrogen deposition. The above-ground tissue nitrogen contents of three plant species were examined: Agrostis capillaris (grass), Galium saxatile (forb) and Rhytidiadelphus squarrosus (bryophyte). The tissue nitrogen content of neither vascular plant species showed any relationship with nitrogen deposition, but there was a weak positive relationship between R. squarrosus nitrogen content and nitrogen deposition. None of the species showed strong relationships between above-ground tissue N:P or C:N and nitrogen deposition, indicating that they are not good indicators of deposition rate.

Dynamics of rural landscapes and their main driving factors: A case study in the Seine Valley, Normandy, France

Land cover and landscape patterns dynamics over a 25 year period are analysed for a case study in Normandy. With the help of cartography, GIS and multivariate analysis, factors contributing to landscape structures and changes are studied. The results point out three main driving factors responsible for the landscape change: Agricultural practices which lead to intensification of some areas and abandonment of others, urbanisation which modifies the structure and organisation of the landscape, and finally, as factor of stability comes the conservation policies which check these changes in certain zones. Despite this last factor, the global resulting impacts are, up to now, the progressive disappearance of the organisation of the sites landscape.

Effects of tree canopy composition on earthworms and other macro-invertebrates in beech forests of Upper Normandy (France)

Summary The effect of canopy composition on soil macro-invertebrate communities in two deciduous temperate forests: a pure beech (Fagus sylvatica L.) and a mixed beech-hornbeam (Carpinus betulus L.) stand was investigated. The initial hypothesis was that heterogeneity of trophic resources within the mixed stand might increase diversity and heterogeneity of soil macro-invertebrate communities at stand level. The macrofauna was sampled in autumn and spring by hand sorting 121 (25 × 25 × 30 cm) soil monoliths regularly distributed within each stand. Earthworms were identified to species level while the remaining macro-invertebrates were identified to family level. Results were analysed by univariate and multivariate (PCA) statistical tools as well as a geostatistical tool. Few differences were observed when comparing the total macro-invertebrate density between sites and dates. In contrast, significant patterns were found for several taxonomic or trophic groups taken separately (e.g. Lumbricidae, detritivore and predator densities were significantly higher in the pure beech stand (PS). The first and the third PCA axes respectively revealed a site and a season effect while the second axis revealed a spatial segregation within the detritivore group as it distinguished high densities of Lumbricidae from those of Isopoda and Diplopoda. The variance of record scores on this axis measured for each site and date revealed that spatial variability of soil macrofauna communities was greater for PS on both dates than for MS. Semi-variance analysis performed on record coordinates on the second axis of the PCA revealed that only macro-invertebrate communities sampled under the pure stand in autumn were spatially structured (autocorrelation range about 32 m). These results do not support the general agreement that resource diversity and patchiness increases soil fauna biodiversity and heterogeneity.

Land use history and botanical changes in the calcareous hillsides of Upper-Normandy (north-western France): new implications for their conservation management

Abstract Historical studies were made of the changing land use (260–1995) of 14 calcareous hillsides in Upper-Normandy to investigate botanical changes over the last 200 years. Before the French Revolution in 1789, most of these hillsides were used as vineyards mixed with common sheep walks. After the French Revolution, they were distributed among inhabitants for cultivation (cereals) but they were abandoned in the nineteenth century and grazed again. Our results show that this history is correlated with important changes in the floristic composition of the calcareous hillsides between 1816 and 1995. The species richness of arable weeds and fallow-land species of former cultivated fields or vineyards decrease faster than that of chalk grassland species. The consequences of these long-term dynamics are discussed with regards to the ecological requirements and the rarity status of the species that have disappeared since 1935. We conclude with the need to take account of land use change processes, e.g. the alternation of arable fields and grasslands, to maintain the present species-richness of calcareous hillsides.

Spatial distribution of earthworm species assemblages in a chalky slope of the Seine Valley (Normandy, France)

The aim of this study was to characterize the spatial distribution of earthworm species assemblages on a chalky slope of the Seine Valley (Upper Normandy, France), with contrasting vegetation cover representing the different stages of a typical post-pastoral secondary succession. Samples were hand sorted in a spatially explicit design consisting of a regular grid. A Principal Component Analysis was performed to identify species associations. Maps of the factorial coordinates of sample points together with geostatistical analysis were used to describe the spatial structure of the assemblages. The first axis of the PCA opposed points with high density to others with low. The resulting spatial structure was significant. The second axis opposed points where species assemblages were dominated either by an endogeic (Allolobophora chlorotica), an anecic (Aporrectodea longa) and an epigeic species (Lumbricus castaneus) to others dominated by two endogeics (Aporrectodea rosea and Octolasium cyaneum). A significant spatial structure was detected, with alternating patches characterised by one species assemblage or the other. The location of these structures did not seem to be clearly associated with a specific vegetation type. These results revealed a complex determinism of species co-occurrence at small spatial scale.