| dc.description.abstract | It has been suggested that clearcutting be followed by prescribed burning as a means of
reconciling effects of clearcutting and wildfire on plant communities. To address the
effectiveness of clearcutting followed by prescribed burning (PB), I assessed understorey
communities in northwestern Ontario using fifty 10 ? 10 m plots, located in 15-37 year old jack
pine (Pinus banksiana Lamb.) stands established after clearcutting, PB, and wildfire. My findings
are presented in two chapters, first I examined structural and compositional differences in plant
communities originating from the three disturbance types, and secondly I examined the
relationship of species' traits to disturbance type. In Chapter 1, I hypothesized that understorey
communities established after PB would resemble those established after wildfire more closely
than those established after clearcutting alone. However, I found that all three disturbance
types had similar understorey species richness and diversity, while species composition within
PB sites differed significantly from clearcut and wildfire sites. Compositional differences
associated with PB were comparable to those found after successive short-interval wildfires.
Indicator species of PB sites were mostly ruderai and disturbance tolerant species; suggesting
that PB created a compound effect on plant communities. Since application of prescribed
burning after clearcutting does not involve a novel disturbance, compositional differences may
be related to the short-interval between clearcutting and PB. In Chapter 2, I hypothesized that
compositional differences between communities originating from PB correspond to the
interaction of short-interval disturbance with species' life history and regeneration traits. I
analyzed traits related to post-disturbance regeneration to quantify relationships with
disturbance type. For trait analysis I used the abundance-weighted analyses RLQ, Fourth-Corner
Analysis, calculation of functional diversity indices (functional richness, evenness, and
dispersion), and community weighted means. I found no significant relationship between the
suite of traits and disturbance type. However I found significant relationships between PB and
species' traits such as Raunkiaer's lifeform, seed banking, wind dispersal, deciduous foliage,
rosettes and alien status. My hypothesis was supported by the prevalence of seed banking and
wind dispersal in the PB sites, both of which are known to increase with short-interval
disturbances. From these results I conclude that application of PB following clearcutting causes
compositional differences that result from disturbance-mediated plant trait selection by short-interval
disturbances. | |
