Winter brings significant changes to the landscape. The brilliant colors of fall foliage were visible precursors to how some trees were preparing for winter. Now, a walk in the forest reveals the two-opposing leaf-retention strategies used by local trees: those that coordinated their loss of leaves in the fall — deciduous trees — and those that retain their leaves, peppering the scenery with a constant canopy of green — evergreens. Either game plan that tree species employ helps them reduce energy loss and minimize winter damage.
When days are short and water less available during the winter season, the evergreen’s approach is to stay in a state of low function. Retaining their leaves in the winter potentially offers a more-extended photosynthetic time than deciduous trees. Not losing all the leaves at once also reduces the number of nutrients absorbed each year from the soil, making them adaptable to grow in a less-favorable substrate. Evergreen leaves are generally long-lived, lowering the cost of leaf production in the spring when compared to their deciduous counterparts. Older leaves are replaced gradually and will provide enough canopy to function throughout the year, making it seem that they have the same foliage year-round. Leaves of conifers and flowering evergreen trees prevent moisture loss by having a greater thickness and waxy covering, plus it helps them withstand frost without suffering possible irreparable damage. Notable evergreens at the Fort Worth Nature Center & Refuge are Eastern red cedars, Ashe junipers, and live oaks.
Deciduous trees’ approach to winter is to cut their losses when the photosynthetic period becomes unproductive. In winter, the energy cost of retaining leaves is too high for the minimal returns of food production. These trees drop their leaves to conserve resources rather than expend energy to protect the fragile foliage. Fallen leaves will decompose and add nutrients to the soil needed for spring leaf reconstruction. The advantage comes in the spring with increased day lengths, available water, and faster growth rates, allowing deciduous trees to grow fast and outcompete evergreens. Deciduous tree leaves are not structured to live long. Losing them in the fall is another way to conserve moisture within the trunk and allow the wind to blow through the branches, putting less strain on the tree during inclement weather conditions. The Nature Center’s forests are mainly composed of deciduous trees and provide different scenery from season to season.
Winter strategies for survival are not just for wildlife. Trees use different tactics when resources are limited, and we can see some of those tactics during this time of the year. We may perceive that evergreens grow slowly and steadily throughout the year compared to deciduous trees’ fast and intermittent growth style. The goal for these producers is to be as efficient as possible as they adapt to the changes of the season. On your next outdoor walk, take a closer look at the trees nearby and marvel at their winter tactics for survival.