Anthony Zhao
GEOG 510
Spring 2018
Prescribed Burning in the Eastern U.S. from a Landscape Ecology Perspective
Introduction: Prescribed Burning in the Eastern U.S.
Fire is an important ecological process for many fire-adapted ecosystems worldwide
(Bond and Keeley 2005). These include temperate forests throughout eastern North America
such as oak (Abrams 1992) and pine communities (Little 1946; Brose and Waldrop 2006;
Grissino-Mayer 2016). The practice of prescribed burning in fire-dependent forests holds great
value for ecological restoration and landscape management, despite its sociopolitical
controversies (Ryan et al. 2013). For instance, prescribed fire may help to restore and preserve
the oak communities that dominated eastern deciduous forests for centuries (Abrams 2005). As a
result of 20th-century fire suppression policy, fire-adapted oaks and pines are being replaced by
shade-tolerant, fire-sensitive hardwood species that further reduce the likelihood of natural fire
occurrence (Nowacki and Abrams 2008). The effectiveness of fire in helping to regenerate and
sustain oak is well-established (Arthur et al. 2012; Brose et al. 2013; Brose 2014); prescribed
fire, in combination with selective overstory removal, may also help to maintain fire-dependent
pine communities such as those in the New Jersey Pine Barrens (Boerner et al. 1988; Olson
2011). Owing to its profound effects on vegetation and other biota at variable spatial and
temporal scales, fire is a significant process at the landscape scale and may thus be examined
using the fundamental concepts of landscape ecology. The specific assessment of prescribed
burning using this approach incorporates the dimension of application, and therefore may be
useful in informing fire management at the landscape level.
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Landscape and Fire
The integrated discipline of landscape ecology emerged from a number of important
scientific perspectives, including both traditionally ecological and geographical approaches. The
landscape may be conceptualized as the outcome of interrelationships and interactions between
the natural component, i.e. the land and its resources, and the cultural component, i.e. the people
occupying the land and their cultural expression (Sauer 1925). A landscape can be characterized
by the composite form and function of its elements, and landscape ecology explores the
functional interrelations and the scale-based hierarchical structure of landscape elements such as
vegetation, macroclimate, microclimate, and soil properties (Troll 1950). The landscape ecology
perspective is thus readily applicable to the study of the spatial and temporal dynamics of
vegetation and its interactions with the abiotic environment (Watt 1947). From these
perspectives, fire may be viewed as both a natural and a cultural landscape element that is
strongly interwoven with the patterns and functions of vegetation and other biota. Observable
characteristics and outcomes of this relationship depend strongly on spatial and temporal scale.
Prescribed Fire as Part of Landscape Ecology
Modern landscape ecology is strongly rooted in the field of geography; landscapes as
geographic entities are fundamentally characterized by a uniform structure on the Earth’s surface
and the interrelationships and interactions between its structural components (Neef 1967).
Landscape structure is comprised of an underlying matrix that supports the development and
function of distinct patches of varying size, shape, and spatial configuration; ecologically, these
patches may be distinct communities or species assemblages (Forman and Godron 1981). The
study of landscape ecology applies this perspective in understanding ecosystem processes, and
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emphasizes the important role of spatial heterogeneity as both a landscape feature affecting such
processes and as a focus for natural resource management (Risser et al. 1983).
Such an approach may be used to examine the forested landscape of the eastern U.S. The
New Jersey Pine Barrens, for example, may be characterized as a mosaic of vegetation patches
driven by the frequency, intensity, and extent of recurring fire; fire determines both plant species
composition and variability of patch size, and changes in fire patterns can cause ecological
changes across multiple scales (Forman and Boerner 1981). Local levels of pitch pine (Pinus
rigida) serotiny within the Pine Barrens, for instance, directly result from local fire frequency,
and thus serotiny as a patch characteristic varies across this landscape (Givnish 1981).
Throughout eastern North America during the late 19th and early 20th centuries, widespread and
temporally-variable anthropogenic fires facilitated the establishment of mixed-oak forests
(McEwan et al. 2007). Current oak forest dynamics at the landscape level are linked with the
individual and interactive effects of fire regimes, climate change, human land-use, disappearance
of American chestnut (Castanea dentata), and herbivore population dynamics (McEwan et al.
2011). Fire is clearly an important ecological process in these landscapes; it fundamentally
shapes vegetation patterns and characteristics, generates spatial heterogeneity that affects
subsequent fire patterns, and interacts with other perturbations in driving landscape dynamics.
