Simulating light availability under different hybrid poplar clones in a mixed intensive plantation system

Fast-growing hybrid poplars have been proposed as a means of achieving restoration objectives on former agricultural land by providing shelter for slower-growing species. Intensive two-stage scenarios of mixed plantations are also possible using valuable hardwoods interplanted among hybrid poplars. The latter would be harvested at maturity (approximately 20 years) once their protective role has been accomplished, leaving more space for the full development of the second cohort. We implemented simulations of hybrid poplar growth in the SORTIE-ND model and used it to test scenarios with clones varying in growth and crown allometry, different hardwood species, and spatial arrangements, to maximize production of both groups. Important differences in growth and allometry were manifested among clones over time, which translated into important differences in available light between rows. Sustained growth for most hardwoods appeared optimal using wider spacings of 16 m, compared with 12 m, between poplar rows. To our knowledge, this is the first attempt to integrate fast-growing hybrids and intensive silviculture scenarios into spatially explicit models. These models are necessary support tools for the efforts now being invested in intensive silviculture in the face of diminishing forest resources, increasing wood and fiber demands, and climate change

Fine roots distribution, light conditions and yield in a tree-based intercrop system

Paper presented at the 13th North American Agroforesty Conference, which was held June 19-21, 2013 in Charlottetown, Prince Edward Island, Canada.In Poppy, L., Kort, J., Schroeder, B., Pollock, T., and Soolanayakanahally, R., eds. Agroforestry: Innovations in Agriculture. Proceedings, 13th North American Agroforestry Conference, Charlottetown, Prince Edward Island, Canada, June 19-21, 2013."In tree-based intercrop systems (TBI), trees are planted in widely spaced rows to allow agricultural activities to continue. These agroforestry systems are new in Qu_bec but well known in Europe, USA and China (Baldy et al., 1993; Rivest and Olivier, 2007). The integration of trees into an agroforestry system has the potential to enhance soil fertility, reduce erosion, improve water quality, increase biodiversity and aesthetics, and sequester carbon (Jose, 2009; Montagnini and Nair, 2004). However, the presence of trees also results in aboveground and belowground interspecific interactions with crop, which can include competition, facilitation or complementarity (Jose et al., 2004; Rivest and Olivier, 2007; Van Noordwijk et al., 1996). In theory, TBI systems can be more productive than the respective monocultures if trees have the capacity to take resources like water and nutrients in deeper soil layers than those used by crops (Cannell et al., 1996)."--Introduction.L�a Bouttier (1), Alain Paquette (2), Christian Messier (2) and Alain Cogliastro (1) ; 1. Institut de Recherche en Biologie V�g�tale, 4101 Sherbrooke Est, Montr�al, QC H1X 2B2, Canada. 2. Universit� du Qu�bec a Montr�al, 270 Rue Saint Antoine Ouest, Montreal, QC H2Y 0A3, Canada.Includes bibliographical references

Experiences from southern Quebec provide ecological insights for the implementation of tree-based intercropping systems

