15 research outputs found
Does the type of silvicultural practice influence spruce budworm defoliation of seedlings?
Spruce budworm (Choristoneura fumiferana (Clem)) is the main defoliator in the boreal forest of North America, and its outbreaks have major ecological and economic consequences and represent a challenge for forest management. Numerous studies have addressed the effects of this defoliator on mature trees, whereas the effects of spruce budworm on regeneration remain elusive. Furthermore, intensive exploitation practices during the last decades have left a large area of the Canadian boreal forest in an early development stage. In this context, it becomes vital to understand those factors affecting the severity of spruce budworm-related defoliation on regeneration. Here, we determine the defoliation severity of black spruce and balsam fir seedlings in both mature pure black spruce and black spruce-balsam fir stands subjected to two different silvicultural treatments (clear-cutting and partial cutting). Defoliation intensity varied between stand types, silvicultural treatments, species, and height classes. Seedlings in black spruce-balsam fir stands experienced twice the defoliation of those in pure black spruce stands (black spruce seedlings 10% vs. 23%; balsam fir seedlings 29% vs. 47%, respectively). Harvesting methods also influenced seedling defoliation. Under clear-cutting, black spruce seedlings (24%) were three times as defoliated as black spruce seedlings in partial cutting stands (8%), whereas balsam fir seedlings in clear-cutting plots experienced twice the defoliation (42%) of balsam fir seedlings in partial cutting plots (20%). The level of defoliation also increased with seedling height. This study will help silvicultural strategies adapt to the effects of natural disturbance regimes. As the intensity and severity of defoliator outbreaks are expected to increase under climate change, these results will help guide forest management strategies to select harvesting methods that will limit the effects of defoliation on conifer regeneration
Molecular Variation at a Candidate Gene Implicated in the Regulation of Fire Ant Social Behavior
The fire ant Solenopsis invicta and its close relatives display an important social polymorphism involving differences in colony queen number. Colonies are headed by either a single reproductive queen (monogyne form) or multiple queens (polygyne form). This variation in social organization is associated with variation at the gene Gp-9, with monogyne colonies harboring only B-like allelic variants and polygyne colonies always containing b-like variants as well. We describe naturally occurring variation at Gp-9 in fire ants based on 185 full-length sequences, 136 of which were obtained from S. invicta collected over much of its native range. While there is little overall differentiation between most of the numerous alleles observed, a surprising amount is found in the coding regions of the gene, with such substitutions usually causing amino acid replacements. This elevated coding-region variation may result from a lack of negative selection acting to constrain amino acid replacements over much of the protein, different mutation rates or biases in coding and non-coding sequences, negative selection acting with greater strength on non-coding than coding regions, and/or positive selection acting on the protein. Formal selection analyses provide evidence that the latter force played an important role in the basal b-like lineages coincident with the emergence of polygyny. While our data set reveals considerable paraphyly and polyphyly of S. invicta sequences with respect to those of other fire ant species, the b-like alleles of the socially polymorphic species are monophyletic. An expanded analysis of colonies containing alleles of this clade confirmed the invariant link between their presence and expression of polygyny. Finally, our discovery of several unique alleles bearing various combinations of b-like and B-like codons allows us to conclude that no single b-like residue is completely predictive of polygyne behavior and, thus, potentially causally involved in its expression. Rather, all three typical b-like residues appear to be necessary
Le processus forestier pan-europĂ©en « Forest Europe » : vers un accord juridiquement contraignant sur les forĂȘts ?
