Double-stocking for overcoming damage to conifer seedlings by pocket gophers

Abstract

A 5-yr study was conducted on national forests in Idaho and Oregon to evaluate how doubling the seedling stocking rate of lodgepole pine ( Pinus contorta) would relate to 5-year survival and the uniformity of distribution of seedlings in the presence of northern pocket gopher ( Thomomys talpoides) damage. Either 4 or 8 seedlings were planted in 40-m 2 subplots (1000 or 2000 seedlings/ha) and monitored for gopher damage. We found that the number of seedlings attacked by gophers, and consequently, the number of seedlings surviving for 5 years, were directly proportional to the stocking rate, but the consistency of seedling distribution within each site (as measured by the proportion of 40-m 2 subplots with ≥ 2 surviving seedlings) did not double with stocking rate. In some situations, increasing the stocking rate should be considered as a method for overcoming pocket gopher damage.