Comparing a real and pseudo chronosequence of mining soil reclamation using free-living nematodes to characterize the food web and C and N dynamics

Space-for-time substitution, also known as pseudo chronosequence (PCS), is often used as a method to assess temporal changes in ecosystems without having to wait for the time span that the study is supposed to cover. However, the suitability of PCS studies is often questioned because convergent development of spatially separated plots over time is rarely guaranteed even under optimal conditions. To assess whether the PCS approach is justified and suitable, we studied the nematode soil food web development of free-living nematodes and biological and chemical soil components related to C and N mobilization (CO₂ and NO₃^-) and immobilization (microbial and soil organic carbon), in a PCS focusing on the critical early reclamation period of four years after open-cast lignite mining, and compared it with a real chronosequence (RCS) of a reclamation site monitored over four years. We hypothesized that: (I) nematode-derived indices indicate the same course of nematode soil food web development in the PCS and RCS, tolerating a range of variability in weather conditions, soil components, and management; (II) the development of nematode soil food web indicators can provide information on the status of C and N retention and cycling in the reclaimed soil. Our results show that the PCS and RCS approaches reach similar conclusions, indicating a rapidly developing nematode soil food web during the first four years after reclamation. They also suggest that the nematode faunal profile may indicate the status of C and N retention and cycling in reclaimed soil. Overall, it can be concluded that the PCS approach successfully predicts the temporal development of the nematode soil food web in loess-dominated reclaimed mining soils, even when there is a range of variability in soil components and management conditions.