Lab 6: Coastal Sage Scrub Plant Community, Species Diversity, and Invasive Species
(adapted from Lab 3: Coastal Sage Scrub Plant Community by Michael Fugate, PhD at UCR)
Communities and Community Structure
is an association of interacting populations of
species inhabiting some defined area.
Based on competition, exploitative interactions (predation, disease,
parasitism, etc.), and mutualisms, communities represent the biotic portion of an ecosystem that
participate in energy flow and matter cycles.
Community ecologists seek to understand how abiotic and
biotic aspects of the environment influence the structure of communities.
attributes such as the number of species, relative abundance of species, and kinds of species within a
Our Local Community
The California Coastal Sage Scrub and Chaparral ecoregion ranges from
northern Baja California, Mexico to coastal southern California and extends eastward to the Colorado
(a.k.a. Sonoran) Desert and southward to Punta Baja, Mexico.
The landscape is flat to foothills and is
only 1 of 5 Mediterranean-climate ecoregions in the world.
The winters are cool and wet, but the
summers are hot and dry.
Annual average rainfall is low, between 150 and 500mm (Dallman, 1998
Coastal Sage Scrub (CSS) has dense stands of typically drought-deciduous subshrubs (0.5-2m in height).
Dominant plants in the Riverside area historically included California sagebrush (
and brittlebush (
Other native shrub species include California buckwheat (
), Black sage (
), White sage (
) and Purple nightshade (
tends to favor and dominate south and east facing slopes while the others north and west
Within the last 2-3 decades, non-native annual grasses invaded CSS communities in southern California
and replaced many native species found on north-facing slopes.
In their native habitat, these species
) are found only in recently disturbed areas
and are replaced by perennial forbs and shrubs.
In California, they also invade disturbed areas, but
replacement by native flora is often delayed indefinitely.
What sort of climate do you think the non-native grasses evolved in?
Given the very hot and dry summers along with human ignition sources (cars, cigarettes, etc.),
what sort of disturbance do you think might be common to our area?
Would this potentially
contribute to the establishment of non-native grasses?
Several factors may contribute to the success of the non-native grasses in our area including life history