Sources of Acidity in Some Forested Udults1
- D. D. Richter2
Three sources of soil acidity (bicarbonate leaching; base-cation accumulation in aboveground wood, roots, and forest floor; and acid atmospheric deposition) were evaluated in relation to exchangeable acidity of three forested Udults in Tennessee. The Udults have low effective CEC (CECe), from 2.4 to 3.7 cmolc kg−1. In the three soils, H+ from bicarbonate leaching averaged 0.60 kmolc ha−1yr−1 over 2 yr. In five forest stands, 30 to 80 yr in age, H+ from accumulation of excess base (EB) cations [EB = (Ca + Mg + K) − (P + S)] in aboveground wood, roots, and forest floor averaged 1.11 kmolc ha−1yr−1. Atmospheric H+ inputs, estimated from bulk precipitation, averaged 0.67 kmolc ha−1yr−1. Total deposition of atmospheric acidity to these eastern Tennessee forests is on the order of 1 kmolc ha−1yr−1. Variations in H+ inputs were caused by annual differences in the hydrologic cycle and by stand differences due to nutrientcycling and soil-chemistry effects. In these forest ecosystems, sources of soil acidity from annual bicarbonate leaching and cation accumulation appeared to exceed atmospheric inputs. Exchangeable acidity in the forested Udults was large compared with annual fluxes of acidity. In the upper 60 cm of the three soils, KCl-exchangeable acidity ranged from 100 to 274 kmolc ha−1, and BaCl2-TEA (trieth-anolamine) acidity ranged from 505 to 820 kmolc ha−1. Despite low precipitation pH and low soil CECe, the additional H+ from acid deposition has not caused significant alteration of soil acidity or base solution of these Udults.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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