Usually microorganisms help keep the nutrients in the soil cycling allowing for nutrients to be distributed all over. But they do what they can unless the disease is damaging to the soil itself therefore damaging the microorganisms working to keep the plant functioning.
The four mechanisms are as follows:
1) Orographic lifting: Air is forced to rise over a mountainous barrier
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2) Frontal wedging: Warmer, less dense air is forced over cooler, denser air along a front
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<span>3) Convergence: Pileup of horizontal air flow resulting in an upward flow
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<span>4) Localized convective lifting: Unequal surface heating causes localized pockets of air to rise because of their buoyancy. </span><span />