Plant traits and soil properties confer stability of black spruce-Kalmia shrub savannah of eastern Canada.

Abstract

Abstract Scope : In eastern Canada, black spruce-Kalmia forests turn to either spruce forest, Kalmia heath, or Kalmia-spruce shrub savannah (SS) depending on fire severity. Patchy distribution of high and low severity fires convert closed canopy forest to SS. Our objective was to identify the plant and soil mediated mechanisms of stability of SS. We hypothesized that traits of dominant plants and microhabitat conditions in island and heath of SS confer stability. Methodology : We compared species composition, habitat condition, and dominant species functional traits in SS island and heath with a multivariate approach. We determined functional hypervolumes of four most abundant species in island and heath using four functional traits of resource acquisition and use. Results We found higher tree cover, cryptogamic species, and organic matter depth in island and incident light, soil moisture, and shrub cover were higher in heath. Soil pH was higher in island than in heath and black spruce litter decomposed faster than Kalmia litter. Heath soil had higher total N, but lower total C, and K than island soil. Kalmia hypervolume was lower in island than in heath but other ericaceous species’ hypervolumes were greater in island than in heath. Ericaceous species showed a tradeoff between resource conservation to resource acquisition traits. Conclusions We conclude that SS persists due to distinct vegetation and soil processes in island and heath conferring its stability. Distinct microhabitat conditions, soil biogeochemical processes, and functional niche utilization act as stabilizing forces to maintain SS structure.