Effect of Root Interaction of Chestnut-leaved Oak (Quercus castaneifolia) and Persian Maple (Acer velutinium) in Pure and Mixed planting on spatial Variability of Urease Enzymes Exudation

Root interactions are the most important factor that influence on enzymes exudations of plant roots in rhizosphere, that depending on root composition, species type and soil depth, so they have different spatial distribution. Further there were restricted researches to identify the spatial significance of forest species rhizosphere processes. Tree species have different rhizosphere regarding to root morphology and physiology as well as nutrients needs. The aim of this research is to examine spatial variability of urease enzymes exudation on rhizosphere of Chestnut-leaved Oak and Persian Maple in pure and mixed planting.

18 modern rhizotrons were applied to study research goal that 12 Raster-Access-Ports placed in each rhizotron to get root exudates. These ports were in distinct depths and distances to calculating spatial variability of root enzymes exudations. Two lower depths (50 and 75 cm) were filled with mineral soil while two upper depths (15 and 30 cm) combined with litter (4% of weigth). One years old seedlings of Quercus castaneifolia and Acer velutinum were planted in four treatments of species composition including pure, mixed and control (without planting seedling). Soil sampling were collected 6 months after planting in different soil depth of rhizotrons and urease activity was determined by Kandeler method. Enzyme efficiency was calculated by subscripted enzyme activity in each place from corresponding amount of control (without root) and don't show catalytic efficiency.

The results showed that urease exudation contents have significant differences in planting composition (p < 0.05) while the most amount of enzyme exudation revealed in the pure Oak and mixed planting and the lowest was in control. Spatial variability of urease activity only revealed significant difference on mixed planting treatment (p<0.05). However spatial variability of enzyme efficiency was significant on pure maple and mixed planting treatments (p<0.05). Urease exudation wasn't significant in different distances from seedlings collar with exception urease efficiency in pure oak planting treatment (p<0.05).

The amount of spatial urease exudation more related to root density in different places so it is related to root interaction of planted seedlings and their root systems. This study revealed root interaction in mixed treatment result in more urease activity and efficiency because of more suitable ecological nich. Because root exudation in different distances from seedlings collar was never significant, so results showed non-confidence in spatial urease exudation.