Chapter 15 Wetlands 369 Copyright Goodheart-Willcox Co., Inc. The water level in nontidal wetlands varies from a few inches to two or three feet and the water itself may be brackish or alkaline. Local geography and the types of minerals found in surrounding soil often determine the water quality and its saline content. Climate and the local geography also determine the type of wetland that forms in a given location. The types of wetlands found in the United States include bogs, fens, marshes, pocosins, prairie potholes, and swamps. Bogs A bog is a freshwater wetland comprised of moist, spongy ground and highly acidic conditions. A bog forms over hundreds or thousands of years as vegetative materials accumulate in a lake until the lake no longer exists. This process is referred to as terrestrialization. The organic materials that accu- mulate in a bog retain a great deal of moisture and do not fully decompose. Eventually, the partially decomposed materials form into peat. The area of a bog that remains covered in shallow surface water varies from very little to a considerable amount. Bogs are more commonly found in cooler climates that have short growing seasons, high humidity, and ample precipitation, Figure 15-14. Bogs are ombrotrophic because they receive almost all of their water from rain and snow rather than other bodies of water. A bog’s soil becomes acidic and has very little nutritive value because rain is acidic by nature and also very low in nutrients. Most bogs have a pH range between 3.2 and 4.2. The acidic soil and water of bogs results in a unique variety of wildlife, such as carnivorous plants, dragonfl ies, and sphagnum moss, Figure 15-15. Pavel_Klimenko/Shutterstock.com Figure 15-14. It may take thousands of years for a bog to form. Bogs are often called heaths after the heather that often blankets the area. Christian Vinces/Shutterstock.com Figure 15-15. Many plants and animals are unique to wetlands. A—Carnivorous round-leaved sundew plant (Drosera rotundifolia) in a northern Wisconsin bog. B—There are more than 5000 known species of dragonflies. How many types of carnivorous wetland plants can you identify? Bryan Neuswanger/Shutterstock.com A B