Decline in the strength of genetic controls on aspen environmental responses from seasonal to century‐long phenomena

Understanding intra-specific variation in climate sensitivity could improve the prediction of tree responses to climate change. We attempted to identify the degree of genetic control of tree phenology and growth of trembling aspen (Populus tremuloides Mchx.) in a natural stand of this species in northwestern Quebec. We mapped and genotyped 556 aspen trees growing within the plot, using seven nuclear microsatellite loci for clone identification. We selected 13 clones (n of trees per clone >5, in total 350 trees) and evaluated the explanatory power of clone identity in (a) variability of spring leaf phenology and (b) short- and long-term growth responses. The clone's identity explained 43% of the variability in spring leaf phenology, between 18% and 20% of variability in response to monthly climate variables significantly affecting growth, between 8% and 26% of growth response to insect outbreaks, and 12% in the long-term growth rates. Strong clonal control of aspen phenology and moderate control of growth responses to monthly weather do not result in an equally large impact on long-term growth rates. The result suggests an important role of environmental extremes and within community interactions as factors averaging aspen growth performance at the stand level

Willow short-rotation production systems in Canada and Northern United States: A review

Willow short rotation coppice (SRC) systems are becoming an attractive practice because they are a sustainable system fulfilling multiple ecological objectives with significant environmental benefits. A sustainable supply of bioenergy feedstock can be produced by willow on marginal land using well-adapted or tolerant cultivars. Across Canada and northern U.S.A., there are millions of hectares of available degraded land that have the potential for willow SRC biomass production, with a C sequestration potential capable of offsetting appreciable amount of anthropogenic green-house gas emissions. A fundamental question concerning 1 sustainable SRC willow yields was whether long-term soil productivity is maintained within a multi-rotation SRC system, given the rapid growth rate and associated nutrient exports offsite when harvesting the willow biomass after repeated short rotations. Based on early results from the first willow SRC rotation, it was found willow systems are relatively low nutrient-demanding, with minimal nutrient output other than in harvested biomass. The overall aim of this manuscript is to summarize the literature and present findings and data from ongoing research trials across Canada and northern U.S.A. examining willow SRC system establishment and viability. The research areas of interest presented here are the crop production of willow SRC systems, above- and below-ground biomass dynamics and the C budget, comprehensive soil-willow system nutrient budget, and soil nutrient amendments (via fertilization) in willow SRC systems. Areas of existing research gaps were also identified for the Canadian context

Environmental benefits of improved water and nitrogen management in irrigated sugar cane : a combined crop modelling and life cycle assessment approach

The application of irrigation water and nitrogen (N) fertilizer in excess of crop demand reduces profitability and has multiple detrimental impacts on the environment. N dynamics in agroecosystems are extremely complex, and mechanistic crop models are most often required to quantify the impact of improved management practices on reducing fertilizer N losses. In this study, Life Cycle Assessment (LCA) methodology and mechanistic modelling was used to quantify the environmental benefits of improved management of water and fertilizer N by sugarcane farmers in a case study in Pongola, South Africa. A baseline scenario, representing farmer intuition-based irrigation scheduling management, and two additional scenarios in which water, and water and N were more rationally managed, were compared. Results show that improved water and N management can lead to a 20% reduction in non-renewable energy consumption per functional unit (FU), with sustained or even increased yields. Total GHG emissions can potentially be reduced by 25% through more efficient water and N management. Limiting the rates of fertilizer N applied, made possible by decreasing N leaching through improved irrigation scheduling, resulted in the highest reductions for both impact categories. While total water consumption was very similar between the scenarios, more efficient use of rainfall was achieved through accurate scheduling, reducing blue water requirements. Through the simultaneous consideration of multiple environmental impacts, combining mechanistic crop modelling and LCA shows potential to identify improved management practices as well as to establish environmental stewardship incentives.L'application d'eau d'irrigation et d'engrais azotés (N) en excès par rapport à la demande des cultures réduit la profitabilité et a de multiples impacts négatifs sur l'environnement. La dynamique de l'azote dans les agrosystèmes est extrèmement complexe, et des modèles de culture mécanistes sont souvent nécessaires pour quantifier l'impact de pratiques de gestion améliorées sur la réduction des pertes en azote. Cette étude utilise la méthodologie de l'Analyse du Cycle de Vie (ACV) combinée à la modélisation mécaniste pour quantifier les bénéfices environnementaux d'une gestion améliorée de l'eau et des fertilisants azotés par des producteurs de canne à sucre, dans une étude de cas à Pongola, Afrique du Sud. Un scénario de base représente les pratiques courantes et intuitives des producteurs en termes d'irrigation, et deux scénarios supplémentaires représentent des pratiques de gestion plus rationnelles de l'eau, et de l'eau et des engrais, respectivement. Les résultats montrent qu'une meilleure gestion de l'eau et de l'azote peut générer une réduction de 20% de la consommation en énergie non-renouvelable, avec des rendements maintenus voire améliorés. Les émissions totales de GES peuvent potentiellement être réduites de 25%. La réduction des applications d'engrais, rendue possible par le moindre lessivage de l'azote sous irrigation raisonnée, résulte en de fortes réductions de ces deux catégories d'impacts. La consommation totale en eau est similaire entre scénario de base et scénarios de meilleure gestion de l'eau; cependant l'utilisation de l'eau de pluie est plus efficiente avec les irrigations raisonnées, réduisant ainsi les besoins d'extraction de la ressource. Par la prise en compte simultanée d'impacts environnementaux multiples, la combinaison de l'ACV et de la modélisation mécaniste de culture montre un potentiel pour identifier les pratiques améliorées et pour développer un accompagnement en éco-conception de systèmes.http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1531-03612016-04-30hb201

Soil organic matter: a sustainability indicator for wildfire control and bioenergy production in the urban/forest interface.

This work was presented at the “North America Forest Soils Conference, Montana 2013”, in the “New Technologies in Soil Research” session.Incluye material complementarioMany rural communities in British Columbia (western Canada) are increasingly at risk from wildfire as temperatures rise and droughts become more frequent. In addition, these communities are also faced with rising fuel costs, and a growing demand for heat as their populations increase. The fact these communities are surrounded by forests presents an opportunity to combine community wildfire risk abatement with bioenergy development. Here we show how the ecological model FORECAST was linked with GIS and economic models to create a freely available on-line tool (FIRST Heat) to help other communities make their own screening-level ecological assessments of combining wildfire risk control with district heating systems. The tool incorporates an ecological sustainability index based on the relative change in soil organic matter (SOM) after 50 years of management compared to initial levels. Two thresholds were defined: 10% SOM lost as “warning” level, and 20% SOM lost as “critical” level. The tool was able to adequately capture the influences of ecological zone, stand age, site quality, and intensity of forest management on SOM losses. Stands in the sub-boreal and arid interior were significantly more exposed to SOM losses than in other ecological zones, as well as soils in old-growth forests. Stands in poor sites were significantly more sensitive to forest management than young and fertile sites. All things considered, our results show the suitability of incorporating ecological models and SOM thresholds in user-friendly decision-support tools to successfully transfer scientific knowledge on forest soils to local stakeholders and decision makers