A management-oriented classification of pinyon-juniper woodlands of the Great Basin

Abstract

Research SummaryPinyon-juniper woodlands cover about 7.1 million ha (17.6 million acres), constituting about 18 percent of the land area of the Great Basin, yet no comprehensive ecological classification of them has been attempted before. To begin a classification, we sampled a random set of 66 of the approximately 110 mountain ranges within the Great Basin. Macroplots were systematically placed at 200 m elevation intervals up and down cardinal slopes. ~a t a on tree age, vegetational cover, soils, and land form were collected from 1972 to 1975 within 463 stands used to either develop or test the classification presented here.We used the already delineated National Hierarchical Frameworkof Ecological Units (ECOMAP 1993) down to the Section level to frame our classification to an intermediate coarseness. This subdivided the Great Basin into nine relatively environmentally homogenous Sections. Observable vegetational characteristics were used at lower layers because ECOMAP delineations are not yet available. Nine categories were recognized at the Series level based on variation in the relative cover contributions by the various junipers and pinyons. Subdividing the nine Sections by the nine possible Series gave 45 actual geographically distributed Series. The next lower level of the vegetation-based classification is the Association, identified by the dominant shrub species. Twenty-six species of dominant shrubs, combined with the Sections and Series, gave 183 Associations. The Sub-association level was based primarily on the 23 dominant native perennial grasses. When, rarely, a native, perennial grass was not present, the native perennial forb showing the greatest relative cover was used instead to name the Sub-association. This resulted in 326 Subassociations distributed over the entire Great Basin. The manager needs only be concerned with the subset that occurs in their Section of interest, however.With most Sub-associations found only once, our classification is only a beginning toward the desired end. It also reflects the complexity of the communities associated with Great Basin woodlands. Much more sampling redundancy will be required before we can begin to find out which Sub-associations are most common and how they relate to topographic and edaphic patterns. Our approach, however, provides a substantial beginning to a hierarchical classification of these woodlands and is easily modified and expanded. Using and building on our approach should allow the manager to better relate the results of previous as well as new studies and management experiences to each other.

Impacts of Western Juniper on Plant Community Composition and Structure

“…En la asociación de "Mountain big sagebrush" la cobertura de "Sagebrush" disminuyó a aproximadamente 80% del maximo potencial conforme el la cobertura de copa del "Juniper" incremento a aproximadamente 50%. El "Aspen" (populus tremu-Conversion of shrub steppe communities in the Intermountain West to J u n i p e r u s woodlands has been an active process during the past 120 years (Tausch et al 1981, West 1984, Miller and Wigand 1994, West et al 1998. Over 90% of the 3.2 million ha of western juniper (Juniperus occidentalis Hook.)…”

Environmental, genetic, and ecophysiological variation of western and Utah juniper and their hybrids: A model system for vegetation response to climate change. Final report

“…members of woodland communities in the intermountain west (West et al 1978). Along with single leaf pinyon (Pinus monophylia Torr.…”

“…& Frem. ), J. osteosperma forms the overstory of woodlands that cover about 71,500 km2 in the Great Basin (West et al 1978). In contrast, J. occidentalis is confined largely to the Sierra Nevada and Cascade ranges, although a few populations occur in the extreme northwestern portion of the Great Basin floristic province (Little 1971).…”

Rangeland resource trends in the United States: A technical document supporting the 2000 USDA Forest Service RPA Assessment

“…It should be noted that non-federal lands occupy less than one-fourth of all lands in the two principal pinyon-juniper states of the Great Basin, Nevada and Utah (USDA Soil Conservation Service 1990). Further, private lands in the Great Basin are situated primarily at lower elevations and do not include many productive sites (West et al 1978). Research has shown that woodlands have greater canopy cover at higher elevations in the Great Basin, and that the median cover for all sites is on the order of 45-50 percent (fi gure 3.3) (Tausch andTueller 1990, West et al 1998).…”