Download CALIFORNIA`S PLANT DIVERSITY Susan Harrison, UC Davis

CALIFORNIA’S PLANT DIVERSITY
Susan Harrison, UC Davis
WHAT IS DIVERSITY?
•  Many native species in a given site
(alpha) or region (gamma)
•  Much variation in species from site
to site within a region (beta)
•  Geographically restricted (endemic)
species
•  Taxonomically distinctive species
•  What about California?
UNITED STATES
“BIODIVERSITY
HOTSPOTS”
Stein et al., 1999
THE WORLD’S 25
BIODIVERSITY HOTSPOTS
(Myers et al., 2000)
•  Definition: > 1500 endemic plant
species.
•  Tropical Andes, Central America,
Caribbean, Atlantic rainforest of
Brazil, Madagascar, California
Floristic Province…
•  44% of all plant species and 35% of
vertebrates in 4 groups.
•  1/2 to 2/3 of plants and vertebrates
on the IUCN Red List are hotspot
endemics
•  Only 1.4% of earth's land surface!
CALIFORNIA....*
•  4400 native
species
•  48% endemic
•  >20% rare or
endangered
•  CA Floristic
Province
Roles of: climate, history,
geology, topography,
disturbance, invasions….
THE CALIFORNIA
FLORISTIC PROVINCE
THE MEDITERRANEAN
CLIMATE
THE WORLD’S
MEDITERRANEAN
CLIMATE REGIONS
DIVERSITY AND
ENDEMISM IN
MEDITERRANEAN
REGIONS
(from Dallman, 1998)
PLANT ADAPTATIONS IN
MEDITERRANEAN CLIMATES
Evergreen, sclerophyllous shrubs
Chaparral
PLANT ADAPTATIONS IN
MEDITERRANEAN CLIMATES
Spring annuals
THE EVOLUTION OF
CALIFORNIA’S
MEDITERRANEAN FLORA
THE EVOLUTION OF
CALIFORNIA’S
MEDITERRANEAN FLORA
ORIGINS OF THE CALIFORNIA
FLORA
Raven & Axelrod 1978
•  Northern elements “Arcto-Tertiary”
50%
From warm wet temperate forests that
were widespread 50 mya
•  Southern elements “Madro-Tertiary”
33%
From semiarid habitats that
developed about 20 mya
•  Desert elements 14%
•  California Floristic Province (CFP)
endemics
(% of species in the CFP belonging to genera or
families of this origin; total = 4452 species)
Hotspots within California
(Stebbins and Major 1964):
Mt. St. Helena area, Santa Lucia Mts.
“Intermediate” climate; topographic and
geologic complexity
All three major elements present
Role of geology and topography
Serpentine (ultramafic) rocks
Klamaths
North
Coast
Sierra Nevada
South Coast
Napa, Lake, and
Sonoma Counties
CALIFORNIA
Serpentine (ultramafic)
rocks and soils:
<2% of California’s surface area,
>10% of its endemic species
Allium falcifolium
(sickle-leaved onion)
Serpentine mixed
chaparral with
leather oak and
McNab’s cypress
‘The redrock forest may seem hellish to
us, but it is a refuge to its flora... it is the
obdurate physical adversity of things
such as peridotite bedrock which often
drives life to its most surprising
transformations.’
- David Rains Wallace,
The Klamath Knot (1983)
Role of fire in California’s
Mediterranean vegetation
Sandstone chaparral 1 year post-fire
FIRE SPECIALISTS:
Emmenanthe penduliflora
Dicentra chrysantha
Serpentine chaparral 1 year post-fire
Streptanthus breweri:
Calystegia collina:
Calochortus amabilis:
Post-fire increase in local diversity:
45% in serpentine chaparral,
140% in sandstone chaparral
Fire is less severe and less frequent
in serpentine chaparral
INVASIONS
1,045 naturalized non-native species
Around 10% threaten biodiversity
Many/most are from the Mediterranean
Napa vegetation mapping project
Partners: NatureServe, CDFG, Information
Center for the Environment (UCD),
regional stakeholders (BRBNA)
For: local biodiversity hotspot analyses;
conservation and planning decisions