Growth rate

Water is essential for development of weeds, insects and pathogens. Moisture content of the air affects plants and externally feeding insects, but insects in living plant tissues are not normally limited by moisture. Moisture content of the soil affects growth of terrestrial plants. Surface moisture from dew or rain is usually necessary for infection by fungal pathogens.

Rain and increasing soil moisture, as indicators of favourable plant growing conditions in the future, switch on the development of many insects and plants after diapause or dormancy.

Birth rate

Moisture availability has a major effect on 'birth' rates of plants. Some trees are stimulated to flower by water stress. Flowering and seed set by other plants are inhibited by water stress. Initiation of new modules by individual plants is usually restricted by water stress. Rainfall may also prevent oviposition by insects.

Mortality rate

Mortality of insects and plants increases in dry environments due to desiccation and wilting. High moisture may indirectly increase mortality rates of insects and weeds by favouring pathogens. Rainfall may increase mortality of adult and immature insects.

Dispersal/migration rates

Floods are an important means for dispersal of many plants.

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