BIOLOGICAL SURVEY AND HABITAT RESTORATION NEEDS ANALYSIS
FOR THE ALTADENA FOOTHILLS, LOS ANGELES COUNTY, CALIFORNIA
Prepared for: The Arroyos & Foothills Conservancy
Prepared By: Toyon Design, Landscape Architecture (626) 335-2534
Project Coordinator: Richard W. Fisher ASLA (toyond@earthlink.net)
Consulting Biologist: Michael C. Long, B.S. Biological Sciences
(mlongbird@charter.net)
Submitted August 5, 2004
Introduction and Methods
At the request of The Arroyos & Foothills Conservancy, a biological
survey of selected riparian foothill canyon watershed areas
was conducted for the purpose of assessing extant (and historic)
species diversity, habitat, and watershed quality; to identify
potential threats and strategies with regard to invasive non-native
species; and to create a baseline for further study and monitoring.
The area of study included the lower elevation/urban interface
portions of Millard, Alzada, Chiquita, Las Flores, and Rubio
canyons from the urban edge to approx 2500’ in elevation
(see appendix III for maps outlining study area); primarily
in the undeveloped wildland areas below the Angeles National
Forest. Where needed, specific permission was obtained from
private landowners to gain access to their properties. Part
I of this report discusses the biological values of the habitat
in regard to restoration needs analysis.
Fieldwork to assess the habitats, plant communities and record
wildlife observations was performed on May 11, May 25, and
May 31, 2004 by Michael Long and Rick Fisher, also including
several follow-up visits for mapping and review in June of
the same year. Fieldwork consisted of walking surveys, to
the extent possible, of the habitats occurring within the
study area. For those portions of the study area for which
direct access was physically impossible (due to private ownership,
extremely steep terrain, dense vegetation or cover of poison
oak, etc.), habitat was surveyed from vantage points using
binoculars and with reference to existing maps. Surveys were
conducted via roads and trails, including primitive, un-maintained
trails, traversing the study areas. The focus of the survey
work was to characterize the habitats present, define and
map invasive non-native plants, and to record plant and animal
species occurring within the study area, with particular attention
to sensitive flora and fauna potentially present. Additional
work supporting this report included review of existing literature,
previous Environmental Assessments or EIR’s conducted
in the vicinity, Sensitive Species Lists, and the California
Natural Diversity Database.
Summary: Biological Significance of the
Natural Communities
Overall the vegetation and varied habitats within the study
area are in good to excellent condition. This is due in large
part to the landform of steep, undeveloped slopes, canyons
and ridges and to the geographic location of the sites, contiguous
with the Angeles National Forest upslope and to the north.
Human disturbances of the flat or gently sloping zones (remnant
gardens of the Cobb Estate adjacent to Las Flores Canyon,
and apparent vegetation removal for fire safety on the Zorthian
property in upper Alzada Canyon) and along road and trail
edges has created habitat for non-native grasses and herbs.
Numbers of exotic trees and shrubs have been intentionally
introduced into several canyons (especially lower Millard
Canyon, below Canyon Crest Rd.). However, much of the watershed
is as wild as any of the isolated slopes and canyons in the
San Gabriel Mountain foothills and provides valuable floral
and wildlife habitat. A number of plant and wildlife species,
some exhibiting local or regional declines and considered
“sensitive” by the State or Federal government,
utilize these habitats and watershed.
The study area supports stands of at least two sensitive
plant communities: southern coast live oak woodland and southern
sycamore/alder riparian woodland (California Natural Diversity
Database). The location and nature of the continuous oak woodland
stands in the canyon bottoms and slopes and the riparian stands
such as occur in Las Flores, Rubio, and lower Millard Canyon,
make them significant on a regional basis as representative
of the low foothill canyons, much of which has been lost to
development. The density as well as the mosaic pattern of
oak woodlands, chaparral and coastal sage scrub adds to the
floral and faunal diversity, typical of such ecotonal zones
(or transition areas between communities). The Altadena foothills
area includes both deep and shallow canyons and ridges oriented
in a generally north-south direction, and along with the adjacent
watershed adds diversity of slope exposure and habitats. The
shady, moist oak woodlands and riparian woodlands in the canyon
bottoms and on north-facing slopes provide a critical resource
for wildlife in an otherwise dry environment.
The area surveyed forms an important portion of the extensive
Altadena foothill watershed that supports several other Agency
Sensitive species. Two locations for Plummer's Mariposa Lily
were found: one in Las Flores Canyon just above the Cobb Estate,
and the other just south of Millard Canyon along the Arroyo
Seco. Small stands of Humboldt Lilies are present or expected
in all the survey area canyons. The Coastal western Whiptail
lizard was found in Rubio and Millard Canyons and is expected
in the other drainages surveyed; and the coast range newt
has been recorded in upper Millard Canyon. The mountain kingsnake,
coast patch-nosed snake and two-striped garter snake have
all been recorded in the Altadena foothills and likely occur
within the study area. Cooper's hawks nest in low numbers
in the adjacent watersheds (Arroyo Seco) and undoubtedly utilize
the areas surveyed, along with other raptors. Yellow warbler
and blue grosbeak have also been recorded in the Arroyo Seco
and would be expected (at least as migrants) in the Oak and
Riparian woodland stands within the study area. Habitat exists
for the San Diego desert woodrat and the ringtail cat, and
mountain lions are known from the drainages.
The sites surveyed, especially Las Flores and Chiquita Canyons,
contain a number of scrub oaks with hybrid characters of Engelmann
oak and with San Gabriel Mountains leather oak, a type of
scrub oak known only from the San Gabriel Mountain foothills,
from 1300 to 3000 feet elevation. California black walnut
trees were found in all Canyons in Riparian and north slope
chaparral habitats.
