Understory Responses to Tree Thinning and Seeding IndicateStability of Degraded Pinyon Juniper Woodlands
Degraded ecological conditions stemming from intensive land use (e.g., heavy livestock grazing, overharvesting, etc.) are common in pinyon-juniper woodlands and savannas in the western United States. In some cases, conditions on highly impacted sites may represent degraded stable states, resistant to change from management. A goal of ecological restoration is to drive systems from stable, degraded states toward more desirable conditions, closer to historical ranges of variability. To facilitate such transition, woodland systems may require active restoration treatments that include manipulation of vegetation structure and alteration of microclimate and soil conditions. Treatments found to be successful on other sites have included tree thinning, slash additions, and augmentation of understory communities with seeds or propagules of native plants. In this work, we examined understory plant community responses to ecological restoration treatments at two pinyon-juniper woodland sites in northwestern Arizona. We asked the following questions: 1) do restoration treatments, that include tree thinning prescriptions guid-ed by reference conditions, scattering thinning slash, and seeding, lead to increases in plant cover and species richness; and 2) how do understory responses differ across sites with contrasting soils characteristics?