Want to know why the trees are brown?

I wondered, as fall approached, what the effect of the drought we had this summer would be on the forest. One really clear outcome is the way trees are dropping their leaves. In the woods around my house, fall colors are muted because the leaves are so dry. The oaks in my driveway are dropping green leaves still on twigs. The canopy is studded with bare branches where trees shed leaves during the hot spell this summer.

Dropping leaves is a way to conserve water. Trees absorb water through their roots and then give off water vapor through pores in their leaves in a process called transpiration. If the leaves are releasing more water vapor than the roots can supply, the tree sacrifices some leaves.

The coastal forest thrives on abundant water.

According to Penn State Professor James Finley, our trees need at least 2 inches of rain every seven to 10 days. On average, they pull a whopping 100 gallons of water daily from the soil and water table. In drought years, the trees can't get enough water.

In addition, our rain patterns have changed over the past several years. Instead of steady all-day rain, we have downpours that flood creeks and rivers.

For the past two years, we have had fog and rain in December and a low snow pack. Winter rain runs off frozen ground instead of seeping into the aquifer.

If you have trees and shrubs in your landscape, you can help them by giving them water right up until a hard freeze. This is especially true for evergreens because they transpire all winter. The second thing you can do is mulch under your trees and shrubs with 2 inches of undyed wood chips. This will help keep down evaporation, and will condition the soil so that it can absorb more rain water.

If this cycle of heat and drought followed by winters with low snow falls continues, we are going to see some changes in our forest. Trees in stress are more vulnerable to attack by insects and pathogens. Some of the larger trees may die because they can't get enough resources to maintain themselves.

It's going to take a few good wet years in a row for the forest to recover, and we may lose some mature trees to drought. Now is the time to plant and nurture saplings so the next generation will be ready when the rains come again.