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Ecological Biogeography examines the factors (principally physical) that control the range and abundance of organisms ENVIRONMENT (climate, soil, . . .) BIOTA Species-environment relations Individual performance (e.g. growth or reproductive success) Biogeographic consequences Extreme conditions may control a species distribution Low temperatures (polar areas) High temperatures (deserts) today Dessication (deserts) Saturated soils (bogs) High salinity (ephemeral lakes) Low nitrogen (dune-fields) next week The rotation of the Earth produces a 24h daynight cycle QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Image: earthobservatory.nasa.gov Diurnal temperature variation in a nonvegetated (desert) environment Effects of vegetation on diurnal rhythms: thermal regimes in a tropical rain forest Seasonal variations in day and night length are a product of axial tilt Day and night length varies with latitude Graphic: M. Pidwirny Biogeographic implications of variations in daylength: photoperiodism red clover QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. vegetative “Japanese” anemone night night vegetative day day QuickTi me™ a nd a TIFF (Uncompre ssed ) decomp resso r are need ed to se e th is p icture. Long-day plants: flower after exposure to long days/short nights (spring); predominant in cool temperate and polar latitudes Short-day plants: flower after exposure to short days/long nights (fall); predominant in warm temperate and subtropical latitudes Seasonal solar radiation receipt varies with latitude (as a result of variations in daylength and solar angle) Graphic: M. Variable radiation receipt produces seasonal variations in surface temperature above: Manaus, Brazil (3°S) below: Fairbanks, Alaska (65°N) Graphics: M. Extremophiles • Archaeans (bacteria) can survive and grow over an extreme temperature range, from >113°C in oceanic thermal vents to -18°C* in bubbles of brine in Arctic sea ice. *the bacterium Colwellia, which grows in microbial mats in Arctic sea ice, can metabolize in liquid nitrogen (at -196°C)! Source (and graphic): New Scientist, August 12, 2006 Temperature ranges of some common “coldblooded” organisms (poikilotherms) Thermally limited growth/activity season (e.g. Fairbanks, Alaska) Surviving extreme temperatures [migration, hibernation, dormancy (eggs, seeds, pupae, etc.)] Temperature and habitat occupation Water temperatures and fish distribution dormant desert pupfish dormant ? goldfish bald rock cod (Antarctica) coho (adults) 0 10 20 30 Water temperature (°C) 40 © Joan Barnett pupfish in a hot spring stream, Death Valley pupfish in Salt Creek, Death Valley A eurythermal/haline animal: the desert pupfish (Cyprinodon spp.) Photosynthesis-temperature relations for major plant groups Cardinal temperature Thermal limits for trees from tropical, temperate and boreal biomes compare tropical, temperate and boreal species Extreme temperature resistance in plants Cold resistance chilling resistance frost avoidance by supercooling Heat resistance frost resistance frost tolerance heat tolerance heat avoidance by shielding & reflection thermal insulation cooling by transpiration Cold-resistance strategies • Evolved responses growth of fur & feathers, shorter/smaller extremities, larger body size • Seasonal responses fat storage, metabolic changes (e.g. glycoproteins supress ice formation in plants), deciduousness (loss of sensitive parts), migration, hibernation • Daily behavioural responses habitat choice, refuging (nest, roost, burrow, den….), body position and orientation (especially for poikilotherms) Tropical species e.g. effects of frost on Saguaro cacti in central Arizona injured dead 1961 1962 (after frost) many dead or dying 1979 (frosts: 1971, 1978) Thermal control on polar limit of saguaro (Carnegiea gigantea) Saguaro (Carnegiea gigantea) range in relation to frost frequency Polar limits of other tropical desert species Temperate forest trees: common polar limits = similar limiting temperatures? American beech red oak red maple (plus white oak, black