VARIATION IN SOIL ORGANIC CARBON STOCKS IN THE SOILS OF FOOT AND TOE SLOPES OF MOUNTAIN VUKAN, EAST–CENTRAL SERBIA

Abstract

The global estimates of soil organic carbon (SOC) stocks using modeling approaches are prone to under and overestimations. The aim of this work is to present the variation of SOC stocks at the foot and toe slopes of Mt. Vukan, East-Central Serbia. Investigated area is located at the contact of Jurassic limestones and dolomites, and fluviatile-colluvial deposits. Soil survey encountered 42 soil profiles and collection of 183 soil disturbed samples, and five undisturbed samples per each horizon. Humus content was determined by Tjurin method. Five different soil mapping units, according to national classification, were discovered at 168 ha of Great Field: Colluvial Kalkomelanosols, Calcaric Chernozems, non-carbonate Chernozems, Eutric Cambisols, and Colluvial Soils. SOC stocks extracted from Soilgrids ranges between 65–72 t ha-1 for 0–30 cm depth (avg. 67.0 t ha-1). Measured data indicate much higher variations, between 50.2 and 110.6 t ha-1, with an average value of 77.8±16.3 t ha-1. Hence, around 15% difference was found between measured and estimated data. Eutric Cambisols have the lowest SOC stocks, 61.3±9.9 t ha-1, lower then estimated value. All other soil types have higher SOC stocks compared with modeled data. Non carbonate Chernozems have an average SOC stocks of 72.6±10.8 t ha-1, whereas Colluvial soil have similar values, 73.6±8.2 t ha-1. The highest SOC stocks was found in Colluvial Kalkomelanosols, 89.6±15.8 t ha-1, followed by Carbonate Chernozems, 84.3±9.3 t ha-1. These values are for 25–33% higher compared with modeled data. Variation of SOC stocks data has normal distribution for all soil types (11.0–18.0%). Our results indicate that global SOC stocks are underestimated in the area of Great Field and that SOC stock can face large variations on small area. These variations might be related to the impact of landscape and land use practices, and are relevant to soil mapping units. Another raising question raised from this study is related to the number of samples that should be collected in SOC campaigns in the conditions of high soil spatial variability.