Studies of biodiversity–ecosystem function in treed ecosystems have generally focused on aboveground functions. This study investigates intertrophic links between tree diversity and soil microbial community function and composition. We examined how microbial communities in surface mineral soil responded to experimental gradients of tree species richness (SR), functional diversity (FD), community-weighted mean trait value (CWM), and tree identity. The site was a 4-year-old common garden experiment near Montreal, Canada, consisting of deciduous and evergreen tree species mixtures. Microbial community composition, community-level physiological profiles, and respiration were evaluated using phospholipid fatty acid (PLFA) analysis and the MicroResp™ system, respectively. The relationship between tree species richness and glucose-induced respiration (GIR), basal respiration (BR), metabolic quotient (qCO2) followed a positive but saturating shape. Microbial communities associated with species mixtures were more active (basal respiration [BR]), with higher biomass (glucose-induced respiration [GIR]), and used a greater number of carbon sources than monocultures. Communities associated with deciduous tree species used a greater number of carbon sources than those associated with evergreen species, suggesting a greater soil carbon storage capacity. There were no differences in microbial composition (PLFA) between monocultures and SR mixtures. The FD and the CWM of several functional traits affected both BR and GIR. In general, the CWM of traits had stronger effects than did FD, suggesting that certain traits of dominant species have more effect on ecosystem processes than does FD. Both the functions of GIR and BR were positively related to aboveground tree community productivity. Both tree diversity (SR) and identity (species and functional identity—leaf habit) affected soil microbial community respiration, biomass, and composition. For the first time, we identified functional traits related to life-history strategy, as well as root traits that influence another trophic level, soil microbial community function, via effects on BR and GIR.
Bibliographical noteFunding Information:
Natural Sciences and Engineering Research Council of Canada. Discovery grant to Alison D. Munson and Project to Christian Messier, Bill Shipley, Dominique Gravel; Natural Sciences and Engineering Research Council
We acknowledge the Collaborative Research and Development program of the Natural Sciences and Engineering Research Council (funded NSERC project to C.M., B.S., D. G., and A.D.M.) for financial support to R. Khlifa for a partial PhD fellowship as well as a NSERC Discovery grant to A.D.M. We thank J.G. Catford, M. Coyea, and A. Brousseau of the Département des sciences du bois et de la forêt at Université Laval for assistance with MicroResp™ analysis and soil chemical analyses. We are grateful to M. Mazerolle from the Centre d’étude de la forêt at Université du Québec en Abitibi-Témiscamingue for his help with statistical analysis and C.M. Tobner at Université du Québec à Montréal (UQAM) for helpful discussions on computing of functional diversity indices. We acknowledge T. Handa and C. Archambault, UQAM, for their help with root biomass harvest and processing, and undergraduate students in our research group at Université Laval, especially M.H. Sauvé and F. Bernard-Brouillard, for their field assistance.
© 2017 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.
- belowground ecosystem functioning
- phospholipid fatty acids
- soil microbial community
- tree species diversity
- tree species identity