Variability of cutting regimes in small private woodlots of south-western France

Abstract

-The small scale forest holdings are very common in Europe, but their management is not well known. The classical principes of forest management and of silviculture being rarely applied, their management is often seen as purely opportunistic, and even chaotic. To overcome this first sight, a detailed analysis of management practices in six private woodlots from two municipalities in south western France was done, with semi-directive interviews of the owners and an dynamic analysis of a chronological series of aerial pictures. The "said" practices (from the interviews) and the "seen" practices (from the aerial pictures) were crossed in a GIS and allowed to build the chronology of logging operations in any points of the woodlots from 1938 to 2003. The data from interviews and from aerial pictures fit together provided useful complementary information. They showed that there were no permanent spatial management unit, the logged areas being defined according to the local and current conditions. The silvicultural strategies and their dynamic have been described. The spatial-temporal complexity of the social and technical factors of the logging decision was acknowledged as a key explanation of the discrepancy between these small scale silvicultural systems and the classical systems.coppice / fragmented forest / forestry practices / logging dynamic Résumé -Variabilité des régimes de coupes dans des taillis de petites forêts fragmentées du sud-ouest de la France. La petite propriété forestière est très commune en Europe, mais sa gestion est mal connue. Les grands principes d'aménagement et de sylviculture la pénétrant très peu, sa gestion est souvent perçue comme purement opportuniste voire chaotique. Pour dépasser cette première approche nous procédons à une analyses fine des pratiques de gestion dans six petits bois privés de deux communes du sud-ouest de la France, au moyen d'entretiens semi-directifs avec les propriétaires et d'analyses d'une série de photos aériennes. Une méthode d'interprétation dynamique des photos aériennes est mise en oeuvre. Les pratiques « dites », les pratiques « observées » et leur croisement dans un SIG permettent de décrire la suite des coupes réalisées en chaque point des six bois de 1938 à 2003. Les données issues des entretiens et des photos se contredisent rarement et se complètent utilement. Nous montrons qu'il n'existe pas d'unités de gestion permanentes, les unités de coupe étant définies de manière conjoncturelle. Nous décrivons les stratégies sylvicoles au moyen de plusieurs indicateurs et montrons leur évolution. L'étude met l'accent sur la complexité de l'organisation spatio-temporelle des coupes et des facteurs techniques et sociaux permettant de l'expliquer, et analyse la cohérence de stratégies sylvicoles en rupture avec les évolutions de la filière-bois internationale.taillis / forêt fragmentée / pratiques forestières / dynamique des coupes

Woody plant composition of forest layers: the importance of environmental conditions and spatial configuration

“…De Blois et al (2001) hypothesized that the absence of relationship for the tree layer was linked to the past disturbances and that trees had a lower response rate to edge effect, leading more to changes in density than in composition for this forest layer (Murcia 1995). In our forest fragments, forest edges are more frequently logged than forest interiors (De Warnaffe et al 2006). This may explain the discrepancies between our results and those of de Blois et al (2001).…”

“…Several works have shown that land-use history can have long-term effects on woody species composition (de Blois et al 2001;Bellemare et al 2002;Onaindia et al 2004). In our study area, previous works (Guyon et al 1996;De Warnaffe et al 2006) have shown a lengthening of cutting regimes which could also explain the distribution of the tree species in the upper and understory layers according to their shade tolerance.…”

“…Moreover, such differences between forest layer responses to environmental conditions could be linked to the vertical changes of physical parameters from field to canopy level, such as humidity or temperature (Cantlon 1953). However, given the importance of human activities in these forests (De Warnaffe et al 2006), the canopy layer may also reflect the influence of past or current management practices that can disrupt the correspondence between canopy composition and environmental conditions (Decocq 2000;de Blois et al 2001). For the canopy layer, the composition described by plot scores on axis 1 (CA of the canopy layer) differs from those found for the three understory layers.…”

“…Woody plant diversity and their driving factors are likely to be affected by forest logging interventions at the stand scale. Forest fragments in agricultural landscapes, particularly those owned by farmers, frequently pertain to several owners (Guyon et al 1996), and, as a consequence, different management practices can be found in a given forest fragment (De Warnaffe et al 2006).…”

Diversity of woody plant seedling banks under closed canopy in fragmented coppice forests

“…Indeed, increased light intensity is commonly found at open edges, a feature that is reversed as edges mature (Ranney et al, 1981). Our results are consistent with this statement, as we suspect that our edges are "open edges", as they are more frequently logged than woodlot interiors (De Warnaffe et al, 2006). Birddispersed species had higher seedling abundances at forest edges, consistently with previous work reporting higher densities of bird-dispersed species at edges (Ranney et al 1981).…”