A scale-based hierarchical perspective to studying landscape ecology is useful for
understanding the interplay between landscape patterns and processes within and across
functional scales. For instance, a forested landscape hierarchy may, from larger to smaller scales,
comprise of the entire landscape, watersheds within the landscape, forest stands within
watersheds, and tree gaps within the stands (Urban et al. 1987). Human activity can rescale
landscape patterns and processes and alter the nature of cross-scalar relationships; thus, resource
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management may be more effective if it is scaled in congruence with natural patch dynamics to
maintain existing patch structure and function (Urban et al. 1987). Anthropogenic influence is
ultimately inseparable from the multi-scalar structure and function of contemporary landscapes
(Naveh 1988). Prescribed burning in fire-adapted eastern forests may be considered a positive
anthropogenic influence intended to reverse the undesired consequences of historical fire
suppression, which have produced landscape-level effects throughout the eastern U.S. Therefore,
although prescribed fires are applied at the scale of the individual forest stand, the practice of
prescribed burning must expand across much larger spatial and temporal scales throughout the
eastern U.S. in order to realize its ecological benefits at the landscape level.
Both increased anthropogenic ignition and fire suppression represent shifts in fire regime
within an ecosystem or landscape, and more broadly exemplify the global trend of changing
disturbance regimes (Turner 2010). Such changes may have profound effects on forest
ecosystems at broad spatial and temporal scales, including loss of adaptive and material legacies
that support recovery and resilience to disturbance (Johnstone et al. 2016). Resilience-based
forest management that considers the fundamental role of disturbance in impacting resilience is
thus important to maintaining forest ecosystem services (Drever et al. 2006; Seidl et al. 2016).
Prescribed burning may be readily implemented as part of such resilience-based management
approaches, and may be used to reinstate historical fire regimes to fire-adapted communities in
enhancing ecological resilience at the landscape level. Contemporary landscapes are increasingly
composed of mosaics of ecosystems that are altered to different degrees from historical
conditions (Hobbs et al. 2014); thus, the use of prescribed burning must be spatially and
temporally explicit across the landscape in order to yield ecological benefits across scales.
4
Spatial Patterns and Prescribed Fire
Ecological disturbance interacts with landscape patch dynamics both spatially and
temporally, creating heterogeneity and enhancing ecological diversity (Levin and Paine 1974).
Patch structure has both spatial and temporal dimensions, and spatial patterning consists of
vertical as well as horizontal dimensions; in terrestrial ecosystems, spatial heterogeneity is
largely determined by vegetation patchiness (Wiens 1976). Fire is a predominant driver of patch
structure and spatial heterogeneity in the New Jersey Pine Barrens, where it determines the
presence or absence of vegetation, plant species composition and reestablishment, and horizontal
and vertical forest structure (Boerner 1981). In the central Appalachian Mountains, fire activity
is strongly linked to local climate, topography, and vegetation characteristics (Lafon and
Grissino-Mayer 2007). At the stand level, fire-adapted forests contain complex spatial patterns of
tree distribution resulting from recurring fire, and this spatial heterogeneity in turn enhances
resilience and ecosystem function (Churchill et al. 2013). Fire is thus an important driver of
spatial and temporal patch dynamics across multiple scales, and these patch dynamics influence
subsequent fire patterns across the landscape. These reciprocal interactions exemplify the
interrelationships between patterns and processes on the landscape, and such interrelationships
enhance spatial heterogeneity and enable landscapes to support diverse ecological communities.
Human activity has long had a profound effect on landscape patterns. The protected Pine
Barrens landscape in New Jersey has undergone increased human disturbance and considerable
forest fragmentation within the past several decades; while the use of prescribed fire yields
positive ecological outcomes, the increasing dangers of fire must also be considered (Luque et al.
1994). In addition, recurring anthropogenic fire in forest ecosystems not adapted to such regimes
drastically changes species composition and micro-environmental conditions over time (Curtis
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1956). However, when carefully implemented in suitable forest sites, recurring anthropogenic
fire can be a valuable tool in restoring and preserving fire-adapted forest ecosystems (Wright
1974; Ryan et al. 2013). Natural disturbance regimes such as fire are important to maintaining
overall community structure and composition, and their effects on landscape patch dynamics and
species responses should be considered in management activities such as the designation of
protected areas (Pickett and Thompson 1978). Implementation of prescribed burning at the
landscape level must therefore be considered in accordance with other large-scale development
and management activities that may facilitate or hinder its effectiveness.
The Importance of Scale
Scale, both in the spatial and temporal dimensions, is a critical component of landscape
studies and applications. The characteristics of pattern-process interactions are scale-dependent,
and scale of investigation must be carefully selected on a contextual basis in order to make useful
observations and appropriate inferences (Meentemeyer 1989; Wiens 1989). For example,
ecological scale may be viewed from an organismal perspective and linked with organismal
processes as a way to assess ecological effects of spatial heterogeneity (Addicott et al. 1987;
Wiens 1989). In the case of fire management, this approach may consider individual trees, of
which species, size, and age all influence organismal processes and thus may be used to assess
individual tree response to landscape processes. Data on individual trees within a stand may then
be aggregated and used to evaluate the suitability for prescribed burning within that stand.
