PARENT SESSION
Contributed Oral Session 59: Bacterial Communities and Diversity
Tuesday, August 9, 1:30 PM - 5:00 PM, Meeting Room 515 A, Level 5, Palais des congrès de Montréal
Forest floor bacterial diversity and function in relation to landscape features in Quebec's southern boreal forest.
Bradley, Robert*,1, Lamarche, Josyanne2, Hooper, Elaine3, Shipley, Bill, Simao-Beaunoir, Anne-Marie, Beaulieu, Carole, 1 Université de Sherbrooke, Sherbrooke, Québec, Canada2 Service canadien des forêts - Canadian Forest Service, Ste-Foy, Québec, Canada3 Université de Montréal, Montréal, Québec, Canada
ABSTRACT- Bacterial communities mediate many of the processes in boreal forest floors that determine the functioning of these ecosystems, but the incidence of bacterial diversity patterns is unknown. Although the spatial variability of these communities can be very high over short distances (< 1 m), we tested the hypothesis that factors affecting bacterial diversity operate on a larger spatial scale as well. More specifically, we tested whether forest floor bacterial communities would vary predictably over the landscape according to stand type (spruce/fir, aspen, paper birch), stand age (57, 78-85, 131 y old), and geologic parent material (clay and till). Bacterial community structure was examined by terminal restriction fragment length polymorphism (T-RFLP) analysis of genes encoding for 16S rRNA, extracted from forest floor samples collected in 54 treatment plots. Distance-based redundancy analysis of T-RF patterns revealed that each of the three predictor variables, as well as their interaction terms, had a significant effect on the genetic diversity of bacterial communities. The 15 T-RFs with the highest percent fit on the first two ordination axes of each factor's ordination plot were different, indicating that each landscape feature affects a distinct group of bacterial genotypes. Given that the link between bacterial diversity and soil functions is still a major challenge, we also assessed the effects of the same landscape features on community level physiological profiles (CLPPs) of the extractable forest floor microflora, as well as on a suite of 18 variables describing chemical and biochemical properties of the forest floor. Results of multivariate permutation ANOVA tests and principal component analysis on these two data sets confirmed similar effects of landscape features on bacterial functional diversity and forest floor properties. Our results suggest that bacterial community structure is an important component of ecosystem functioning.
Key words: forest floor bacterial diversity, southern boreal forest landscape, T-RFLP / distance-based redundancy analysis, ecosystem functioning