Modelización de la riqueza de aves mediante redes neuronales para la gestión forestal a escala de paisaje

For preserving biodiversity of European-Mediterranean forest ecosystems in current and future scenarios of global change by means of sustainable forest management it is necessary to determine how environment and forest characteristics correlate with biodiversity. For this purpose, neural networks were used to model forest bird species richness as a function of environment and forest structure and composition at the 1x1 km scale in Catalonia (NE Spain). Univariate and multivariate models respectively allowed exploring individual variable response and obtaining a parsimonious (ecologically meaningful) and accurate neural network. Forest area (with a canopy cover above 5%), mean forest canopy cover, mean annual temperature and summer precipitation were the best predictors of forest bird species richness. The resultant multivariate network had a good generalization capacity that failed however in the locations with highest species richness. Additionally, those forests with different degrees of canopy closure that were more mature and presented a more diverse tree species composition were also associated with higher bird species richness. This allowed us to provide management guidelines for forest planning in order to promote avian diversity in this European-Mediterranean region.Para preservar la biodiversidad de los ecosistemas forestales de la Europa mediterránea en escenarios actuales y futuros de cambio global mediante una gestión forestal sostenible es necesario determinar cómo influye el medio ambiente y las propias características de los bosques sobre la biodiversidad que éstos albergan. Con este propósito, se analizó la influencia de diferentes factores ambientales y de estructura y composición del bosque sobre la riqueza de aves forestales a escala 1x1 km en Cataluña (NE de España). Se construyeron modelos univariantes y multivariantes de redes neuronales para respectivamente explorar la respuesta individual a las variables y obtener un modelo parsimonioso (ecológicamente interpretable) y preciso. La superficie de bosque (con una fracción de cabida cubierta superior a 5%), la fracción de cabida cubierta media, la temperatura anual y la precipitación estival medias fueron los mejores predictores de la riqueza de aves forestales. La red neuronal multivariante obtenida tuvo una buena capacidad de generalización salvo en las localidades con una mayor riqueza. Además, los bosques con diferentes grados de apertura del dosel arbóreo, más maduros y más diversos en cuanto a su composición de especies arbóreas se asociaron de forma positiva con una mayor riqueza de aves forestales. Finalmente, se proporcionan directrices de gestión para la planificación forestal que permitan promover la diversidad ornítica en esta región de la Europa mediterránea

Increasing crop heterogeneity enhances multitrophic diversity across agricultural regions

International audienceAgricultural landscape homogenization has detrimental effects on biodiversity and key ecosystem services. Increasing agricultural landscape heterogeneity by increasing seminatural cover can help to mitigate biodiversity loss. However, the amount of seminatural cover is generally low and difficult to increase in many intensively managed agricultural landscapes. We hypothesized that increasing the heterogeneity of the crop mosaic itself (hereafter “crop heterogeneity”) can also have positive effects on biodiversity. In 8 contrasting regions of Europe and North America, we selected 435 landscapes along independent gradients of crop diversity and mean field size. Within each landscape, we selected 3 sampling sites in 1, 2, or 3 crop types. We sampled 7 taxa (plants, bees, butterflies, hoverflies, carabids, spiders, and birds) and calculated a synthetic index of multitrophic diversity at the landscape level. Increasing crop heterogeneity was more beneficial for multitrophic diversity than increasing seminatural cover. For instance, the effect of decreasing mean field size from 5 to 2.8 ha was as strong as the effect of increasing seminatural cover from 0.5 to 11%. Decreasing mean field size benefited multitrophic diversity even in the absence of seminatural vegetation between fields. Increasing the number of crop types sampled had a positive effect on landscape-level multitrophic diversity. However, the effect of increasing crop diversity in the landscape surrounding fields sampled depended on the amount of seminatural cover. Our study provides large-scale, multitrophic, cross-regional evidence that increasing crop heterogeneity can be an effective way to increase biodiversity in agricultural landscapes without taking land out of agricultural production

Factores determinantes de la riqueza, distribución y dinámica de las aves forestales a escala de paisaje en Cataluña: implicaciones para la gestión forestal sostenible

Resumen de Tesis Doctoral. Departamento de Ingeniería Agroforestal, Escuela Técnica Superior de Ingeniería Agraria, Universidad de Lleida. Julio de 2009. Dirección: Santiago Saura y Lluís Brotons

La connectivité biologique des prairies permanentes dépend-elle de la structure des paysages?

National audienc

La connectivité biologique des prairies permanentes dépend-elle de la structure des paysages?

