Four chapters cover the major components of trees: leaves; trunks and branches; roots; and flowers, fruits and seeds. These are structured around questions. The chapter on trunk and branches, for example, asks: how does the trunk grow? do all trees get wider? how does water get up a tree? how does bark cope with the tree expanding? — as well as describing elements such as bark, growth rings, rays, and knots.
There are chapters on tree growth — the limits to size, the balance between roots and shoots, the role of budding, the timing of annual growth, growth rings — and on the various factors that determine a tree's shape — gravity and wind and light, biomechanics, and budding and branching and flowering. There are chapters on propagation — seeds, vegetative propagation, grafting, and breeding — and on aging and senescence — defences against herbivores, insects and fungi and threats from cold, fire, wind and drought as well as water stress as an ultimate limit to growth.
"We have seen above that the tree is built up by continually adding new modules, just like a wall is built by adding new bricks, small in themselves but capable of adding up to a large imposing structure. But if every bud on a tree grew into a branch the canopy would soon become a hopeless tangle of dense branches. A 100-year-old oak should have 99 orders of branching rather than the 5-6 that actually exist. Temperate trees rarely show more than 5-8 orders, and tropical trees 2-3 or at most 4 orders of branching (tropical trees generally have bigger leaves requiring a less-fine network of branches to hold them. The potential tangle is prevented in three main ways." [Preventing too many buds, shedding branches, and reducing branch lengths.]
A brief final chapter "Trees and Us" touches on some of the benefits of trees — carbon storage, pollution control, heat management, psychological well-being — and problems with roots. The other chapters also have material on human-tree relationships: on protecting trees from digging, transplanting trees, shaping trees, and so forth.
Trees is nicely illustrated, with both diagrams and photographs. I found it an engaging way to approach the subject, really nicely presented: I found the first edition secondhand and then bought this second edition, which is substantially expanded and improved.
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