Organic Matter Content and Standard Material Decomposition Rate in Soils of the High Mountain Plant Communities of the Teberda National Park

Abstract

Soils of the high mountain areas are very diverse by their organic matter content (SOM), by the factors underlying such diversity are still not fully known. In 16 subalpine, alpine and subnival plant communities of the Teberda national park (the north-western Caucasus) we studied physico-chemical and microbiological soil properties, and estimated parameters of standard material decomposition based on the Tea bag index (TBI): stabilization factor (STBI) and decomposition constant (kTBI). We tested the following hypitheses: (1) the SOM is one of predictors of STBI and kTBI in high mountain zone along with other physico-chemical soil properties; (2) the most of SOM content belongs to high STBI and low kTBI values; (3) the SOM content correlates with below-ground plant productivity. The main gradients of the studied soils are water content (automorphic vs. hydromorphic soils) and the concurrent SOM accumulation, as well as the altitudinal gradient with the decrease of soil basal respiration with elevation. The extent of nitrogen enrichment (e.g. SOM quality) of the labile fraction was the best predictor of the decomposition constant. STBI decreased with the increase of total carbon content and the losses on ignition, while the positive link between kTBI and SOM was observed only in automorphic soils. Thus, the soils rich in organic matter typically have low stabilization factor and relatively high decomposition constant. In the plant communities with herbaceous dominants, the SOM content was positively correlated with fine root production, this stresses the important role of productivity in the accumulation of organic matter.