Herbaceous Response to Cattle Grazing Following Juniper Cutting in Oregon

Abstract

The rapid expansion of western juniper (Juniperus occidentalis spp. occidentalis Hook.) across the northern Great Basin has diminished shrub and understory plant composition and reduced forage production. Juniper removal has accelerated during the past decade in Oregon and California to restore shrub-steppe plant communities. Livestock grazing can affect posttreatment successional dynamics, but these impacts have not received adequate study. This study evaluated herbaceous plant recovery in a cut western juniper woodland subjected to grazed and ungrazed prescriptions over 4 growing seasons. The study consisted of 4 treatments: ungrazed cut, grazed cut, ungrazed woodland, and grazed woodland. Stocking rates were 0.78 cow-calf pairs per ha for 5 days in the first year following treatment and 0.94 cow-calf pairs per ha for 4 days in the second year after treatment. The grazing portion of the study lacked true replication because grazed plots were not independent of each other (cattle had access to all plots simultaneously). This limits the strength and interpretation of the grazing results. Juniper cutting removed overstory interference and resulted in significant increases in herbaceous cover, biomass, and seed production when compared to adjacent woodlands. Herbaceous cover, standing crop, perennial grass density, and seed production all increased in the ungrazed cut treatment compared to ungrazed woodland. A similar level of response was measured in the grazed pasture where herbaceous responses were greater in the grazed cut vs. the grazed woodland. Grazing in the cut treatment did not limit herbaceous recovery except that perennial grass seed production was lower in the grazed cut than in the ungrazed cut. Rest or deferment is required the first several growing seasons after juniper cutting to provide plants the opportunity to maximize seed crops. These results imply that juniper cutting had a greater effect on herbaceous dynamics than did the grazing application.