PLS 147 Lecture Notes - Lecture 21: Ceanothus Velutinus, Pinyon Pine, Great Basin Desert
East side of Sierra, Cascades, & Transverse Ranges
Deserts: Great Basin, Mojave
East side: Non Desert vegetation:
● dry in general due to the rainshadow effect
● more continental
○ they block the maritime influence
○ cold winter, hotter summer with rain
Species
● Alpine and subalpine sagebrush (Artemisia)
● Mountain Hemlock (Tsuga mertensiana) in the subalpine
● Mixed Limber Pine(P. flexilis)
● Bristlecone pine (P. longeva)
● round-leaf snowberry
● montane meadows
● Aspen (populus tremuloides) more common in wetter sites of the east side
● Jeffrey Pine woodland
● Mountain mahogany
● Mountain brush communities (Ceanothus velutinus, prunus spp, Arctostaphylos patula)
● lower elevation: Jeffrey Pine P. jeffreyi and Pinyon pine P. monophylla (open woodland)
Single-leaf (single needle) Pinyon,
P. monophylla
Woodland
●most widespread type of pinyon
●slow-growing because dry
●live for hundreds of years, and height of only 12 m
●Begins bearing cones at 35 years, exhibitsmasting
●establishment and early growth facilitated by partial shade of mature shrubs "nurse plants"
●fossil packrat middens suggest that as recently as 7500 years ago, much of Mojave Desert was
pinyon pine and juniper vegetation
●not fire-adapted
●pinyon pines (pine nuts) as staples for Native Americans
●fire management
○fuels were historically insufficient to carry fire
■understory plants in closed stands do not respond well to fire
○fires were often high severity and deplete soil seed reserves
○prescribed fires used by range managers to open stands and promote grass cover for
livestock foraging
○conversely, when open, without successful post-fire seeding, highly flammable annual
grasses become established
○changes in fire throughout range likely a combination of human intervention and high
cover of Bromus tectorum (cheatgrass) which carries fire
