Influence of some environmental variables on organic carbon and nitrogen stocks in grassland mineral soils from various temperate-climate ecosystems

Abstract

Soils represent the largest terrestrial organic carbon sink. Less-anthropized ecosystems, like grasslands, generally sequester more soil organic carbon (SOC) than croplands under similar conditions. The purpose of this study was to determine SOC and soil total nitrogen (TN) stocks and their variability within grassland soils under diverse ecological conditions. We studied 159 grassland soils, ranging from steppe-specific soils like chernozems to mountain-soils like spodosols. We tested the relationships between essential soil properties, environmental variables, SOC and TN, identifying also differences between soil classes and types. The paper novelties refer to how environmental and soil factors influence grasslands SOC and TN storage. Climate has less influence on SOC and NT contents and on stocks from deeper soil horizons than from topsoil; conversely, soil properties have a stronger influence on SOC and TN stocks deeper in soil profiles. The best predictive multiple model explains 62% of the SOC content variability in the surface layer, and 48% in the 0.5 m layer; in the case of soil TN content, the model explains 54% of TN content variability in the surface layers, and 40% in 0.5 m depth layers. There were significantly higher SOC and TN stocks in spodosols, vertisols, followed by cambisols, chernozems, as well as in finer-texture soils, except loamy-sandy texture soils, which were only met in spodosols. Soil acidity also differentiated the SOC and TN contents generally decreasing from alkaline to acid range. The results can be useful in various regions worldwide when designing grassland management programs/policies.