comparison of some soil properties under canopy and inter-row trees in different poplar clones in north of iran

poplar trees are becoming extremely important as fast growing species due to the increasing need for wood and decreasing productivity of some lands in iran. the present study aimed to find the effect of canopy of poplar clones as one of the most important effective factors on soil properties compared to the distances inter-row trees. five poplar clones and species included: populus euramericana triplo, p. deltoides 69/55, p. deltoides 63/51, p. euramericana 45/51 and p. caspica as native species were selected. they were planted about 18 years ago with 4×4 m spacing in frame of completely randomized block design with three replications. the soil samples were taken from 0-20 cm depth of soils under canopy of each tree and inter-row trees. the results showed the impression of the canopy on the soil properties, in a way that many physical and chemical properties of soil under the canopy and inter-row trees have significant differences. p. deltoides 63/51 clone and inter-row the trees; p. euramericana triplo clone had greater positive effects on the soil properties compared to the other clones. our results suggested that the presence of poplar clones may be an important source of soil spatial heterogeneity.