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Toulouse, France

Alletto L.,Purpan Engineering School | Coquet Y.,French National Institute for Agricultural Research | Roger-Estrade J.,French National Institute for Agricultural Research
Soil Use and Management | Year: 2010

Soil physical properties are known to be variable as a result of tillage in both space and time; however, small-scale variations (<1-m) related to tillage are poorly characterized. In this study, morphological descriptions of soil structures created by tillage under conventional (CT) and conservation or mulch (MT) tillage are related to bulk density (Ρb) and hydraulic conductivity (K) measurements to determine causality and to predict the effects of tillage practices on these properties. Mouldboard ploughing in CT tended to create marked spatial heterogeneity in soil physical properties within the tilled layer, a finding well expressed in the results from morphological description. This method was much less applicable to MT due to a more homogeneous spatial distribution of soil physical properties. Under both tillage systems, rows had higher bulk density values and lower hydraulic conductivity than inter-rows. The global geometric mean of the saturated hydraulic conductivity was higher and more variable under CT than under MT (66 vs. 41-mm/h). Under each tillage system, zones with a high capacity to conduct water were identified (inter-furrows under CT with a mean KS of 720-mm/h, and soil zones with earthworm burrows and cracks in MT with a mean KS of 400-mm/h). In the untilled layer, higher K values were measured under MT than under CT (40 vs. 22-mm/h). The contrast in K between the tilled and the untilled layers was very limited for MT compared to CT where mouldboard ploughing resulted in marked contrast between both layers. The assessment of this small-scale variability in soil physical properties aids our understanding of water and solute movement through topsoil layers. © 2010 The Authors. Journal compilation © 2010 British Society of Soil Science.

Gossner M.M.,TU Munich | Lachat T.,Swiss Federal Institute of forest | Brunet J.,Swedish University of Agricultural Sciences | Isacsson G.,Swedish Forest Agency | And 5 more authors.
Conservation Biology | Year: 2013

With the aim of wood production with negligible negative effects on biodiversity and ecosystem processes, a silvicultural practice of selective logging with natural regeneration has been implemented in European beech forests (Fagus sylvatica) during the last decades. Despite this near-to-nature strategy, species richness of various taxa is lower in these forests than in unmanaged forests. To develop guidelines to minimize the fundamental weaknesses in the current practice, we linked functional traits of saproxylic beetle species to ecosystem characteristics. We used continental-scale data from 8 European countries and regional-scale data from a large forest in southern Germany and forest-stand variables that represented a gradient of intensity of forest use to evaluate the effect of current near-to-nature management strategies on the functional diversity of saproxylic beetles. Forest-stand variables did not have a statistically significant effect on overall functional diversity, but they did significantly affect community mean and diversity of single functional traits. As the amount of dead wood increased the composition of assemblages shifted toward dominance of larger species and species preferring dead wood of large diameter and in advanced stages of decay. The mean amount of dead wood across plots in which most species occurred was from 20 to 60 m3/ha. Species occurring in plots with mean dead wood >60 m3/ha were consistently those inhabiting dead wood of large diameter and in advanced stages of decay. On the basis of our results, to make current wood-production practices in beech forests throughout Europe more conservation oriented (i.e., promoting biodiversity and ecosystem functioning), we recommend increasing the amount of dead wood to >20 m3/ha; not removing dead wood of large diameter (50 cm) and allowing more dead wood in advanced stages of decomposition to develop; and designating strict forest reserves, with their exceptionally high amounts of dead wood, that would serve as refuges for and sources of saproxylic habitat specialists. © 2013 Society for Conservation Biology.

