Tuatara: Volume 19, Issue 1, November 1971
Review — Grassland Ecology
Here is an attempt to describe the anatomy of grassland ecology; it is not intended to be a review of the subject. The author believes there is an increasing need to achieve a synthesis of ecology and agriculture and that this is particularly so in the field of grassland ecology. He attempts to unify the components of the system although he believes a synthesis will be achieved only by the use of mathematical models.
The introduction, where legumes are included in grassland, is followed by seven chapters describing grasses and legumes as individual plants and as populations; their morphology and growth habit; their mineral nutrition; photosynthesis; their rate and pattern of growth and reproduction; and the cycle of vegetative parts. The efficiency of production (the ratio of output of products to the input of resources) and the factors affecting the efficiency of production are discussed in terms of land area, light, nitrogen, carbon and water. It is pointed out that most of the world's grasslands are natural plant communities and are ‘exploited’ because production is derived with the minimum of input. Natural grasslands are characterised by their varied species composition and this is related to competition and productivity. The significance of ecological principles to the maintenance of grass as an agricultural crop are outlined and the limitations of grasses as food for animals; nutrient cycles and the effect of grazing on grassland. Factors altering the efficiency of utilisation (yield relative to amount grown) are outlined, and the concept of efficiency in secondary production with regard to such factors as animal size and climate are discussed. Three chapters describe the production of milk, meat, wool and hides. The final chapter deals with the contribution of grasslands to man. Here it is suggested that their possible future role may be altered taking into account changes in their economic, cultural and social setting. There is a very good appendix giving an example of mathematical simulation of a biological system; pasture contamination by the excreta of grazing animals being the case in point.
The text makes very easy reading and there is a pleasing absence of unqualified technical terms. Quantified descriptions involving formulae are used to describe some of the relationships and there are about seventy figures and tables. Each chapter is followed by a comprehensive reference list. The book is fully indexed both by authors and subjects.
It is easy to criticise anything so wide as the scope of this book, on grounds of incompleteness. However, in view of the plea in the page 52 preface for agriculturalists to heed ecological principles I thought I would find the contents a little more provocative. Although Spedding does say that even for the well fed man it matters what is done with the land, he presents no new ideas on how efficiency in agricultural production may be reconciled with aesthetic, social and ecological values.
New Zealanders will feel a little let down; snow tussock grassland is not mentioned and the index contains mohair and partridge but neither mountain nor phosphorus. Nevertheless, as an ‘ecologist’ I found the book interesting and easy to assimilate, despite its somewhat dry appearance. It will no doubt find a place in under-graduate levels of agricultural curricula, and it would do no harm if it found its way into the ivory tower.
Peter A. Williams