Soil carbon storage in unreclaimed post mining sites estimated by a chronosequence approach and comparison with historical data

anglais. Soil carbon (C) storage affects many ecosystem properties and, consequently, is an important measure of reclamation success in sites where soil develops de novo. In this study, we have used the chronosequence of unreclaimed heaped post-mining sites (16–56 years old) after open cast coal mining near Sokolov (Czechia) in order to study C stock on the floor and the topsoil layers (0–5 and 5–10 cm) of a developed broadleaf forest. The carbon content on the forest floor was higher in depressions where C in the Oe layer showed the highest C stock of intermediate ages; the litter C stock in heap positions decreased during succession. The soil C stock in both depression and heap positions increased with succession age at the same speed, but this trend was significant only for a depth of 0–5 cm. Based on the slope of this linear regression between C stock and time, the annual rate of C storage in soil was 0.53 t ha−1 year−1. Making a comparison with an earlier study exploring the same chronosequence in the same manner from 15 years ago, we were able to determine the increase in C stock over time in individual sites, which was on average 0.50 t C/ha year−1. It is noteworthy that the C stock increase rate was highly variable and did not show a significant trend with time but was highest in intermediate succession. With an increasing C content in soil, soil pH decreased while C/N and C/P ratios significantly increased.

anglais. Soil C storage, Coal mining, Unreclaimed soils, Chronosequence, Succession - Soil C stock

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