Phosphorus forms in technosols afforested with N-fixing and non-N-fixing tree species

Tree species capable of forming a symbiosis with N-fixing bacteria may affect P availability in reclaimed technosols. The objective of this study was to compare the effect of N-fixing tree species and non-N-fixing species on phosphorus forms in technosols developing from various materials. Soil samples were taken under black locust (Robinia pseudoaccaccia), black alder (Alnus glutinosa), silver birch (Betula pendula) and Scots pine (Pinus sylvestris) from two depths (0-5 cm and 5 – 20 cm). The soil substrates were fly ashes, sands and clays. In the soil samples measured were concentrations of total P (P_t),  water soluble P (P_H2O),  dilute salt-extractable P (P_ex), microbial biomass P (P_mic) and total labile P (P_labil). Multifactor ANOVA revealed that tree species did not influence contents of P_t, P_ex and P_H20. However, there was a statistically significant effect of soil substrate and soil horizon on these forms of P. The factors tree species, soil substrate and soil horizon had statistically significant effect on P_mic content whereas content of P_labil was affected by tree species and soil horizon. Multiple Range Tests by tree species showed that soils under Scots pine contained significantly less P_mic than soils under other tree species studied. There were no significant differences in P_mic between the soils under silver birch, black alder and black locust. The soils under Scots pine contained also significantly less P_labil than the soils under black locust and silver birch. Our study included P forms that are considered labile (except P_t). The obtained results indicated that the effect of N-fixing trees on these forms of P was weak. Instead we noticed that Scots pine had negative effect on some forms of labile P. 

The study was financed by The National Science Centre, Poland, grant No. 2018/31/B/ST10/01626.