Mico E.,University of Alicante | Garcia-Lopez A.,University of Alicante | Brustel H.,Purpan Engineering School | Padilla A.,University of Alicante | Galante E.,University of Alicante
Biodiversity and Conservation | Year: 2013

Saproxylic beetle diversity is high at the Cabañeros National Park (central Spain), where woodland habitats exhibit remarkable heterogeneity. Our aim was to explain the diversity of saproxylic beetles, focusing on species turnover among mature woodland types. We surveyed five woodland types that represented the heterogeneity of the park's woodland habitats. Beetles were collected using window traps over a period of 20 months. The Jaccard Similarity Index was used as indirect value of beta diversity among woodlands and to test the relation between species turnover and geographical distance. We also identified the contribution of species turnover to landscape diversity by using a partitioning model. Moreover, the presence of mixed woodlands (more than one tree species) allowed us to attempt to valorise the effect of tree species (coupled with their historical management) on species turnover among woodlands. Finally, we looked for different saproxylic beetle preferences for habitat and tree species using an indicator value method. We found that saproxylic beetle species composition varied significantly among the studied woodlands. The variation in species turnover was independent from the distance among woodlands, which suggested that beetle dispersal abilities could not explain this high turnover. Tree species within woodlands were a key factor that increased diversity turnover in woodlands and, consequently, the diversity of the park. Moreover, we found saproxylic beetle species that had different habitat and tree species preferences. We conclude that woodland heterogeneity (highly affected by woodland composition) seems to be the driving force for saproxylic beetle diversity in this protected area. © 2013 Springer Science+Business Media Dordrecht.

Jacquin A.,Purpan Engineering School | Goulard M.,French National Institute for Agricultural Research
International Journal of Agricultural and Environmental Information Systems | Year: 2013

Fire is acknowledged to be a factor for explaining the disturbance of vegetation dynamics interacting with other environmental factors. In this study, the authors want to clarify the importance and the role of fire on the dynamics of savanna vegetation. The study area is the Marovoay watershed located on the north-west coast of Madagascar. In this site, burning herbaceous cover is the main practice in the extensive grazing system. They analyzed the relationship between two indicators, one related to vegetation activity changes and one about fire regime that results from a combination of fire frequency and seasonality. All indicators were measured between 2000 and 2007 using a time series of MODIS images. In this work, the authors implemented two approaches of spatial analysis. The first one analyzes the spatial structure of the residuals of a per-pixel non-spatial GLM model. In the second approach, a spatial GLM model is directly computed. In both approaches, the authors proposed two levels of stratification for the study area according to the spatial variations of the relationship established between vegetation activity changes and fire regime. The use of spatial statistical tools produced parsimonious models which they found to be consistent with expert knowledge. The authors demonstrated that a statistical analysis based on spatial GLM is able either to stratify an area when non ancillary data on land use exist or to validate an existing stratification. © 2013, IGI Global.

Bouget C.,IRSTEA | Larrieu L.,French National Institute for Agricultural Research | Larrieu L.,Center Regional Of La Propriete Forestiere Of Midi Pyrenees | Brin A.,Purpan Engineering School
Ecological Indicators | Year: 2014

Managing and monitoring forest biodiversity is challenging and rapid habitat assessment protocols should be developed to provide us with general key features based on field data. A rapid habitat assessment protocol was implemented over a wide forest gradient in France to analyze surrogacy patterns and performance consistency of presumed key attributes for saproxylic beetle diversity (large trees, microhabitat-bearing trees with trunk cavities, fruiting bodies of saproxylic fungi, tree crown deadwood and sap runs, large logs and snags) and of stand openness. Data compiled in this study include standardized deadwood and window-flight trapped beetle data from 313 plots in oak, lowland and highland beech, lowland pine, highland spruce-fir and mixed temperate forests throughout France. The most structuring factors for species richness and composition of saproxylic beetles were the density of cavity- or fungus-bearing trees and of snags, as well as the degree of openness in the 1-ha surrounding the stand. These key habitat features were nevertheless inconsistent over the different types of temperate forests, and for rare species vs. all species combined. No one variable robustly explained variations in species richness in the deciduous or conifer forest types. The influence of deadwood and "habitat trees" was affected by meso- and micro-climatic features. A significant effect of stand openness on saproxylic beetles was observed both in deciduous and in conifer forests, but only in lowlands. Effects on species richness due to an interaction between substrate availability and openness were observed in montane forests only. Our results point toward the relevance of ecological attributes in tracking changes in saproxylic beetle biodiversity in specific forest contexts, but our study failed to identify any universal structural biodiversity indicators which could be surveyed in part with data from national forest inventories and used to track progress in sustainable forest management or in the protection of sensitive areas. © 2013 Elsevier Ltd. All rights reserved.

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