Box 9E. 1 Continued FIGURE 2. The C–S–R triangle model (Grime 1979). The strategies at the three corners are C, competiti- winning species; S, stress-tolerating s- cies; R,ruderalspecies. Particular species can engage in any mixture of these three primary strategies, and the m- ture is described by their position within the triangle. comment briefly on some other dimensions that Grime’s (1977) triangle (Fig. 2) (see also Sects. 6. 1 are not yet so well understood. and 6. 3 of Chapter 7 on growth and allocation) is a two-dimensional scheme. A C—S axis (Com- tition-winning species to Stress-tolerating spe- Leaf Economics Spectrum cies) reflects adaptation to favorable vs. unfavorable sites for plant growth, and an R- Five traits that are coordinated across species are axis (Ruderal species) reflects adaptation to leaf mass per area (LMA), leaf life-span, leaf N disturbance. concentration, and potential photosynthesis and dark respiration on a mass basis. In the five-trait Trait-Dimensions space,79%ofallvariation worldwideliesalonga single main axis (Fig. 33 of Chapter 2A on photo- A recent trend in plant strategy thinking has synthesis; Wright et al. 2004). Species with low been trait-dimensions, that is, spectra of varia- LMA tend to have short leaf life-spans, high leaf tion with respect to measurable traits. Compared nutrient concentrations, and high potential rates of mass-based photosynthesis. These species with category schemes, such as Raunkiaer’s, trait occur at the ‘‘quick-return’’ end of the leaf e- dimensions have the merit of capturing cont- nomics spectrum.

This textbook is remarkable for emphasising that the mechanisms underlying plant physiological ecology can be found at the levels of biochemistry, biophysics, molecular biology and whole-plant physiology. The authors begin with the primary processes of carbon metabolism and transport, plant-water relations, and energy balance. After considering individual leaves and whole plants, these physiological processes are then scaled up to the level of the canopy. Subsequent chapters discuss mineral nutrition and the ways in which plants cope with nutrient-deficient or toxic soils. The book then looks at patterns of growth and allocation, life-history traits, and interactions between plants and other organisms. Later chapters deal with traits that affect decomposition of plant material and with plant physiological ecology at the level of ecosystems and global environmental processes.

Physiological plant ecology is primarily concerned with the function and performance of plants in their environment. Within this broad focus, attempts are made on one hand to understand the underlying physiological, biochemical and molecular attributes of plants with respect to performance under the constraints imposed by the environment. On the other hand physiological ecology is also concerned with a more synthetic view which attempts to under stand the distribution and success of plants measured in terms of the factors that promote long-term survival and reproduction in the environment. These concerns are not mutually exclusive but rather represent a continuum of research approaches. Osmond et al. (1980) have elegantly pointed this out in a space-time scale showing that the concerns of physiological ecology range from biochemical and organelle-scale events with time constants of a second or minutes to succession and evolutionary-scale events involving communities and ecosystems and thousands, if not millions, of years. The focus of physiological ecology is typically at the single leaf or root system level extending up to the whole plant. The time scale is on the order of minutes to a year. The activities of individual physiological ecologists extend in one direction or the other, but few if any are directly concerned with the whole space-time scale. In their work, however, they must be cognizant both of the underlying mechanisms as well as the consequences to ecological and evolutionary processes.

This richly illustrated text covers the ecophysiology of plants of all major tropical ecosystems, from tropical rain forests, epiphytic habitats, mangroves and savannas to salinas, inselbergs and paramos and their ecophysiological adaptation to these different tropical environments. The physiognomy of biotopes and characteristic life forms of plants are depicted with photographs.

Although, as W.D. Billings notes in his chapter in this book. the development of physiological ecology can be traced back to the very beginnings of the study of ecology it is clear that the modern development of this field in North America is due in the large part to the efforts of Billings alone. The foundation that Billings laid in the late 1950s came from his own studies on deserts and subsequently arctic and alpine plants, and also from his enormous success in instilling enthusiasm for the field in the numerous students attracted to the plant ecology program at Duke University. Billings' own studies provided the model for subsequent work in this field. Physiological techniques. normally confined to the laboratory. were brought into the field to examine processes under natural environmental conditions. These field studies were accompanied by experiments under controlled conditions where the relative impact of various factors could be assessed and further where genetic as opposed to environmental influences could be separated. This blending of field and laboratory approaches promoted the design of experiments which were of direct relevance to understanding the distribution and abundance of plants in nature. Physiological mechanisms were studied and assessed in the context of the functioning of plants under natural conditions rather than as an end in itself.

In the spring of 1969 a small meeting was convened at the CSIRO Riverina Laboratory, Deniliquin, New South Wales, to discuss the biology of the genus Atriplex, a group of plants considered by those who attended to be of profound importance both in relation to range management in the region and as a tool in physiological research. The brief report of this meeting (Jones, 1970) now serves as a marker for the subsequent remarkable increase in research on this genus, and served then to interest the editors of the Ecological Studies Series in the present volume. This was an exciting time in plant physiology, particularly in the areas of ion absorption and photosynthesis, and unknowingly several laboratories were engaged in parallel studies of these processes using the genus Atriplex. It was also a time at which it seemed that numerical methods in plant ecology could be used to delineate significant processes in arid shrubland ecosystems. Nevertheless, to presume to illustrate and integrate plant physiology and ecology using examples from a single genus was to presume much. The deficiencies which became increasingly apparent during the preparation of the present book were responsible for much new research described in these pages.