Abstract Functional traits are commonly used to calculate a wide array of functional diversity indices to infer different mechanisms of community assembly and species coexistence. Recently, the degree of interspecific covariation between multiple functional traits has been suggested as a mechanism influencing both species distributions and abundances in communities. However, empirical assessments of this theory along environmental gradients are still scarce due to the lack of an appropriate method and of sufficiently strong environmental gradients. Here we compare interspecific trait integration (ITI) across plant communities along a marked gradient of copper toxicity in the soil, using new multivariate and bivariate indices. This was achieved using the range of the eigenvalues of a principal component analysis on the traits of the species in a local community (multivariate ITI index) and the correlations between traits in local communities (bivariate ITI index). We show that the plant metal tolerance strategy (i.e. leaf metal content) is relatively independent from leaf economics, while negatively correlated to plant size. In addition, our results indicate a weak support for the expected general patterns of trait syndromes, such as the ‘leaf economics spectrum’ or the ‘leaf–height–seed’, at the whole‐community scale. This arises from an increase in multivariate trait integration along the soil copper gradient. The strongest trait integration is caused by an increase in the degree of association between certain traits on metal‐rich soils. The multivariate trait integration explains species richness better than other commonly used functional diversity indices. Our study highlights the power of ITI, as well as its complementarity to other functional diversity indices, to investigate the variation in functional strategies and their drivers along environmental gradients. The increase in trait integration with soil metal toxicity in plant communities supports that highly constraining environments select increasingly coordinated sets of functional traits, in turn possibly driving the decrease in species richness. Further studies should assess the generality and underlying physiological mechanisms of such ecological patterns.
variability in the morphology of soils across the hills. The levels of Cu and Co contents in soils were very high compared to forest soils. Total, available and mobile contents appeared significantly correlated. Multivariate analysis indicate that pH and TOC might be important factors regarding distribution of elements in soils (Figure 1).Typical Cu profiles show homogeneity, at « low » or high level of Cu, surface contamination or relative depletion MOBILITY OF CU AND CO IN METALLIFEROUS ECOSYSTEMS: comparison of soil profiles and experimental results
Recemment, l’Union europeenne a depose un projet de reforme de la Politique Agricole Commune (PAC). Parmi les projets de reformes, figure celle de reserver 7 % de l’espace occupe par les cultures sous labours a des surfaces d’interet ecologique. C’est dans ce contexte qu’une conference-debat s’est tenue a Gembloux le 9 novembre 2011. Des systemes similaires sont deja d’application dans plusieurs pays voisins, avec des modalites specifiques a chacun. A ce titre, les systemes suisses et francais ont ete presentes en vue d’en exposer les avantages et les limites. Ensuite, les arguments scientifiques en faveur d’une telle mesure ont ete presentes. Il apparait clairement que la creation d’elements semi-naturels dans l’espace agricole est de nature a y promouvoir la biodiversite, tant leur quantite que leur qualite devant etre considerees. Cette biodiversite est par ailleurs susceptible de rendre des services a l’agriculture elle-meme, notamment en termes de pollinisation des cultures et de controle des ravageurs. A l’heure actuelle, il subsiste une incertitude sur les surfaces qui seront eligibles pour atteindre ces 7 %. Cependant, sur base des divers scenarios envisageables, la part de la superficie agricole utile exercant une influence a priori favorable sur la biodiversite en Wallonie atteindrait 4,3 % en moyenne et seule une minorite des exploitations (moins de 20 %) atteignent le seuil des 7 % propose par l’Europe. Si le projet europeen est adopte, il sera donc important de considerer l’effort du secteur agricole pour le mettre en œuvre au travers d’une reconnaissance societale. Afin d’en optimiser l’impact pour la biodiversite, il faudra veiller a la qualite du reseau de surfaces d’interet ecologique et realiser un suivi effectif par rapport a des objectifs clairement fixes. La reussite passe par la mise en œuvre de mesures pertinentes, tant sur le plan economique qu’environnemental et social, afin que l’agriculture en ressorte plus durable et que l’erosion de la biodiversite soit stoppee.
An increasing number of agricultural transition initiatives are taking place, seeking more autonomy and resilience on the farms. This undeniably reshapes the landscape and the delivery of ecosystem services (ES). To date, little research includes the knowledge and perceptions of local communities on rural landscapes in agricultural transition. Yet, farmers shape the landscape and ES delivery, and local inhabitants are directly impacted. The present work aims at assessing the extent to which locals (local inhabitants and farmers) appreciate and view landscapes undergoing agricultural transitions. To do so, questionnaires were submitted to locals enquiring about appreciation and ES perceptions of transitioning landscapes. These landscapes were shown in manipulated photographs simulating an agroecological landscape, a conventional agriculture landscape, and landscapes including each isolated agroecological practice (resulting in six ‘scenarios’). In order to put locals’ perceptions in perspective, the same questionnaire was submitted to ‘ES experts’, and ES perceptions were compared to field-based ES measurements in agroecological and conventional parcels of the same study region. The results show that locals and ES experts appreciate and perceive these scenarios similarly. The agroecological scenario was seen as the most appreciated and the one delivering the most ES, while the conventional one was the least appreciated and seen as the one delivering the least ES. These perceptions of ES delivery partially correspond to the ES field measurements, which showed a similar productivity within agroecological and conventional parcels and more regulating ES in agroecological parcels. We discuss how our results call for the assessment of the multi-performance of agricultural systems in terms of ES rather than focusing on yield only, and how future research addressing agroecological transition should rely on integrated valuations and mixed methods to better embrace the complexity of such transitioning systems.
