Issues in Ecology Number 6 Spring 2000 issues underlies policies and practices that have been blamed mosphere.a phenomenon expected to drive warming of the for repeated over-cutting of national forest lands.Consid global climate.However,one way the earth maintains a erations of spatial pattern are essential in management plans balanced atompshere is by storing or "sequestering"car that strive to assure normal ecological functioning within bon (Perry 1994).Forests help mitigate the accumualtion the landscape(Harris 1984.Franklin and Forman 1987). of CO,in the atmosphere by absorbing this trace gas from As an example,consideration of forest patch size and the air to fuel photosynthesis.Half of the carbon absorbed shape and the extent of edge influences is critical in assess- is released back to the atmoshpere during respiration.while ing whether the interior forest conditions required by many the other half is sequestered in soils.sediments.and wood species are actually present in a landscape.The influenceof This makes forests a significant global resevoir for carbon recently cut areas on adjacent forest patches (edge effects) but it is unknown how much this sequestration will mitigate For instance,micro tic increasing emi sions of( rcut patch pernaps greater sunlig ner tem orest rworld with incr ed at y extend or 10to 30 meters mospheri are ha to pre KE earch on individua meters) etting es y El gro en e 1993 ant g et a dscape in whi such fin ng 981 empera dictable t in the landscape are not would require availability to duce th nes associated extra wood.roots.and lea eindications that lands lakes and n ds are nd nutrient eveling example.In many for some re earch show and gr rowth by producing leaves and other tissues with upon the root strength of the standing forest:clearcut this lower nitrogen concentrations (Schlesinger 1997)Organic forest and the likelihood of landslides increases dramatically matter low in nitrooen decomposes more slowly.raisino the Other sensitive areas in a landscape may be source areas for specter of reduced nitrogen availability and constraints on woody debris and sediments for streams and rivers,rock potential increases in plant growth. outcrops and scree slopes.and calving areas for deer.elk. A larger scale consequence of altered global climate pat and other ungulates.All of these types of sensitive areas terns could be changes in the distribution of species,includ should be recognized and protected as part of landscape ing the geographic regions suitable for important forest spe level forest management planning cies.Recent predictions for the eastern U.S.suggest,for Some have proposed that spatial issues can be adequately example,that changes in climate could lead to the complet addressed simply by providing that a certain percentagef loss of species such as sugar maple,with its new range lying each watershed be maintained in a series of four or five struc entirely in Canada.In the central states,a north vara shit 1997.How of loblolly pine populatio from Ok and ever,p and I s pr adequately com with the of loblo y pines mo Gu ccurs an orgla 94 of ho espec ally 03 est ed.populated. -altere nd goa dition d de ides alter ing the and climate.nollutio pend upor regional c ext and il fl h manageme direct i acts whic GLOBAL CHANGE:IMPLICATIONS FOR ear the Farth's su e is a very rea FOREST MANAGEMENT tive.short-lived gas that accumulates mainly on hot Combustion of fossil fuels.deforestation.and other hu- nant summer days ozone damac s plants by penetratin man activities are contributing to the buildup of carbon di- the leaf pores (stomata)and oxidizing cell membranes and oxide(CO)and other so-called greenhouse gases in the at- other structures.The result is a reduction in net photosyn 9 Issues in Ecology Number 6 Spring 2000 issues underlies policies and practices that have been blamed for repeated over-cutting of National Forest lands. Consid￾erations of spatial pattern are essential in management plans that strive to assure normal ecological functioning within the landscape (Harris 1984, Franklin and Forman 1987). As an example, consideration of forest patch size and shape and the extent of edge influences is critical in assess￾ing whether the interior forest conditions required by many species are actually present in a landscape. The influence of recently cut areas on adjacent forest patches (edge effects) can be very extensive. For instance, microclimatic influences of a clearcut patch perhaps greater sunlight, higher tem￾peratures, drying winds may extend for 10 to 30 meters (with extremes of 200 to 400 meters) into an adjacent old￾growth forest patch (e.g., Chen et al. 1993). Edge influ￾ences can be so pervasive that a landscape in which 10- hectare patches of cutover and forest are interspersed will entirely lack interior forest conditions after half of the land￾scape has been harvested (Franklin and Forman 1987). Recognizing the sensitivity of portions