Historical fire regimes varied widely throughout eastern North America across spatial
and temporal scales as a result of dynamic variables such as temperature, drought occurrence,
and human population density, as well as relatively stable topography (Guyette et al. 2006).
Recurring fire drives forest development and succession across landscapes, and therefore impacts
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landscape diversity over large temporal scales (Romme and Knight 1982). In the Appalachian
Mountains, fire and vegetation have interacted at the landscape level for millennia, and drastic
changes in fire regimes over time have resulted in large-scale changes in forest composition and
landscape character (Brose et al. 2001; Lafon et al. 2017). In the New Jersey Pine Barrens, the
effects of prescribed burning on upland forest carbon dynamics varies with spatial and temporal
scale; although burning results in stand carbon loss in the short-term, forest carbon dynamics
stabilize with increasing spatial and temporal scales (Clark et al. 2015). The impacts of largescale, long-term burning on landscape pattern and function should thus differ considerably from
those of localized, short-term burning. If implemented with consideration of variables such as
frequency, intensity, and spatial extent (Turner 2005), persistent burning may provide valuable
opportunities to achieve large-scale forest management goals across the eastern U.S.
Historical landscape dynamics over vast temporal scales can be examined using
paleoecological techniques; these observations may improve understanding of current landscape
trends and aid in the prediction of future trends (Delcourt and Delcourt 1988; Turner 2005).
Historical and current landscape dynamics may also be used in conjunction with spatiallyexplicit simulation modeling (Turner 2005) to explore potential long-term impacts of prescribed
fire scenarios on forest landscapes. Such approaches that consider both past and future landscape
dynamics may be of considerable practical use. Even as approaches to using historical
knowledge continue to evolve to better cope with the dynamic nature of landscapes (Higgs et al.
2014), such knowledge will continue to play an important role in informing and guiding
landscape management (Turner 2005). This is particularly true in the case of fire management,
where knowledge of historical fire patterns at the landscape level is essential to preserving pine
and oak communities over large scales.
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Synthesis and Conclusion
Landscape ecology as an integrated discipline provides a useful framework for assessing
the use of prescribed fire in forests throughout the eastern U.S. Both natural and anthropogenic
fire are important landscape processes that significantly affect vegetation patterns and functions
across multiple spatial and temporal scales. Fire as a process generates spatial heterogeneity
across the landscape and interacts with other large-scale disturbances. At the same time,
landscape patch structure resulting from fire affects subsequent fire patterns; such an
interrelationship between pattern and process supports ecological diversity across the landscape.
Throughout the eastern U.S., fire has been essential to the development and persistence of
oak and pine forest communities. In the absence of fire, these communities are shifting toward
dominance of shade-tolerant, fire-sensitive hardwoods. Prescribed burning in these forests may
be used to reverse the landscape-level consequences of historical fire suppression and to restore
ecological resilience to oak and pine forests. Implementation of prescribed burning at large
spatial and temporal scales is necessary. However, the use of prescribed burning must also be
spatially and temporally explicit within the landscape, accounting for the wide range of
ecosystem types that are present and the necessity of fire for individual ecosystems, in order to
maximize ecological benefits across scales. Prescribed burning at the landscape level must also
account for, and potentially coordinate with, other large-scale development and management
activities that may impact its effectiveness.
Although prescribed burning occurs at the stand level, its conditions and implications
may be considered from multiple scales that range from individual tree response to landscapelevel effects. Consideration of individual tree response informs decisions to burn in particular
stands. Prescribed burning conducted at various spatial and temporal extents would differentially
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impact landscape pattern and function, with more pronounced effects at larger extents. Thus,
widespread and persistent burning with specific regime characteristics may help to achieve
landscape-level management goals. The important role of historical knowledge, particularly
concerning landscape-level fire patterns, cannot be discounted in the restoration and management
of forest communities across the eastern U.S.
Overall, this synthesis illustrates the ways in which landscape-oriented approaches can be
used in fire management. In the eastern U.S., prescribed fire will remain a practical management
tool for restoring and preserving fire-dependent forest communities, reducing hazardous fuels,
and enhancing ecological resilience to climatic stress (Clark et al. 2014; Vose and Elliott 2016).
Interactions between pattern and process and between different processes, spatial heterogeneity,
relationships present within and across scales, and human activity as a driver of landscape
dynamics all provide useful conceptual foundations to inform the use of prescribed fire as a
management tool. Broad-scale considerations of spatial relationships remain important to
planning and managing at the landscape level (Turner 1989). For fire-dependent oak and pine
communities, fine-scale considerations and broad landscape principles should be integrated and
subsequently incorporated into management to as high of a degree as possible, given the
extensive area and heterogeneous nature of the region. Integrative, flexible, and adaptive
perspectives and approaches connect the theoretical foundations of landscape ecology to
practical and successful fire-based management of eastern forests.
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