Economic assessment of ungulate herbivory in commercial forests of eastern Oregon and Washington, USA

Abstract

Four forest stands in eastern Washington and Oregon, USA, containing exclosures to prevent or impede ungulate herbivory, were modeled to forecast timber yields and soil expectation values (SEVs) at harvest. Contrasts of ponderosa pine ( Pinus ponderosa Dougl. ex Laws.) growth and yield inside and outside exclosures show that ungulate herbivory may either promote or depress tree volume growth. Projected income from stands with more intensive stocking management and with inclusion of regulated livestock herbivory was higher than that of less intensively managed stands without livestock for scenarios with projected rising stumpage price levels for 2040. Under an assumption of future stumpage prices held constant at 1990 levels, the reverse was true. Ungulate herbivory plus planted stock and prescribed fire in site preparation provided the highest stand value at two sites. Sites without prescribed fire fared better when fenced to prevent livestock or big game herbivory. The results illustrate that ungulate herbivory alone is not the determinant factor of the economic yield of stands, but ungulate herbivory can have substantial impact on site productivity when used in conjunction with prescribed fire, stocking control, and species selection.