Canada is home to millions of hectors of forested land from its Atlantic coast to its Pacific coast. These forests are fundamental to the nation’s biological, economical and social wealth. Due to Canada’s latitude and climate around three-quarters of its forested land is classified as boreal forests (Millennium Ecosystem Assessment 2005; Dhar et al. 2018a). This forest region serves as a significant reservoir for biodiversity and terrestrial carbon (Pan et al. 2011; Bradshaw and Warkentin 2015; Lake and Christianson 2019). The boreal forests in Canada are far from uniform. The soil composition, moisture, climate, species, forest cover, density and structure can vary drastically across the country (Brandt et al. 2009; Brandt et al. 2013). Despite these variations, the boreal forests operate on the same foundation of ecological principles and work is conducted to sustainably manage them to achieve similar goals (Gustafsson et al. 2012). These management goals must be able to reflect the anthropogenic impacts on the boreal forests.
Ecosystem-based Management
Through the lens of Ecosystem-Based Management land managers developed a specific treatment style that involved emulating natural disturbances of the area through harvesting practices termed Natural Disturbance-Based Management. Because this concept was developed in the West, forest managers used wildfire as their disturbance to emulate. Forest fires act as one of the largest natural disturbances in Canada’s boreal forests. To emulate this disturbance, it is necessary to comprehend the characteristics of forest fires in the boreal forests. Centuries of wildfires on the landscape has morphed ecosystems to adapt to disturbances (Packard 1993). Over the course of a fire varying conditions and fuel forces the fire to move in dynamic, unique patterns (Kafka et al. 2001). Not all fire is equal. Each fire can move through a forest with a variety of severities: ground, surface and crown. A ground fire is designated as low-severity and consists of matter below the ground burning. Surface fires are classified as medium-severity and includes the burning of leaf litter and fallen woody debris on the forest floor. Lastly, a crown fire means the fire would burn from canopy to canopy of the trees within the forest. This type of fire is the most destructive and, likewise, classified as a high-severity fire. As stated before, when a wildfire works its way across a landscape patches of unburned or low-severity burned forests are left behind (Gasaway and DuBois 1985; DeLong and Kessler 2000; Bergeron and Fenton 2012). Observations of these matrices demonstrated that the island remnants act as a source of refugia for the surrounding forests and the original biodiversity of the area (Gasaway and DuBois 1985; Gandhi et al. 2001; Pearce et al. 2005; Schmiegelow et al. 2006; Perhans et al. 2009; Highlander and Johnson 2012). Forest industries should strive towards sustainable stewardship of their management areas to ensure long-term production and preserve biodiversity (Gustafsson et al. 2012). One way to accomplish this goal would be using retention forestry to balance economic, cultural and environmental objectives (Gustafsson et al. 2012) by leaving remnants in the forest after harvest to allow regeneration from those species remaining and to protect biodiversity by providing a life-boat for species in a patch of untouched forest.
Retention
The idea of retention in forestry is not a new concept, but it has taken time for forest industries to adopt and implement retention strategies. Likewise, the research examining the efficacy of the industries’ actions have been lacking, especially as it relates to western Canada. One of the difficulties with attempting to emulate retention is the preferences of the harvest island remnants often differ from the preferences of the fire island remnants. Fire disturbed areas tend to be young and sparse stands; meanwhile, harvested stands are productive old-growth areas (Kafka et al. 2001; Martin et al. 2020). Younger stands are more likely to experience fire disturbances due to a higher volume of coarse woody debris from a previous disturbance and the lower canopy height
Edge Effects
Area has an important influence on the ability of a remnant to act as an effective lifeboat for regeneration. Tree mortality, which represents island resilience, decreases as the size of the island remnant increases (Jönsson et al. 2007; Franklin et al. 1997; Matlack et al. 1994; Matlack et al. 1994). In this study it was identified that eighteen years post disturbance the remnants less than a hectare showed little success in remaining intact. Likewise, Franklin et al. ascertained that the islands remnants would not achieve interior forest conditions below 25-40 hectare islands (1997). Additional work suggested that the lower limit is closer to 0.8 hectares for achieving interior forest conditions, but the mortality of a single tree could disrupt that area recommendation. Instead the authors set 2.7 hectares as the appropriate size to meet the interior forest goal (Matlack et al. 1993; Matlack et al. 1994).
Coarse Woody Debris
The original forest structure, flora and fauna preserved in an island remnant acts as a propagator for post-disturbance regeneration. In a remnant, as well as any forest, coarse woody debris provides a significant ecological service. In research as early as the 1940s coarse woody debris has been documented to forming a positive correlation with biodiversity, carbon storage and nutrient cycling (Arnborg 1942; McCullough 1948; Harmon et al. 1986; Freedman et al. 1996; Stevens 1997; Jonsson and Kruys 2001). Although the importance of coarse woody debris was identified over half a century ago forest management objectives did not create provisions for it until recent decades. By providing organisms with essential needs such as nesting, shelter, food etc., coarse woody debris allows species of bryophytes, saprobes, invertebrates, mammals, birds, reptiles, amphibians, vascular plants and fungi to thrive in habitats that may otherwise be challenging (Jönsson and Jonsson 2007). Due to coarse woody debris’ relationship with biodiversity and forest structure it can be used as a predictor for forest biodiversity and fire dynamics (Hobson and Schieck 1999; MacNally et al. 2002; Astrom et al. 2005; Kail et al. 2007; Hart and Chan 2008). Therefore, examining the coarse woody debris of both post-fire and post-harvest island remnants can estimate the capacity for maintaining biodiversity and stability (Moussaoui et al. 2016).
Objectives
The objective of this research is to ascertain the coarse woody debris volume comparison between post-fire and post-harvest island remnants, specifically in reference to the recent coarse woody debris. We want to gauge the effectiveness of forest industries at emulating island retentions, similar to those created after a wildfire. Possessing a higher volume of coarse woody debris typically indicates more biodiversity and it would insinuate the islands' instability long-term. Although this correlation can be made we are not assessing biodiversity or island sustainability with this project. In addition to volume, coarse woody debris attributes will be used to determine the effectiveness of forest industries: decomposition, diameter and species. To verify the claims of our forestry partners we are seeking to find minimal variation between the post-fire and post-harvest island remnants, both in terms of volume and attributes.
Expectations
I expect that the harvest islands will experience greater edge effects because a harvest creates a clean edge that would allow them to experience more wind, temperature changes and variability in humidity. Therefore, I believe a harvest will cause more tree mortality and downfall compared to a wildfire. I suspect the harvest sites will have a greater number of dead trees in the early decay classes and of larger diameter because their predisposition to the clean edge will influence recent deadwood and the largest trees would experience more wind than smaller trees.