National audienc

Disentangling community assemblages to depict an indicator of biological connectivity: A regional study of fragmented semi-natural grasslands

International audienceUnder the current context of global change that largely threatens overall biodiversity in increasingly fragmented landscapes, more insights are needed into the drivers of biological connectivity between communities (i.e. the flow of species among a set of local communities responding to landscape structure). This study aims at estimating an indicator of regional biological connectivity of semi- natural grasslands from the expected correlation between the degree of community assemblage (i.e. composition similarity) and landscape features directly related to dispersal among local communities. Large-scale plant distributions characterizing semi- natural grassland communities were gathered from the atlas of Brittany flora (NW France; UTM grid of 10 km × 10 km). The analysed variables were computed considering the focal UTM square and its immediate neighbours, and the modelling encompassed different regression techniques accounting for spatial autocorrelation [Simultaneous Autoregressive (SAR) error models] and non-stationarity [Geographically Weighted Regressions (GWR)]. The degree of community assemblage allocated to biological connectivity was 10.4% (adjusted-R2); it was mainly correlated to decreasing hedgerow length and secondly to increasing structural connectivity of semi- natural grasslands once spatial autocorrelation was accounted for. The estimation of the indicator of biological connectivity (0.05 ± 0.01 from the SAR models) were improved when considering non-stationarity issues, particularly for the Eastern part of Brittany (up to 0.12 in terms of biological connectivity). Overall, the proposed indicator and estimation methodology represent a step ahead in connectivity analysis at the community level, potentially relevant in the detection of hotspots of biological connectivity which can help buffer current large-scale biodiversity threats due to global change

Species richness of woody plants in the landscapes of Central Spain: the role of management disturbances, environment and non-stationarity

International audienceQuestions: How important is management disturbance on gamma species richness of woody plants at intermediate landscape scales? How is species richness related to other climatic and biotic factors in the study area? How does the assumption of spatial stationarity affect assessment of relationships among species richness and explanatory variables (e.g. management, biotic and climatic factors) across extensive study areas? Location: Central Spain (regions of Castilla y Le ' on, Madrid and Castilla-La Mancha). Scale: Extent: 150 000km2. Grain: 25km2 (5x5-km cells). Methods: Information from 21 064 plots from the 3SNFI was used to evaluate richness of tree and shrub species at intermediate landscape scales. In addition to variables well known to explain biodiversity, e.g. environmental and biotic factors, effect of management treatments was evaluated by assessing clearcutting, selection cutting, stand improvement treatments and agrosilvopastoral systems (dehesas). Results from GWR techniques were compared with those from OLS regression. Results: Patterns of gamma species richness, although strongly affected by both environmental and biotic variables, were also significantly modified by management factors. Species richness increased with percentage of selection cutting stands and improvement treatments but decreased with percentage of clearcutting stands. Reduced species richness of woody plants was associated with agrosilvopastoral practices. Species richness for trees was closely related to basal area, annual precipitation and topographic complexity; species richness for shrubs was closely related to topographic complexity and agrosilvopastoral systems. Most relationships between species richness and environmental or biotic factors were non-stationary. Relationships between species richness and management effects tended to be stationary, with a few exceptions. Conclusions: Landscape models of biodiversity in Central Spain were more informative when they accounted for effects of management practices, at least at intermediate scales. In the context of current rural abandonment, silvicultural disturbances of intermediate intensity increased gamma species richness of woody plants. Exclusion of factors such as agrosilvopastoral systems from models could have led to spurious relationships with other spatially co-varying factors (e.g. summer precipitation). Patterns of spatial variation in relationships, provided by GWR models, allowed formulating hypotheses about potential ecological processes underlying them, beyond generalizations resulting from global (OLS) models

Effects of connectivity on animal-dispersed forest plant communities in agriculture-dominated landscapes

