ABSTRACT.Forests are an integral component of the landscape, and maintaining their functional integrity is fundamental for the sustainability of ecosystems and societies alike. Tools, innovations, and practices, analogous or more than a century, agricultural and biological engineers have provided major advances in science, engineering, and technology to increase food and fiber production to meet the demands of a rapidly growing global population. Much of our agricultural land base originates from historically forested lands (Amatya et al., 2009), which have experienced dramatic declines, as well as periods of resurgence, over the past century, including in the south (U.S. Forest Service, 2011 set asides have decreased the industrial forest base for timber production, leading in some instances to more intensive silvicultural practices on the remaining forest land. Through time, the land use, hydrology, and ecosystem products and services of this mosaic have been modified to an extent that may jeopardize long-term sustainability.Forests cover about one-third of the U.S. (Sedell et al., 2000;Jones et al., 2009), totaling about 300 million ha and making up about 7% of the world's forestland area (USDA, 2001). There are many different types of forests in the U.S., stretching from the subtropical forests in south Florida to boreal forests of Alaska, and from the deciduous and mixed forests of the eastern U.S. to the conifer-dominated forests of the west. These diverse ecosystems provide habitat for wildlife, help clean the air and water, and supply timber, fuelwood, and other harvested products, while serving our recreational needs as places for hiking, camping, hunting, and fishing. U.S. forests are the single largest producer of industrial timber in the world (Prestemon and Abt, 2002). Furthermore, about two-thirds of the nation's scarce freshwater resources originate on forested lands (Jones et al., 2009). Maintaining their functional integrity is fundamental to the sustainability of ecosystems and societies alike. However, there is increased recognition that forest management is needed to maintain forest, ecosystem, and watershed health and resilience.Understanding watershed hydrology is critical to forest ecosystem management, as it drives nutrient cycling and loading dynamics in the soil, through plants, animals, precip- itation inputs, and surface and subsurface flow networks that support downstream water quality. Because forests make up a relatively large portion of many of our watersheds, it is important to understand the hydrology of both natural forests and silvicultural operations, while considering the contribution of other land uses. New activities and forest products often emerge in response to specific needs. Growth in biofuel demand could lead to increased removal of biomass from plantation forests, which would have substantial hydrologic impacts on these lands. In its first comprehensive forecast on southern forests, the U.S. Forest Service (2011) stated that urbanization, bioenergy use, weather pa...
