Growth response of massive sequoiadendron giganteum trees to mechanical treatments

Abstract

We measured the radial growth response of large (˃2 m dbh) giant sequoia (Sequoiadendron giganteum) trees to a wide variety of mechanical treatments. Treatments varied widely in the amount of neighboring competition that was removed. A relatively low-intensity treatment removed surrounding small neighboring trees, a moderate-intensity treatment removed neighboring codominant canopy trees on one side via gap creation, and a high-intensity treatment removed trees from large areas completely surrounding individual large giant sequoias. The majority of study trees ranged in age between 500 and 1,500 years old. The high-intensity treatment that removed all surrounding trees resulted in the strongest and most persistent growth release compared with that of control trees. Surprisingly, the low-intensity treatment, which removed only trees ˂3.4 m tall also resulted in a growth release, although it was not as persistent as with the other treatments. No correlations were found between growth release and distance from perennial surface water or fire scar size. The results suggest that periodic disturbances are important for large tree development and that vigor of even very large giant sequoia can be maintained with removal of surrounding competition from smaller trees. Treatments that remove greater amounts of competition, up to most of surrounding the competition, can be expected to result in the greatest growth release in large giant sequoia.