New Growth Pine — New growth pine trees at LCNP.

Before the droughts of 1980 and 2011, the forest in The Lorraine Cherry Nature Preserve was known for the 100-year-old Loblolly Pines that shaded the entire area. These tall trees were a significant factor in controlling the climate of the forest, affecting what could grow underneath and how fast it could grow. Prior to the drought, they were the main trees growing here in the forest.

Those pine trees used a strategy called “allelopathy” to discourage anything else from growing around them and competing for the available resources. Allelopathy is a common biological phenomenon by which one organism produces biochemicals that influence the growth, survival, development, and reproduction of other organisms. These biochemicals are known as allelochemicals and can have either a beneficial or detrimental effect on target organisms. Another familiar plant that uses allelopathy is the sunflower.

But now, as a result of the droughts, many of the tall trees are gone, and the forest is changing into something very different. There are now other trees among the pines, including many types of Oaks, Elms, Ashes, and even Sweet Gums. These once smaller trees have big, light-gathering leaves that helped them survive in shaded areas. They did not grow very big when the larger pine trees towered over them because they didn’t get enough light and had to struggle to get nutrients. But under the ground, they grew a foundation of roots, ready to start growing tall if anything happened to the pine trees above them. Now the light is getting through.

Section of new growth pine trees at LCNP.

Here you can see a small grove of young Loblolly Pines growing up. Do you see the thick carpet of pine needles underneath the trees? This thick covering serves to prevent light from hitting the ground around the trees, but it does much more than that. As the needles decompose, they increase the acidity of the soil, making it difficult for many other plants to grow. The needles, as well as pinecones from the tree, may also trigger additional chemical reactions to discourage competition. When the pine trees grow taller, even less light will be able to reach the ground, further limiting the growth of competing plants.

At this time, all the trees are about the same height as the young pines. Over time, this area will begin to look different from how it looks now. Do you think the pines will retake this area, or do you think the pines will continue to share this area with the other trees as they are now?