Comparison of growth, nutrition and soil properties of pure stands of Quercus castaneifolia and mixed with Zelkova carpinifolia in the Hyrcanian forests of Iran

The continued existence of oakwoods in the Hyrcanian forests of Iran is threatened by lack of natural regeneration which is limited by several factors. Hence, in order to promote expansion and rehabilitation of the oak forests, a program of oak seedling planting may be required. Quercus castaneifolia (as target species) and Zelkova carpinifolia (as native component species) were planted in five proportions (100Q, 70Q:30Z, 60Q:40Z, 50Q:50Z, 40Q:60Z) in the Noor region (North Iran). After 11 years, the effects of the species on the growth of the trees, nutrient concentrations in the live and senescent leaves and on soil properties were assessed. The results showed the survival, total height and clean bole of the individual Quercus trees were positively affected by the presence of Zelkova. Percent retranslocation of the nutrients in Quercus trees was: K > N > P. Leaf-litter fall production ranged from 4.89 to 6.27 Mg ha−1 year−1. P and Mg fluxes, P retranslocation, P concentration in fully expanded leaves and N, P, K and Mg concentrations in the senescent leaves of Quercus trees were higher in some of the mixed plantations than in the monocultures of the Quercus trees. The obtained results indicated that the mixing with Siberian elm increased the productivity and sustainability of the oak sites. Within the framework of this experiment, it appeared that production was maximized when these two species were grown together in the proportion of 70% Quercus and 30% Zelkova.