Comparison of growth, nutrition and soil properties of pure stands of Quercus castaneifolia C. A. Mey. and mixed with Carpinus betulus L. in the Hyrcanian forests of Iran

In the present study, Quercus castaneifolia (Oak, as target species) and Carpinus betulus (Horn beam, as native component species) were planted in five proportions (100Q, 70Q:30C, 60Q:40C, 50Q:50C, 40Q:60C) in the Noor region (North Iran). After 12 years, the effects of the species on the growth of the trees, nutrient concentrations in the live and senescent leave and on soil properties were assessed. The results showed the survival and diameter at breast height (dbh) of the individual Oak trees were positively affected by the presence of Horn beam. Percent retranslocation of the nutrients in Quercus trees was: K>N>P. Leaf-litter fall production ranged from 4.70 to 6.80 Mg ha-1 year-1. N concentration in fully expanded leaves, N and Ca concentrations in the senescent leaves of Quercus trees and N concentration in topsoil were higher in some of the mixed plantations than in the monocultures of the Quercus trees. N fluxes, N and P retranslocation, and soil P concentrations in the monocultures were intermediate relative to mixed plantations. The obtained results somewhat indicated that the mixing with hornbeam 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 50% Quercus castaneifolia and 50% Carpinus betulus.