Small canopy disturbances are important to the structure and function of forest ecosystems. Fine-scale disturbances (the death of one to many trees) largely control the population dynamics in our forests between larger catastrophic events. An experimental study of ecosystem responses to the creation of tree-fall gaps of varying size was conducted in northwestern coniferous forests. Gaps were created in the fall of 1990 in mature (80 to 150 years) and old-growth (400-500 years old) ecosystems dominated by Douglas-fir (Pseudotsuga menziesii) and western hemlock (Tsuga heterophylla). Five gap sizes ranging from 0 to 2000 m2 were created in four stands, with gap diameters scaled in fixed proportion to the average canopy height in each stand. Roots were severed in trench plots placed in open- and closed-canopy areas to compare with gap responses. Both above-ground and below-ground processes were studied. Establishment, survival, and growth of trees and understory vegetation were measured within and surrounding gaps. Solar radiation, air and soil temperature, and soil moisture were measured. Litter input, decomposition, root density, N-mineralization and N-leaching, soil microbial response and myccorrhyzal mats have been studied. Population biology of selected understory herbs, and composition and abundance of small mammal communities, have also been examined.
Andrew N. Gray, Jerry F. Franklin, Kristiina A. Vogt, Mark J. Easter, Robert Van Pelt, Robert J. Pabst, Robert P. Griffiths, Thomas A. Spies
Small canopy disturbances are important to the structure and function of forest ecosystems. Fine-scale disturbances (the death of one to many trees) largely control the population dynamics in our forests between larger catastrophic events. An experimental study of ecosystem responses to the creation of tree-fall gaps of varying size was conducted in northwestern coniferous forests. Gaps were created in the fall of 1990 in mature (80 to 150 years) and old-growth (400-500 years old) ecosystems dominated by Douglas-fir (Pseudotsuga menziesii) and western hemlock (Tsuga heterophylla). Five gap sizes ranging from 0 to 2000 m2 were created in four stands, with gap diameters scaled in fixed proportion to the average canopy height in each stand. Roots were severed in trench plots placed in open- and closed-canopy areas to compare with gap responses. Both above-ground and below-ground processes were studied. Establishment, survival, and growth of trees and understory vegetation were measured within and surrounding gaps. Solar radiation, air and soil temperature, and soil moisture were measured. Litter input, decomposition, root density, N-mineralization and N-leaching, soil microbial response and myccorrhyzal mats have been studied. Population biology of selected understory herbs, and composition and abundance of small mammal communities, have also been examined.