Amino sugars in soils of the North American cultivated prairie

Characterizing amino sugar dynamics in cultivated soils helps to further understand the influence of cultivation on soil organic matter turnover. This study was designed to evaluate accumulations and patterns of 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) ranged from 0.9 to 22.2 degrees C and mean annual precipitation (MAP) from 300 to 1308 mm. Samples were analyzed for glucosamine, mannosamine, galactosamine, and muramic acid. Amino sugar contents (mg kg(-1) soil) varied markedly among the 17 sites and were controlled by mean annual temperature (MAT) and clay and silt contents, mainly. The relationship between amino sugar-N proportions to total N (%) and MAT followed parabolic 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 correlated positively with MAT (r = 0.77***). Bacterially-derived galactosamine and muramic acid declined preferentially to mainly chitin-derived glucosamine after long-term cropping. The glucosamine-to-galactosamine and glucosamine-to-muramic acid ratios can be used, therefore, as indicators for the identification of land use effects on microbially-derived SOM residues.