Shiloh

Shiloh National Park Service U.S. Department of the Interior Use a “short-hand” version of the site name here (e.g. Palo Alto Battlefield not Palo Alto Battlefield National Historical Site) set in 29/29 B Frutiger bold. Shiloh National Military Park Tennessee-Mississippi The Color of Autumn: Nature’s Masterpiece The Arrival of Autumn Autumn is a season of change. The appearance in leaf color from green to a variety of shades such as red, yellow, orange, and brown is its signature and the reason that many people enjoy this season the most. But what causes the leaves to change colors? Why do specific colors express themselves in some trees, and not in others? Why do leaves of trees appear brighter and more vivid in one region of the country than another? Why are Leaves Green? Plants are producers of their own food in a process called photosynthesis. Photosynthesis is a reaction between light, water, carbon dioxide, and a pigment called chlorophyll to produce sugar (the plant’s food) and oxygen. Chlorophyll is the most abundant pigment in most all plants, and is essential in a plant’s survival. It absorbs all colors except green, and is the reason why leaves appear green in the growing seasons. In the autumn months, the days get shorter and the temperature gets cooler. Plants respond by ceasing chlorophyll production and eventually losing their leaves. As the chlorophyll disappears, the green fades away, and other pigments in the leaf begin to show. These pigments can be divided into 3 Anthocyanins Anthocyanins in various leaves. categories: carotenoids, anthocyanins, and tannins. Chlorophyll causes the green in trees. Anthocyanins are pigments found in certain species of plants. However, they are not stored in the leaves, like chlorophyll and cartenoids. They are made by the plant cells. The decomposition of chlorophyll, the shorter days, and the presence of sugars in the leaves are all factors that contribute to anthocyanin production. These are the first colors to show in the fall, and leaves with this pigment will appear anywhere from a bright red to a dark crimson. The trees and shrubs which exhibit this color are red oaks, sweetgum, black cherry, sumac, black gum, and maple. Carotenoids Carotenoids are common pigments found in the leaves of most plants. They are used as a secondary lightabsorbing pigment to chlorophyll. The chemical make-up of carotenoids is more stable than chlorophyll. As the chlorophyll decomposes and fades away in autumn, the carotenoids are left behind and give the leaf an orange or yellow color. They are the same pigments found in carrots and corn. These colors are usually seen in the leaves after the anthocyanins appear. The trees exhibiting this color are elms, hickories, black walnuts, yellow poplars, and maple. Tannins Tannins make leaves turn brown. Perfect Weather for Expression Carotenoids make leaves turn yellow. Tannins are chemicals found in almost every living plant. They occur in large amounts in oaks, as well as beech and chestnut trees. As fall continues and the weather changes, the chlorophyll production ceases, permitting the tan to dark brown color of the tannins will become visible. They are usually the last pigment seen in the fall and will not be visible until after the carotenoids and anthocyanins have disappeared or become less abundant. Autumn leaf color will be expressed more or less vivid, depending on regional weather conditions. The best conditions which produce the brightest and most vivid color are: · · · · Sunny days Cool nights Low humidity (drier weather) Low precipitation Annually each autumn, these weather conditions routinely occur in the northeastern United States, and it is this region where the autumn colors traditionally express themselves in grand splendor. Shiloh’s Canvas Shiloh National Military Park is populated with a variety of tree species that display remarkable autumn colors. We invite you to plan your fall visit here and enjoy this season of change with us. EXPERIENCE YOUR AMERICA