Development of soil organic carbon pools after vineyard abandonment

Abstract

Abandoned vineyard soils show quick recharge of soil organic carbon (SOC) stocks after cancellation of cultivation. In the study abandoned vineyards with six different age classes concerning the duration of postagricultural development, organized along two lines in different exposures on slope (one S and one SW exposed chronosequence) were selected. Involving an additional recently cultivated vineyard location, totally 13 sites were sampled for topsoil characteristics. In each bulk soil sample density fractions, hot water extraction, and microbial samples were separated. Accordingly the C and N content and C/N ratio of free particulate organic matter (FPOM), occluded particulate organic matter (OPOM), clay-, silt- and sand sized microaggregates, hot water soluble organic matter, and microbial biomass were measured and discussed in the study. We found that labile, active carbon pool (FPOM) have relatively low share of the TOC (in average 11.6% in S and 4.6% in SW sequence) and showed no increase with the time since the cancellation of cultivation. Also this pool has generally higher C/N ratio (20.6±3.7), as more stable pools (OPOM: 19.2±9.6; clay fraction: 9.2±1.2,). Highest part of TOC is stored in clay-sized microaggregates (in average 37.2% in S and 41.5% SW sequence) and its amount correlates significantly with the time since the cancellation of cultivation. By comparison, in recently cultivated soil lower share of C in clay sized microaggregates and (24.0% of TOC) and higher share of labile, FPOM (26.6% of TOC) was found. C-pools in microbial and hot water extractable C forms showed significant changes with the time. Based on exposure and cultivation also proved different, anyway, their contribution to TOC are low.