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Why does the relationship between precipitation and evaporation matter for plant growth?

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Köppen climate classification map — Köppen climate classification The major climatic types are based on patterns of average precipitation, average temperature, and natural vegetation. This map depicts the world distribution of climate types based on the classification originally invented by Wladimir Köppen in 1900.

The relationship between precipitation and evaporation is critical for plant growth because it determines the availability of soil moisture, which is the primary factor controlling vegetation in many environments.1

In the Köppen climate classification, aridity is defined not by precipitation alone, but by the balance between water input to the soil and evaporative losses. Plants require a consistent water balance to maintain turgor pressure within their cells, which keeps them erect and healthy.12

During evapotranspiration, plants lose water through their leaves to facilitate photosynthesis and nutrient transport. If evaporation and transpiration rates exceed the water replenished by precipitation, the soil moisture is depleted. When this loss exceeds the water intake from the roots, the plant’s internal water balance is disrupted, leading to wilting and, if prolonged, potential death. Consequently, this moisture deficit is a primary constraint on the type and distribution of vegetation in a given region.2341