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14 Extension Note
Spatial Patterns and Landscape Ecology:
Implications for Biodiversity
Introduction patterns, the role of disturbances in
ecosystems, and the characteristic spa-
Spatial patterns? To get a good idea of tial and temporal scales of ecological
what we mean by spatial patterns in events.
forested landscapes, bail out of an air- The Forest Practices Code
Biodiversity plane at 10 000 m over British acknowledges the importance of land-
Management Concepts Columbia on a clear day. As you drift scape ecology concepts by enabling
in Landscape Ecology down, you begin to notice patterns in district managers to designate plan-
the landscape, a many-hued mosaic of ning areas called landscape units, each
different patches. Splashes of ice and with specific landscape unit objectives.
Ministry contact: snow top impossibly sharp moun- The Biodiversity Guidebook (B.C.
Marvin Eng tains, branching rivers deeply dissect Ministry of Forests and B.C. Ministry
B.C. Ministry of Forests plateaus, shimmering leaden sheets of Environment, Lands and Parks
Research Program
31 Bastion Square reveal valley-bottom lakes. Angling 1995), a component of the Code,
Victoria, BC, V8W 3E7 down in altitude, you see more detail recommends procedures to maintain
November 1997 in the mosaic, especially the different biodiversity at both landscape and
shapes, colours, and textures of the stand levels. These procedures, which
forested patches. Some patches obvi- use principles of ecosystem manage-
ously contain clumps of large ment tempered by social considera-
old-growth trees, some snake linearly, tions, recognize that an important
protecting stream waters from your way to maintain biodiversity at the
“… an important view. Others are bare or, with their landscape level is to mimic natural
way to maintain slight tinge of green, hold the promise spatial patterns in managed forests.
of regrowth. This extension note is the third in
biodiversity at the All of these patterns are “spatial” a series designed to raise awareness
landscape level is to in the sense that they occupy three- of landscape ecology concepts and
dimensional space. The study of spa- to provide background for the eco-
mimic natural tial landscape patterns is one of the logically based forest management
spatial patterns in central interests of landscape ecolo- approach recommended in the
managed forests …” gists. Landscape ecology enlarges our Biodiversity Guidebook. The focus here
understanding of dynamic ecological is on spatial patterns in forested land-
1 January 2000. Policy direction for biodiversity is now represented by the Landscape Unit Planning
Guide. This Extension Note should be regarded as technical background only.
Ministry of Forests Research Program
scapes.2 We first define basic spatial sities across various space and time
landscape patterns and describe the scales with an attendant range of ef-
“whys and wherefores” of their exis- fects on spatial landscape patterns.
tence. We then discuss some of the Wildfire, insect epidemics, pathogens,
ecological principles underlying spa- windthrow, landslides, and floods are
tial pattern development, and review the major agents of disturbance in the
3
the major spatial processes that can unmanaged landscape. In managed
alter landscape patterns and threaten landscapes, the increasing expansion
biodiversity. We conclude by examin- of urban centres, the growing devel-
ing how these concepts can be applied opment of agriculture, and the
in landscape-level planning situations. continued harvesting of forests all
contribute to changes in landscape
What Spatial Landscape pattern. Both natural and human-
Patterns Are caused disturbances can modify the
landscape’s fundamental structure by
Landscape ecologists talk about land- altering vegetation and hydrologic
scapes as “mosaics.” These complex regimes. Some disturbances may pro-
patterns are composed of inter- duce more complex, resilient spatial
connected or repeating land uses, patterns; for example, small-scale
habitats, or ecosystems over a kilome- windthrow events can deposit large
tres-wide area. The landscape patterns organic debris (trees) in a stream,
we see today result from the interplay of: which can potentially improve its
• environmental, or physical, con- spawning habitat. Other disturbances
straints; may simplify spatial patterns and
• disturbances; and therefore affect biotic processes at a
• biological, or “biotic,” processes landscape scale; for example, large
fires may create even-aged stands
(Bourgeron and Jensen 1994). wild
which can become susceptible to mas-
Physical constraints include a high- sive insect attacks.
fluential array of “abiotic,” or In response to the landscape’s
ly in
non-living, physical factors such as physical constraints and disturbance
climate, geology, landforms, and soil regimes, living organisms evolve and
types. Together these agents create the adapt their biotic processes. These
underlying foundation, or “geomor- processes in forested landscapes in-
phic template,” upon which the clude:
biological landscape is constructed. • soil formation through microbial
The characteristics of this template, activity;
how it was shaped by moving water, • nutrient cycling;
ice, and wind, greatly affect the natur- • seed germination, tree replace-
al patterns and structural elements we ment, and succession; and
see in the overlying landscape • species development, migration,
(Forman 1995). and elimination.
