ISSUES IN ECOLOGY NUMBER THIRTEEN SPRING 2010 ing remote ou managed to restore dam and t the ri adpla reducing the carbon benefit by emissions of e from forest fertilization,reduced etation,and fertilization grow wood four times accomplished by replacing multi-species forests with monocultures s.Forest manag ment:fuel manage- varies by climate,soil,tree species,and man ment to reduce fire threat carbon stocks will erally be Fuel t (Box 3)r s.a1%incrase ingrowth will result ina crown fire because crown fires are difficult,if increase in car stoc not impos ble,to h nagemel fir not change.As shown in Figure3 the rate of imefrom foresrs where historical forest forest growth will naturally slow down as the dens ons for n res,to I fires products if the for. porarily o bio nass an then decompose. harvest urns through a forest that be m hich many of the treesc n ofte survive the fire.In Box3.THINNING AND CARBON st,many or s in ar Thinning is an effective forest management technique used to produce larger ast in ina in th of the that fuel treatments offer a carbon benefit om the forest may h to r the site are two vi ng the science ally lower than or lon on carbon savings through fuel treatments ate the wth Some stud ve shown that thi nned stand 9 ter than that of the ni ymay not pro on losses in a crown fire.or have used mod. The net ca eling to estimate lower carbon losses from hinned stands ney were to bur owever y but also on the ange in fire relative to the length of the harvest interval 8 esa The Ecological Society of America esahq@esa.org ISSUES IN ECOLOGY NUMBER THIRTEEN SPRING 2010 8 esa © The Ecological Society of America • esahq@esa.org U.S. pines, operational plantations using improved seedlings, control of competing veg￾etation, and fertilization grow wood four times faster than naturally regenerated second￾growth pine forests without competition con￾trol. The potential to increase forest growth varies by climate, soil, tree species, and man￾agement. Increases in carbon stocks will generally be proportional to increases in growth rates. That is, a 10% increase in growth will result in a 10% increase in carbon stocks, assuming that the harvest interval and amount harvested do not change. As shown in Figure 3, the rate of forest growth will naturally slow down as the forest ages. Management decisions for increas￾ing carbon stocks should take into account for￾est growth over time, the amount of timber that would end up in wood products if the for￾est were harvested, and how long the harvested carbon would remain sequestered in the wood products. Knowledge of these variables will help determine when or whether to harvest. The area of forestland in the U.S. that could be managed to increase forest growth includes more than 500 million acres and consists of almost all U.S. public and private forestland, excluding remote and reserved areas such as national parks. However, even reserved areas could potentially be managed to restore dam￾aged ecosystems, which could also lead to increased forest growth. Increasing forest growth through manage￾ment has benefits and costs. The benefits include increased wood production and the potential for planting species and genotypes adapted to future climates. The costs include reducing the carbon benefit by emissions of nitrous oxide from forest fertilization, reduced water yield (faster growth uses more water), and a loss of biodiversity if faster growth is accomplished by replacing multi-species forests with monocultures. 5. Forest management: fuel manage￾ment to reduce fire threat Fuel management uses thinning (Box 3) to lower foliage biomass to reduce the risk of crown fire because crown fires are difficult, if not impossible, to control. Fuel management occurs in forests with a variety of historical fire regimes – from forests where historical forest density was lower and the natural fires were mostly surface fires, to forests with stand￾replacement fire regimes in which crown fires naturally occurred. Fuel management tem￾porarily lowers the carbon stored in forest bio￾mass and dead wood because the thinned trees are typically piled and burned or mulched and then decompose. If a crown fire burns through a forest that was thinned to a low density, the fire may change from a crown to a surface fire in which many of the trees can often survive the fire. In contrast, many or all of the trees in an unthinned stand will be killed by a crown fire. This contrast in survival has led to the notion that fuel treatments offer a carbon benefit: removing some carbon from the forest may protect the remaining carbon. There are two views regarding the science on carbon savings through fuel treatments. Some studies have shown that thinned stands have much higher tree survival and lower car￾bon losses in a crown fire, or have used mod￾eling to estimate lower carbon losses from thinned stands if they were to burn. However, other stand-level studies have not shown a carbon benefit from fuels treatments, and evi￾dence from landscape-level modeling suggests that fuel treatments in most forests will Box 3. THINNING AND CARBON Thinning is an effective forest management technique used to produce larger stems more quickly, reduce fire risk, and increase tree resistance to insects and disease. Thinning increases the growth of the remaining individual trees, but generally decreases overall forest wood growth until the remaining trees grow enough to re-occupy the site. The carbon stock in a thinned stand is gen￾erally lower than that in an unthinned stand. If the harvested trees are used for biomass energy or long-lived forest products, these carbon benefits may com￾pensate for the lower biomass and the wood growth of the thinned stand. Because of lower overall growth of a thinned stand, even 100% use of the har￾vested trees for products or biomass energy may not produce a total carbon benefit greater than that of the higher storage and storage rate in an unthinned stand. The net carbon consequences of thinning will depend the most on whether the harvested trees are used for long-lasting wood products or bio￾mass energy, but also on the change in risk of a crown fire relative to the prob￾ability of fire occurring, the species, the site, the thinning regime, and the length of the harvest interval. Figure 8. A hydro-axe is used to grind up trees to reduce canopy fuel loads and lower the risk of crown fire. Photo by Dan Binkley, Colorado State University