Land-use change is one of the most important factors influencing soil microbial communities, which play a pivotal role in most biogeochemical and ecological processes. Using agroforestry systems as a model, this study examined the effects of land uses and edaphic properties on bacterial communities in three agroforestry types covering a 270 km soil-climate gradient in Alberta, Canada. Our results demonstrate that land-use patterns exert stronger effects on soil bacterial communities than soil zones in these agroforestry systems. Plots with trees in agroforestry systems promoted greater bacterial abundance and to some extent species richness, which was associated with more nutrient-rich soil resources. While Acidobacteria, Actinobacteria and Alphaproteobacteria were the dominant bacterial phyla and subphyla across land uses, Arthrobacter, Acidobacteria_Gp16, Burkholderia, Rhodanobacter and Rhizobium were the keystone taxa in these agroforestry systems. Soil pH and carbon contents emerged as the major determinants of bacterial community characteristics. We found non-random co-occurrence and modular patterns of soil bacterial communities, and these patterns were controlled by edaphic factors and not their taxonomy. Overall, this study highlights the drivers and co-occurrence patterns of soil microbial communities in agroforestry systems.

No abstract

No abstract

No abstract

Canadian agriculture is a source of greenhouse gases (GHG) and agroforestry has the potential to sequester carbon (C), and mitigate agricultural GHG emissions. Agroforestry systems are common features in Canada's agricultural landscape; however, there are limited empirical data to support implementation of agroforestry practices for GHG mitigation. This shortfall of data may be a contributing factor to the lack of policy that supports the use of agroforestry for GHG mitigation in the Canadian agricultural landscape. We reviewed published studies that compared C stocks in vegetation and soils, and/or GHG emissions in agroforestry systems to traditional agriculture across Canada, with the aims of assessing the benefit of adopting agroforestry for GHG reduction. We then identified data gaps and obstacles that could direct future research. We found that most studies reported increases in vegetation and soil organic C storage in areas with woody species compared to herbaceous crops. Agroforestry systems also reduced the emission of CH 4 and N 2 O, and increased CO 2 respiration from soil, but few studies have examined these gases. The small set of studies we reviewed demonstrated the potential of agroforestry to store terrestrial C and mitigate GHG emissions. However, additional research is required to verify this pattern across geographic regions, determine the regional potential for development of agroforestry systems, and assess the potential atmospheric GHG reduction at regional and national scales.Keywords: carbon flux, methane, mitigation, nitrous oxide, soil carbon RÉSUMÉ L'agriculture canadienne est une source de gaz à effet de serre (GES) et l'agroforesterie pourrait bien contribuer à piéger le carbone (C) et ainsi atténuer les émissions de GES d' origine agricole. L'agroforesterie fait partie intégrante du paysage agricole canadien; on trouve cependant peu de données empiriques permettant d'appuyer l'utilisation de pratiques agroforestières comme moyen d'atténuer les GES. Ce manque de données pourrait expliquer la rareté des politiques encourageant la pratique de l'agroforesterie comme moyen pour atténuer les GES sur la scène agricole canadienne. Nous avons analysé la documentation existante qui compare les stocks de carbone dans la végétation et les sols ou les émissions de GES dans les systèmes agroforestiers à ceux de l'agriculture traditionnelle au Canada en vue d' évaluer les avantages de l'agroforesterie comme moyen de réduire les GES. Nous avons ensuite déterminé les données qui manquent ainsi les autres obstacles qui pourraient faire l' objet de recherches dans l'avenir. Nous avons constaté que la plupart des études consultées rapportent un niveau plus élevé de carbone organique stocké dans la végétation et le sol sur les étendues boisées que sur celles couvertes d'herbacé. L'agroforesterie réduit aussi les émissions de CH 4 et de N 2 O et augmente le CO 2 venant de la respiration du sol même si peu d' études se sont penchées sur ces gaz. Le corpus limité d' études que nous avons consultées ...