Drought can be last straw for stressed trees

By Jim Griffith
Registered Forester #1616

Many areas of Georgia are seeing record lows of rainfall this year. One good thing about a drought is the opportunity to log forests that are normally too wet to allow equipment in for harvesting. However, the bad thing about drought is that it puts trees under stress.

People under stress tend to have more physical problems than those who aren’t under stress. Serious illnesses find an opportunity to attack humans more readily when they are under stress, not to mention the mental and emotional strains resulting from stress. Because trees are a biological, living entity, they suffer the effects of stress, just like people.

Trees growing on higher ground with dryer, well-drained soils are more susceptible to drought. However, years like this one can affect even low-lying pine in bays and swamps that have dried up.

It’s not always the drought in itself that creates the problem. Drought conditions just exasperate other stress factors like insect infestations, older-aged trees or dense stands.

I just finished a timber harvest on an upland property that was loaded with pine about 30-years-old. The pine was established by natural regeneration and was a fine stand of trees consisting of considerable amounts of chip-n-saw and sawtimber. However, it had never been thinned and was drastically overcrowded. The density of the stand limited the growth of the trees through the years, resulting in the stand having an average diameter way below where it could and should have been for that age of pine, hurting not only its health but its value.

Thirty-year-old trees are approaching the stationary phase of their biological growth cycle. As young trees they grow at an increasing rate. As they mature, they are still growing, but at a decreasing rate. When they get older, the growth rate of trees is static. They do more maintaining than growing because they have lost the vigor of their youth. It’s similar to how we humans age, losing vigor as we grow older.

So, if you have older trees in an over-crowded stand competing for nutrients, light, and space, and then add drought conditions on top of that, you have the potential for tree stress. This is what was happening in the stand I just harvested. There were already many dead spots and many more active beetle spots throughout this property. Trees were dying left and right. It was a choice of salvaging what we could or losing it all. We went to work immediately to make sure this landowner did not come up on the short end of the stick.

I have just looked at another stand of timber that is situated on a low, normally wet tract of land. However, due to the drought conditions, the land has been dry for a year. There are trees dying everywhere. The trees are more than 50 years old, and it is an extremely dense stand that has never been thinned. The remaining trees are at high risk. If this were someone’s savings account or retirement, I would be scared to death to leave it standing under these conditions, taking that kind of risk with my future.

A professional forester shouldn’t tell you what you have to do. They should give you suggestions of what to do under your circumstances so you can make an informed decision about your timber asset.

Jim Griffith is general manager of the Georgia Farm Bureau Timber & Realty Cos.
Georgia Farm Bureau Neighbors – September 2007

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