Transcript Environment and range

Environmental Controls on
Life
• Light
• Temperature
• Moisture
Picea glauca & 10°C July isotherm
Light
• Heliophytes –
– sun loving (shade intolerant)
– C4, CAM
• Sciophytes –
– shade loving (shade tolerant)
– C3
Photosynthesis and Light
• PS increases until maximum, then
declines
• Hyperbolic shape
• Compensation point
• Saturation point
• Photoinhibition
Physical Adaptations to High
Light Environment
•
•
•
•
•
•
Small and thick leaves,
Thick cuticle – (covering)
Curled, less surface area
Reflective surface layer
High number of stomata
Leaf orientation
(heliotropic)
Physical Adaptations to Low
Light Environment
•
•
•
•
Large, soft leaves
High amounts of chlorophyll
Long-lived leaves
Heliotropic leaves!
Life History Adaptations to
Light
• Annuals versus perennials
• Canopy trees flower more
• Seeds require light to germinate
– Loblolly pine (Pinus taeda)
Physiological Adaptations to
Light
• Phenology – timing of changes in
growth
– Flowering
– Leaf shedding
– Leaf burst
Temperature - Plants
• Poikilothermic
• Optimum temperature for
photosynthesis - varies
• EX. Circumarctic treeline
– Cold stress, freezing
damage
Black spruce (Picea glauca)
limits and July temps
Plant Adaptations to
Temperature
• Dormancy – deciduous
How do needleleaved plants survive?
• Frost hardening
– Chemical alteration of liquids (“antifreeze”)
– Less water in cells
– Cell walls deformed
Plant Adaptations to
Temperature
• Saguaro
– CAM photosynthesis
– Palo Verde nurse shrubs
Plant Adaptations to
Temperature
• Palm distribution
Why can’t palms be cultivated at higher
latitudes?
Temperature - Animals
• Poikilotherms
– “cold-blooded”
-1.9°C body temp OK for Antarctic
icefish, 6°C lethal
• Homeotherms
– generate heat through
metabolism
– 37-47°C (10°C higher than core
temps.) lethal
Northern Limits of the
Eastern Pheobe
Adaptations to Temperature in
Animals
• Metabolic rates
• Sweating, panting,
licking
• Ratio of body mass
to surface area
• Behavioral
adaptations
• Shivering
• Super-cooling
(gylcerol)
• Hybernation
• Insulation
Latitude and Body Shapes
• Low latitude = high surface area:volume
• High latitude = low surface area: volume
Allen’s Rule
• Low latitude = long extremities
• High latitude = short extremities
Adaptations to Moisture Plants
• Photosynthesis
• Turgor (rigidity)
• Movement of nutrients (vascular plants)
• Xerophytes – dry loving
• Mesophytes – moist loving
• Hydrophytes – water loving
Transpiration
Release of water to atmosphere by plants
Generally through stomata
Evapotranspiration = transpiration +
evaporation
Water Stress and Range
• Moisture deficit =
evaporative demand > root absorbtion
• Creosote (Larrea tridentata)
= -2.0- -2.9 Mpa
• Alder (Alnus spp)
= -1 Mpa
Lower Treeline
• High elevations:
– Lower evaporative demand
– Higher rainfall (orographic)
• Seedlings have highest sensitivity
• Fig 3.9
Plant Adaptations – Moisture
Stress
• Water stress escapees
– Annual plants
• Water stress avoiders
– Cacti
– Drought deciduous (Fouquieria
splendens –ocotillo)
• Water stress tolerators
– Selaginella lepidophylla “resurrection
plants”
Cactus Family - avoiders
•
•
•
•
Fine surface root systems
Enlarged stems to store water
Light colored thorns reflect light
CAM ps pathway (stomota open at
night)
• Slow growth rates
Moisture - Excess
• Diffusion of O2 through
water is slow!!
• Plantanus occidentalis
(sycamore) growth declines
at >50% soil moisture
saturation
Moisture - Animals
•
•
•
•
2/3 water by weight
Mammal losses 15-20% water – fatal
Water loss lower in arid dwellers
Ex. Kangaroo rat (Dipodomys
spectabilis)
– Dry urine, feces
– No sweat
– Nocturnal
– Water from dry food!
Other Physical Factors
• Chemical nutrients/environment
– Nitrate, phosphorous, potassium in plants
– Salinity, oxygen for aquatic orgs.
• Combinations of factors
Geographical Range vs. Density
• Range: Area where
species is found
• Density : Abundance
per unit area (rare
versus common)
• Highest densities in
range center
Gaussian Curve and
Environmental Gradients
• Physiological functioning
• Density
What is a niche?
• Ecological concept
• Species exist in a multi-dimensional
space defined by various limiting factors
that affect physiological functioning and
abundance
Generalist vs. Specialist
• Generalist: wide ranges of
environmental tolerances
• Specialist: restricted gradient
distributions
Correlation Caveat
• If the geographic range of a species and
some climatic variable overlap, does
that mean that this variable controls the
range of this species?
• What other factors might affect a
species’ range?