Ecology - Wildland Fuel Fundamentals and Applications - page 97

6.2 Landscape Ecology

The landscape ecology of wildland fuels is the interaction of the above processes
across multiple space and time scales to create shifting mosaics of fuel conditions.
Understanding the spatial and temporal distributions of fuels may provide a bet-
ter understanding of the impact of various wildland fuel management activities on
fuel properties and it also might help explain unexpected fire behaviors and effects
(Parsons et al. 2010 ). It can also aid in developing effective fuel applications that in-
tegrate spatial variability in their design such as new fuel classifications (Chap. 7),
sampling methods (Chap. 8), and geospatial data (Chap. 9). Patterns of fuel charac-
teristics will be important inputs to the fire effects and behavior models of the future
(Parsons et al. 2010 ; King et al. 2008 ).
While many have extensively studied the landscape ecology of fire (McKenzie
et al. 2011 ), few have looked at the spatial and temporal relationships of the wild-
land biomass that fuels these fires. Reich et al. ( 2004 ) evaluated the spatial vari-
ability of several fuel components over a large landscape in the US Black Hills and
found that the variability was correlated to topography and vegetation. Hiers et al.
( 2009 ) measured small-scale variations in surface fuel using LiDAR and found that
fuelbed depths become spatially independent after small distances (0.5 m 2 ). Spatial
variability of grasslands have been described in the context of population dynam-
ics and restoration potential but have not been related to fuel characteristics (Peters
et al. 2006 ). Theobald ( 2013 ) found that while fine-scale variation in fuels dictated
fire behavior, the distribution of CWD dictated germination in longleaf pine eco-
systems. While some studies have described fuel distributions across landscapes
( Ferrari 1999 ; Jin 2004 ), few have actually quantified the variability of fuel proper-
ties across space (Jia et al. 2006 ; King et al. 2008 ; Miller and Urban 2000 ). And,
while many have identified fuel continuity as a major spatial characteristic of wild-
land fuels (Knapp and Keeley 2006 ; Jenkins et al. 2012 ), few studies have evaluated
fuel patterns using landscape metrics.
Several landscape metrics are important in describing fuel patterns. Contagion
is the probability that a pixel, patch, or polygon will be adjacent to a pixel, patch,
or polygon of the same attributes, such as the same fuel complex, while disper-
sion is the inverse of contagion. Patch density is the number of patches (area of
homogeneous fuel characteristics) per unit area that indirectly represents patch size.
Landscape shape indexes measure the irregularity of patch shapes using perimeter
to area ratios. Few studies have described landscape pattern and patch dynamics
of wildland fuels. Sturtevant et al. ( 2004 ) used proportion of the landscape, mean
patch size, nearest neighbor distance, and juxtaposition as metrics to describe con-
nectivity of high-risk fuel types in Wisconsin, USA. A major limitation of most
landscape metrics is that they were designed for mapped categorical variables, such
as categories in a fuel classification (Chap. 8), but variables to describe fuel prop-
erties are continuous variables and there are a limited set of landscape analyses to
describe spatial distributions of continuous fuel properties and landscape metrics
for continuous variables are more complex and difficult to interpret.