Construction Decline

By Don Williams, the Tree Wizard

Probably the biggest cause of oak tree death in Central Texas is improper land clearing during construction.

The earth is warming and we receive less rainfall in most hot summers. The native live oaks on rocky ground have been declining for years. They are reaching their limits of survival in nature because of environmental changes. It was only the six to eight inches of accumulated cedar mulch covering the rocky ground which held sufficient moisture in hot dry summers that allowed for their survival to date. A walk through the wild areas will show thinning live oaks everywhere, even though their roots are still partially covered with cedar mulch which helps conserve moisture.

Developers invariably remove cedar trees in order to build on the land, leaving native oak tree roots stripped and exposed to the heat. Moisture evaporates in the root zone and kills the shallow feeder roots.

Land developers bulldoze cedar trees, upturning many roots and damaging the feeder roots. They then root plow the ground into the rock to remove upturned roots, cutting and damaging tree roots permanently. The trees will die from this act alone, but then they may install a lawn sprinkler system and cut through the tree roots again. The homeowner then waters the yard shallowly for 20 to 30 minutes several times a week, but never waters trees deeply in hot, dry weather.

Some say cedar trees rob moisture from the oaks, but it is the cedar mulch that prevented total drying of all trees’ root zones. Trees cannot thrive on rocky ground in the Hill Country without mulch covering their roots. Over hundreds of years, this cedar mulch has created six to eight inches of dirt. Try sitting under a large cedar tree and begin removing the cedar mulch an inch at a time. After about six inches you are back to rock. You have just disturbed over 100 years of soil making from decomposing cedar mulch in the small area you just scraped out.

This is also what the land developers do, but they stripped thousands of acres of cedars in the Hill Country to build new subdivisions covered with soon to die live, red or post oak trees. These newly stripped oaks may look fine at first, but begin to decline soon. Post and red oaks die fastest. We can show you how to revive the damaged, ecologically changed, ravaged root systems.

The over 150 years of tree drought since before 1850 (yes 1850, according to the Forestry Service), past water rationing, lack of deep watering, and the restructuring of grade on rocky ground to build new subdivisions have created an environment completely different than the trees existed in 25 to 50 years ago. Trees will fail to adapt, slowly stress and die, mostly from root damage.

Years later some may die from oak wilt. Oaks on rocky ground do not adapt well to continuous drought or grade changes which destroys their feeder roots. Being very sensitive to grade changes, post and red oaks may die or begin to thin out the first or second year after construction. Cedar elms and post oaks die quickly in tree wells from root rot (excess winter bog conditions). Soil texture changes alter the composition of the soil affecting water and air flow, killing native trees.

Live oaks may take longer to die, but begin thinning and losing leaf count. To allow the stripped bare ground to become completely dried out even once kills the fine feeder roots. Improper grade changes bury roots too deeply, creating problems serious problems with yellowing elms and post oaks. So many mature trees have smaller leaves, thinned out foliage and excessive amounts of deadwood. This decline occurs “silently” for years until you see leaves browning on one of your trees and call me. The tree you called about may be near death or severely damaged, but I will show you other trees that are declining as well. Trees may have been declining for years and the changing growth patterns are noticeable to warn you years before, but people do not see or know to look for gradual growth pattern changes.

Live oaks are moderately fast growing trees and, in decent conditions, can grow to a 40-inch diameter in 37 ears. Over time, the native trees reach the peak of their growth (according to available moisture and nutrients) to then thin and slowly die. A smaller, younger tree requires a certain amount of nutrients and water, but as it grows it requires more. What we don’t realize is that the larger tree is still receiving the same amounts of nutrients and water it received when it was young. When it doesn’t receive a greater supply, it thins and declines. This is similar to a baby doing well on Gerber baby food. Now that person at age 50 still tries to exist on the same volume of baby food and water.

This is why trees do not grow well on rocky ground, as there are less resources available to support mature trees. It can take three to six years for root reconstruction to take place if trees are treated and watered deeply. Without intervention the tree will continue to weaken and die. This is why treatment with Mauget trunk injections is so necessary to rebuild the roots that absorb available moisture and nutrients. A tree in this weakened condition loses leaf count each year. You may not even notice this thinning until a tree is terminal. It is important for me to examine your trees, repair the root damage, increase leaf count, and ultimately restore health and vigor.

Have any questions about this tree topic? Give Big Country Trees a call at (512)983-4148.

Root rot from construction decline can affect the whole tree. Call us to bring your trees back to health.