18 Variation in Gas Exchange Characteristics
Among Desert Plants
l.R. Ehleringer
IS.1 Introduction
Professor Otto Lange and colleagues have made significant contributions to
our understanding of ecophysiological aspects of plant performance under
arid land conditions. It was their pioneering field research in the Negev
Desert during the 1960s and 1970s that firmly established our understanding
of the impacts of drought and high temperature on photosynthetic gas
exchange, respiration, and transpiration in extreme environments. These
field studies described the mechanistic bases for photosynthetic adjustment
to desert habitats and evaluated the carbon gain significance of different
acclimation patterns. During the past decade, Lange and colleagues have
extended this research by examination of plant performance in sclerophyllous
shrub and tree species in the arid mediterranean climate zones of Portugal,
and these studies have provided further insights into the cellular adjustments
of plants to arid conditions.
In this chapter, I would like to build on the foundation laid down by
Lange and colleagues and to examine a question related to the physiological
and evolutionary ecology of plants in arid zones. Namely, given the spatial
and temporal diversity of deserts: what kinds of photosynthetic gas exchange
characteristics are expected under different selective regimes? In particular,
what patterns are expected within different life forms and how do life-formrelated physiological characters relate to species composition in different
desert locations? Are the known gas exchange patterns from field studies
consistent with these relationships? The primary focus of this chapter will be
the deserts of North America with special emphasis on the Sonoran Desert,
since it is the most diverse of the North American deserts (Shreve and
Wiggins 1964). However, the patterns that emerge should be applicable to
other desert regions of the world.
IS.2 Species Distribution Gradients in the Desert
The deserts of western North America (Chihuahuan, Colorado Plateau,
Great Basin, Mojave, and Sonoran) are defined by a limited-precipitation
Among Desert Plants
l.R. Ehleringer
IS.1 Introduction
Professor Otto Lange and colleagues have made significant contributions to
our understanding of ecophysiological aspects of plant performance under
arid land conditions. It was their pioneering field research in the Negev
Desert during the 1960s and 1970s that firmly established our understanding
of the impacts of drought and high temperature on photosynthetic gas
exchange, respiration, and transpiration in extreme environments. These
field studies described the mechanistic bases for photosynthetic adjustment
to desert habitats and evaluated the carbon gain significance of different
acclimation patterns. During the past decade, Lange and colleagues have
extended this research by examination of plant performance in sclerophyllous
shrub and tree species in the arid mediterranean climate zones of Portugal,
and these studies have provided further insights into the cellular adjustments
of plants to arid conditions.
In this chapter, I would like to build on the foundation laid down by
Lange and colleagues and to examine a question related to the physiological
and evolutionary ecology of plants in arid zones. Namely, given the spatial
and temporal diversity of deserts: what kinds of photosynthetic gas exchange
characteristics are expected under different selective regimes? In particular,
what patterns are expected within different life forms and how do life-formrelated physiological characters relate to species composition in different
desert locations? Are the known gas exchange patterns from field studies
consistent with these relationships? The primary focus of this chapter will be
the deserts of North America with special emphasis on the Sonoran Desert,
since it is the most diverse of the North American deserts (Shreve and
Wiggins 1964). However, the patterns that emerge should be applicable to
other desert regions of the world.
IS.2 Species Distribution Gradients in the Desert
The deserts of western North America (Chihuahuan, Colorado Plateau,
Great Basin, Mojave, and Sonoran) are defined by a limited-precipitation