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9 Lessons from the Trees, the Truffles, and the Beasts Drawing lessons from interactions among trees, belowground fungi, and forest animals and relating them to the policies and practices of forest management may seem a stretch at first glance. But remember, this group of organisms is simply our surrogate to represent the myriad other interdependent groups of seen and unseen organisms that form self-reinforcing feedback loops with one another and their forested environment. Collectively, these organisms, as well as the soil, are the biological capital—the intrinsic value—of the forest . Let’s briefly summarize some of their functions, using our surrogate to represent all self-reinforcing feedback loops in terrestrial ecosystems across the Earth. Photosynthesis provides the energy needed to sustain life on Earth. Trees depend on it directly, and the mycorrhizal fungi, which obtain their energy from the trees, depend on photosynthesis indirectly. The tree, in turn, depends on the fungi as suppliers of nutrients from the soil. Among the mycorrhizal fungi, truffles produce fruit-bodies that are important as food for many animals. By consuming the truffles and later defecating the spores, the animals disperse the fungi. The animals depend on trees as habitat for nesting and other activities. Raptors, such as owls, use the trees as well and prey on the animals that eat the truffles, sometimes carrying their prey with spore-laden stomachs for considerable distances, which further disperses those spores. Then, recall the simile of the handful of pebbles tossed into a pond. The expanding circles of ripples from one pebble intersect with those of others to create innumerable intersections. Thus our tree-truffle-beast combination intersects with other functional groups. For example, the nitrogen cycle includes free-living, nitrogen-fixing bacteria that thrive alongside the mycorrhizal fungi in the soil. Furthermore, plants that form nitrogen-fixing nodules with symbiotic bacteria also depend on mycorrhizal fungi for their nourishment. The nitrogen fixed by those nodules feeds into plant tissues and is returned to the soil by leaf fall or exudation of nitrogen compounds from leaves and roots. Nitrogen-fixing lichens in the tree crowns contribute nitrogen to the soil by similar actions. Meanwhile, nitrogen is returned to the soil in animal excretions. Nearly all the nitrogen is captured by the mycorrhizal R4432.indb 225 R4432.indb 225 9/25/07 11:58:41 AM 9/25/07 11:58:41 AM 226 Trees, Truffles, and Beasts fungi and cycled back into the host trees or used by other soil organisms. So now the functional ripples of the tree-truffle-animal combination intersect with those of bacteria, leaves, lichens, and other soil organisms. Although we could go on and on and on, here are a few examples of such feedback loops: (1) Photosynthesis provides the energy required for nitrogen fixation. In turn, the fixed nitrogen is vital for functioning of the plants with nitrogen-fixing nodules and for decomposer organisms, which cycle the nitrogen throughout the system. The cycled nitrogen supports more plant growth, more photosynthesis, more nitrogen fixation, and more nitrogen cycling. (2) Trees, which grow from the soil, eventually die and fall to provide animal habitat and improve the health of the soil from which they originally grew. (3) Soil fungi and bacteria thrive best in healthy soil, which they improve by enhancing soil texture, so that aeration and water infiltration are improved to the benefit of the very same fungi, bacteria, and other soil organisms. (4) Animals dig to obtain truffles. The excavations then enable the soil to better capture rainwater and thereby enhance production of the truffles desired by the animals. The ripples of these and the countless other feedback loops keep expanding and intersecting, seemingly without end. A large proportion of these feedback loops and their interactions are unseen and thus not considered in how we humans treat forests worldwide. Taken together, however, they are how forests function. They are the biological capital of the forest. Our intent in writing this book is to reveal a glimpse of this mostly unseen biological capital to all who care about the forest, whether a lover of nature; a receptionist in an office; users of ecosystem services, such as clean water or sequestration of carbon; or workers and business people who earn their living from products of the forest. It is not our purpose to prescribe forest policy or forest practices. However, if the lessons of the trees, truffles, and beasts are to have meaning, we need to consider the...

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