بررسی اثر جنگلکاری گونه های مختلف اکالیپتوس بر پوشش گیاهی کف عرصه و خصوصیات فیزیکی، شیمیایی و حاصلخیزی خاک

The aim of the study when started in 2005 was to investigate the effects of eucalypt plantation on ground vegetation, different soil properties and nutrition status of the eucalypt species. For this reason, a eucalypt trial consisting of six species: E. camaldulensis, E. macarthurii, E. maidenii, E. rubida, E. saligna, E. vimina/is which were planted in 1983 under experimental design of Randomized Complete Blocks with four replications at 2 x 2 m. spacing and total number of 100 seedlings at each plot, was used for this research. At each plot different investigations including phytosociology, pedology and eucalypt nutrition were made. For phytosociology study, three subplots were allocated randomly at each plot and at the adjacent natural degraded oak forest (totally 75 subplots). For the pedology study, soil samples were taken from each plot, including four control ones by an auger up to 60 em. depth (totally 28 samples). Soil morphology was studied by digging three soil profiles at the eucalypt site and two adjacent parcels, including poplar and the oak forest. Soil samples were taken trom four soil horizons of each profile (totally 12 samples). Eucalypt nutrition was investigated by selecting three trees randomly at each plot and sampling leaves from their crown at end of summer in 2007. The results showed that there was not significant difference between the species in respect to ground vegetation species frequency and association. Therefore, the ground vegetation density of the eucalypt site was less than the oak forest. In addition the species differed significantly in respect to only few soil properties, including silt percentage, litter dry weight, bulk density,. penetration resistance, pH and phosphorous amount. The soil profiles at the eucalypt site and the two adjacent sites of poplar plantation and oak forest consisted of four horizons, including. A, AC, Band C. Root development at eucalypt, poplar and oak sites limited to 100, 85 and 150 cm soil depth. The leaf analysis showed that there was not significant difference between the replications in respect to amount of N, P an K, but there was significant difference between the eucalypt species in respect to amount of N. The lowest amount of N belonged to E. maidenii and there was not significant difference between the other specIes. Overall, eucalypt plantation was able to improve soil structure and porosity, particularly at topsoil. Although there was intensive livestock traffic in the eucalypt site, but soil compaction was significantly less than the control plots and there was not significant difference between the eucalypt species in response to penetration resistance. Keywords: Eucalyptus, soil, plant cover, productivity, compaction, leaf analysis