Soil organic matter quantity and quality in mountain soils of the Alay Range, Kyrgyzia, affected by land use change

Changes in soil management practices influence the amount, quality and turn over of soil organic matter (SOM). Our objective was to study the effects o f deforestation followed by pasture establishment on SOM quantity, quality and turnover in mountain soils of the Sui Checti valley in the Alay Range, Kyrgyzia. This objective was approached by analysis of total organic C (TOC ), N, lignin-derived phenols, and neutral sugars in soil samples and primar y particle-size soil fractions. Pasture installation led to a loss of about 30% TOC compared with the native Juniperus turkestanica forests. The pastu re soils accumulated about 20% N, due to inputs via animal excrement. A cha nge in land use from forest to pasture mainly affected the SOM bound to the silt fraction; there was more microbial decomposition in the pasture than in the forest silt fraction, as indicated by lower yields of lignin and car bohydrates, and also by a more advanced oxidative lignin side-chain oxidati on and higher values of plant:microbial sugar ratios. The ratio of arabinos e:xylose was indicative of the removal of carbohydrates when the original f orest was replaced by pasture, and we conclude that this can be used as an indicator of deforestation. The accumulation of lignin and its low humifica tion within the forest floor could be due to the extremely cold winter and dry summer climate.