AMINO-SUGARS IN SOILS OF THE NORTH-AMERICAN CULTIVATED PRAIRIE

Characterizing amino sugar dynamics in cultivated soils helps to furth er understand the influence of cultivation on soil organic matter turn over. This study was designed to evaluate accumulations and patterns o f four four amino sugars in 17 surface (0-10 cm) soil samples along a climosequence in the North American long-term cultivated prairie from Saskatoon, Candada, to Texas, USA. Mean annual temperature (MAT) range d from 0.9 to 22.2 degrees C and mean annual precipitation (MAP) from 300 to 1308 mm. Samples were analyzed for glucosamine, mannosamine, ga lactosamine, and muramic acid. Amino sugar contents (mg kg(-1) soil) v aried markedly among the 17 sites and were controlled by mean annual t emperature (MAT) and clay and silt contents, mainly. The relationship between amino sugar-N proportions to total N (%) and MAT followed para bolic regression models. Compared with native sites, amino sugars were depleted by 53% and the amino sugar-N by 18% of the total, on average , after longterm cropping. The intensity of amino sugar-N depletion co rrelated positively with MAT (r = 0.77**). Bacterially-derived galact osamine and muramic acid declined preferentially to mainly chitin-deri ved glucosamine after long-term cropping. The glucosamine-to-galactosa mine and glucosamine-to-muramic acid ratios can be used, therefore, as indicators for the identification of land use effects on microbially- derived SOM residues.