The Mojave and Sonoran desert - impact of climate Flashcards
How is the biodiversity achieved in the Mojave and Sonoran desert?
● The biodiversity is achieved due to the range of elevation and rainfall patterns.
● Overall, the region receives less than 10 inches of rain per year, but the two rainy seasons provide enough moisture for an array of plants – wildflowers and grasses, cacti, shrubs and even trees.
How biodiverse is the Sonoran desert?
● With nearly 3500 species of plants, 500 species of birds, and 1,000 species of bees, the Sonoran is the most biodiverse desert on earth.
Describe unique plants found in the Sonoran desert.
● Saguaro and organ pipe cactus are unique to the region, and several small trees in the bean family, the mesquite, ironwood and palo verde, are particularly important to wildlife.
Give some examples of how animals avoid the heat of the desert.
● Many mammals, such as ringtails or kangaroo rats, are never active during the day, this is avoid extreme heat.
● Another avoidance strategy is to seek out a cool microclimate, a peregrine falcon will sit in a cool north facing cliff.
Describe some adaptations of the kangaroo rat.
● A kangaroo rat can produce urine twice as concentrated as sea water and feces five times drier than a lab rat’s droppings. It conserves moisture further by being nocturnal.
● A kangaroo rat typically breeds only when green vegetation or insects are available to supplement its water balance.
● A Kangaroo rat also chooses seeds with low high fat and protein levels as metabolising them produces too much heat, and it can live on water produced when food is metabolized (one gram of grass seeds produces half a gram of oxidation water.
How can birds and mammals increase the amount of heat transferring from their bodies to the environment?
● Birds or mammals can conduct heat from their bodies to the environment by decreasing the insulating value of feathers or fur - on a hot day, a curve-billed thrasher sleeks its feathers which creates a thinner insulating layer coyotes lose their thick winter coats in late spring; their early summer coats are relatively thin
● Vultures use evaporative cooling in an interesting way. A vulture urinates on its legs if the daytime temperatures are over 70°F (21°C). The urine will evaporate, cooling the legs and drawing more heat from the body of the hot vulture.
What physical factors make the sonoran desert ecologically vulnerable
● Annual precipitation in the Sonoran Desert averages from 76 to 500 mm
● The Sonoran is a hot desert. Summer air temperatures routinely exceed 40°C, and often reach 48°C
● Soils in the Sonoran desert are thin, relatively infertile and alkaline.
● Seasonal rains leach soluble salts down through the soil which are then drawn up again under high evaporation in the dry season. Flash-flooding can compact soil creating impermeable surfaces.
● Salt flats in the Salton Trough are covered with thick crusts of sodium chloride, gypsum and calcium carbonate.
What recent physical factors have the sonoran desert ecologically vulnerable.
● Pronghorn normally roam over long distances in search of food and water, but in 2001-02 a drought caused their numbers to fall.
● Recent series of cold winters has damaged the frost-sensitive Saguaro cactus, which grows at its northern limit in Saguaro National Park – this tall cactus can also be struck by lightning.
What human factors make the sonoran desert ecologically vulnerable,
Describe the impact of construction
● Cities such as Phoenix (Arizona) have replaced deserts covered with cacti and creosote bushes
● Road construction and gas and water pipelines have displaced natural habitats. .
● Fenced highways restrict the movement of animals such as the pronghorn (antelope) and the desert tortoise.
● Drought caused numbers of pronghorn to decline, this was, made worse because fences prevented the pronghorn reaching water supplies.
What human factors make the sonoran desert ecologically vulnerable,
Describe the impact of water abstraction
● Taking water from rivers together with groundwater abstraction has adversely affected mesquite bushes and cottonwood trees which grow along stream banks. (Overall irrigated land area in Sonora nearly doubled between 1950 and 1960 and peaked in 1970 at 3% of the land surface)
What human factors make the sonoran desert ecologically vulnerable,
Describe the impact of land overuse.
● Increasing numbers of off-road vehicles for recreation and establishment of military bases in the Mojave Desert have damaged soil and vegetation – tracks and tyres crush stems, leaves and seeds and compact the soil reducing soils ability to hold air and water.
● Overgrazing by cattle has left only unpalatable species and trampling has compacted soils. Delicate cytobiotic soil crusts composed of cyanobacteria, lichen, algae and fungi, which prevent erosion, absorb water and fix nitrogen, have also been destroyed. Livestock trampled lizard dwellings and eaten their food.
What human factors make the sonoran desert ecologically vulnerable,
Describe the impact of introduction of alien species.
● Domesticated animals, such as the burro or donkey, have escaped into the wild and multiplied causing a decline in the native desert bighorn sheep population.
● Introduction of non-native plant species such as tamarisk, first introduced as an ornamental or as a windbreak and has displaced native cottonwoods and deserts willows growing along the river banks.
● Buffle grass, another non-native plant species – introduced in Mexico and Texas to improve pasture in the 1960’s has since spread into Arizona. By occupying gaps in the sparse vegetation cover it has increased the fuel load and fire risk. In 1994, fire engulfed 1150 acres of desert scrub, and killing many desert tortoises. The Saguro cactus with its fleshy stem was not fire resistant and 20% dies following the burn. The Palo Verde, which provides shade for Saguaro seedlings to become established, was also lost. Removal of native species has hastened the spread of the non-indigenous grasses.
What human factors make the sonoran desert ecologically vulnerable,
Describe the impact of introduction human removal of desert plants.
● The Saguaro cactus is also sometimes illegally removed for garden ornaments.
● The chauckwalla, gila monster, desert tortoise and some snakes are also targeted by collectors.
list all the types of human factors making the Sonoran desert vulnerable.
● human removal of desert plants. ● introduction of alien species. ● land overuse. ● water abstraction ● construction
