When the first winter storm blasts through southeastern Virginia, Dragon Run-part swamp, part marsh, part old-growth woodland-pays tribute to the wind. Oaks, maples, gums, and beeches release dead leaves by the millions and these shower to earth, where they pile up as crisp, ankle-deep mounds. Branches snap off, sometimes trees crash down. Sheaves of dead grasses sink into marsh muds, and other plants buckle into the shallow, murky waters of the bottomlands. The storm kills uncounted numbers of insects, some birds, a few squirrels. By late December, Dragon Run is partially buried in organic debris.
Dig down through the debris and you will discover the accumulated litter of many past seasons-moist cushions of decayed leaves, bits of spiders and insects, mouldering branches, the carcasses of small mammals.
Fungi are nature’s premier decomposers. Like other heterotrophs, they feast on organic compounds produced by other organisms. But few organisms besides fungi digest their dinner out on the table, so to speak. As fungi grow in or on organic matter, they secrete enzymes that digest it into bits that their individual cells can absorb. This “extracellular digestion” of organic matter liberates carbon and other nutrients that also can be absorbed by plants-the primary producers of Dragon Run and nearly all other ecosystems on earth.
1. Fungi are heterotrophs. Together with heterotrophic bacteria, they are decomposers of the biosphere. Saprobic types obtain nutrients from nonliving organic matter. Parasitic types obtain them from tissues of living hosts.
2. Most fungi are multicelled. They form a mycelium, which is the food-absorbing part of the fungal body. A mycelium is a mesh of hyphae, which are elongated filaments that develop by repeated mitotic cell divisions.
Dig down through the debris and you will discover the accumulated litter of many past seasons-moist cushions of decayed leaves, bits of spiders and insects, mouldering branches, the carcasses of small mammals.
Fungi are nature’s premier decomposers. Like other heterotrophs, they feast on organic compounds produced by other organisms. But few organisms besides fungi digest their dinner out on the table, so to speak. As fungi grow in or on organic matter, they secrete enzymes that digest it into bits that their individual cells can absorb. This “extracellular digestion” of organic matter liberates carbon and other nutrients that also can be absorbed by plants-the primary producers of Dragon Run and nearly all other ecosystems on earth.
1. Fungi are heterotrophs. Together with heterotrophic bacteria, they are decomposers of the biosphere. Saprobic types obtain nutrients from nonliving organic matter. Parasitic types obtain them from tissues of living hosts.
2. Most fungi are multicelled. They form a mycelium, which is the food-absorbing part of the fungal body. A mycelium is a mesh of hyphae, which are elongated filaments that develop by repeated mitotic cell divisions.
3. Fungi secrete enzymes that digest food outside their body, then fungal cells absorb breakdown products. Their metabolic activities also release carbon dioxide to the atmosphere and return many nutrients to the soil, where they become available to producer organisms.
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