Comparison of Soil Carbon and Nitrogen Stocks in Gareh-Bygone Plain of Fasa in Fields with and without Flood Spreading

Land use change is a major factor in changes in soil organic carbon and nitrogen storage and the global carbon cycle. The aim of this study was to investigate the changes in soil organic carbon and nitrogen storage after afforestation and rangeland cultivation along with flood spreading.

This investigation was carried out on the sandy lands of Gareh-Bygone Plain of Fasa located at southeastern of Fars province. A total of 45 soil composite samples were collected from Acacia, Eucalyptus, Atriplex and Planted Range from a depth of 0-30 cm in two conditions with and without flood spreading. The organic carbon and the total nitrogen content were measured in laboratory. Then, the amount of carbon and nitrogen storage was calculated and their economic value was determined by carbon tax method. The data were analyzed using SAS software as a factorial experiment in a completely randomized block design and the means were compared with Duncan's test at p<0.05.

The results showed that the effect of flood spreading on the percentage of organic carbon and the amount of organic carbon storage in the soil was significant at the p<0.01, not significant on the percentage of the total nitrogen, but its effect on the amount of nitrogen storage at the p<0.05 was significant. The effect of land use (vegetation type) on all these indices were significant at the p<0.01. The interaction effect of flood spreading and land use on the percentage of organic carbon and soil nitrogen storage at the p<0.01 was significant, but its effect on the amount of carbon storage and the percentage of total nitrogen was not significant. The amount of organic carbon storage in the soils of Acacia, Eucalyptus, Atriplex and Range, from 10.23, 22.49, 12.3 and 6.21 Mg/ha in conditions without flood spreading, respectively, increased to 23.14, 40.23, 24.12 and 13.96 Mg/ha in flood spreading conditions. The spread of floods on these land uses increased the economic value of carbon and nitrogen storage equal to 53.59, 48.00, 75.46 and 43.52 percent, respectively.

On average, flood spreading increased the economic value of total carbon and nitrogen storage in the soil equal to 54.31%.