![]() (Figure 4)įigure 3: Tree defoliating from the top and branch extremitiesįigure 4: Bark cracking due to drought stress. During prolonged droughts, trees might develop longitudinal cracks in the bark, especially in thin-barked species like maples. Trees will generally begin to lose their leaves from the top and branch ends. Leaf margins will have a brown or burned appearance. Prior to dropping foliage, leaves will turn yellow and exhibit fall color. As droughts progress, leaves will remain wilted even in the early morning. Leaves will recover and appear normal by morning. Wilting and drooping leaves will occur during the day. Look for the following symptoms in times of short-term drought. Signs of drought will be most visible in the foliage of trees. Drought tolerant trees by contrast generally have thicker and waxier leaves capable of minimizing water losses through their foliage (all trees transpire moisture through leaf opening called stomata necessary for photosynthesis and growth). Trees adapted to flood plains, riverbanks, or swamps will likely suffer greater stresses. Some species of trees will be more tolerant to drought than others. These trees are less likely to be impacted by short-term droughts. Trees with deep roots are more resilient to drought and are capable of mining deeper soils. Trees adapted to regular short-duration irrigation will develop shallow roots and be subject to drought if irrigation systems are turned off. ![]() These trees will have shallow root systems and will be subjected to hotter and drier surface soils. These include trees growing in rocky soils, shallow planters, or compacted soils. ![]() Trees in shallow soils will be more susceptible to drought stress. Opportunistic disease, such as hypoxylon canker, are common in the months and years following drought events. In hardwoods, drought can cause trees to be susceptible to insects such as ambrosia beetles, black twig, flathead, and round head borers. For pine species, pine bark beetles (Ips, Black Turpentine and Southern Pine Beetle) will be a significant concern for the rest of this year and next year as well. Root loss leads to tree stress and dramatic increased susceptibility to a number of insects and diseases. Once root loss has happened, it can take days to weeks for the trees to re-grow the root hairs necessary to take advantage of rainfall. Under prolonged droughts, even the larger, fibrous roots are lost. If these conditions persist, the fine hair-like roots, whose primary function is to absorb moisture, begin to die back. While most soils will still retain some moisture, the soil “holds on” to this moisture, making it unavailable to trees and other landscape plants. Effects of Drought on Treesĭuring a drought, the amount of water available in the soil declines to a point where the tree’s roots aren’t capable of absorbing moisture. As a result, it may become necessary to irrigate certain trees during a drought, assuming there are no water restrictions. The effects are not always immediate and the full extent of the damage to trees can take one to two years to become apparent. Droughts, especially prolonged droughts, affect trees and other woody plants in serious ways. Alabama is in the midst of a drought with unusually warm fall weather and trees are beginning to exhibit signs of stress.
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