What determines the effectiveness of pinyon-juniper clearing treatments? Evidence from the remote sensing archive and counter-factual scenarios
Colorado Plateau in the Upper Colorado River Basin above Lake Mead in eastern Utah and western Colorado (a few sites in New Mexico).
Description of Site
Regional study of 302 separate treatment events in 1,569 distinct treatment polygons across a broad range of pinyon-juniper woodland communities in the Colorado Plateau.
Included prescribed burning, mastication, chaining, hand-cutting, or other, seeded or not; all sites all measured had a single treatment application; Time period – time since treatment 5-30 years, with most treatments applied between 2005 and 2010; Measurements – cover estimates for bare ground, litter, annual forb and grass, perennial forb and grass, shrubs, and trees from the Range Assessment Platform ver. 2.
Authors found evidence that treatments reduced tree cover and increased shrub and perennial herbaceous cover for 10 or more years. Treatments were also associated with increases in annuals, mostly non-native species. Some geometrographic settings were likely to return to pretreatment conditions within 10-15 years, while other posttreatment conditions were more persistent. Despite these trends, authors reported a high degree of variation that was not explained by ecological site factors.
In literature from across the Colorado Plateau and Great Basin, plant cover is the most common trait response monitored following tree removal. Across the broad range of study sites there was considerable variation in the responses of different plant cover groups across the study area, which obscured the relationship between posttreatment plant response to ecological site characteristics.
Soils, topography, and climate play an important role in plant community resilience and resistance to invasives. Other factors including treatment type, treatment severity, disturbance histories, pretreatment vegetation, post-treatment management, and weather can blur the relationships between vegetation response and ecological site characteristics (see Primary Components that influence plant succession following disturbance). Range management has always been a combination of art and science, and the art largely comes from experience in land management.