As the warmth of summer draws to a close, we are seeing fall color and leaf drop on Gathering Place’s deciduous trees! Deciduous trees are those that lose their leaves (unlike evergreens). Fall’s shorter days result in less photosynthesis, and deciduous trees no longer need leaves for food production. To prepare for winter, nutrients found in the leaves are remobilized to the stems and trunk for the next growing season.
The beautiful leaf colors appear as the chemical composition of the leaves change. Chlorophyll, the green pigment that is produced through photosynthesis, starts to degrade. As chlorophyll degrades, beta-carotene and flavonols are more visible. Beta-carotene reflects yellow and red light from the sun, creating a beautiful orange hue. Flavonols are present year-round and contribute to the yellow hues. Additionally, anthocyanins increase production in autumn and provide a blue, purple, red, and brown color. Plants that produce anthocyanins do so for individual reasons including leaf protection and ecological benefits.
As the trees return their leaves to the soil, the leaves create habitat and improve soil health. When temperature and light levels drop, a rise in the chemical ethylene flows to the leaf stem base, causing cells to weaken and tear away from the trees. This is called leaf abscission. Leaf drop also decreases the potential of tree damage from heavy snow, ice, and wind. In just a few short weeks, Gathering Place will be covered in millions of leaves from over 6,000 trees! While we remove leaves on the pathways and in the landscape, we leave some leaves in the horticulture beds because they serve a great purpose for the entire food web of the Park.
Leaves left in the landscape help protect insects through winter. Leaf coverage on top of the soil hides burrows of native bees. Fritillary butterflies, wooly bear caterpillars, millipedes, spiders, worms, snails, lace bugs, and many others seek shelter and warmth in all varieties of leaves. Crumpled brown leaves are perfect camouflage for the chrysalises and cocoons of luna moths and swallowtails. The red-banded hairstreak butterfly uses oak leaves as a nursery habitat for their eggs, and the hatched young caterpillars feast off the oak leaf litter through spring.
Weather and time break down leaves, twigs, and branches. This decaying matter is called detritus, which is a food source for detrivores, such as earthworms, millipedes, and snails. Fungi and bacteria process the remaining matter and transform it into nutrient-rich humus, which is loved by plants of all kinds. This recycling process speeds up when moisture levels are high. Fallen leaves are also an excellent source of water retention and act as a soil erosion barrier when left as mulch.
Millipede in Detritus
Beneficial Beetle in Leaf Litter
Lacewing on Leaf Litter
Although leaf fall marks the end of summer, it is a vital step in securing the well-being of all wildlife at Gathering Place!