questions, that approach should be used with caution because it will help identify pattern but cannot
generate an understanding of the processes that
create these patterns (Bailey 1988).
12.3.3 Natural Ecosystem Patterns
Historically, a high level of landscape heterogeneity was caused by natural disturbance and environmental gradients. Now, however, many forest
landscapes appear to have been fragmented due
to management activities such as timber harvesting
and road construction. To understand the severity
of this fragmentation, the nature and causes of the
spatial patterns that would have existed in the
absence of such activities should be considered.
This analysis provides insight into forest
conditions that can be attained and perpetuated
(Knight and Reiners 2000).
12.3.4 Effects of Climatic Variation
Current climate exerts a very strong effect on
ecosystem patterns, and climate change may
cause shifts in those patterns (Neilson 1995, see
Chap. 10). Anthropogenic and climatic change
could yield ecoregions that are much different, or
less useful, after many years. Therefore, temporal
variability is an important research issue. While
several researchers are doing work on the effect of
climate change on tree species distribution (cf.
Iverson and Prasad 2001), others are working on
the impact of climatic change on the geography of
ecoregions. For example, Jerry Rehfeldt of the
Rocky Mountain Research Station (personal communication) has predicted the potential distribution of the American (Mojave-Sonoran) Desert
ecoregion under the future climate scenario produced by the IS92a scenario of the Global Climate
Model,
4 with about 21
C warming and 50 %
increase in precipitation. He has produced maps
that show a greatly expanding desert under this
scenario. Despite the percentage increase in precipitation, the amount of rainfall fails to keep pace
with the increase in temperature, so the climate
becomes more arid.
There are limits to the number of sites that can
be established for monitoring changes in the
global environment. Obviously, sites should be
representative. Stations also should be located
where they can detect change. The boundaries
between climate-controlled ecoregions are suitable for this purpose. FIA has roughly 160,000
forested sample sites. This criterion could identify a subset of these sites which could be more
intensively sampled to provide the needed monitoring information.
12.3.5 Relationships Between
Vegetation and Landform
The relationships between vegetation and landform position change from ecoregion to
ecoregion, reflecting the effect of the
macroclimate. Vegetation strongly influences
where animals live—some more so than
others—and such factors as soil moisture and
topoclimates determine which plants live where;
hence site-specific vegetation character. Trees
make a simple example: they change their
positions in different regions (Table 12.2). Any
such changes invoke related changes such as in
the vigor of other tree species, ecosystem productivity, and so on. Knowledge of these differences
is important for extending results of research and
management experience and for designing sampling networks. These relationships have been
extensively studied in some regions (cf. Odom
and McNab 2000) but, unfortunately, not in
others. Where sufficient studies have been done,
these relationships might be modeled and mapped
to improve understanding of these ecosystems.
All of the applications discussed in this chapter involve expanding our perspective to see the
patterns that exist within a region. These
patterns, interpreted in terms of process, can be
very useful to land managers and scientists. In
the next chapter, we discuss fire regimes of different ecosystems at the scale of ecoregion, and
4 This is one of the emissions scenarios developed in 1992
under the sponsorship of the Intergovernmental Panel on
Climate Change. IS92a has been widely adopted as a
standard scenario for use in impact assessments.
12.3 Significance to Research
123
generate an understanding of the processes that
create these patterns (Bailey 1988).
12.3.3 Natural Ecosystem Patterns
Historically, a high level of landscape heterogeneity was caused by natural disturbance and environmental gradients. Now, however, many forest
landscapes appear to have been fragmented due
to management activities such as timber harvesting
and road construction. To understand the severity
of this fragmentation, the nature and causes of the
spatial patterns that would have existed in the
absence of such activities should be considered.
This analysis provides insight into forest
conditions that can be attained and perpetuated
(Knight and Reiners 2000).
12.3.4 Effects of Climatic Variation
Current climate exerts a very strong effect on
ecosystem patterns, and climate change may
cause shifts in those patterns (Neilson 1995, see
Chap. 10). Anthropogenic and climatic change
could yield ecoregions that are much different, or
less useful, after many years. Therefore, temporal
variability is an important research issue. While
several researchers are doing work on the effect of
climate change on tree species distribution (cf.
Iverson and Prasad 2001), others are working on
the impact of climatic change on the geography of
ecoregions. For example, Jerry Rehfeldt of the
Rocky Mountain Research Station (personal communication) has predicted the potential distribution of the American (Mojave-Sonoran) Desert
ecoregion under the future climate scenario produced by the IS92a scenario of the Global Climate
Model,
4 with about 21
C warming and 50 %
increase in precipitation. He has produced maps
that show a greatly expanding desert under this
scenario. Despite the percentage increase in precipitation, the amount of rainfall fails to keep pace
with the increase in temperature, so the climate
becomes more arid.
There are limits to the number of sites that can
be established for monitoring changes in the
global environment. Obviously, sites should be
representative. Stations also should be located
where they can detect change. The boundaries
between climate-controlled ecoregions are suitable for this purpose. FIA has roughly 160,000
forested sample sites. This criterion could identify a subset of these sites which could be more
intensively sampled to provide the needed monitoring information.
12.3.5 Relationships Between
Vegetation and Landform
The relationships between vegetation and landform position change from ecoregion to
ecoregion, reflecting the effect of the
macroclimate. Vegetation strongly influences
where animals live—some more so than
others—and such factors as soil moisture and
topoclimates determine which plants live where;
hence site-specific vegetation character. Trees
make a simple example: they change their
positions in different regions (Table 12.2). Any
such changes invoke related changes such as in
the vigor of other tree species, ecosystem productivity, and so on. Knowledge of these differences
is important for extending results of research and
management experience and for designing sampling networks. These relationships have been
extensively studied in some regions (cf. Odom
and McNab 2000) but, unfortunately, not in
others. Where sufficient studies have been done,
these relationships might be modeled and mapped
to improve understanding of these ecosystems.
All of the applications discussed in this chapter involve expanding our perspective to see the
patterns that exist within a region. These
patterns, interpreted in terms of process, can be
very useful to land managers and scientists. In
the next chapter, we discuss fire regimes of different ecosystems at the scale of ecoregion, and
4 This is one of the emissions scenarios developed in 1992
under the sponsorship of the Intergovernmental Panel on
Climate Change. IS92a has been widely adopted as a
standard scenario for use in impact assessments.
12.3 Significance to Research
123