This mantle of landscape is trans-
formed by both natural and Through the interplay of physical
human-caused disturbances. Natural constraints, disturbances, and biologi-
disturbances occur at differing inten- cal processes, the spatial patterns in a
2 Eng’s chapter in Voller and Harrison’s Conservation Biology for Forested Landscapes (1997, in prep.)
is a good reference for those readers wanting an in-depth understanding of spatial patterns in forest-
ed landscapes.
3 Natural disturbance ecology is discussed in more detail in Part 2 of this Extension Note series.
forested landscape can strongly influ- A Model to Describe Landscape
ence both energy flows and functions. Patterns
For instance, the flows of energy The key to describing these land mo-
(e.g., the movement of fire) create saics is to be able to detect patterns
patterns (e.g., the patchy landscapes and recognize how and why they vary.
created by wildfire movement), which Some landscape ecologists use a sim-
in turn, because of their underlying ple, three-component model as a
structure, can influence other flows of conceptual tool to classify a land-
energy and the movement of species scape’s spatial elements (or “structure”):
(e.g., burnt-over lands may alter air every point is either within a patch, a
drainage and affect seed germination corridor, or a background matrix
and dispersal patterns). Linkages or (Forman 1995) (Figure 1).
feedback between a landscape’s exist- Matrix The “matrix” is the most
ing structure (i.e., the composition common and extensive pattern in a
and arrangement of its basic ele- landscape mosaic. Because it tends to
ments) and those biological functions be the most uniform of these land-
is also evident, further transforming scape elements, the matrix exerts the
the spatial patterns of the land mosaic greatest control over landscape func-
over time. tion. It can be likened to an open
Matrix Patch
Patch
Patch
Aerial photo showing patch and matrix elements of a landscape mosaic (adapted from U.S. Forest Service 1993).
Landscape Patterns:
expanse of ocean in which energy
(waves) and objects (fish) can move Ecological Principles
freely from one portion of the water
to another. In reality, the matrix may Hierarchy Theory and Scale
not be completely uniform. Never- To landscape ecologists, the concept
theless, in a forested landscape a of spatial patterns and the scale at
non-uniform matrix can still fulfil the which they occur are intimately
habitat needs of many species, and woven together. Hierarchy theory
therefore it will seem homogeneous. helps explain the connections between
In British Columbia, the matrix complex landscape patterns and the
may consist of continuous mature for- scale of the many processes that influ-
est cover or grass lands. The kind of ence these patterns. When applied to
matrix vegetation will depend largely landscape ecology, this theory allows
on the geomorphic template (as indi- the components of an ecosystem, or
cated by the area’s biogeoclimatic set of ecosystems, to be defined, their
ecosystem classification) and the land patterns and processes identified, and
uses (e.g., forestry, agriculture) to the linkages between the different
which the template is subjected. scales of ecological organization
Patch An area within the landscape traced (Bourgeron and Jensen 1994).
that is distinct from the matrix and Hierarchy theory divides multi-
isolated from other similar areas is scaled systems (such as forested
called a “patch.” Patches can be large landscapes) into an ordered progres-
or small, elongated or round, convo- sion of interrelated spatial scales or
luted or smooth. Like islands in the levels. This concept of interrelatedness
ocean, patches in a forested landscape is important in the theory. Ecological
lack apparent connections with the systems at every level are functional
matrix. Because of their heterogeneity, entities that also exist as part of a larg-
various patches will have different val- er whole. Like the layers of an onion,
ues for different species. A patch may each spatial level is embedded within
consist of a single unvegetated open- another. Our forest management
ing or gap in a forest created by efforts usually occur at regional, land-
fire, windthrow, or harvesting, scape, watershed, and stand levels.
wild
or it may be a remnant mature forest Progressing through the hierarchy in
stand in a landscape dominated by one direction takes one down to ever
regenerating young trees or harvested smaller (or finer-grained) spatial units
cutblocks. such as tree gaps and patches of vari-
Corridor The third element in this ous species and sizes within a forested
conceptual model is the “corridor.” matrix. Progressing in the other direc-
Corridors are strips that differ from tion takes one up to ever larger (or
their surroundings on both sides. Like coarser-grained) spatial scales such as
warm currents in the ocean, corridors the continental and global (Table 1).
in a forested landscape provide im- An Example of Spatial Scale To get a
portant connections between portions better idea of how spatial hierarchies
of the matrix. Corridors provide suit- relate to the complex patterns we see
able habitat to link populations of in landscapes, imagine this scenario:
species. Natural features such as ripar- A fierce coastal wind storm snaps the
ian habitats along a stream or river bole of a 400-year-old western hem-
provide important landscape connec- lock. As the windthrown tree falls to
tions, often joining upper elevations the forest floor, its trunk damages two
and midslopes with valley bottoms. or three smaller conifers, creating a
gap in the canopy of about 0.1 ha. The
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