Revegetating Disturbance in National Parks: Reestablishing Native Plants in Saguaro National Park, Sonoran Desert

Abstract

Habitat in national parks is periodically disturbed for road maintenance, and few revegetation protocols of known financial cost exist for this disturbance, especially in deserts where extreme environments constrain natural revegetation. In Saguaro National Park of the Arizona Upland Subdivision of the Sonoran Desert, we monitored survival of 1587 outplanted individuals of 33 native perennial species for revegetating a 2006 re-construction project of the park's Cactus Forest Drive. Outplants were caged to deter vertebrate herbivory and provided with supplemental water in the hot, dry part of summer. Overall plant survival was high — 84% (1340 of 1587 outplants) — one year after planting. Survival was generally consistent across species, with survival >50% for 32 of 33 (96%) species. Survival of two tree species (Parkinsonia microphylla (yellow paloverde) and Prosopis velutina (velvet mesquite)), monitored for two years, declined little or not at all from the first to the second year and was 55% and 67%, respectively, at two years. The project met management goals of reestablishing a 1:3 lost: restored ratio of tree density required for habitat restoration of an endangered owl species and of reestablishing a range of native species for aesthetic and vegetation structural restoration. Budget estimates indicated a cost per plant of $54 from grow-out in a nursery through plant maintenance in the field. This cost also included supporting activities of site preparation, exotic plant control, and effectiveness monitoring. The monitoring data, combined with longer term observations, suggest that the National Park Service's revegetation strategy effectively established a range of native plant growth forms and met habitat restoration targets.