International audienceQuestions: How does connectivity affect animal-dispersed plant assemblages in woodlots of agriculture-dominated landscapes? Is this effect dependent on zoochorous dispersal modes? Location Long-Term Socio-Ecological Research (LTSER) site of "Zone Atelier Armorique" (ca. 150 km(2)), Brittany, western France.Methods: We sampled 26 small post-agricultural woodlots embedded in an agricultural matrix (1-7 ha). We assessed the connectivity of each woodlot using habitat reachability metrics (i.e. Proportion of Total Potential Dispersal Flux in the Landscape) calculated along a range of dispersal distances from 100 to 1,500 m. This metric was based on graph theory and was calculated as a function of landscape matrix permeability to animal movement (i.e. seed plant dispersal vectors). We analysed the composition of plant assemblages in the core and margins of woodlots. We calculated the proportion of species richness and cover of zoochorous species within these assemblages and for specific zoochorous modes (i.e. epi-, endo- and dys-zoochorous species). We analysed the effects of Proportion of Total Potential Dispersal Flux at different dispersal distances and woodlot sizes on the functional dispersal structure of the plant community using linear models.Results: We demonstrated that overall plant zoochorous assemblages only depend on woodlot size in the range of dispersal distances tested. The proportion of richness of zoochorous species within the community increased with habitat size. Connectivity influenced only the relative proportions of the different zoochorous modes, except for the dys-zoochorous group, which was primarily influenced by woodlot size. Both epi-zoochorous and endo-zoochorous species were impacted by the interaction between connectivity and woodlot area. Connectivity increased the proportion of epi-zoochorous species richness and the proportion of endo-zoochorous cover in assemblages in large woodlots. These effects were detected at short dispersal distances. Our results were supported in both total and core plant assemblages.Conclusion: This study indicates that both habitat isolation and decrease in habitat size contribute towards shaping the functional structure of the plant community, but they act at different levels of dispersal mode. Our results suggest that in these fragmented landscapes long-distance dispersal has been lost either because of the selection of small-sized animal movements or of the rareness of plant species needing large habitat size. Maintaining woodlot connectivity in the woodland surroundings seems to be sufficient to preserve short-distance dispersal, although a more thorough restoration of landscape connectivity is necessary to recover the functional composition of the community with the whole set of dispersal patterns

Assessing the role of landscape connectivity in recent woodpecker range expansion in Mediterranean Europe: forest management implications

International audienceWoodpecker species have significantly expanded their ranges in the last decades of the twentieth century in Mediterranean Europe, which seems to be closely related to forest maturation following large-scale decline in traditional uses. Here we assess the explicit role of forest landscape connectivity in the colonization of the Great Spotted Woodpecker (Dendrocopos major) and the Black Woodpecker (Dryocopus martius) in Catalonia (NE Spain). For this purpose we combined data on breeding bird atlas (10 9 10 km; 1980-2000) and forest inventories (c. 1 9 1 km, 2000). Forest connectivity was measured through graph theory and habitat availability metrics (interand intra-patch connectivity) according to species median natal dispersal distances. The best regressions from a set of alternative models were selected based on AICc. Results showed that connectivity between areas of mature forests [diameter at breast height (dbh) >= 35 cm] affected Black Woodpecker colonization events. The probability of colonization of the Great Spotted Woodpecker was greater at localities near the sources of colonization in 1980 and with a high connectivity with other less developed forest patches (dbh < 35 cm). The spatial grain at which landscape connectivity was measured influenced the model performance according to the species dispersal abilities, with the species with the lower mobility (D. major) responding better to the forest connectivity patterns at finer spatial scales. Overall, it seems that both species could expand further in European Mediterranean forests in upcoming years but at slower rates if landscape connectivity according to species requirements does not continue to increase. Hence, a proactive and adaptive management should be carried out in order to preserve these species while considering the related major impacts of global change in Mediterranean Europe

Agricultural landscape composition as a driver of farmland bird diversity in Brittany (NW France)

International audienceIn agriculture-dominated landscapes, agricultural intensification and associated landscape homogenization have caused large declines in farmland biodiversity. This study was aimed at determining how agricultural landscape composition drives community diversity and composition of farmland birds in the characteristic bocage landscape in Brittany (NW France) on a broad scale. Using bird atlas data from the region (2004–2008; 10 x 10 km), we analyzed the importance of different components of agricultural landscape composition (types of crops, amount of semi-natural covers and elements, and artificial lands) on the alpha diversity and beta diversity of farmland birds of different functional groups, defined depending on the degree of farmland specialization and ecological requirements. Agricultural landscape composition features explained a small amount of variation in alpha and beta diversity, particularly for specialists and residents. Cereal crops were negatively correlated with alpha diversity of all the functional groups considered whereas rotational grasslands were negatively associated with migrant and insectivorous alpha diversity. Although shrublands are not common in Brittany, they were positively associated with the occurrence of some species and particularly with alpha diversity of all the functional groups but specialists and residents. At the spatial grain of analysis, community composition was mainly driven by a gradient of alteration of the bocage.To conclude, we claim for the consideration of regional idiosyncrasies in far-reaching planning schemes to prevent future biodiversity loss in agriculture-dominated landscapes due to agricultural intensification. In view of the observed large-scale trends gathered from atlas data analysis and the small amount of explained variation, we also advocate for subsequent finer scale bespoke surveys to determine the biodiversity status associated with the valuable bocage agricultural landscape