Element concentrations of roots play an important role for plant growth and below ground biochemical cycles in forest ecosystems. It can show a change among species. This research aimed to determine changes in the nutrient content for different root diameters of trees in the Belgrad forest. Natural species of Sessile oak (Quercus petraea L.), Scots pine (Pinus sylvestris L.), Austrian pine (Pinus nigra Arnold.), Turkish fir (Abies bornmuelleriana L.), and Oriental spruce (Picea orientalis L.) were studied. Root sampling was carried out by randomly collecting twenty soil samples within each species once every three months (from April 2007) over one year. Roots were classified by fine root (< 2 mm), small root (2-5 mm) and coarse root (>5mm) diameter classes. Total concentration of elements (K, Ca, P, Fe, Mg, Cu, Mn, Al, Ni, Zn, Na) in each root classes were determined. The macro elements Mg, K, and P and all microelements in the included species showed a tendency to decrease in concentration with increasing root diameters. Macro elements except K and P and microelements except Pb, Al, Zn, and Cu showed a significant temporal difference between species based on the root diameters. Al, Pb, Ni, Mn, and Fe showed different antagonistic relations with Ca, Mg, P, and K between species with regard to their concentration in fine roots. There was no significant negative correlation between small and coarse roots in species (except in oak species). The results have shown that nutrient storage characteristics differ between different species in the same site.