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Thursday, August 22, 2019

Review: The Hidden Life of Trees

After reading The Weather Detective, I had to read The Hidden Life of Trees, which many have praised as being a better book. It's definitely a fascinating one, about how trees can communicate to each other:
The acacia trees that were being eaten gave off a warning gas (specifically, ethylene) that signaled to neighboring trees of the same species that a crisis was at hand. Right away, all the forewarned trees also pumped toxins into their leaves to prepare themselves. The giraffes were wise to this game and therefore moved farther away to a part of the savannah where they could find trees that were oblivious to what was going on. Or else they moved upwind. For the scent messages are carried to nearby trees on the breeze, and if the animals walked upwind, they could find acacias close by that had no idea the giraffes were there. (Pg. 7)
 I loved the chapter on "street kids", on why the isolated trees in cities, suburbs, and even various preserves and parks don't do well, which is because they're not actually part of a forest, and therefore not part of a community. He explains why trees that grow naturally in a forest are longer lived than the "street kids": the reason is that for trees to be long lived, they need to grow slowly, and straight up. A tree in an open area would grow in all directions quickly, but that would lead to a short life.

There are lots of little secrets for your garden:
 These secret reserves can be activated at any time, and depending on the tree species, they contain a selection of defensive compounds produced by the tree. These so-called phytoncides have antibiotic properties, and there has been some impressive research done on them. A biologist from Leningrad, Boris Tokin, described them like this back in 1956: if you add a pinch of crushed spruce or pine needles to a drop of water that contains protozoa, in less than a second, the protozoa are dead. In the same paper, Tokin writes that the air in young pine forests is almost germfree, thanks to the phytoncides released by the needles.56 In essence, then, trees disinfect their surroundings. But that isn’t all. Walnuts have compounds in their leaves that deal so effectively with insects that garden lovers are often advised to put a bench under a canopy of walnuts if they want a comfortable place to relax in the garden, because this is where they will have the least chance of being bitten by mosquitoes. The phytoncides in conifers are particularly pungent, and they are the origin of that heady forest scent that is especially intense on hot summer days. (Pg. 156)
 There's also lessons in forestry, on how to get back those old growth forests. Unfortunately, the time scales involve are truly immense, on the order of 500 years:
if the conifers that have now fallen into disfavor were to be removed, the future old-growth forest would develop a bit more quickly. But once you understand that the first generation of trees is going to grow too quickly anyway and, therefore, is not going to get very old—and that the stable social structure of the forest is not going to be laid down until much later—then you can take a more relaxed view. The plantation trees growing in the mix will depart in less than a hundred years because they will grow above the tops of the deciduous trees and stand unprotected in the path of storms that will ruthlessly uproot them. These first gaps will be vanquished by the second generation of deciduous trees, which can now grow up protected by the leafy canopy formed by their parents. Even if these parents themselves don’t grow very old, they will still grow old enough to give their children a slow start. Once these youngsters reach the age of retirement, the future old-growth forest will have achieved equilibrium, and from then on, it will hardly change at all. It takes five hundred years from the time a national park is established to get to this point. Had large areas of an old deciduous forest that had seen only modest commercial use been put under protection, it would take only two hundred years to reach this stage. However, because all over Germany the forests chosen for protection are forests that are far from their natural state, you have to allow a little more time (from the trees’ point of view) and a particularly intense restructuring phase for the first few decades. There’s a common misconception about the appearance of old-growth forests in Europe (pg. 237)
 In any case, the book is well written, easy to read, conversational, and education. How often do you get that great combination all put together? Recommended.

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