Paper presented at the 11th North American Agroforesty Conference, which was held May 31-June 3, 2009 in Columbia, Missouri.In Gold, M.A. and M.M. Hall, eds. Agroforestry Comes of Age: Putting Science into Practice. Proceedings, 11th North American Agroforestry Conference, Columbia, Mo., May 31-June 3, 2009.Recent experiments in Quebec aimed to provide scientific arguments favouring the adoption of tree-based intercropping (TBI) systems in eastern Canada's rural landscape. The specific objectives of this research were to: (1) test whether a soybean intercrop between tree rows increases soil microbial biomass C, soil N fertility and tree growth compared to a harrowing treatment between tree rows; (2) determine the effects of the soybean intercrop on the diversity of arbuscular mycorrhizal fungi (assessed using SSU rRNA genes) compared to harrowing; and (3) determine whether TBI increases soil microbial beta-diversity (assessed using extractable phospholipid fatty acid (PLFA) profiles) compared to an adjacent conventional monocropping system. The TBI field was set in 2000 in southwestern Quebec using alternating rows of hybrid poplars (Populus spp.) and hardwood species spaced 8 m apart. Soybean (Glycine max L. (Merr.)) was grown between tree rows since 2004. During the 2005-2006 study period, soil microbial biomass C and N availability were higher in the soybean intercrop treatment or on par with those in the harrowing treatment. Hybrid poplar biomass increment in the soybean intercrop treatment was greater by 51 [percent] to that in the harrowing treatment and diagnostic of leaf nutrient status indicated that hybrid poplars were positively affected by the increase in N supply provided through intercrop management. The arbuscular mycorrhizal fungal diversity, as expressed by the Shannon-Wiener indices, were 0.82 for the soybean and 0.70 for hybrid poplar under the soybean intercrop treatment, and 0.53 for hybrid poplar under the harrowing treatment. The neighboring trees and soybean plants hosted different arbuscular mycorrhizal fungal communities, suggesting that TBI systems may enhance arbuscular mycorrhizal fungal richness compared to monocultures. The soil microbial beta-diversity, based on a measure of dispersion among the PLFA profiles within each sampled grid, was higher in the TBI than in the conventional soybean monocropping system, suggesting that TBI systems could play an important ecological role in the conservation of microbial functions (e.g., nutrient cycling), even in the face of wide variations of environmental conditions and inputs.David Rivest (1), Vincent Chifflot (2), Simon Lacombe (3), Alain Cogliastro (4), Robert Bradley (3), Anne Vanasse (1), Damase Khasa (2) and Alain Olivier (1) ; 1. De_partement de phytologie, Universit� Laval, Qu�bec (QC), Canada. 2. D�partement des sciences du bois et de la for�t, Universit� Laval, Qu�bec (QC), Canada. 3. D�partement de biologie, Universit� de Sherbrooke, Sherbrooke (QC), Canada. 4. Institut de recherche en biologie v�g�tale, Universit� de Montr�al & Jardin botanique de Montr�al, Montr�al (QC), Canada.n and 0.70 forIncludes bibliographical references

Successful under-planting of red oak and black cherry in early-successional deciduous shelterwoods of North America

Underplanting early-successional forest stands with red oak and black cherry was tested as a way of improving productivity on abandoned agricultural land of North American temperate deciduous forests. A partial release treatment was applied during the third growing season and compared to a control. The growth increment after six years is analyzed with respect to treatment and competition layers. Although the release treatment reduced competition at all vegetation layers, growth was mostly determined by the density of the upper layer. Deer herbivory was not increased by the release. The release treatment succeeded in significantly increasing available light for the duration of the study, while the understory recovered quickly. Planted trees, particularly red oak, responded well to the release treatment. Results substantiate the need for dynamic silviculture in sensitive, rural landscapes, where conservation of forest structure is important.Plantation sous-couvert de chêne rouge et cerisier tardif en forêt décidue pionnière d'Amérique du Nord.. Des chênes rouges et cerisiers tardifs ont été introduits sous couvert de jeunes peuplements d'origine agricole dans une étude visant l'amélioration de la productivité de peuplements pionniers de la forêt décidue tempérée d'Amérique du Nord. Un dégagement partiel appliqué au cours de la troisième saison de croissance est comparé à un témoin. La croissance après six ans est analysée en fonction du traitement et des strates de compétition. Alors que le traitement avait significativement diminué la compétition à tous les niveaux, la croissance était surtout fonction de la densité de la strate supérieure. L'herbivorie par le cerf n'a pas été augmentée par le dégagement. Le traitement de dégagement a significativement accru la lumière disponible pour toute la durée de l'étude, alors que le sous-étage s'est reconstitué rapidement. Les plants, particulièrement les chênes rouges, ont bien répondu au dégagement. Les résultats supportent une sylviculture plus dynamique dans les paysages ruraux sensibles, où la conservation des structures forestières est importante

Successful under-planting of red oak and black cherry in early-successional deciduous shelterwoods of North America

International audienc

Spatiotemporal patterns in seedling emergence and early growth of two oak species direct-seeded on abandoned pastureland

