Environmental Controls on Life Light Temperature Moisture Picea glauca & 10°C July isotherm.
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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)
• Large, soft leaves
• High amounts of chlorophyll
• Long-lived leaves
• Heliotropic leaves!
Physical Adaptations to Low Light Environment
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
• Saguaro – CAM photosynthesis– Palo Verde nurse shrubs
Plant Adaptations to Temperature
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
Allen’s Rule
• Low latitude = high surface area:volume
• High latitude = low surface area: volume
• Low latitude = long extremities
• High latitude = short extremities
Latitude and Body Shapes
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?
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