Transcript BIO100--TORREY_PINES--MARITIME_SCRUB_and_CHAPARRAL

Torrey Pines State Park and
Reserve:
Maritime Succulent Scrub and
Maritime Chaparral
Biological Levels of Organization
Individuals < Population < Community < Ecosystems < Biome < Biosphere
Chaparral Biome
Mediterranean Climate
• Mid-latitude (30 deg), coastal regions
• Sea level – ~5500’
• Seasonal precipitation
– Precipitation 8-20”, mostly in winter (Dec – Mar)
– Summers are dry—seasonal drought.
– frequent drought years
– Rain/precipitation highly variable from year to year.
• Seasonal Temperatures
– long dry summers 80-100+ F
– spring, winter, fall are cool (50’s-70’s)
– winters moderately cold in coastal regions, but higher elevation
can experience frost and small amounts of snow
In more coastal regions:
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Santa Ana winds in summer (hot and dry)
fog, mist, marine layer in some seasons
Common Communities of the Mediterranean
Climate (Chaparral Biome) in CA
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Chaparral (true/hard chaparral)
Coastal Sage scrub (soft chaparral)
Oak woodland
Riparian
Grassland
Number of Chaparral Species
• 100+ shrubs
• 40 common
• A given site will have 1-10 common shrub
species.
• A very diverse community for having such
a limited geographic distribution.
Adaptations for Dry Environments
LEAF CHARACTERISTICS
• small leaves
– low surface area results in less water loss
• Thick cuticle
– thicker cuticle makes water loss difficult, bigger barrier to evaporation
– Oily/resinous leaves accomplish the same result
– These leaves are often shiny
• dull leaves
– reduces heat build, and thus reduce evaporation/water loss
• hairy leaves
– create a boundary layer of humidity, and reduce water loss
• stomata concentrated on underside of leaf
– shaded side of leaf reduces transpiration
• Spiny leaves
– can be important in collecting dew/fog
• Leaf Orientation
– Directing/orienting leaf so as to reduce direct sunlight, reduces water loss
xerophytic leaf adaptations
Ecological (Adaptive) Strategies for Water
Stressed Environments
1. Drought Deciduous:
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Drops Leaves during extended dry season
2. Evergreen
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Keeps leaves year round
3. Succulents
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Stores water in thick, fleshy leaves
Ecological (Adaptive) Strategies for Water
Stressed Environments
Drought Deciduous:
• Plant has leaves that are dropped/lost seasonally with
low water availability.
• These leaves lose a lot of water (poor resistance to
water loss), but are highly photosynthetic.
• Trades short periods of high productivity that correspond
with water availability with prolonged periods of water
conservation but no productivity after leaves are lost.
Ecological (Adaptive) Strategies for Water
Stressed Environments
Evergreen
• Plant has leaves all year long (although individual leaves
are lost and replaced regularly throughout the year).
• Leaves are thick and high resistant to water loss, but
perform lower levels of photosynthesis (at least at some temps).
• It compensates for low rates of photosynthesis by
performing photosynthesis year round.
• Requires access to water for most of the year, thus these
plants often have deep taproots to acquire water during
dry season.
Ecological (Adaptive) Strategies for Water
Stressed Environments
Succulents
• Store water in fleshy leaves and stems.
• Often have CAM metabolism
– A form of photosynthesis where stomata are open at night
and CO2 is “stored” for day when it is used for
photosynthesis
– This reduce water loss, because stomata are closed during
day.
• Results in slow growth as only a small amount of CO2 is stored
and so can only perform photosynthesis for a short period of
each day.
Coastal Sagescrub
Climate and Water Availability
• 8”-10” of precipitation during winter
• prolonged dry season (summer through fall)
• However, moderate temperature reduce evaporation
stress
• Winter growing season
General Patterns in Plant Characteristics
• 2-4’ tall, few truly woody plants (sub-shrubs)
• moderately spaced
• Shallow root systems: capture rain/precipitation as soon
as it falls.
• Mostly drought deciduous
• frost intolerant
• generally burned areas must be re-colonized
– this is done through wind dispersal
Coastal Sage scrub
Coastal Sage scrub
Coastal Sage scrub
The Chaparral Community
Climate and Water Availability
• 10-25” of precipitation, mostly during winter, little as snow
• Prolonged dry season during summer
• Temperature range more extreme then coast
– Colder in winter, often hotter in summer
• Winter and spring growing season
General Patterns in Plant Characteristics
• Shrub dominant, mostly woody
– 6-15’ tall
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Closely spaced plants (often interlacing)
Evergreen plants are dominant.
Dual root systems—shallow and long taproot
Frost tolerant
Few understory plants
Fire adapted
– Seed banks
– Re-sprouters
Chaparral in foreground with trees in background (which is wetter)
More chaparral plants
Chaparral is Fire Adapted, NOT
fire dependent
• Because fires are common in chaparral
communities the plants have adaptations that
allow the rapid regrowth/repopulation of plants.
• It is simplistic and incorrect to say it needs to
burn. Individual plants can continue to grow just
fine without fire
– Although some do need fire to complete life cycle
• Fires too frequently (<15 yrs) will cause replacement
of chaparral by non-native plants
Fire Strategies
• Crown sprouters
– Burls (roots) that store water and nutrients
– Somewhat protected from fire
– Give rise to new shoot systems after fires (from roots)
• Seed Banking
– A large number of dormant seeds in the soil
– Require fire to sprout, repopulate area post fire.
– Often sit dormant for decades resulting in areas with plants that
are cohorts—little intermediate stages
• Fire Followers
– Increased nitrogen triggers germination (or other chemical
triggers/changes to seed)
– Annuals will complete lifecycle year after fire and then sit
dormant again for decades
– Important in soil stabilization
Chaparral and Fire
• Pre-human fire cycle is estimated to be 30-100 years
• American Indians frequently burned chaparral to
increase tuber herbs (for food), frequency of game
animals, and growth of willows for basket weaving
• For much of the 1900’s there was an active policy of fire
suppression or prevention
• More recently (~30 yrs) there is a recognition that burns
are natural events.
– Controlled Burns
Chaparral one year after a fire
Torrey Pines--Maritime Shrub-dominant
Communities (uncommon communities)
Maritime Succulent Scrub
• Exists in southern—more dryer—regions
• Includes:
– common coastal sagescrub plant
– increased number of evergreens
– Increased succulents
• central Baja through Laguna Beach
• most species rich of all scrub communities
– reduced fire frequency
Maritime Chaparral
• Community of evergreen plants that includes a diminutive form of
Chamise
• presence of some desert-typical plants
– these plants are not typical of coastal areas
• once common throughout San Diego Co. and northern Baja
• Intermixes with Maritime succulent scrub
Torrey Pines S.P.
Sagescrub v. Chaparral
(physical structure and ecological strategies)
• Coastal Sagescrub
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• Chaparral
Human Impacts
• Much of the chaparral has been destroyed
by urbanization and agriculture.
• Suppression of natural fire cycles (according to
some sources)
Chaparral & Sage Scrub
impacts on Humans
• Fires that destroy property
Did You Know?
Did you know that the coastal sage scrub habitat is
one of the most endangered ecosystems in the
world? Only 10-15% of the original habitat now
exists. Once the dominant ecosystem, the coastal
sage scrub community now only exists in small
remnant pockets
n.p.s. cabrillo national monument website
Due to urban development, grazing, and agriculture