Depauperate understory plant communities resulting from intensive livestock grazing in pinyon-juniper woodlands of the western United States may represent degraded stable states, resistant to ecological restoration treatments. In this study, we analyzed 10-yr understory plant community responses to restoration treatments that included tree thinning to approximate historical densities of pinyon pine (Pinus edulis) and juniper (Juniperus osteosperma), scattering of thinning slash to improve soil conditions, and seeding at two woodland sites (Craig Ranch and Goose Pond) in northwestern Arizona. Results showed that thinning resulted in significant reductions in tree density at both sites, as well as reductions in tree basal area at the Goose Pond site. Boles, branches, and tops of the thinned trees scattered across the study sites resulted in few changes to woody surface fuel loading. Thinning and addition of woody material, along with seeding, resulted in only minor changes in understory cover and species richness at both sites. However, plant cover and species richness were both negatively correlated with tree density. Degraded conditions at the sites appeared to be stable, and we suggest that treatments implemented in our studies may have not been intensive enough to produce significant understory responses and meet restoration objectives. Managers aiming to restore understory diversity at similar sites may be required to use heavier thinning prescriptions and repeated seeding. More work is needed to test new restoration approaches that are designed to drive degraded pinyon-juniper woodlands over resilience thresholds toward more diverse understory communities.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.
Vol. 70 • No. 4