Land-use effects on amino sugars in particle size fractions of an Argiudoll

Identifying amino sugar pools from different land-use systems may advance o ur knowledge of land-use effects on the fate of microbially-derived substan ces. Surface soils (0-10 cm) from (1) native pasture, (2) a >80-years-arabl e site, and (3) a >80-years-afforested site were fractionated into clay, si lt, fine-, and coarse-sand fractions. Then, soil organic carbon, N, glucosa mine, galactosamine, mannosamine, and muramic acid were analyzed. Afforestation did not influence the amino sugar content in bulk soil, where as cultivation reduced the content by 54%. The concentrations of amino suga rs in g kg(-1) SOM declined after both long-term cropping and afforestation by 6% and 13%, respectively, relative to that in the grassland. The amino sugar depletion at the forest site occurred mainly from the silt fraction ( by 25%), while that in the cultivated site was mainly due to preferential l oss of amino sugars from clay (by 19% compared with the grassland). Both ra tios of glucosamine to galactosamine and glucosamine to muramic acid increa sed when the prairie was converted to forest or cultivated land, suggesting that bacterial N especially is better preserved than fungal N under prairi e conditions. (C) 1999 Elsevier Science B.V.