Introduction
Forest
managers are
“…increasingly mandated to provide critical habitat for endangered
plant and
animal species while simultaneously ensuring healthy, sustainable
ecosystems
and landscapes capable of providing a broad range of commodity and
amenity
values” (Camp et al. 1996). Their
decisions are guided by specific management goals, including wood
production,
park or wilderness management, or wildlife habitat (Agee
1993).
With goals of habitat
restoration, for
example, management decisions focus on “restoring” current conditions
or
processes to those of a previous point in time.
By extension, managers deem present conditions in many
ecosystems to be unsuitable,
having deviated from historic trajectories due to human environmental
impacts. Thus, to
achieve goals of habitat
“restoration,” resource managers must understand historic conditions to
properly
assess current levels of departure (Daniels et al. 2007).
These historic conditions
become “reference
conditions” by which future management strategies are based.
Historic
conditions
oscillated within a “range of natural variability” (RNV), the range of
which was
determined by the temporal and spatial distribution of natural
ecological
processes and structures (Swetnam et al. 1999; Wong and Iverson
2004).
Natural disturbances are
examples of ecological
processes that drive structures.
Natural disturbances are defined as any relatively discrete event in time that disrupts ecosystem, community, or population structure and changes resources, substrate availability, or the physical environment (White and Pickett 1985). In forest ecosystems, disturbance events, controlled primarily by regional climate and local topography, drive forest structure at various temporal and spatial scales (Turner et al. 1993; Lertzman and Fall 1998; Swetnam and Betancourt 1998; Wong et al. 2003).
Wildfire is one
of the most
dramatic and most costly disturbance events – monetarily, ecologically,
and in
human life – that forest ecosystems endure (e.g., Blackwell et al.
2003). The
escalation in wildfire activity over the
past thirty years has been associated with changes in ecosystem health
and
stability (Blackwell et al. 2003), the level of which has been linked
to climate
variability of the past three centuries (Johnson and Larsen 1991;
Swetnam and
Baisan 1996; Lutz et al. 2009).
To
properly assess fire as
a disturbance mechanism and guide ecologically-based management,
several
questions must be asked: How
do regional
climate and local topographic factors effect fire?
Have humans affected the natural cycles of fire? How have the
spatial and
temporal variations
of historical fires impacted current forest structures and
dynamics?
What are the possible
implications for
management strategies? When
managing
land for a specific purpose, such as habitat restoration, these
questions
become increasingly important, but take on a tone of the past;
understanding
the RNV becomes the underlying focus.
My thesis project
will address these questions by quantifying the effects of wildfire as
a
disturbance agent in the forests of the Darkwoods
(Figure 1),
the
largest
single private land purchase for conservation in Canadian history (The
Nature
Conservancy of Canada, 2008). In an
effort to address current management goals of restoring and/or
maintaining habitat for
Mountain
Caribou and Grizzly Bear, I will assess one aspect of the
RNV: the
Natural Fire Regime (NFR). Therefore, I
intend to quantify both the historic and current NFRs to determine the
degree of
deviation from historic trends. I will
focus on local topography (bottom-up),
forest structure
and anthropogenic impact as controls on the NFR.
