Damage reduction to ponderosa pine seedlings from northern pocket gophers by vegetation management through grass seeding and herbicide treatment

Abstract

2,4-D herbicide treatment was applied to 2 treatment units to remove the forbs that are the preferred food of pocket gophers. One of these units also was seeded with grasses prior to the 2,4-D treatment. The effect of 2,4-D and grass seeding plus 2,4-D treatments were compared to an untreated control unit. Long-term monitoring (7 yr) was conducted on the 3 units for vegetative cover (7 yr), pocket gopher activity, and individual survival times and time until gopher damage for 2 cohorts of seedlings (5 and 6 yrs). The 2,4-D treatments greatly reduced vegetative cover of the forbs and seeding increased grass cover on the unit receiving that treatment. Pocket gopher activity was reduced somewhat on the unit receiving only the 2,4-D treatment and more so on the unit receiving grass seeding and 2,4-D, although gophers remained active to some degree throughout the study. Both cohorts of seedlings for both treatments units showed greater average times until gopher damage over seedlings on the control unit. However, seedling survival from all sources of mortality was not positively affected by the treatments for the first cohort of seedlings. The 2,4-D treatment appeared to have killed some of the seedlings; however, seedlings that survived the treatment were in a situation where they were less likely to be damaged by gophers and seemed to have improved growth rates.