A Natural History of Conifers has thirty four largely independent chapters, divided into seven sections, which makes for easy reading. Readers can focus on the material of interest — and the breadth of material ensures that anyone curious about natural history should find plenty of that.
Farjon begins with a brief explanation of conifers' distinctive anatomy:
"The female conifer cone is a compound structure that is unique to this group and derived from ancient and more complex structures that originated in the Carboniferous about 310 million years ago ... they consist of an axis with two types of appendices: a bract (the subtending leaf) and a scale bearing the ovules or seeds derived from a fertile dwarf shoot."Conifers also have distinctive wood and only one copy of a large inverted repeat in the chloroplast DNA, where all other plants have two. The extant conifers total some six hundred odd species, divided into seventy genera in eight families; they don't like salt or deserts, but are found in most environments. Farjon also touches in his introduction on the image problem of conifers, which are mostly known in Britain as Christmas trees, hedges, and plantations.
Turning to systematics, Farjon gives some background on botanical naming and the work done by systematists. The number of species actually declines with time, as different names are found to be synonyms by detailed studies carrying out "the winnowing task of the monographer".
Next he uses the fossil record to trace the evolutionary history of conifers. The earliest conifer fossils are found in the Upper Carboniferous, the heyday of conifers was in the Mesozoic, and there has been a decline to the present.
Six chapters tackle different topics in conifer ecology. The huge boreal conifer forests, the taiga, are the result of rapid dispersal during interglacial phases. In some places conifers survive where there are poor soils and short growing seasons. Giant conifers persist by outliving and outgrowing their angiosperm rivals, taking advantage of rare mass destruction events. Conifers have their own adaptations for seed dispersal by animals, which Farjon describes as "imitating" angiosperms but which seem entirely independent. They deploy a range of defences against grazing herbivores, especially insects, and parasitic plants. And large conifers can support entire epiphytic ecosystems — some giants carry more weight in soil and other plants than in their own foliage!
New Caledonia is "a showcase of conifer biogeography" and Farjon explores the relationships of its conifer species with others around the world, trying to distinguish vicariance — species divided by changing geography — from dispersal. He goes on to look at the role of continental drift in the distribution of Gondwanan conifers, the dispersal of conifers following the retreat of ice sheets in the northern hemisphere, some relict conifers, and the distribution of conifers around the Pacific.
The most important economic use of conifers is as a source of timber. They are also used ornamentally, and Farjon looks at tree-planting on 19th century British estates, the accompanying employment of collectors to find new species and varieties, and in more recent times the hunt for conifer varieties for gardens, horticulture, and fashion. And conifers are the source for a range of other products: food, incense, resins and amber.
Conifers in general are important as keystone species and providers of ecosystem services. "Living fossils" such as the Wollemi pine deserve protection for their "phylogenetic distinction". New Caledonia has a number of conifers that grow on nickel-rich ultra-mafic soils and are at particular risk from mining. Our best understanding of the overall picture comes from the International Union for Conservation of Nature Red List and its criteria, where conifers are among the best documented taxa. Finally there are the threats posed by conifers, which in some circumstances can become invasive — examples include Scots pine on Dutch heathland and pines in the southern hemisphere and especially New Zealand.
There's a glossary at the end, but there are technical terms used in the text that don't appear in that — for example "acicular" and "fastigiate". And concepts such as cladistics are explained very rapidly. So there are bits of A Natural History of Conifers that may be too technical for someone with no background at all in biology. Those are only a small part of what's on offer, however, so this should not put off anyone with a curiosity about the natural world. On the other hand, Farjon is a specialist who can usefully be read by botanists — though apparently he makes original claims here which haven't yet been backed up by journal publications.
A Natural History of Conifers is illustrated with a superb array of photographs, which are integrated into the text except for the decorative double-page spreads at the beginning of each section (which unfortunately lack captions). There are also some excellent line drawings of both trees and details. The result is a handsome as well as informative volume, which should command a wide audience.
January 2009
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