Inhibiting Effect of Ponderosa Pine Seed Trees on Seedling Growth

Abstract

Ponderosa pine seed trees, numbering 4, 8, and 12 per acre, were left standing for 9 years after harvest cutting on the Challenge Experimental Forest, Calif. Seedling heights were measured at ages 5, 9, and 14, and for all ages were poorest if within 20 feet of a seed tree. Seedlings 20 feet or less from a seed tree at the ages given lost the equivalent in years of height growth: 5(4.1); 9(6.8); 13(10.6). Seed-tree density greatly affected seedling height–the greater the density, the poorer the height growth. The inhibitory effect of the seed trees extended outward at least 40 feet, and persisted 4 years after their removal.