Effects of Floodwater Spreading on the Vegetation and Soil in an Arid Rangeland

Abstract

Floodwater spreading is a recognized means of controlling floods, recharging groundwater, and improving the quality of degraded ecosystems in arid and semi-arid rangelands. This study aimed to assess the effect of a floodwater spreading project (FWS) on both vegetation and soil in an arid rangeland in Iran. Ten years after the project was implemented, soil and vegetation were compared between two areas: the first within the FWS and the second a nearby control area with natural vegetation. For vegetation, we measured the cover of all species and the forage-yield of palatable species, and for soil, we analyzed pH, EC, organic matter, organic carbon, texture, sodium absorption rate, and Ca + Mg, Na, and CaCO3 concentrations. There was evidence of change in species composition within the FWS: 28 species were common to the FWS and control sites, 36 species were unique to the FWS, but only five species were present in control site. There were a large proportion of annuals and palatable species in the FWS, where forage-yield was increased significantly. There were no differences in either species richness or diversity between control and FWS sites. Few changes were found in the soil properties as a result of FWS, but further changes in the soil may take a longer time to develop. Overall floodwater spreading caused changes in vegetation development but did not have any negative impact on soil. Managers should be aware of the potential for greater change in vegetation and soil properties in future as a result of continuing sedimentation.