Amino sugars in native grassland soils along a climosequence in North America

Characterizing amino sugars is important for further understanding soil organic matter (SOM) dynamics in terrestrial ecosystems. This study was designed to evaluate the impart of climate on amino sugars in 18 surface soil (0-10 cm) samples along a climosequence of native grasslands from central Saskatchewan, Canada, to Southern Texas, USA. Mean annual temperature (MAT) ranged from 0.9 to 23.4 degrees C and mean annual precipitation (MAP) from 300 to 1308 mm, In all samples, the contents of soil organic C, glucosamine, mannosamine, galactosamine, and muramic acid were determined. Both the ratios of glucosamine to galactosamine and of glucosamine to muramic acid were related to the moisture regime. With increasing MAP, increasing proportions of amino sugars were glucosamine, This glucosamine is possibly derived from the chitin of fungi. The proportion of bacterial-derived amino sugars, such as muramic acid, declined as MAP increased. The relationship between amino sugar concentrations (mg kg(-1) soil organic C) and MAT followed a parabolic regression model; the maximum of the amino sugar concentration occurring at the mesic temperature regime. On the basis of hierarchical cluster analysis the sites could be divided into two groups, which coincided with the Northern-central and Southern grasslands. We hypothesize that in the Northern-central grasslands frost limits amino sugar production whereas in the Southern grasslands higher winter temperatures >0 degrees C favor amino sugar decomposition.