Natural regeneration as restoration strategy to restore functional soils and ecosystems in post mining sites

Post mining ecosystems are severally degraded.  This is particularly true for soils which are either excavated or buried and replace by overburden which differ remarkably, from normal soils. Despite these severe degradation, post mining soils of numerals opportunities: they are valuable secondary habitat for rare and endangered species, and soils developing in these areas are able to sequester carbon in much higher rate than soils in surrounding landscape.. Here we compare effect of reclaimed and unreclaimed sites on provisioning ecosystem services in Sokolov (Czech Republic) and on climatic gradient across USA. In suitable substrates, the succession is driven mainly by site topography. In sites which were leveled grassy vegetation develops. In sites where original wave like topography was preserved the ecosystem develops towards shrubs and forest. Reclaimed and unrecaimed forest sites have similar development of canopy cover,   stems number gradually decreased with age in reclaimed sites and increased in succession, in 20 year both reaching the same density.  Tree biomass was higher in young reclaimed sites, in sites 30 years old or older tree biomass in succession sites was comparable or higher than in reclaimed sites.  Initial rate of soil carbon storage in reclaimed sites namely those planted by alder was faster than in succession sites but it decrease with plot age.  In unclaimed sites, the rate of C storage increase and peaked in site 20-30 years old. Amount of C stored in unreclaimed sites c 50 years old is comparable to alder plantations of the same age.  Alder plantation of intermediate age store more water than unreclaimed sites but water budget is similar due to higher water demand of alder.  In leveled sites where grassland establish, reclaimed sites are slightly higher in all studied parameters. In conclusion, development of key ecosystem process is fasted in reclaimed sites but latter on difference disappear. The reasons are, soil   leveling, promote soil compaction, which slows root growth. Focus on achieving a close cannopy often lead to dense three stand which limit a light availability for trees. This is even supported by leveling and homogenous pattern of planting which lead to one layer cannopy, compare to multi-layer cannopy in unreclaimed sites. Also planting N fixers, my contribute, to this slow down, as nitrogen fixing plant often fixed nitrogen even in conditions when nitrogen is already plentiful in soil. This cause additional energy expense for the trees.

Comparison of benefits of reclamation and spontaneous ecosystem development vary depending on climatic conditions and target ecosystem. For example, in dry cold conditions when target is grassy vegetation such as short grass prairie in Wyoming (USA), to reclamation practices show often much better results than unassisted ecosystem development. In contrary in wet warm climate, when broadleaf forest is a target (e.g. in Eastern USA), unassisted ecosystem development often shows better results in many parameters namely in long run.  These results show that we should try to better understood naturel processes of ecosystem development so we can implement them in improvement of reclamation technologies.