High organic carbon stock in a karstic soil of the Middle-European Forest Province persists after centuries-long agroforestry management

Abstract

Little is known on soil organic carbon (SOC) stocks in karst areas worldwide, although many of them have seen long-term application of agroforestry systems with a potential for carbon sequestration. Therefore, our study aimed to assess landscape-level SOC concentration and stock in the Silica Plateau, a part of the Slovak Karst Biosphere Reserve located in the Western Carpathians (Slovakia) with a centuries-long agroforestry record. The most represented local soil units are Chromi-Rendzic Leptosols and Chromic Cambisols with clayey loam texture, C/N ratio 9-12, and pH H2O 6.6-6.2 in their organo-mineral surface horizons. Mull surface humus form prevails under mixed forest stands dominated by hornbeam (Carpinus betulus L.), oak (Quercus petraea L.), and beech (Fagus sylvatica L.). A total of 2,700 soil samples were collected from 150 soil pits. Both SOC concentrations and stocks were determined for the 0-60 cm mineral soil layer. Soil stoniness was accounted for by means of electrical resistivity tomography. According to the analysis of covariance, cropland SOC concentration (0.026 g g -1) is significantly lower compared to forestland (0.040 g g -1) and pastureland (0.041 g g -1) (P < 0.01). During the period of 130 years after forest clearing, cropland SOC stock has been reduced at an exponential decay rate of ca 0.002 year -1, while the SOC stock in pastureland has increased following land use change from cropland by approximately 30% during the same period of time. Irrespective of land use history, overall SOC stock is high reaching on average 207.4 Mg ha -1, out of which 66% are stored within 0-30 cm and 34% within 30-60 cm soil layers. © 2012 The Author(s).