ST. LOUIS, Mo. – Before you know it, trees will be changing colors, but the summer has been one of many extremes which will likely impact our fall landscapes.
The drought conditions earlier in the summer may have more of an impact on the foliage than we expect, despite the multiple heavy rain events that followed.
“So sometimes when we’re in a drought situation but get rain, the water falls so hard and so quickly that it doesn’t actually recharge the soil like we may think it does. It actually runs off much quicker than it normally would if it absorbed into the soil in a normal year, said Sam Lord, an instructor of Soil Science at the University of Missouri.
This means our trees might not have the same amount of water even though we had historic rains.
“Those trees can still be impacted in the fall foliage. Once again, maybe shortened or the fall colors could be very abrupt. Maybe yellow to brown very quickly,” Lord said.
Soil composition is highly variable across Missouri and soils have a certain capacity to handle water infiltration in a given amount of time.
“When we have these large precipitation events, sometimes our soils get inundated very quickly and they reach that capacity very quickly, leading to runoff and then further that flash flooding event very quickly,” he said.
The soil composition in urban areas has been manipulated over time, which changes the ability of the soil to recharge since it’s been reworked from its natural state.
“Either it’s been put into an impervious state like concrete or road or building, or it’s been reworked to the point where it just cannot handle the water. It’s been reworked to where the clay’s at the surface, for instance, and it doesn’t allow that infiltration to happen,” said Lord.
This increases the importance of green space in cities.
“It’s that much more important how green space and impervious surfaces really interact with each other. When we have complete concrete monotonous cityscapes, we are moving that water off of the landscape very rapidly, not so it can infiltrate the soil but it is going somewhere else to essentially accumulate and causes issues down river for a lot of people,” he said.
And all these factors combined with our current weather will ultimately shape the shades of leaves this fall.
“We saw some slightly cooler temperatures overnight but when we have this heat wave come back and go into the 90s you may see that foliage really start to shrivel up depending on how long those high temperatures go,” said Lord. “Because you all are not in a significant drought right now, I will say that you will have a shortened, but still see some fall colors from some of our maples and our oaks.”