Primary Mid-Succession Carbon Fluxes in a Spontaneously Recovering Post-Mining Ecosystem

Limited research exists on the carbon sequestration potential of spontaneously developing post-coal-mining sites in the mid-stage of primary succession. Therefore, in 2023, net ecosystem exchange (NEE) was quantified in Czechia using an eddy covariance (EC) tower to assess carbon fluxes in a spontaneously developing ecosystem dominated by pioneer tree species such as willow, along with aspen and birch, growing on a wave-like microtopography. The ecosystem functioned as a strong carbon sink, with an annual NEE of −415 g C m−2 yr−1, ~39 years after coal mining. This NEE was derived by gross ecosystem exchange (GEE) of −1423 g C m−2 yr−1 and ecosystem respiration (Reco) of 1008 g C m−2 yr−1. Seasonal variation was driven by higher GEE in summer rather than by Reco. Consequently, Reco accounted for ca. 51% of GEE in summer, compared to 56% in spring. In addition, temperature was an important climatic factor in spring, whereas vapor pressure deficit (VPD) and global radiation (Rg) were more critical in summer. Overall, our results highlight the robust carbon sequestration capacity of naturally developing pioneer forests, suggesting their potential role in restoring mined areas in Central Europe and other regions without water limitations following coal mining.