Environmental Controls on Life Light Temperature Moisture Picea glauca & 10°C July isotherm

Light Heliophytes – –sun loving (shade intolerant) –C 4, CAM Sciophytes – –shade loving (shade tolerant) –C 3

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

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) = 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 O 2 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?