Desert - Plant Geography - Lecture Slides | BOTANY 422, Study notes of Geography

Download Desert - Plant Geography - Lecture Slides | BOTANY 422 and more Study notes Geography in PDF only on Docsity! 1 Deserts  what are deserts?  relative term - transitions occur with more xeric thorn forests and with grass savannas Mojave Desert Namib Desert Deserts  what are deserts?  relative term - transitions occur latitudinally with more xeric thorn forests and with grass savannas Mojave Desert Namib Desert Deserts  what are deserts?  relative term - high elevation tropical mountains (paramo, etc.) are essentially “desert” like Haleakala Crater - Maui Deserts  what are deserts?  relative term - high elevation tropical mountains (paramo, etc.) are essentially “desert” like Opuntia (Cactaceae) in high Andean puna (Peru) 2 Deserts  what are deserts?  subtropical arid regions where potential evaporation (>2000mm) is >> annual precipitation (<200mm) Deserts  distinction between subtropical and temperate (cool or cold winter) deserts Great Basin Gobi Desert Patagonian Desert Desert Locations  lie between 15o and 30o centered on Tropics of Cancer and Capricorn on west sides of continents Sonoran, Mojave, Chihuahuan Atacama  lie between 15o and 30o centered on Tropics of Cancer and Capricorn on west sides of continents Saharan Namib, Australian Desert Locations 5 1%15%61%23%0%Tundra 12%22%49%2%15% Temperate Deciduous Forest 41%14%27%7%11%Desert 0%2%0%2%96%Rainforest Thero. (annuals) Crypto. (under ground) Hemicrypto. (leaf litter) Chamae. (near ground) Phanero. (trees/shrubs)  Ephemerals - adaptations to water stress by short life Desert Life Forms  Plant defenses - physical and chemical Desert Life Forms Cactaceae - New World spine protected Euphorbia - Old World spine & toxin protected Desert Floristics  Three families species richer in deserts than elsewhere  Three families species richer in deserts than elsewhere Desert Floristics Frankeniaceae Frankenia chilensis 6  Sahara African Deserts Yellow indicates lowest photosynthetically absorbed radiation  Sahara African Deserts Woody plants: Phoenix (date palm) and shrubs (Acacia, Tamarix, Ephedra) Tamarix - tamarisk Phoenix dactylifera (date palm) - Tunisia“mustard” (Brassicaceae) Annuals: Brassicaceae; but also perennial herbs like grasses  Sahara African Deserts Stem succulents: Apocynaceae (milkweed and relatives) Caralluma & Sarcostemma (Apocynaceae) Ethiopia Loranthaceae parasitic on Acacia Ethiopia Parasites: Loranthaceae  Namib - western southern Africa African Deserts 7 African Deserts  Namib - western southern Africa Fog desert: fog only moisture for most of the year along coast Darkling beetle - dew specialist African Deserts  Namib - western southern Africa Fog desert: fog only moisture for most of the year along coast Darkling beetle - dew specialist Welwitschia mirabilis  nephelophyte - fog specialist African Deserts  Namib - western southern Africa Stem succulents: Aloe (Liliaceae s.l.), Euphorbia, Pachypodium (Apocynaceae) Pachypodium Aloe - quiver plant African Deserts  Namib - western southern Africa Stem succulents: Stapelia (Apocynaceae) - cactus mimic; Adenia (Passifloraceae) Stapelia - carrion flower Adenia 10 South American Deserts  Atacama - western Chile & southwestern Peru - straddles Tropic of Capricorn on Pacific Ocean edge of South America Coastal cloud wall in Pan de Azucar  orographic precipitation is always inland at higher elevations due to adiabatic effect  a fog desert: note moisture laden clouds over cold Humboldt current stop at edge of continent Tillandsia landbeckii (Bromeliaceae) - same genus as Spanish moss South American Deserts  Atacama - western Chile & southwestern Peru - straddles Tropic of Capricorn on Pacific Ocean edge of South America  rainless desert with plants (nephelophytes) adapted to capture fog moisture as lomas (small hill) vegetation South American Deserts Eulychnia iquiquensis (Cactaceae), Copiapoa (Cactaceae) & Euphorbia latifolia (Euphorbiaceae) South American Deserts Malesherbia tocopillana (Malesherbiaceae) - family of 1 genus and 24 species restricted to west coast of South America 11 South American Deserts  Patagonian - temperate desert formed by rainshadow of Andes  4 recognized: variation in seasonality of precipitation Mojave - winter rains (Mediterranean!) Sonoran - light winter rains and heavier summer rain (bimodal) Chihuahuan - only summer rain (subtropical!) North American Deserts Great Basin - cold winter desert (temperate)  floristically related & intergrade  Chihuahuan - subtropical North American Deserts  Chihuahuan North American Deserts Yucca Larrea tridentata (Zygophyllaceae) creosote bush - also in South America 12 Flourensia cernua (Asteraceae) tarbush Acacia constricta - white thorn acacia  Chihuahuan North American Deserts Gran Desierto del Pinacate National Park, Mexico - sand verbena (Verbena) & creosote  Chihuahuan North American Deserts Ariocarpus (Cactaceae) - Big Bend National Park, Texas  Sonoran - subtropical/Mediterranean - divided into floristic/climatic subgroups North American Deserts Carnegiea gigantea (Cactaceae) - saguaro “Queen of the Sonoran”  Sonoran North American Deserts Opuntia bigelovii - cholloCereus thurberi - organpipe