PJ101-Soils & Topography
Soils: Pinyon and juniper woodlands occupy a wide variety of soils, but there are some general differences in soil characteristics that occur between post-settlement and persistent woodlands. Soils occupied by persistent or old-growth woodlands are most commonly associated with shallow to restrictive layers including claypans, fractured basalt, and calcareous horizons and extremely cobbly, or very coarse-textured with gravelly surfaces, often resulting in shallow and transient soil moisture storage. The highest tree densities are most frequently found on Mollisols, which are typically the most productive among the soil orders common in the semi-arid West (Nettleton and Mays 2007), and have the highest potential for encroachment (Campbell 2015). Woodlands found on deeper and more productive soils (often with higher levels of organic matter) are relatively young (<150 yrs) and were previously occupied by shrubland or grassland communities.
Topography: The majority of Utah juniper (Juniperus osteosperma) and pinyon (Pinus spp.) woodlands are located between 4,500–8,000 feet (1,400-2,400 m) and western juniper (J. occidentalis) between 1,500–6,000 feet (460-1,800 m). But elevations occupied by these woodlands vary with latitude and, at local scales, with aspect. In the White Mountains just east of Bishop, California, woodlands grow between 6,500–9,500 feet (2,000-2,900 m). At 9,500 feet (2,900 m), they are replaced by limber pine (Pinus flexilis) and bristlecone pines (P. longaeva). In the northern range of western juniper along the Columbia River, trees are found at 600 feet (180 m). Another exception is Sierra juniper (J. grandis), which typically grows in open scattered stands with other conifers near the treeline on the east slopes of the Sierra Nevada Mountains and at high elevations in the mountains of central and western Nevada above 9,000 feet (2,700 m). Woodlands also grow across a broad range of landforms including ridges, hill and mountain slopes, terraces, tablelands, plateaus, alluvial fans, broad basins, and valley floors.
For more detailed information and citations refer to: Miller, R.F. and others. 2019. The Ecology, History, Ecohydrology, and Management of Pinyon and Juniper Woodlands in the Great Basin and Northern Colorado Plateau of the Western U.S. US Forest Service, Rocky Mountain Research Station. RMRS-GTR-403. 284 pg.