How Do Dense Forest Conditions Affect Plant and Animal Diversity?
Grasses, forbs and shrubs: When a dense canopy of trees shades the ground, grasses and shrubs are less likely to grow. Where grasses abounded in the past, trees now dominate. The overwhelming majority of the plant biological diversity in Southwestern forests is in the understory community with over 600 understory species versus about 10-15 tree species in the overstory. This diversity of plants in turn comprises the essential habitat for many species of native fungi, soil microorganisms, arthropods, mammals and birds. Tree size and age: There are relatively few very young or very old ponderosa pine trees. In addition, trees have not grown to their potential because of competition. For example, an 80-year-old tree might be 14-16 inches in diameter or it could be as small as five inches in diameter if grown in very dense conditions. Types of trees: In mixed conifer forests there has been a decrease in ponderosa pine, limber pine and aspen over time because infrequent fires have allowed t
