Influence of Slope Aspect and Plant Type on Some Soil Chemical Properties

Slope aspect, vegetation type, and depth of sampling are factors affecting soil chemical properties. These factors affect soil quality by increasing or decreasing organic matter content. However, the simultaneous effects of plant type and aspect on some soil properties have rarely been studied. For this purpose, the effect of aspect, plant type, and depth of sampling on soil chemical properties were studied based on factorial experiment in a completely randomized design with 6 replications, in the Gonbad Paired Watershed Research Station. Soil sampling was done in August 2016 and chemical properties were measured. The soil pH was higher in the southern slopes than in the northern slopes. The pH of the soil under Astragalus parrowianus was significantly lower than that of Bromus tomentellus. In the northern slope, CEC of soil under Astragalus parrowianus was higher compared to that under Bromus tomentellus and inter-plant position, while in the southern slope, soils in the inter-plant position had significantly lower CEC in comparison with those under Bromus tomentellus and Astragalus parrowianus plants. At all plant and inter-plant positions, the CEC and organic matter content were significantly lower in the southern slope than in the northern slope. At the first and second depths of the northern and southern slopes, soil under Astragalus parrowianus plants had significantly higher organic matter and calcium carbonate compared to the Bromus tomentellus and inter-plant position. Also, at the first depth of the northern slope, soil under Bromus tomentellus plants had significantly higher organic matter and calcium carbonate compared to the inter-plant position. Generally, influence of the factors of aspect and vegetation type was more than that of the depth of sampling.