Dynamics of ectomycorrhizal fungi in an Eucalyptus globulus plantation: Effect of phosphorus fertilization

Eucalyptus globulus is the most widely planted temperate eucalypt in regions of Mediterranean climate. Plantations in Western Australia (WA) are common on sandy soils where fertilization is necessary (especially N, P, K and Cu) to sustain high growth rates. Ectomycorrhizal (ECM) fungi are common in these plantations and are probably ecologically important in nutrient cycling. Whether fertilization with phosphorus (P) could alter fungal dynamics in these plantations is investigated in this study. Three rates of P (nil, low = 100 kg P ha-1 and high = 1000 kg P ha-1), including basal nutrients, were applied to a 4-years-old E. globulus plantation in WA and the following measured over a 2 years period: fungal diversity, fungal biomass, soil hyphal production, tree biomass, litter production, and accumulation of N, P, K and Cu in the fungal and tree components. The addition of P reduced the number of basidiocarps by 5 (low P)-14% (high P), basidiocarp and soil hyphal biomass by 26-40% and 29-44%, respectively, without affecting above-ground ECM fungal diversity, species of Laccaria, Pisolithus and Scleroderma. There was no response in whole tree biomass or litterfall to P, but low P increased fine root biomass in ingrowth cores at 6 months to 364 kg ha-1. Accumulation of N, P, K and Cu generally declined in fungi and litterfall with P, but increased in tree biomass (except N and Cu). The total nutrient load was in the order: above-ground tree > soil hyphae > below-ground tree > litter > fine root > basidiocarp. The combined nutrient pool in the fungal component was approximately 10% of that in the tree. This illustrates the potential significance of ECM fungi in immobilizing P and other nutrients, and in their subsequent cycling during fungal decomposition in plantations. The impact of P on fungal dynamics therefore requires consideration when applying fertilizers in eucalypt plantations