$\bullet$ Fine-scale spatial and temporal establishment patterns of direct-seeded oaks on abandoned agricultural land have been little studied despite their potential importance for long-term stand structure. $\bullet$ Here we periodically monitored seedling emergence and early growth of bur oak (Quercus macrocarpa Michx.) and red oak (Q. rubra L.) on an abandoned pasture, and tested the effects of herbaceous competition, rodents, and soil physicochemical properties. $\bullet$ Herbaceous competition slightly decreased diameter growth, but rodents had little impact on establishment. Red oak seedlings emerged earlier than bur oak and in a greater proportion (92% vs. 56%). Seedling emergence and early growth of both species showed significant spatial structures that were partly explained by variation in soil physicochemical properties. Bur oak was more responsive to microenvironmental heterogeneity than red oak, yet much of the variation in emergence and growth of both species remained unexplained. $\bullet$ This suggests that other factors, such as acorn size or genetic variability, may exert equal or greater control than microenvironmental heterogeneity over seedling emergence and early growth of these two oak species on abandoned pastureland.Patrons spatio-temporels d'émergence et de croissance initiale des semis de deux espèces de chênes semées dans un pâturage abandonné. $\bullet$ Les patrons spatiaux et temporels à échelle fine de l'établissement de chênes semés en friche agricole ont été peu étudiés bien que ceux-ci puissent avoir des impacts à long terme sur la structure du peuplement. $\bullet$ Nous avons périodiquement suivi l'émergence et la croissance initiale de semis de chêne à gros fruits (Quercus macrocarpa Michx.) et de chêne rouge (Q. rubra L.) dans un pâturage abandonné et évalué l'effet de la compétition herbacée, des rongeurs et des propriétés physico-chimiques du sol. $\bullet$ La compétition herbacée a légèrement réduit la croissance en diamètre, mais les rongeurs ont eu peu d'impacts sur l'établissement. Les semis de chênes rouges ont émergé plus rapidement que ceux du chêne à gros fruits et dans une plus grande proportion (92 % vs. 56 %). L'émergence et la croissance en hauteur des deux espèces exhibaient des structures spatiales significatives qui étaient partiellement expliquées par la variation des propriétés physico-chimiques du sol. Le chêne à gros fruits était plus influencé par l'hétérogénéité microenvironnementale que le chêne rouge, bien que la plus grande partie de la variation de l'émergence et de la croissance des deux espèces soit restée inexpliquée. $\bullet$ Cela suggère que d'autres facteurs, tels que la grosseur des glands ou leur variabilité génétique, pourraient exercer un contrôle aussi ou plus important que l'hétérogénéité microenvironnementale sur l'émergence et la croissance initiale de ces deux espèces semées dans des pâturages abandonnés

Variation in soil and foliar nutrition status along a forest edge-interior gradient in sugar maple forest fragments

The consequences of forest fragmentation and edge effects on soil nutrient availability and nutrition of sugar maple forests remain understudied. We assessed soil chemistry (bulk pH, total C and N, extractable P, exchangeable cations, mineralizable N) and foliar nutrition (N, P, K, Ca, Mg) of mature sugar maple forests along an edge-interior gradient (10, 20, 30, 50, 50, 70 and 120 m from the forest edges) in seven sugar maple forest stands (three on sandstone and four on dolomite bedrock) that are embedded within an agricultural landscape in southern Quebec. We hypothesized that foliar nutritional imbalances of sugar maple forests would decline along this gradient. Foliar nutrition was analyzed using the Diagnosis and Recommendation Integrated System (DRIS) and Compositional Nutrient Diagnosis-isometric log-ratio (CND-ilr) methods. At the sandstone sites, rates of N mineralization and nitrification increased with increasing distance from the forest edge. Other soil chemical properties and all sugar maple foliar indices of nutritional diagnostics weakly varied along the edge-interior gradient. Assessment of sugar maple forest nutritional status through different nutritional indices revealed K and P deficiencies in all stands that were sampled, and at all distances from the forest edge. Overall, we found weak forest edge effects on soil chemical properties and sugar maple forest nutritional status.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Temperate Agroforestry Development: The Case of Québec and of France

This study sought to shed light on the political and organizational dynamics favoring the deployment of agroforestry in temperate environments. Development paths of agroforestry practices in Québec (Canada) and France were analyzed regarding five different issues: political status and recognition, regulation and financing, knowledge acquisition, knowledge transfer and training, development actors and implementation in the field. Scientific studies and results continue to accumulate concerning temperate agroforestry and its environmental benefits. Political recognition of the field appears to be stronger in France (and the EU), which makes state financial aid conditional upon the adoption of the practices. In Québec, only the Ministry of Agriculture provides limited support. It financially assists research at a moderate level, as well as the installation and maintenance of trees by participating farmers to perform specific functions, i.e., erosion control, water quality, and biodiversity. A large number of actors are active in France, where efforts are being made to improve consultation and to reduce redundancy. Stakeholders in Québec are linked to the broader agri-environment field and act partially through agroforestry, according to varying degrees of competency, creating a disparity between regions. Recognition at the highest level, i.e., training for councillors and advisors, greater flexibility in obtaining assistance, inclusion of a greater diversity of systems, and a structure that ensures promotion and consultation, would favour the further development of agroforestry in the industrialized nations of the temperate zone