Determination of suitable mixed plantation of rangeland, tree and shrub species with different row spacings in order to produce forage and biological stabilization of sand dunes in Khouzestan

In order to study and design a mixed plantation of rangeland and forest species (silvopastoral system)، four rangeland species and three shrub and tree species were planted with different row spacings on the sand dunes of Karkheh river، in Khuzestan province. The biological stabilization of sand dunes and production of forage were the aims of this study. The selection of species was done according to their ability to improve the production of forage، firewood، and industrial wood as well as species diversity. The study was performed using split plot in a completely randomized design with three replications for four years. The main treatment included tree and shrub species (Eucalyptu camaldulensis 9616، Acacia victoriae، Prosopis juliflora). Row spacings of 4*4، 5*5، 6*6، and rangeland species (Panicum antidotale،Cenchrus ciliaris، Cymbopogon olivieri، Pennisetum divisum) were considered as the first and second sub-treatments، respectively. Vitality percentage of all species، forage yield of rangeland species، and height growth of shrub and tree species were measured. Data were analyzed by SAS software and mean comparisons were performed by Duncan''s Multiple Range Test. According to the results، C. olivieri (90%) and C. ciliaris (60%) showed the highest and lowest vitality of rangeland species. Among tree and shrub species، E. camaldulensis (80%)، P. juliflora (65%)، and A. victoriae (50%)، showed the highest vitality، respectively. In four-meter row spacings of E. camaldulensis، forage yield of all range species decreased. In terms of height growth، E. camaldulensis، with a height of around 3. 5 m، was better as compared to the other two species. The highest average dry matter yield was recorded for P. divisum (1437 Kg ha-1)، P. antidotale (1035 Kg ha-1)، C. olivieri (380 Kg ha-1)، and C. ciliaris (235 Kg ha-1)، respectively. Therefore، the determination of appropriate row spacing for trees causes to increase of species diversity as well as continued and increasing forage production and utilization.