Natural and anthropogenic fire events in northern hemispherical systems are the dominant form of disturbance for boreal forests, and are becoming more pronounced in the face of a changing climate and increasing human use [1]. The boreal is a dynamic system, with habitat structure constantly in flux throughout a range of post-fire successional stages [2]. Though the boreal system exhibits dynamic responses to disturbance, fire regimes can result in landscape scale interruptions of phenological networks [3]. Climate change is worsening impacts associated with wildfire, including frequency, size, severity, and intensity [3,4]. These events are worsened by drought, a primary driver of stand mortality in terms of low, continuous dry conditions from season-to-season; droughts on a long-term scale are causing accumulating stress in trees, leading to mortality and a long-term increase in loss of biomass [1]. As dry conditions worsen, burn frequency increases and promotes a narrower network of early seral stage associated avian communities [5,6]. The boreal forest is experiencing an increase in natural and anthropogenic fire events, and this continual increase is exerting pressure on avian diversity and community richness [6,7].
Birds have been experiencing a broad spectrum decline in populations across most families and genera. These declines can be primarily attributed to climate change as it leads to an increase in wildfires and phenological mismatches [12]. Resident and transient individuals are adjusting to a change in timing of prey emergence, leading to a loss in available food resources as their habitat and its connectivity disappears. Hemiptera and coleoptera are predominantly impacted by wildfires as well, experiencing short-term declines post-disturbance, which can have negative implications for insectivorous avian networks relying on their abundance [12]. Wildfires are sweeping through boreal habitat and breaking up connectivity, separating habitat patches, and causing die offs in insect prey stocks. Avian assemblages rely on unbroken habitat to disperse and thrive, and as these fire regimes worsen in the coming years, declines could be further exacerbated.
How this potential impact applies to insular systems and narrower ecotones can be applied to the Lac La Ronge boreal archipelago, located in Saskatchewan (55°06’ N, 105°01’ W). The area comprises a system of post-glacial islands characterized by natural fire regimes and even-aged forest structures [14]. These islands possess their own spatially delineated and unique boundaries, and as such provide excellent mesocosms for exploring and testing questions related to fire-based disturbance regimes. Studying the effects of cyclic and shifting fire regimes can be done here on a smaller, insular scale. By summarizing the islands in a set of 40 with a range of burn ages, we are able to explore how avian assemblages shift as a direct relation to biogeography, pyrodiversity parameters, and disturbance recovery in forest systems.
The Lac La Ronge archipelago
Objectives
In Lac La Ronge, the study islands display a diverse range of habitat characteristics and structural traits in response to fire recovery. This provides an insular system for observation, and has allowed us to observe how habitat selection amongst species shifts as it relates to habitat quality, and increasing rates of change stemming from pyrodiversity and disturbance regimes.
We are seeking to clarify four questions of interest: 1. How does avian species richness vary as habitat parameters shift? 2. How does time since fire influence habitat suitability and diversity? 3. How does forest structure and island biogeography influence diversity? 4. Does distance to the mainland have any affect on diversity and dispersal rates?
Expected Results
We expect to see a fair range of variance in diversity rates across islands based upon the magnitude of effects on habitat structure. Primarily, as “time elapsed since fire” increases, we will see a reduction in volume of coarse woody debris (CWD) and an increase in basal area; total habitat quality will increase in relation to older disturbance age classes. As habitat quality "increases", we expect to see a rise in diversity of boreal bird species within detected assemblages, and apply the effects of fire regimes and pyrodiversity to mechanisms of dispersal.