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16 Cards in this Set
- Front
- Back
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desert
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an area defined by a low mean annual precipitation, little vegetation cover and aridity, which expresses the dryness of the climate
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aridity
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lacking moisture, especially rainfall yet
* not necessarily indicator of aridity * depends ALSO on supply of water as precip ANd the evaporative demands of the atmosphere * defined on basis of long term average climatic conditions |
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drought
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period of below normal water availability, deviation from the normal / long-term mean conditons
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meteorological drought
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prolonged period with below average precipitation
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hydrological drought
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prolonged period in which the water levels in lakes and rivers are below average. Depends both on meteorological drought and water usage
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agricultural drought
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period of below average agricultural production induced by meteo/hydro drought
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societal drought
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when soil water deficit affects crop production to the point that there are significant economic losses
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sea shrinking
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due to irrigation and diversions, salinization of surrounding areas ( the irrigation water was salt rich)
* exposure of dry lake bed sediments rich in fertilizers and pesticides |
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allogenic dryland river
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long dryland river that originates in other regions with wetter climates
( lose water as they move through dry climates) * high salinity, discharge decreases * some don't even reach the ocean |
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endogenic
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shorter dryland rivers - ephemeral and/ or intermittent
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desertification
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diff, but the land degredation in arid, semi-arid and dry subhumid areas resulting from various factors, including climatic variations AND human activities
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land cover - climate precipitation
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loss of vegetation leads to soil surface changes in albedo, roughness, rotts etc, leads to less precip which prevents the re-establishment of vegetation
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land use - land degredation
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after loss of veg. the soil is exposed to wind and water erosion
consequent loss of soil nutrients prevents the re-establishment of veg when nutrient rich soil is lost or grass is lost, = LOSS OF PRODUCTIVITY |
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shrub encroachment
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wood/shrubby plants are replacing the grasslands
* caused by land use, climate warming, increase in atmospheric CO2 *involves replacing a semi-uniform grass covered with scattered shrubs separated by bare soil... INDICATOR OF DESERTIFICATION |
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dust sources
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* soil erosion leads to - dust emissions, have detrimental effects on regional and global climate - more dust emissions in the northern hemisphere than in the southern
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dryland veg
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thin/ sparse vegetation cover, vegetation density is limited by water availability
veg is well adapted to cope with scarce water resources...mixed plant communities optimize water usage |
