Forest Soil Sulfur in the Adirondack Mountains: Response to Chemical Manipulations

Chemical manipulations were conducted on plots during the growing seasons from 1991 through 1993 in four forest ecosystems (Woods Lake [WL], Pancake‐Hall Creek [PHC], Huntington Forest [HF], and Pack Forest [PF]) in the Adirondack Mountains of New York. Sulfate was added as (NH 4 ) 2 SO 4 (all sites at 1000 and 2000 mol c ha −1 yr −1 ), H 2 SO 4 (WL and HF at 1000 mol c ha −1 yr −1 ), or (Ca,Mg)SO 4 (WL and HF at 1000 mol c ha −1 yr −1 ). At WL and HF additional sets of plots were also treated with HNO 3 (1000 mol c ha −1 yr −1 ). Soil solutions were sampled at 15 and 50‐cm depths. Changes in the S constituents of the soil were evaluated by buried mineral soil bags installed below the forest floor. Additions of SO 2− 4 increased solution SO 2− 4 and total S and phosphate‐extractable SO 2− 4 in soil. Although organic S constituted >71% of the total soil S, no treatment effects on organic S were found. The response of SO 2− 4 was not influenced by the form of addition. Extractable sulfate and soil solution SO 2− 4 both increased with increases of (NH 4 ) 2 SO 4 . For the three hardwood sites (WL, PHC, and HF), there was a positive relationship ( P < 0.05) between soil solution SO 2− 4 concentration at 15 cm and extractable SO 2− 4 in soil bags, suggesting that these Haplorthod soils responded similarly to S inputs. For the Typic Udipsamment at PF, beneath red pine ( Pinus resinosa Aiton), no such relationship was found. The similarity of response of Haplorthod soils suggests that similar soils across the Adirondack Mountains will show synchronous responses to S inputs.