This is due to reduced gas exchange and changes in drainage. Weather and climatic stresses include high temperature combined with drought conditions and cold, windy conditions. Drought combined with high temperatures causes leaf scorch. The plants are forced into dormancy to cope with the conditions. A similar condition occurs when the soil freezes and plants are exposed to drying winds.
Moisture is lost through the leaves of evergreen plants, desiccating the tissue.
Heat and moisture stress can result from roots covered with pavement. The paving limits moisture penetration of the soil and causes heat buildup. Street trees are subjected to this problem plus confined root area and road salt buildup during winter months. A soil test for soluble salts can potentially identify salt problems. Pollution is an increasing problem in some areas.