March 27, 2014: Introduction to climate. If you have not yet taken Exam 1 or Exam 2, please email me to set up a time to take a makeup. All makeup exams should be completed before taking Exam 3. Climate: long term average weather 30 year average in U.S. precipitation temperature seasonal variations in monthly averages wind speed and direction cloud cover Use climograph to display climate data Climograph graph that shows monthly average temperature and precipitation for a given place Average Annual Precipitation = 60 Climate regions cover large areas Within these large regions are MICROCLIMATES local anomaly in overall climate pattern. Boundaries between climate types are not sharp lines like on a map. Ecotone: transition zone between one ecosystem and another along some kind of environmental gradient (temperature, moisture, etc.) An oasis in desert is one example of a microclimate Ecosystem: biological community and its physical environment. 1
Example of ecotone Köppen Climate Classification System Six Major Climate Types: Arid vs. humid B climates = arid Humid climates subdivided by temperature: Wet Moisture gradient Dry Distribution of tree species in Santa Catalina Mountains, Arizona. Note that species replace each other gradually (Whittaker, 1967) warmest coldest A C D E Altitude H Subdivisions of major types based on seasonality of precipitation. General location of major climate types KOPPEN MAJOR CLIMATE TYPES Name Parameters Vegetation B: Arid P<PET Xerophytes/annuals E: too cold for trees Treeline D: long winter H A: Tropical Never freezes Broadleaf evergreens in wet places C: Mesothermal Long summer Broadleaf deciduous Mild mid-lat. B: arid C: long summer Freezeline A: never freezes D: Microthermal Long winter Needleleaf evergreens Severe mid-lat. E: Polar Too cold for trees Shrubs & herbs in warmer parts H: Highland Up in altitude = Alpine up in latitude Biomes: Plant formations associated with major climate types. Relationship between plant form and and climate based on needs for plant photosynthesis How plants make a living : PHOTOSYNTHESIS Tropical rainforest Tropical savanna Desert Temperate grassland Temperate forest Mediterranean scrub Boreal forest Tundra Ice carbon dioxide + water + sunlight glucose + oxygen 6 CO 2 + 6 H 2 0 + energy C 6 H 12 O 6 + 6 O 2 2
Things plants must have to survive for long: carbon dioxide water light some nutrients/minerals some warmth Calcium, Magnesium, Iron, Zinc Plant form = overall shape, lifestyle, shedding habit, leaf design. Individual plant form allows plants to take advantage of water light temperature nutrient/mineral levels These resources vary spatially with climate and soil, except for? Form helps plant to acquire/conserve necessary ingredients and to optimize photosynthesis and growth. Transpiration Plants lose water through their leaves Leaf shape: Broad leaves Plants take in water through their roots Stomates allow CO 2 in, O 2 and H 2 O out LEAF SHAPE Leaf shape: Needle leaves Surface Area/pho. rate Water Loss Foliage Cost Water/ Nutrient Needs Broadleaf High High High High Needleleaf Low Low Low Low 3
Shedding habits also differ SHEDDING HABIT Loses Leaves Water Needs Payment Plan Length of Growing Season Deciduous All once a year, may go dormant Only when tree has leaves Cash up front Long enough to save up for new leaves Evergreen Loses some during the year, never dormant All year Installment plan All year Broadleaf evergreen High water/nutrient/ warmth needs all year High photosynthetic rate High growth rate TROPICAL RAINFOREST Needleleaf evergreen Low water/nutrient/ warmth needs all year Low photosynthetic rate Low growth rate SHORT SUMMER CLIMATE Broadleaf deciduous High water/nutrient/ warmth needs during growing season only Lower overall growth rate than Broadleaf evergreen LONG SUMMER CLIMATES Needleleaf deciduous Low water/nutrient/ warmth needs during growing season only Lowest overall growth rate HIGH STRESS CLIMATES OR SITUATIONS Broad leaves and evergreen in Mobile Magnolia has stiff almost woody leaves Needle leaves and deciduous in Mobile Live oak is techically deciduous because it loses all of its leaves at one time and has to replace them all each year. Baldcypress lives in high stress conditions of swamps 4
Arid B climates: P<PET precipitation < potential evapotranspiration moisture is the determining factor rainfall low AND unreliable mainly lack of mechanism to lift air some B climates freeze, some do not most extensive climate type Within B (arid) major climate, two subtypes BW: Desert P < ½ PET plants drought evaders = annuals drought resistors = perennials BS: Steppe PET > P > ½ PET short grasses high risk of desertification BW Climate BS Climate Characteristics of B low relative humidity no clouds... high atmospheric transparency high diurnal (daily) temperature range precipitation low and unreliable erosion and flash flooding severe dew and fog important moisture sources (Chile) strong winds due to unequal heating dunes present only if adequate sand supply desert pavement common Hypothetical continent 60 30 0 30 What is where and why? Four Major Causes of Arid Climates 1. Location near subtropical high pressure belt 30 N or 30 S 2. Location in continental interior 3. Location behind mountain barriers 4. Location near cold ocean currents 60 No B climates at high latitudes. Why? 5
Location of B climates North American Deserts Causes of B climates STH Interior Mt. barriers Cold currents 30 STH, Interior, Mt. barriers, Cold currents Great basin Mojave Sonoran Chihuahuan Desert plants cope with water deficiency in two ways 1. Drought evaders: annual plants that have a short life after it rains. Spend most time as dormant seeds. 2. Drought resistors: perennial plants that tough it out and have adaptations that enable them to live with very little water. These are called xerophytic plants. Drought evaders Annuals Drought resistors Perennial xerophytes Characteristic spacing of xerophytes (ocotillo) Characteristics of xerophytes Foliage most can be shed during drought sparse small needle shaped leaves waxy coatings hairs or...no leaves just green stems, succulents Photosynthesis CAM pathway common stomates open at night to take in CO 2 close in day to reduce water loss photosynthesis uses daylight and CO 2 stored the night before 6
North American Cactaceae African Euphorbiaceae Characteristics of xerophytes, contd. Roots deep rooted (160 mesquite) and/or widespread shallow roots Growth habit relatively short succulent spiny or toxic Example of convergent evolution Sonoran Desert has more rain and more vegetation Kangaroo rat Namib Desert How they do it... Desert animals Body temperature range 98-108 Most nocturnal Blood volume kept high at expense of tissue fluid Get water from food Most are small Can safely lose 40% of body water weight Urine thick, feces dry Lizard 7
BS or Steppe climates transition between tall-grass prairies and true desert vegetation short grasses bunch grasses good pasture overgrazed easily vulnerable to desertification Short grass prairie associated with BS climate Spring greening Desertification of arid and semi-arid lands Process whereby productive potential of arid or semi-arid land falls by 10% or more, primarily due to human activities. 8