Journal of Rangeland

Background and objectives: The climatic features governing the arid and semi-arid areas of the Iranian plateau have created sensitive and fragile conditions in these areas. In these areas, soil erosion and desertification are among the processes that threaten water and soil resources directly and indirectly. The present study was conducted with the aim of investigating the effect of different degrees of desertification on the chemical balance (stoichiometry) of carbon, nitrogen, and phosphorus in soil and plant organs in Bampur desert region.

Methodology: According to soil and vegetation criteria, five degrees of desertification including potential desertification, light desertification, moderate desertification, severe desertification, and very severe desertification were considered in the region. In each degree of desertification, sampling of soil (45 soil samples) and vegetation using quadrats (total of 45 quadrats) was done in a completely random design in sites with dimensions of 100 m x 100 m (total of 15 sites). In each square, the existing plant species, litter, and roots of plant species were collected. Soil and plant samples (leaves, stems, roots, litter) were prepared for elemental analysis after drying. In the laboratory, carbon, nitrogen, and phosphorus concentrations of all plant tissues, litter, and soil samples were measured in terms of percentage of dry matter with standard methods. The data obtained from this research were subjected to a one-way analysis of variance in the form of a completely randomized design in three replications. To determine the correlation of the amount of elements and their stoichiometry between plant tissues and soil, a correlation matrix was drawn.

Results:The results showed that the highest amount of soil carbon, nitrogen, and phosphorus was related to the potential desertification stage, and with the increase in the desertification intensity in the studied area, the amount of soil carbon decreased significantly (p<0.01). Desertification in the study area has a significant effect (p<0.01). There was a decrease in C:N, N:P, and C:P ratios in the soil. The C:N ratio in the potential desert stage (0.32) was higher than other desert stages. With the increasing intensity of desertification, there was a significant decrease in the amount of carbon in the aerial part of the plant (p<0.05). The highest amount of carbon in aerial parts was related to the stage of potential desertification (37.29%) and the lowest amount was related to the stage of severe desertification (27.04%). The N:P ratio of roots and leaves decreased significantly with increasing intensity of desertification (p<0.01). This ratio was the minimum in the case of plant roots and leaves in the potential stage, and very severe and severe stages respectively showed the highest N:P ratio of roots and leaves. The lowest and highest C:P ratios were related to the very intense and potential stages, respectively.

Conclusion: In general, considering the changes observed in the structure of vegetation, soil fertility, and carbon and nitrogen storage, it can be concluded that desertification had a significant effect on reducing soil nutrients and saving plant tissue elements in Bampur desert region. These results justify management efforts to combat land degradation through desertification and deserve the attention of decision-makers.