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Savanna


KIRK ANDSERSON CURATOR OF GARDENS


Elephants help create savannas by clearing woodlands SCENES ON THE SAVANNA


T e elephant coaxes the marula tree to release its intoxicating bounty of fruit by shaking the tree’s trunk. T e dexterous tongue of a giraff e strips a prickly knobthorn branch of its leafy fare. Kudu and eland munch on red bushwillow while zebra and gazelles graze the grassy clearings. A pride of lions sleeps languorously beneath the fl attened crown of an umbrella thorn while, overhead, vervet monkeys comb the upper branches for the acacia’s relished seed pods. Black-backed jackals and vultures squabble over the remains of the pride’s last kill and the spotted hyena dogs eye a hungry cheetah as it stalks the grazing gazelles. T e African savannas support a diversity of wildlife unmatched anywhere else in the world. Occupying wide parallel belts of the continent, more or less sandwiched between tropical rain forest in the middle and desert on either side, the savanna blends expansive grasslands with thorn studded woodlands to create a fl oral smorgasbord for the browsers and grazers found there. And where herbivores abound carnivores cannot be far behind.


GEOGRAPHY AND ENVIRONMENTS


Savannas are most often thought of as vast grasslands interspersed with widely spaced trees. But the density of trees and shrubs can be signifi cant as long as the canopy remains


6 www.LivingDesert.org


broken and enough light reaches the ground to allow for the uninterrupted growth of an herbaceous layer consisting mostly of grasses. Defi ning upper and lower limits of tree coverage varies by author from a low of 5-10% to highs of 25-80%. T e mosaic pattern of plant distributions combines staggered vegetation heights and open spaces to create a myriad of ecological niches eagerly fi lled by an incredibly diverse array of fauna. Over 40 diff erent species of ungulates (hoofed mammals) graze and browse on the African savannas. Up to 16 grazing and browsing species may coexist in the same area with each animal making use of its preferred plant species, feeding heights and times of day and season.


Savanna communities are found around the globe, covering approximately 12.5% of the Earth’s surface. Pastoral Californian landscapes of oaks and grasses are illustrative of Mediterranean savannas with wet winters and hot, dry summers while remnants of our country’s prairie heartland off er a sample of temperate savannas. T e savannas of Africa are classifi ed as tropical and sub-tropical with warm to hot, semi-arid to semi-humid conditions and year around temperatures ranging from the mid 60’s to mid 80’s (F). T e seasons revolve not so much around summer/winter as they do around wet/dry.


T e climate is marked by a pronounced wet (summer) and dry (winter) season. Annual rainfall can vary appreciably from 10 to 50 inches or more and is restricted almost entirely to


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