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بررسي تأثير گونه هاي Haloxylon persicum و Atriplex lentiformis بر خصوصيات خاك و گونه هاي بومي درعرصه بياباني شهرستان نيريز

Employing vegetation and soil correlation information is a fundamental issue in natural and cultivated vegetation management and planning. Considering the high expenditure of the plant species cultivating importance on soil erosion control and windbreak construction, it is essential to investigate the positive and negative affects of these species on the habitat, intending the studied species selecting or deselecting for the other similar site planning. The aim of the present study is to discover the affects of 20 years old mixed cultivated Haloxylon persicum and Atriplex lentiformis plantation on their habitat soil properties as well as indigenous species of the Neyriz deserted region in Iran. The stratified random sampling method was employed for field sampling and studying, therefore the following four region were selected: 1- Under canopy of the Haloxylon persicum shrub, 2- Under canopy of the Atriplex lentiformis shrub, 3- Out of the shrub canopy but between the above named shrub species in the plantation site, and 4- The control region which had distance from the plantation site. The soil was sampled for the region 1 and 2 with 50, 100 and 150 Cm detachments from the Haloxylon persicum and Atriplex lentiformis trunks. The soil under canopy was dogged to collect the samples from 0-15 Cm and 15-30 Cm in depth. For the site 3 and 4, soil samples were collected from the same depths. But additional samples were collected from 30-70 Cm and below 70 Cm as well. The soil samples were sent to the laboratory of the Department of Natural Resources, Isfahan University of Technology for further analysis. The soil pH, EC, clay%, sand%, silt%, concentration of the sodium, potassium, calcium and organic matter were measured. Species data collected with a 5m by 5m quadrat which located in systematic randomized plan and the plant height, density and crown cover diameter were measured. Analyses of variance and ordination method used to study the soil and species data relations utilizing the CANOCO and    software's. The results demonstrates which the both studied species increase remarkably the soil pH, EC, sodium, potassium, calcium, and organic matter under their canopy. Also these factors increase between the planted shrubs and the changes are statistically significant. The measured elements changes are in a manner that their concentration is higher towards the plant trunk so they absorb the elements with their roots and deposits on the soil surfaces through the leaf and small branches shedding. The Haloxylon persicum increases the studied soil parameters more than the Atriplex lentiformis. The amount of studied materials decreases with soil depth increasing. It is noticeable that the 20 years old Haloxylon persicum plantation has more effects on soil parameters increasing but none of them has effect on soil texture. Both species have omitted most of the indigenous annual and perennial species from their canopy beneath and from the spaces between shrubs. On the other hand, the height of the established indigenous species has reduced; the density and crown diameter of these species contracted under the studied species canopy.

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