of a landscape is another essential element in landscape planning. All parts of the landscape are not created equal. Floodplains, banks, and shallow-water zones associated with streams, rivers, wet￾lands, lakes and ponds are examples of sensitive areas. Areas of unstable soil provide another example. In many forested mountainous landscapes, soil stability depends substantially upon the root strength of the standing forest; clearcut this forest and the likelihood of landslides increases dramatically. Other sensitive areas in a landscape may be source areas for woody debris and sediments for streams and rivers, rock outcrops and scree slopes, and calving areas for deer, elk, and other ungulates. All of these types of sensitive areas should be recognized and protected as part of landscape￾level forest management planning. Some have proposed that spatial issues can be adequately addressed simply by providing that a certain percentage of each watershed be maintained in a series of four or five struc￾tural stages of development (e.g., Oliver et al. 1997). How￾ever, proponents of this approach use structural stages that do not adequately represent complex structural development that occurs in natural forest stands, and they often fail to incorporate principles of landscape ecology just discussed. Such simplifications have value in dealing with plantations or intensively managed stands, but not in designing sustain￾able policies for National Forest lands managed to meet di￾verse values and goals. The proportion of various forest conditions or stages present in a given landscape should de￾pend upon regional context and management objectives. GLOBAL CHANGE: IMPLICATIONS FOR FOREST MANAGEMENT Combustion of fossil fuels, deforestation, and other hu￾man activities are contributing to the buildup of carbon di￾oxide (CO2 ) and other so-called greenhouse gases in the at￾mosphere, a phenomenon expected to drive warming of the global climate. However, one way the earth maintains a balanced atompshere is by storing or sequestering car￾bon (Perry 1994). Forests help mitigate the accumualtion of CO2 in the atmosphere by absorbing this trace gas from the air to fuel photosynthesis. Half of the carbon absorbed is released back to the atmoshpere during respiration, while the other half is sequestered in soils, sediments, and wood. This makes forests a significant global resevoir for carbon, but it is unknown how much this sequestration will mitigate increasing emissions of CO2 . Forest responses to a warmer world with increased at￾mospheric CO2 are hard to predict. Research on individual plants in controlled settings indicates that a primary effect of rising CO2 will be enhanced plant growth (DeLucia et al. 1999). However, it is unclear how such findings will trans￾late to ecosystems in the field over time. A changing climate will likely bring not just a shift in temperatures but unpre￾dictable changes in precipitation, cloudiness, disturbance pat￾terns, and perhaps timing of growing seasons (Perry 1994). Increased tree growth in enriched CO2 environments would require increased nutrient availability to produce the extra wood, roots, and leaves. Yet there are indications that decomposition and nutrient cycling could be hampered. For example, some research shows plants respond to increased CO2 and growth by producing leaves and other tissues with lower nitrogen concentrations (Schlesinger 1997). Organic matter low in nitrogen decomposes more slowly, raising the specter of reduced nitrogen availability and constraints on potential increases in plant growth. A larger scale consequence of altered global climate pat￾terns could be changes in the distribution of species, includ￾ing the geographic regions suitable for important forest spe￾cies. Recent predictions for the eastern U.S. suggest, for example, that changes in climate could lead to the complete loss of species such as sugar maple, with its new range lying entirely in Canada. In the central states, a northward shift of loblolly pine populations from Oklahoma, Tennessee and North Carolina to central Illinois and Indiana is predicted, with the southern limit of loblolly pines moving from the Gulf Coast into central Alabama and Georgia (Perry 1994). Such projections raise the question of how quickly plant and ani￾mal species will be able to migrate as their suitable climatic range shifts, especially when they must migrate across fragmented, populated, and otherwise human-altered landscapes. Besides altering the atmosphere and climate, pollution from fossil fuel burning could have direct impacts on forest distribution by raising levels of tropospheric ozone, which accumulates near the Earth’s surface. Ozone is a very reac￾tive, short-lived gas that accumulates mainly on hot, stag￾nant summer days. Ozone damages plants by penetrating the leaf pores (stomata) and oxidizing cell membranes and other structures. The result is a reduction in net photosyn-