Saturday, 15 July 2006

Spatial Variability of Soil Salinity Due to the Presence of Atriplex spp. (saltbush).

Reza Soleimani, Soil and Water Research Institute, Ilam, Iran

The study site is located in the Kazeroon range in southern Iran with coordinates 51o,54/E and 29o,16/N. The name of the soil taxonomy was fine-loamy, carbonatic, hyperthermic, Ustic Haplocalcids(in American soil taxonomy). Random composite samples prepared by six cores in depths of 0-10 and 10-40 centimeters of under-canopy (directly beneath the zone of maximum litter accumulation) and inter-canopy (center of an adjacent bare space) of saltbushes for classic statistics. All superficial organic residues were removed. For the geostatistical method, the first step was to collect samples from known locations on a Cartesian coordinate system based on a base line. Electrical conductivity values, apart from plant species and depth, increased from 1.69 dam-1 in soil of inter-canopy to 2.2 dam-1 in soil of under-canopy (equal to 30 percent increase). The principle causes of salt accumulation are evaporation and salt deposition, but the causes of canopy salinity were due to the accumulative effects of evaporation and the deposition of Atriplex aerial parts fall such as bladder hairs and salt bladders. On the other hand, at the 0-10 cm depth, soil EC of the under-canopy is 3.09 dam-1 and that of inter-canopy is 1.78 dsm-1; an increase of 74 percent. It is evident that the vertical and horizontal gradients of soil electrical conductivity is toward the soil surface and from interspaced to the under-canopy microsite and that accumulation of a significantly higher quantity of soluble salts in the surface layers has occurred as a result of the large addition of salts from dropped leaves and fruits. Variorum in affected and no affected conditions showed increasingly strong autocorrelation at distance of less than 40 meters and 80 meters respectively.

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