Sierran
vegetation: A gap analysis
Frank W. Davis and David M. Stoms
(Full
Chapter)
Gap
analysis assesses the distribution of plant community types and
vertebrate species distributions among land classes defined by
ownership and levels of protection of biodiversity. Gap analysis
helps to identify which plant communities and species might be
especially vulnerable to different human activities that can lead
to habitat conversion or degradation.
This
chapter presents a gap analysis of plant community types the Sierra
Nevada region, an area of 63,111 km2 (24,368 mi2). Ownership of
the region is 37% private, 47% national forests, 10% national
parks, 5% Bureau of Land Management, and less than 2% in other
public lands. Land ownership and land management patterns contrast
sharply between the northern Sierra Nevada versus the central
and southern subregions. Parks and reserve lands contribute less
than 2% of the northern region versus 27% of the central/southern.
We
mapped eighty-eight natural plant community types within the region.
Sixty-seven types were mapped over areas greater than 25 km2 (9.65
mi2. The ownership profiles of Sierran plant communities systematically
reflect the concentration of private lands at lower elevations
and of national parks in the central and southern portion of the
range. Less than 1% of the foothill woodland zone of the Sierra
Nevada is in designated reserves or other areas managed primarily
for native biodiversity, and over 95% of the distribution of most
foothill community types is available for grazing. Low to middle
elevation Sierran forests are not well represented in designated
reserves, especially in the northern Sierra Nevada. However, large
areas of most of these forest types on U.S. Forest Service lands
have been administratively withdrawn from intensive timber management
based on current forest plans. Many high-elevation forest and
shrubland community types are well represented in parks and ungrazed
wilderness areas. Our analysis identifies thirty-two widespread
community types whose conservation status warrants concern and
twelve types that appear well protected based on their present
distributions.