Arylsulfatase activities in soils of the Black Forest/Germany - seasonal variation and effect of (NH4)(2)SO4 fertilization

Arylsulfatase activities in the soil of two high-elevation sites in the Bla ck Forest/Germany (haplic podzol Schluchsee. dystric cambisol Villingen) we re determined in quarterly intervals over a period of 24 and 30 months. Bot h sites, are forested with Norway spruce (Picea abies L. [Karst.]). At each study site, one untreated soil and one soil fertilized repeatedly with (NH 4)(2)SO4 (3 X 700 kg ha(-1) in 1988, 1991, and 1994) was investigated. Aryl sulfatase activities generally were highest in the forest floor, medium in the mineral topsoil and lowest in the subsoil. The small-scale (< 10 m(2)) spatial variability of arylsulfatase activity in most cases exceeded the se asonal variation. At Schluchsee, arylsulfatase activities tended to be lowe r in summer and autumn than in spring, and inversely followed the seasonal fluctuation of SO42- concentration in the soil seepage water. No systematic seasonal changes in soil arylsulfatase activities were observed for Villin gen, where SO42- concentration in soil seepage water also showed lower seas onal variation. For more than 2 years after the third fertilizer amendment in 1994, mean arylsulfatase activities in the (NH4)(2)SO4-fertilized soils were considerably decreased compared to the untreated soils. The decreases were largest in the forest floor (-80%), but also considerable in the miner al topsoil (-70 to -80%), and in the subsoil (-45 to -60%). The decrease in soil arylsulfatase activity after fertilization lasted considerably longer than the period of elevated SO42- concentration in the soil solution. This is likely to result in decreased enzymatic ester sulfate degradation, and thus may contribute substantially to the observed accumulation of ester sul fates in B horizons of the fertilized soils. (C) 2001 Elsevier Science Ltd. All rights reserved.