Influence of land use on the dynamics of soil organic carbon in northern Kazakhstan

Abstract

The practice of monoculture land use without regard for local environmental conditions can accelerate organic matter decomposition. In the agriculturally and environmentally important soils of northern Kazakhstan, which primarily support cereal cultivation, economic rewards might encourage such monoculture practices. The purpose of this study was to clarify the influence of land use on the dynamics of soil organic carbon in situ for the three different soil classes, Dark Chestnut (DC), Southern Chernozem (SC) and Ordinary Chernozem (OC), in this region. Fluctuations in CO2 emission from the soils showed a similar pattern to temperature fluctuations. Land use markedly influenced the seasonal variation of CO2 emission, in particular fluctuations in CO2 sensitivity to soil temperature. To estimate daily CO2 emission, a prediction equation of CO2 emission using stepwise multiple regression of the Arrehenius model was derived from environmental soil factors by soil type and land use type. Using soil environmental factors, 40–80% of the variation in CO2 emission could be estimated. For cereal fields, the mean annual CO2 emission was estimated to range from 0.75 (DC) to 1.14 (SC) Mg C ha−1, and carbon input as plant residues ranged from 0.75 (DC) to 1.82 (SC) Mg C ha−1. The annual carbon budget ranged from 0.10 to 0.35 Mg C ha−1. In contrast, the carbon budget of summer fallow fields was approximately −0.8 Mg C ha−1. Thus, the carbon budget of the typical 4-year crop rotation system was estimated to range from −0.42 (DC) to 0.25 (OC) Mg C ha−1. It should be noted that carbon budgets were negative at DC and SC sites. Although the carbon budget of meadow fields ranged from 0.81 to 1.26 Mg C ha−1, meadow management at all sites contributed to carbon sequestration. Therefore, to prevent depletion of soil organic carbon in northern Kazakhstan, we recommend that meadow management be introduced as part of the crop rotation system, especially at SC and DC sites.