E: too cold for trees. C: long summer Freezeline A: never freezes. General location of major climate types. GEO 101, April 1, 2014.

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1 GEO 101, April 1, 2014 General location of major climate types Finish climates A: Tropical climates E: too cold for trees Treeline D: long winter H : arid C: long summer Freezeline A: never freezes Hypothetical continent 60 What is where and why? Four Major Causes of Arid Climates 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 climates at high latitudes. Why? Location of climates 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. STH, Interior, Mt. barriers, Cold currents 1

2 Drought evaders Drought resistors Annuals Perennial xerophytes Characteristics of xerophytes Characteristic spacing of xerophytes (ocotillo) North American Cactaceae African Euphorbiaceae 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 CO2 close in day to reduce water loss photosynthesis uses daylight and CO2 stored the night before Example of convergent evolution Sonoran Desert has more rain and more vegetation Characteristics of xerophytes, contd. Roots deep rooted (160 mesquite) and/or widespread shallow roots Growth habit relatively short succulent spiny or toxic 2

3 Namib Desert Kangaroo rat Desert animals Most nocturnal Get water from food Most are small Lizard How they do it... ody temperature range lood volume kept high at expense of tissue fluid Can safely lose 40% of body water weight Urine thick, feces dry S 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 S climate Spring greening 3

4 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. A = Tropical climates = never freezes Three tropical climate subtypes Af: Tropical rainforest climate f means no dry season, doldrums seasonless, monotonous, high humidity tropical rainforest, broadleaf evergreen, selva multistoried upper Amazon, northern Congo basin, East Indies Am: Tropical Monsoon ( m = monsoon) short but not severe dry season summer rainfall maximum (onshore winds) tropical rainforest, broadleaf evergreen less dense, more deciduous trees primarily coastal locations, east side of continent Af Am : Tropical savanna (wet & dry, winter dry) w = dry winter influenced by doldrums and subtropical high grassland, thorn scrub dormant season due to drought What do these all have in common? Small group question: What leaf shape/shedding habit do you expect to find in each of these and why? 4

5 Af: tropical rainforest biome Epiphytes: plants that perch on the branches orchids, bromeliads Af: tropical rainforest biome Jungle roadleaf evergreens Vines (lianas) common Tropical rainforest is multistoried, competition for light Af: tropical rainforest biome Arboreal animals Pollen vector wind Low stress High diversity Lemur Fruit bat Examples of tropical tree root systems. uttresses are common Tropical Leaves often have drip tips 5

6 Despite lush growth, tropical rainforest soils are poor. Nutrients are washed away by the constant rain. Recycling is rapid. Nutrients stored in biomass of forest itself. Temperate Forest Distribution of organic carbon Tropical Forest Impact of tropical forest clearance 1. Releases stored CO 2 2. Destroys carbon sink 3. Destroys transpiration mechanism 4. Increases erosion Tropical rainforest soils are poor. Nutrients stored in biomass. Tropical Monsoon (Am) Found primarily along eastern coastlines Result of seasonal reversal of winds Onshore, bringing rain in summer Offshore, bringing drier conditions in winter No severe drought Long growing season (it s tropical) Forest not as tall or diverse as Af roadleaf deciduous trees lose leaves in dry season Desertification : loss of productive potential due to human activity Can happen in A climates as well as in arid climates 6

7 = Tropical savanna Period of severe drought long dry season during winter low sun season High temps. = high P Located between Af and iomes: Plant formations associated with major climate types. Tropical rainforest Tropical savanna Desert Temperate grassland Temperate forest Mediterranean scrub oreal forest Tundra Ice : dry period is so long that broadleaf deciduous trees cannot earn enough during wet season to pay for leaves. Needleleaf trees or small leaves are best. Trees are dormant in dry season. Grasses and shrubs dominate aobab or Upside-Down Tree grows in Africa and Australia. The legend says that after it was planted by God it kept moving, so God replanted it upside down Af 7

8 Where is located? What causes it to be predictably wet and dry? Pressure belts follow direct vertical rays of sun. In July, when sun is north of Equator, ITCZ affects rain in summer. In January, when sun is south of Equator, Subtropical High affects dry in winter. Af Where is located? What causes it to be predictably wet and dry? Pressure belts follow direct vertical rays of sun. In July, when sun is north of Equator, STH affects dry in S. Hemis. winter. In January, when sun is south of Equator, ITCZ affects rain in S. Hemis. summer. Af Changes in vegetation along precipitation gradient in A E D A C Af Am A Decreasing precipitation Decreasing precipitation Mangrove: tropical, low energy coastal, woody plants, tolerate saltwater Mangrove Global mangrove distribution 8

9 Environmental issues associated with A climates Mangrove destruction for aquaculture/wood chips Deforestation for agriculture / ranching Honduras Shrimp ponds, Indonesia 9