Issues in Ecology Number 6 Spring 2000 tent and value of the knowledge base that has been developed forest ecosystems and also how management practices af on forest ecosystem dynamics and response to disturbance. fect soil quality (eg.Cole 1995 and Perry and rose 1998) The purpose of this report is to outline key ecological Although very little research has been published on systems considerations that should underlie sound forest manage for evaluating or monitoring soil quality.defining it and ini ment.The complexity and variability of forest ecosystems tiating programs to evaluate its maintenance and promo throughout the United States make it difficult to formulate tion are central to achieving demonstrable sustainability in ecological principles that apply uniformly to all.Yet there is our National Forests.The ability to define and measure so consensus among forest ecologists about one generalization: quality is important for applications at a number of scales All forests should be regarded and managed as ecosystems from monitoring soil compaction and nutrient supply at spe ecosystems that represent a variety of resources and val- cific .em est this report we management in tive catego Wha cycles blend of minerals. .living .In n pro of the suppo explicitly a te em propo mite h rests (USDA NRCS 1996) tha Healthy soil e critical ec ical functions (An in forested eco ont cy lino.a on the scientific hasis of for de nted by david perry (1998)in the annual reu dead organic matter and release vital nlant nutrients such a and phosphorus for reuse.This activity accounts A single overarching prir nciple sets the context for this for the majority of nutrients taken up by plants in matur report:the national forest system should be viewed as a forests.Second.healthy soil enables a forest to maintain multifaceted resource of continuing value.and current man some productivity (tree srowth)during periods of shortase agement policies and practices should not devalue the re- especially droucht Third.healthy soil is capable of retain source for future generations.Any set of management prac ing fertility and thereby facilitating plant recovery follow tices should therefore be sustainable for the indefinite future ing disturbances such as fire or timber harvesting.The lat ter capability quickly degrades,however.when plant cover ECOLOGICAL CONSIDERATIONS IN is removed and the soil is left bare(Perry 1998). R5MANA Soi Structure and Oranic Matter From the early the.Forest Ser A significant concern in the maintenance of forest soil has had two soil o ing compa wers e expande agency s matter includ sity c m he as catego 180 de signed to the d h ms,many which perform th ersity:(4 scape level iss and (5) As lon of soil car ine lit SOIL AND NUTRIENT CYCLES will be th ofc the st Soil quality is central to sustainable forest tus soil nutrients because it defines the current and future productivity of the More problematic is the replenishment of those co land and promotes the health of its plant and animal com nents of soil carhon that are derived from large wo munities (Doran and Parkin 1994).A great deal is known bris,especially tree stems(Figure 2:Harmon et al.1986) about the importance of soil quality for the functioning of The practice of leaving tree stems on site is not common in 3 Issues in Ecology Number 6 Spring 2000 tent and value of the knowledge base that has been developed on forest ecosystem dynamics and response to disturbance. The purpose of this report is to outline key ecological considerations that should underlie sound forest manage￾ment. The complexity and variability of forest ecosystems throughout the United States make it difficult to formulate ecological principles that apply uniformly to all. Yet there is consensus among forest ecologists about one generalization: All forests should be regarded and managed as ecosystems ecosystems that represent a variety of resources and val￾ues for different forest users. In the first section of this report, we discuss ecological considerations for forest management in five broad catego￾ries: 1) soil and nutrient cycles, 2) hydrology, 3) biodiversity, 4) landscape level issues, and 5) global change. In the sec￾ond section of the report, we examine and critique some of the ecological assumptions that explicitly or implicitly un￾derlie several current forest policy proposals. In particular, we analyze acceptable or desirable levels of direct human manipulation and use of federal forests based on current eco￾logical understanding. Rather than presenting a comprehen￾sive review of the literature, we discuss principles that are generally accepted among ecological scientists. (An excel￾lent review of the literature on the scientific basis of forestry was presented by David Perry (1998) in the Annual Review of Ecology and Systematics.) A single overarching principle sets the context for this report: The National Forest System should be viewed as a multifaceted resource of continuing value, and current man￾agement policies and practices should not devalue the re￾source for future generations. Any set of management prac￾tices should therefore be sustainable for the indefinite future. ECOLOGICAL CONSIDERATIONS IN FOREST MANAGEMENT From the early days of its creation, the U.S. Forest Ser￾vice has had two primary goals: to support local industry and to protect and sustain watersheds. Over time, new laws and policies have expanded the agency’s mission to include recreation, biodiversity conservation, and maintenance of soil quality and natural processes. We examine here five broad categories of ecological considerations that should go into management practices designed to fulfill this complex mis￾sion and to sustain forest resources into the future: (1) soil and nutrient cycles; (2) hydrology; (3) biodiversity; (4) land￾scape level issues; and (5) global change. SOIL AND NUTRIENT CYCLES Soil quality is central to sustainable forest management because it defines the current and future productivity of the land and promotes the health of its plant and animal com￾munities (Doran and Parkin 1994). A great deal is known about the importance of soil quality for the functioning of forest ecosystems and also how management practices af￾fect soil quality (eg., Cole 1995 and Perry and Rose 1998). Although very little research has been published on systems for evaluating or monitoring soil quality, defining it and ini￾tiating programs to evaluate its maintenance and promo￾tion are central to achieving demonstrable sustainability in our National Forests. The ability to define and measure soil quality is important for applications at a number of scales, from monitoring soil compaction and nutrient supply at spe￾cific sites to addressing global concerns about the amount of carbon sequestered in the wood of the world’s forests. What is soil? Soil is a unique and complex blend of minerals, living organisms, and the organic products of organisms. It pro￾vides habitat and physical support as well as sustenance for a teeming array of creatures, from bacteria and fungi to mites, earthworms and plants. The soil and its living com￾munity store and cycle nutrients, regulate water flows, and also filter, buffer, degrade, immobilize, or detoxify a myriad organic and inorganic materials (USDA NRCS 1996). Healthy soil performs three critical ecological functions in forested ecosystems. One is nutrient cycling, a process carried out by invertebrates and microbes that decompose dead organic matter and release vital plant nutrients such as nitrogen and phosphorus for reuse. This activity accounts for the majority of nutrients taken up by plants in mature forests. Second, healthy soil enables a forest to maintain some productivity (tree growth) during periods of shortage, especially drought. Third, healthy soil is capable of retain￾ing fertility and thereby facilitating plant recovery follow￾ing disturbances such as fire or timber harvesting. The lat￾ter capability quickly degrades, however, when plant cover is removed and the soil is left bare (Perry 1998). Soil Structure and Organic Matter A significant concern in the maintenance of forest soil quality is assuring the replenishment of surface and soil or￾ganic matter and avoiding compaction of the soil (Powers et al. 1990). Soil organic matter includes highly decomposed material called humus, less decomposed leaf litter and other detritus, and large woody debris such as branches and stems. This organic material stores nutrients and water and sup￾plies the carbon to nourish the myriad belowground organ￾isms, many of which perform the critical tasks of releasing the mineral nutrients necessary for continued plant growth. As long as plant communities regrow vigorously after timber harvesting, losses of soil carbon derived from fine litter will be replenished. Regrowth, of course, depends on the sta￾tus of soil nutrients, soil carbon, and soil biology after harvest. More problematic is the replenishment of those compo￾nents of soil carbon that are derived from large woody de￾bris, especially tree stems (Figure 2; Harmon et al. 1986). The practice of leaving tree stems on site is not common in