Alternative site for the Global ecosystem typology with additional information for ecosystem profiles and indicative maps.
This site is maintained by jrfep
The deserts and semi-deserts biome includes low to very-low biomass ecosystems occurring in arid or semi-arid climates, principally associated with the subtropical high pressure belts and major continental rain-shadows. Primary productivity is low or very low, and dependent on low densities of low-stature photoautotrophs that sustain a complete but ‘sparse’ trophic web of consumers and predators. Productivity is limited by severe water deficits caused by very low rainfall. Rainfall deficits are exacerbated by extremes of temperature and desiccating winds. Resources, productivity and biomass are highly variable in space and time in response to both the amount of annual rainfall and the size of individual rainfall events and the lateral movement of resources from sources to sinks.. Landscape heterogeneity and resource gradients are therefore critical to persistence of desert biota in the context of highly stochastic, aseasonal temporal patterns of rainfall events that drive ‘pulse and reserve’ or ‘boom-bust ecosystem dynamics. There may be high rates of erosion and sedimentation due to the lack of surface stability provided by sparse vegetation cover, and this can be amplified by activity of large mammals and people. The extreme and prolonged water deficits, punctuated by short episodes of surplus, impose severe physiological constraints on plants and animals which exhibit a variety of physiological, morphological and behavioural/life history traits enabling water acquisition and conservation. Life history spectra of desert systems are polarised between long-lived drought tolerators with low metabolic rates and opportunistic drought evaders with either high mobility to track resources over very large areas or short-lived active phases and long dormant phases of the life cycle. Competitive interactions are weakly developed, although herbivory and predation are more evident in the most productive ecosystems and during the decline in resource availability that follows rainfall events.