ABSTRACT
Trees are capable of altering dramatically the conditions of the ecosystem of which they are part (Chapter 17, pp. 247). Belowground, a tree’s roots penetrate deeper than those of annual crops, affecting soil structure, nutrient cycling, and soil moisture relations. Aboveground, a tree alters the light environment by shading, which in turn affects humidity and evapotranspiration. Its branches and leaves provide habitats for an array of animal life and modify the local effects of wind. Shed leaves provide soil cover and modify the soil environment; as they decay they become an important source of organic matter and nutrients.
