Comparative Evaluation of the Effects of Acid Precipitation, Natural Acid Production, and Harvesting on Cation Removal from Forests.

摘要

A comparison was made of the effects of acid deposition, natural leaching, and harvesting on base cation export from coniferous forests in Maine, coniferous and deciduous forests in Tennessee, a coniferous forest in South Carolina, a deciduous forest in North Carolina, and coniferous and deciduous forests in Washington. Sulfate dominated leaching in the Tennessee sites, whereas HCO sub 3- dominated leaching in the Maine, North Carolina, South Carolina, and Washington sites (the latter because of very high HCO sub 3- and NO sub 3- leaching rates). Nitrate leaching was negligible in all but a red alder site in Washington where nitrogen fixation resulted in net NO sub 3- leaching. Total base cation export by leaching exceeded Ca exp 2+ + Mg exp 2+ + K exp + export that results from whole-tree harvesting in most sites. The export of Na exp + via harvesting was assumed to be negligible compared with that of Ca exp 2+ , Mg exp 2+ , and K exp + . However, leaching, even as augmented by acid deposition, does not appear to pose an imminent threat to soil base cation supplies on sites for which soil data are available. This is basically because soil base cation reserves are very large relative to leaching rates. Some sites showed a net Ca exp 2+ or K exp + accumulation from atmospheric deposition until they were subjected to whole-tree harvesting. Thus, leaching need not cause a net export of all nutrient cations, even if total base cation export is accelerated by acid deposition. 32 refs., 2 figs., 5 tabs. (ERA citation 10:026096)