Floristic composition and functional stability of black spruce-Kalmia shrub savannah

Abstract

Scope: In eastern Canada, black spruce (Picea mariana)-Kalmia angustifolia forest revert into forest, or become Kalmia heath, or Kalmia-spruce shrub savannah (SS) depending on fire severity. My main research objective was to identify the mechanisms that maintain SS vegetation structure and function. I hypothesized that microhabitat conditions and function of dominant plants of island and heath confer SS stability. Methodology: I used a multivariate approach to quantify the difference in habitat condition, floristic structure and composition between island and heath of SS. I compared soil nutrient availability and litter decomposition between island and heath to assess growth limitations and nutrient cycling. This was followed by determining functional hypervolumes of the four most abundant species in island and heath considering four functional traits representing resource acquisition and use. I used a dendrochronological approach to determine island expansion rate to predict future island cover. Results: Shrub cover, light availability, and soil moisture were positively related to heath, and cryptogamic species and tree cover and organic matter depth were positively related to island. Heath soil had higher total N, but lower total C, and K than island. All other measured nutrients were similar. Black spruce litter decomposed faster than Kalmia. [...]