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Ecosystems in hot arid and semi arid environments
Stomata- pores in leaves and sometimes stems from which water vapour
escapes and CO2 and O2 are exchanged.
Transpiration- Loss of water vapour to the atmosphere mainly via plant
Cuticle- A waxy layer covering the outer plant wall designed to reduce
Annuals- These are drought evading plants. Seeds will germinate after
seasonal rains and complete life cycles very quickly
Aridsols- soil of hot arid/semi arid environments with high salinity and low
net primary productivity.
Crassulacean Acid Metabolism (CAM) - A process by which CO2 taken in at
night is stored until the day when photosynthesis can occur without the
plant opening its stomata.
Halophytes- plants that have adapted to high salinity in the soil
Phreatophytes- plants with exceptionally long roots to tap ground water
deep below the surface.
Succulents- plants which store water in fleshy stems and leaves.
Aridsols (desert soils)
Soils have little quality nutrients because:
Weathering is limited because moisture levels are low, so little nutrients
can be released from bedrock.
Any animals or plants are rare so biomass is small meaning hardly any
nutrients goes into the soil from dead animals and plants.
Nutrients can be brought by rain but because there is little precipitation
few nutrients are brought this way.
Rain doesn't soak into soil as it is impermeable and just runs off the surface
as flash floods so it doesn't get the nutrients into the soil. Rain is also
evaporated due to high levels on insolation.
Reasons for high salt concentration (capillary action)
Water in the ground contains salt.
The water rises up from the water table to the surface due to insolation
The water is evaporated and carried away by strong fairly consistent
desert winds- so the process continues over and over.
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This removes a lot of water and leaves the salt behind- increasing the
concentration of salt, making it hard for plants to survive as plants can't
use soil with high salt concentrations.
The winds help the evaporation of water to repeat.
Cryptobiotic soil crust
Cyanobacteria (bacteria that can perform photosynthesis) such as green
algae, lichen and fungi.
It is a very fragile type of ground cover.
In the Colorado plateau, crytobiotic crusts cover 70% of living ground