Effects of deforestation on contents and distribution of amino sugars within particle-size fractions of mountain soils

Identifying amino sugar pools in soil may advance our knowledge about microbially derived substances. Our objective was to study the effects of deforestation followed by pasture establishment on amino sugar contents and patterns in mountain soils of the Sui Checti Valley in the Alay Range, Kyrgyzia. Soil A horizons (0-10 cm) under pasture and forest were fractionated into clay, silt, fine and coarse sand fractions. Soil organic C, N, glucosaminc (GlcN), galactosamine, mannosamine and muramie acid (MurAc) were analysed in the fine earth, particle-size fractions and humus layers. Deforestation of Juniperus turkestanica and pasture establishment led to a significant increase in the amino sugar content in the fine earth and soil organic matter (SOM) reflecting different accumulation of amino sugars in different ecosystems. Deforestation affected principally the amino sugars in the coarse and fine sand fractions that generally are related to particulate organic matter. High concentrations of amino sugars were found in the clay fraction, corroborating the general assumption that it contains a hi-li microbial biomass and microbially altered organic matter. The pasture soil samples have a significantly higher GIcN to MurAc ratio indicating a higher fungal contribution to SOM than in forest soils. Although other studies revealed that pasture is associated with high amounts of bacterial amino sugars, our study gave evidence that deforestation tends to lead to the accumulation of mainly fungi-derived amino sugars. It is proposed that this might be due to a lowering of soil pH.