Increase in biomass of two woody species from a seasonal dry tropical forest in association with AMF with different phosphorus levels

The study aimed at assessing whether there is association between arbuscular mycorrhizal fungi (AMF) and two woody species from a seasonal dry tropical forest, Poincianella pyramidalis and Cnidoscolus quercifolius, besides the occurrence of an increase in biomass under different availability of phosphorus (P) in the soil. The experimental design was completely randomized, with a factorial design with two mycorrhizal levels [inoculated (+AMF) and control (−AMF)] × six phosphorus levels (3, 9, 15, 21, 27, 33 mg dm−3). The presence of mycorrhizal structures, mycorrhizal growth, mycorrhizal efficiency, leaf relative water content (RWC) and gas exchange were evaluated. +AMF plants of both species had mycorrhizal structures, while −AMF showed no structures. In P. pyramidalis, +AMF plants had benefits with increasing phosphorus level, while −AMF plants had increases biomass only at the P9 level if compared to the P3-AMF level. The total leaf area was correlated with total dry weight (TDW) in +AMF and −AMF plants. However, +AMF plants had more responses in RWC. In C. quercifolius, +AMF and −AMF plants did not differ in RWC and showed reductions in gas exchange with increased phosphorus level. However, these reductions were lower in +AMF plants, besides having a better performance over −AMF plants. The growth and mycorrhizal efficiency were higher at the P15 level, and relationship between total leaf area and TDW were significant only in +AMF plants. Thus, both species perform association with AMF and show increases in growth. The concentrations of phosphorus in the soil for P. pyramidalis (33 mg dm−3) and C. quercifolius (15 mg dm−3) are indicated for increased effectiveness of mycorrhization, promote increases in gas exchange and growth in +AMF plants.