Plant physiological ecology, 2nd edn

Abstract

Plant ecophysiology is the science that seeks to explain the physiological mechanisms underlying ecological observations. Much is made these days of the value of interdisciplinarity but, as the authors point out, ecophysiology is interdisciplinary by definition, since success requires an appreciation of the important ecological questions, and of the biophysical, biochemical and molecular processes needed to understand them. Clearly therefore, one measure of the success of a book like this is how far it helps us to answer some current ecological questions. For example, the long-running controversy about mechanisms of competition. Here I have to say the authors make one of their rare mistakes (even if it is only a semantic one), since they are happy to attribute the success of one species relative to another to ‘competition’, irrespective of the circumstances. It has always seemed to me that if a plant excludes a competitor by tolerating stresses that kill or debilitate the competitor, calling that process ‘competition’ removes most of the term's usefulness. However, once we get onto actual mechanisms, all is clear. The authors quote (without comment) the results of Wedin and Tilman (1990) and Tilman and Wedin (1991), but then note dryly that ‘the uptake kinetics of species from infertile soils are unlikely to result in low soil nutrient concentrations’. In other words, R* doesn't – indeed can't – work. In a fine chapter on the ecophysiology of ecosystem processes, we learn that the controls on ecosystem productivity include temperature, rainfall, soil nutrients, parent rocks, drainage, topography, fire, successional age, grazing, symbionts, canopy structure and albedo, and plant traits including palatability, leaf area index, litter quality and root exudates. I've probably missed a few as well, but nowhere is much (in fact any) space wasted on the effects of biodiversity. If local biodiversity has any effect on productivity, it can only be measured in circumstances where the controls on productivity in the real world have been carefully eliminated. The authors don't always get it right. For example, they are too ready to accept the role of allelopathy in the success of the invasive Centaurea maculosa, despite studies that cast serious doubt on this phenomenon (Qin et al., 2007). Generally, however, wherever you look in this book, important topics are examined with thoroughness and clarity. You will not find a better account of how nutrient uptake strategies vary with soil nutrient status, and why even mycorrhizas are not enough when the going gets really tough. Mycorrhizas are remarkably effective at scavenging P, but even they are of little use when there's virtually no P to scavenge; here only cluster roots (which can ‘mine’ P) are equal to the task. The authors are also good at drawing attention to important areas where little is known, but where we can expect to discover much more in the future. We are left in little doubt that in a third edition the section on endosymbionts will be much longer, and no doubt contain some quite unforeseen surprises. And who could dislike a book that quotes Eeyore from The House at Pooh Corner? Two minor complaints. One is that the index does not contain any plants or animals, which is annoying if you're looking for information on Plantago or Casuarina. I've also seen some odd printing errors over the years, but new to me is an index (in my copy) that has completely lost the letter R, so if you want to know about respiration, roots or rubisco, you're on your own. Typos are few, but there is a persistent tendency to spell Arrhenatherum as Arrhenaterum, and I guess an over-enthusiastic spellchecker decided to call Briza media ‘quacking grass’. Minor quibbles apart, however, this is a very fine book indeed, and one that should be read by all plant ecologists, not just those who call themselves ecophysiologists.