AcadĂ©mie dâAgriculture de France 10 dĂ©cembre 2014 SĂ©ance publique Le secteur forĂȘt-bois en Europe sâorganise : objectifs, avancĂ©es, perspectives Le processus forestier pan-europĂ©en « Forest Europe » : vers un accord juridiquement contraignant sur les forĂȘts ? Christine FARCY UniversitĂ© de Louvain, Belgique Correspond Ă©tranger de lâAcadĂ©mie dâAgriculture de France En 1990, Ă lâinitiative de la France et de la Finlande, eut lieu Ă Strasbourg la premiĂšre ConfĂ©rence MinistĂ©rielle pour la Protection des ForĂȘts en Europe, Ă©vĂ©nement qui entĂ©rina une volontĂ© commune de protĂ©ger ces Ă©cosystĂšmes dans le cadre dâune coopĂ©ration rĂ©gionale dĂ©passant le cadre de lâUnion EuropĂ©enne. CâĂ©tait le dĂ©but dâun processus volontaire, toujours en cours, rythmĂ© par la prĂ©paration et lâorganisation de confĂ©rences rĂ©unissant les Ministres des forĂȘts de 46 pays pan-europĂ©ens ainsi que le reprĂ©sentant de lâUnion EuropĂ©enne, au cours desquelles ceux-ci ont pris diffĂ©rents engagements via lâadoption de dĂ©clarations et autres rĂ©solutions. FocalisĂ©s dans un premier temps sur la question de la protection des forĂȘts, les centres dâintĂ©rĂȘt ont Ă©voluĂ© vers des thĂ©matiques qui ont progressivement couvert, bien que de façon inĂ©gale, les trois piliers du dĂ©veloppement durable. Plate-forme dâĂ©change et siĂšge dâun apprentissage collectif, le processus rebaptisĂ© Forest Europe en 2009, a permis une percolation lente mais continue de concepts et mĂ©thodes de gestion durable des forĂȘts qui, en dĂ©pit de leur caractĂšre volontaire initial, constituent aujourdâhui des instruments clĂ© de la politique forestiĂšre de nombreux pays de la rĂ©gion. On pense en particulier aux critĂšres et indicateurs de gestion durable des forĂȘts (Lisbonne, 1998) et aux programmes forestiers nationaux (Vienne, 2003). Deux sĂ©ries dâĂ©vĂ©nement ont contribuĂ© Ă insuffler une rĂ©orientation au processus. Tout dâabord, lâĂ©mergence de conventions contraignantes dans des secteurs connexes mais touchant Ă des composantes du systĂšme forestier : la Convention sur la DiversitĂ© Biologique en 1992, la Convention-cadre des Nations unies sur les Changements Climatiques toujours en 1992 et la Convention des Nations unies sur la Lutte contre la DĂ©sertification en 1994. Ensuite les dĂ©saccords persistants manifestĂ©s lors des sessions successives du Forum des Nations Unies sur les ForĂȘts (FNUF) quant Ă lâintĂ©rĂȘt dâune convention mondiale/globale sur les forĂȘts. Dans ce contexte, soucieux de renforcer le niveau dâengagement des pays en matiĂšre de gestion durable des forĂȘts, de (re)positionner le secteur forestier sur la scĂšne internationale voire de constituer une plate-forme permettant dâassurer une coordination avec les autres secteurs, les signataires de Forest Europe ont jugĂ© opportun de tenter dâobtenir Ă lâĂ©chelle rĂ©gionale ce quâils nâavaient pu obtenir Ă lâĂ©chelle mondiale. Un processus contraignant a ainsi Ă©tĂ© adossĂ© au processus volontaire de Forest Europe et un mandat de nĂ©gociation a Ă©tĂ© adoptĂ© lors de la ConfĂ©rence MinistĂ©rielle dâOslo en juin 2011. Un ComitĂ© Intergouvernemental de NĂ©gociation (Intergovernemental Negotiating Committee - INC) pour un Accord Juridiquement Contraignant (Legally Binding Agreement - LBA) sur les ForĂȘts en Europe a Ă©tĂ© constituĂ© et sâest rĂ©uni Ă 6 reprises en 2012 et 2013. Il a travaillĂ© Ă lâĂ©laboration dâune convention cadre sur la gestion durable des forĂȘts. Le texte rĂ©digĂ© de façon gĂ©nĂ©rique envisage une sĂ©rie dâobligations gĂ©nĂ©rales ainsi que des obligations spĂ©cifiques structurĂ©es autour des six critĂšres de gestion durable des forĂȘts adoptĂ©s Ă Lisbonne. Un accord a Ă©tĂ© obtenu sur toutes les composantes techniques du texte ; en revanche, des visions trĂšs divergentes ont subsistĂ© quant Ă lâancrage institutionnel du futur TraitĂ© au point de mener Ă un situation de blocage et Ă un constat dâĂ©chec qui devrait ĂȘtre actĂ© lors dâune ConfĂ©rence MinistĂ©rielle Extraordinaire de Forest Europe prĂ©vue en octobre 2015 en Espagne
MARC-ANDRĂ GIASSON FLUX DE CARBONE Ă LâĂCHELLE DE LâĂCOSYSTĂME AVANT
Ă la FacultĂ© des Ă©tudes supĂ©rieures de lâUniversitĂ© Laval dans le cadre du programme de maĂźtrise en sciences forestiĂšres en vue de lâobtention du grade de MaĂźtre Ăšs sciences (M.Sc.) DĂ©partement des sciences du bois et de la forĂȘ