Phosphorus limitations and mycorrhizae in a proglacial serpentinitic area

Limitations to plant growth because of the lack of nutrients are particularly evident in proglacial areas on serpentinite. The high Mg concentration, the unbalance between Ca and Mg, the low amounts of K and P and the excess of Ni interact and originate the harsh conditions known as the serpentine syndrome. Phosphorus deficiency is particularly interesting from an ecological point of view as this element, generally abundant at the beginning of soil formation, may be a limiting factor in young serpentinitic soils. In this work, we evaluated the capacity of mycorrhizae to offset P deficiency for plant establishment in a serpentine proglacial chronosequence in NW Italy. Organic (inositolphosphate) and inorganic (K2HPO4) P forms were added to a mixture of quartz and goethite, and placed into meshbags allowing the entrance of mycorrhizae but not of roots. The bags were placed in the soils of three different terms of the chronosequence in June 2016 and picked up in September. An increasing mycorrhiza developmentwith soil age (after three months only) and the depletion of inorganic P from the bags highlighted a different capacity of mycorrhizae to use organic and inorganic forms as source of P.