rational observation of underlying processes.
Likewise, both Dryer (1919) and Sauer (1925)
called for a genetic approach to landscape classification. The need to classify landscapes based on
a reasoning of the causes of the phenomena as
opposed to empirical classifications that are only
descriptive and do not explain why regions
should be distinguished is emphasized by
Mackin (1963). Building on this work, I have
developed, and continue to refine, a system of
mapping ecosystems using the genetic approach
(Bailey 1985, 1987, 1988, 1996, revised 2009),
which spawned from concepts advanced by
Crowley (1967). Delineating units involves
identifying the factors thought to differentiate
ecosystems at varying scales and drawing
boundaries where they change significantly.
1.4
The Role of Climate
Energy is the prime driving force and controller
of conditions on Earth. The three main sources of
energy are (1) solar radiation, providing heat and
light, (2) the kinetic energy of the rotation and
orbit of the Earth, and (3) internal forces of both
heat and kinetic energy. Figure 1.6 shows the first
two sources. Internal forces will be discussed in
Chap. 4.
As a result of the way, the Earth revolves
about the sun and rotates on its axis, the low
latitudes or tropics receive more solar radiation
than do middle and higher latitudes.
3 Only about
40 % as much solar energy is received above the
poles as above the equator. To balance this
energy there is a large-scale transfer of heat poleward, which is accomplished through atmospheric and oceanic circulation. The frictional
effects of the rotating Earth’s surface on air
flow cause these circulations to be relatively
complex. Nevertheless, the solar energy and
atmospheric and oceanic circulations are
distributed over the Earth in an organized fashion. These controls, in turn, produce recognizable world patterns of temperature and
precipitation, the two most important climatic
elements.
Climate, as a source of energy and water, acts
as the primary control for ecosystem distribution.
As climate changes, so do ecosystems, as a
petrified forest lying in a desert attests (Fig. 1.7).
1.5
Macroclimate
If the Earth had a homogeneous surface (either
land or water), there would be circumferential
zones of climate resulting from variations in the
Fig. 1.6 Fundamental sources of energy that control
conditions on Earth. Base from Mountain High Maps.
Copyright # 1995 by Digital Wisdom, Inc.
Fig. 1.7 Petrified forest that now lies in a desert zone in
Arizona. Photograph by D.B. Sterrett, U.S. Geological
Survey
3 Zones of latitude may be described as follows: from the
equator to 30
are low latitudes; from 30
to 60
are the
middle latitudes; from 60
to the poles are the high
latitudes.
1.5 Macroclimate
5
Likewise, both Dryer (1919) and Sauer (1925)
called for a genetic approach to landscape classification. The need to classify landscapes based on
a reasoning of the causes of the phenomena as
opposed to empirical classifications that are only
descriptive and do not explain why regions
should be distinguished is emphasized by
Mackin (1963). Building on this work, I have
developed, and continue to refine, a system of
mapping ecosystems using the genetic approach
(Bailey 1985, 1987, 1988, 1996, revised 2009),
which spawned from concepts advanced by
Crowley (1967). Delineating units involves
identifying the factors thought to differentiate
ecosystems at varying scales and drawing
boundaries where they change significantly.
1.4
The Role of Climate
Energy is the prime driving force and controller
of conditions on Earth. The three main sources of
energy are (1) solar radiation, providing heat and
light, (2) the kinetic energy of the rotation and
orbit of the Earth, and (3) internal forces of both
heat and kinetic energy. Figure 1.6 shows the first
two sources. Internal forces will be discussed in
Chap. 4.
As a result of the way, the Earth revolves
about the sun and rotates on its axis, the low
latitudes or tropics receive more solar radiation
than do middle and higher latitudes.
3 Only about
40 % as much solar energy is received above the
poles as above the equator. To balance this
energy there is a large-scale transfer of heat poleward, which is accomplished through atmospheric and oceanic circulation. The frictional
effects of the rotating Earth’s surface on air
flow cause these circulations to be relatively
complex. Nevertheless, the solar energy and
atmospheric and oceanic circulations are
distributed over the Earth in an organized fashion. These controls, in turn, produce recognizable world patterns of temperature and
precipitation, the two most important climatic
elements.
Climate, as a source of energy and water, acts
as the primary control for ecosystem distribution.
As climate changes, so do ecosystems, as a
petrified forest lying in a desert attests (Fig. 1.7).
1.5
Macroclimate
If the Earth had a homogeneous surface (either
land or water), there would be circumferential
zones of climate resulting from variations in the
Fig. 1.6 Fundamental sources of energy that control
conditions on Earth. Base from Mountain High Maps.
Copyright # 1995 by Digital Wisdom, Inc.
Fig. 1.7 Petrified forest that now lies in a desert zone in
Arizona. Photograph by D.B. Sterrett, U.S. Geological
Survey
3 Zones of latitude may be described as follows: from the
equator to 30
are low latitudes; from 30
to 60
are the
middle latitudes; from 60
to the poles are the high
latitudes.
1.5 Macroclimate
5