Thirty-Five-Year Growth of Ponderosa Pine Saplings in Response to Thinning and211 Understory Removal

摘要

Diameter increments for individual trees increased curvilinearly and stand basal211u001earea increments decreased curvilinearly as spacing increased from 6.6 to 26.4 211u001efeet. Average height growth of all trees increased linearly. and stand cubic 211u001evolume growth decreased linearly as spacing increased. Large differences in tree 211u001esizes developed over the 35 years of study with various spacing treatments. Plots 211u001ewithout understory grew more during the first 20 years of study but soil quality 211u001edecreased. During the last 15 years, growth rates on plots without understory 211u001ewere not superior to plots with understory when adjusted to common basal areas 211u001eand volumes. Growth rates for the largest trees on the plots were decreased by 211u001ecompletion from smaller trees. After 35 years, total cubic volume yield decreased 211u001elinearly as spacing increased but Scribner board-foot yields increased 211u001ecurvilinearly as spacing increased, and spacings of 13.2, 18.7, and 26.4 feet 211u001eproduced about the same board-foot yield. Live crown ratios increased with 211u001eincreasing spacing, primarily because of increased height growth. Twenty years 211u001eafter thinning, crown width increased curvilinearly as spacing increased and was 211u001egreater in the absence of understory.