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Patterns of growth, mortality and biomass change in a coastal Picea sitchensis ‐ Tsuga heterophylla forest
Author(s) -
Greene S. E.,
Harcombe P. A.,
Harmon M. E.,
Spycher G.
Publication year - 1992
Publication title -
journal of vegetation science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 115
eISSN - 1654-1103
pISSN - 1100-9233
DOI - 10.2307/3235838
Subject(s) - tsuga , biomass (ecology) , western hemlock , disturbance (geology) , competition (biology) , environmental science , ecology , forestry , biology , agronomy , geography , paleontology
. Ten years (1979‐1989) of growth and mortality were determined in a 130‐yr old stand on the Oregon coast based on periodic remeasurements in 441000 m 2 plots. Western hemlock ( Tsuga heterophylla ) constituted 90 % of the individuals and 57 % of the biomass. Wind is a major form of disturbance in this area, creating both small discrete and large diffuse disturbance patches; wind therefore has a direct effect on the location and extent of regeneration. Rates of tree mortality were high for this coastal stand (2.8 %/yr), especially compared to similar‐aged stands in the western and eastern Cascade Ranges. Though low in absolute density, Sitka spruce ( Picea sitchensis ) persisted in competition with the more tolerant western hemlock. Net production of bole biomass (4.9 Mg ha ‐1 yr ‐1 ) did not equal mortality (8.7 Mg ha ‐1 yr ‐1 ), and total biomass declined over the 10‐yr measurement period from 499 to 460 Mg/ha; this trend may have begun as early as the mid‐1950's at a peak biomass of about 600 Mg/ha. The decline may have been due to a positive feedback in which new gaps and enlarging gap perimeters exposed more and more trees to potential wind damage.