oak, 2 hickories . . . . ) Is polar limit controlled by the length and warmth of the growing season? mean daily temperatures >10°C for more than 4 months mean July temperature 18°C Is polar limit controlled by dormant season temperatures? mean January temperature -12°C Ice formation in beech (and red oak, red maple, etc.) tree trunks extracellular -10 -20 Intracellular; Cells ruptured (°C) -30 -40 Intra-cellular Extra-cellular Exothermic reactions (ice-formation events) in temperate and boreal tree species Tree anatomy and thermal limits Ring porous chestnut American elm Diffuse porous birch red maple Probability of temperatures falling below -40°C A = common B = rare C = never American beech Hardiness zones: annual temperature minima zone 1 (-50°C) to zone 11 (0°C) http://www.glfc.cfs.nrcan.gc.ca/frontline/bulletins/bulletin_no.13_e.html 0b Shining willow Saule brillant Salix lucida ssp. lucida 1 1 1b White spruce Lodgepole pine Laurel willow Épinette blanche Pin tordu latifolié Saule laurier Picea glauca Pinus contorta var. latifolia Salix pentandra 2 2a 2b White elm Cranberry viburnum Ponderosa pine Orme d'Amérique Viorne trilobie Pin ponderosa Ulmus americana Viburnum trilobum Pinus ponderosa 3 3 3b Rocky Mountain juniper Red maple White ash Genévrier des Rocheuses Érable rouge Frêne blanc Juniperus scopulorum Acer rubrum Fraxinus americana 4 4a 4b Black locust Rocky Mountain Douglas-fir Scotch elm Robinier faux-acacia Douglas bleu Orme de montagne Robinia pseudoacacia Pseudotsuga menziesii var. glauca Ulmus glabra 5 5 5a 5b Norway maple English oak Douglas maple Horsechestnut Érable de Norvége Chêne pédonculé Érable nain Marronnier d'Inde Acer platanoides Quercus robur Acer glabrum var. douglasii Aesculus hippocastanum 6 6b Western redcedar Eastern flowering dogwood Thuya giant Bois bouton Thuja plicata Cornus florida 7 7b Sweetgum Coastal Douglas-fir Copalme d'Amérique Douglas vert Liquidambar styraciflua Pseudotsuga menziesii var. menziesii 8 8 Arbutus Western flowering dogwood Arbousier d'Amérique Cornouiller du Pacifique Arbutus menziesii Cornus nuttallii http://sis.agr.gc.ca/cansis/nsdb/climate/hardiness/trees2000.html ZONE HARDINESS OF SOME INDICATOR TREES When is cold good for a plant? • Short days signal plants of impending cold period • Many deciduous plants require chilling to grow well in subsequent growing season • Vernalization required for buds to break out of dormancy and to develop into flowers. These plants (e.g. apple, lilac) cannot be grown “successfully” at lower latitudes because the winters never get cold enough (a few days at 0– 10°C). • Hardening Accclimation to winter cold initiated by falling temperatures and reduced photoperiod in autumn Temperature effects cold hardiness vs. dormancy • Cold hardiness is ability to withstand cold • Dormancy is inability to achieve normal growth – Biological adaptation to region with decreasing temperatures and shortened daylength – Apples: require about 1000-1600 hours of chilling (45F) to break dormancy. http://www.uga.edu/fruit/apple.htm Freezing resistance acclimation in two willow (Salix) species in northern Japan buds form leaves yellowing leaves open Freezing resistance in red-osier dogwood (Cornus stolonifera) ecotypes growing in Minnesota Ecotypic variation in cold resistance in Douglas-fir (Pseudotsuga menziesii) Seeds planted May, 1954; Seedling response to severe frost (-16°C at ground level), mid-November, 1955. P. menziesii var. menziesii N S N var. glauca S 100% 90% 80% 70% 60% % undamaged 50% % damaged 40% % killed 30% 20% 10% 0% 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Seedling response to severe frost (-16°C at ground level), midNovember, 1955. Freezing damage in tree species ecotypes What controls equatorward limits of temperate and boreal species? • Similar heat injury ranges • Stratification: chilling requirements for seed germination • Vernalization: chilling requirements for blossoming In tropical areas the stratification and vernalization requirements of temperate and boreal plant species are not met; they are unable to produce seed.