Standing crop, production, and turnover of fine roots on dry, moderate, and wet sites of mature Douglas-fir in western Oregon

Standing crops of live and dead fine ( On the basis of changes in standing crops of live and dead fine roots, we estimatedfine-root production on the dry, moderate, and wet sites to be 6.5, 6.3, and 4.8 Mg/ha/year ;turnover to be 7.2, 7.2, and 5.5 Mg/ha/year ; and decomposition to be 8.2, 8.0, and6.9 Mg/ha/year. The effect of site conditions may be indicated by the number of timesthat the mean standing crop of live fine roots turned over per year : 2.8 on thedry site, 2.0 on the moderate site, and 1.7 on the wet site. Cyclic death and re-placement of fine roots in a succession of favorable microsites may be an adaptivestrategy to maintain the largest number of active roots at a minimum metabolic cost.Results of this study confirm the importance of fine roots as a major pathway of carboncycling in temperate forests.
Key words : Douglas-fir, Pseudotsuga menziesii, roots, fine roots, root production, rootturnover, root decomposition, root growth, moisture stress.