字幕表 動画を再生する 英語字幕をプリント Hi, I’m Ranger Jim and I’d like to share with you a few things that have recently been discovered in the tops of ancient redwood trees, the old-growth redwood forest canopy. Research in old-growth forest canopies has increased dramatically since 1996 with the initiation of scientific tree climbing by Dr. Stephen C. Sillett at Humboldt State University in Arcata, California. His research has revealed a previously under-appreciated ecosystem high in the tops of the trees—an arboreal ecosystem that is virtually impossible to study from the ground. As they age over many hundreds of years, and in response to wind, fire, and other falling trees, redwoods develop very unique and individual crown structures. Their complicated crowns consist of re-sprouted, or “reiterated” trunks arising from the main trunk, other trunks, and limbs. Also over many years, these woody structures in the trees’ crown interact, sometimes rubbing against each other and eventually fusing so that living cambium produces sapwood that bridges regions of the crown hydraulically. Right here I’m standing next to an example of a huge reiterated trunk that came crashing down out of this monster redwood here last wintertime. Fusions, very old limbs, and crotches between reiterated trunks form platforms on which organic soils begin to build from falling leaf litter. These organic soils in turn provide a substrate for epiphytes, or tree-dwelling species like leather fern, which forms huge sprawling mats that develop arboreal soils that are over a meter deep in places. A set of fern mats in an old tree crown can weigh over 1,700 pounds dry mass, and hold over 2,000 gallons of water. Soils beneath fern mats and decaying wood inside trunks and limbs can store huge amounts of water that can sustain drought-sensitive organisms high above the ground throughout the year. The wandering salamander, an arboreal species and the only amphibian denizen of redwood forest canopies, resides in cavities within fern mats and decaying wood and feeds on a rich invertebrate community that includes aquatic crustaceans called copepods that are also found in local streams. In addition to huge leather fern mats, redwood forest canopies are home to at least 265 epiphyte species, or tree dwelling species, including: lichens, mosses, liverworts, flowering plants, ferns, and even other conifers. All of the flowering plants found in the canopy are usually found on the forest floor, including huckleberries, salal berries, tanoak, and bay-laurel. Even in the oldest and most complex redwood forests, just a very few old trees provide the majority of arboreal diversity, because these trees have the majority of gnarly structures available in the forest. What amazes me is that we’ve only begun to investigate the complexity of the ancient redwood forest canopy, and only about 100,000 of the original 2,000,000 acres is still ancient forest. Thanks to our forbearers, almost half of that is now protected within Redwood National and State Parks.