Agricultural abandonment in Mediterranean reclaimed peaty soils: Long-term effects on soil chemical properties, arbuscular mycorrhizas and CO2 flux

In the last century, most peatlands were reclaimed for agricultural purposes, which led to peat degradation and to severe subsidence, and thus too wet conditions for crops. In some areas this has therefore led to wide agricultural abandonment. However, studies on the effect of agricultural abandonment as a potential restoration tool are lacking. In this study, the effectiveness and the restoration potential of agricultural abandonment in reducing peat degradation and in improving soil microbial biodiversity were evaluated. The main chemical parameters, arbuscular mycorrhizal (AM) fungal diversity and soil respiration partitioning were used to assess the long-term effect of 15 years of agricultural abandonment (Aband) in a Mediterranean reclaimed peatland. An intensive maize cultivation (Cult) in the same area was used as a comparison. Multivariate analyses showed that 15 years of agricultural abandonment: did not affect the main soil chemical parameters, except for NH4+ which was lower in the Aband than in the Cult; increased AM fungal root colonization and the diversity in terms of number of families of AM fungi retrieved in roots, but decreased soil AM fungal richness; reduced total soil respiration and its autotrophic component but increased respiration by heterotrophs; determined a lower fluctuation of soil CO2 flux response to air temperature than the Cult. Thus, although some soil quality parameters were significantly improved, 15 years of agricultural abandonment may not lead to an effective restoration. Consequently, alternative and sustainable solutions for the protection and preservation of Mediterranean peatlands need to be developed.