Consequences of high soil temperatures

"Soil temperature is altered by urbanization and can increase enough to damage trees in urban landscapes. Although elevated soil temperatures affect the physiology and growth of both root and shoot systems of trees, species and selections within species are known to vary in their capacities to resist root-zone heat stress. A review of data collected on diverse, temperate taxa reveals that the development of below-ground urban heat islands probably will not cause direct heat injury of trees unless the temperature of soil remains above 32°C (90°F) for extended periods of time. Slight increases in root-zone temperature above 32°C (90°F) can result in reduced growth and water uptake of roots, reduced surface area and stomatal conductance of leaves, stunted stems, and alterations in nutrient content that cause severe chlorosis of young leaves. When considering the impact of elevated root-zone temperatures in urban ecosystems, it is necessary to recognize the effects of other root-zone stressors that may interact with temperature. We are just beginning to learn more about such interactions, but already there is evidence that the severity of the impact of drought on tree growth can depend on the temperature of the soil when the water deficit occurs." [Abstract]

[San Francisco, Mar. 5-6, 1998]

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