Botkin Environmental Science Earth as Living Planet 8th txtbk

90 CHAPTER 5 Ecosystems: Concepts and Fundamentals
5.10 shows birch trees in a New Hampshire forest, both
as we see them, using standard film, and with infrared
film. The infrared film shows tree leaves bright red, indicating
that they have been warmed by the sun and are
absorbing and reflecting energy, whereas the white birch
bark remains cooler. The ability of tree leaves to absorb
energy is essential; it is this source of energy that ultimately
supports all life in a forest. Energy flows through
life, and energy flow is a key concept.
The Laws of Thermodynamics
and the Ultimate Limit
on the Abundance of Life
When we discuss ecosystems, we are talking about
some of the fundamental properties of life and of the
ecological systems that keep life going. A question that
frequently arises both in basic science and when we
want to produce a lot of some kind of life—a crop,
(a)
(b)
(c)
(d)
FIGURE 5.10 Making energy visible. Top: A birch forest in New Hampshire as we see it, using normal
photographic film (a) and the same forest photographed with infrared film (b). Red color means warmer
temperatures; the leaves are warmer than the surroundings because they are heated by sunlight. Bottom:
A nearby rocky outcrop as we see it, using normal photographic film (c) and the same rocky outcrop
photographed with infrared film (d). Blue means that a surface is cool. The rocks appear deep blue,
indicating that they are much cooler than the surrounding trees.