| Popis: |
To determine how Vaccinium alaskaense, Cornus canadensis, Coptis asplenifolia, Tiarella trifoliata, and Rubus pedatus invade and maintain themselves in conifer forests, we conducted experiments on seed germination and seedling survival and examined clonal development in old-growth, young-growth, and 4- to 6-year-old stands. Seed of all species germinated well in laboratory and field tests (average 23 – 90%), but low germination rates of C. canadensis and T. trifoliata under actual field conditions may retard their invasion of young stands. Survival of all species at 3 and 4 years was lower in the young stand (40 years) than in the old stand (250 + years) and may be related to incident solar radiation. Regressions of the percentage of survival on percentage of transmitted solar radiation were significant (P ≤ 0.05) for all species except C. canadensis. Seed predation and type of seedbed (moss, logs, duff) had little effect on germination and survival rates. Average annual rhizome or stolon growth was slower in the young stand (1 – 3 cm) than in the old stand (1 – 34 cm). In the clearcut, clones had dense foliage because of shorter internodes and more leaves per node and annual rhizome and stolon growth averaged 77 – 160 cm. Both seedling establishment among clones and continual clonal expansion maintain species in old stands, while invasion in young stands is primarily by seedling establishment. |
