Fire effects on the composition of soil seed bank and soil properties in Iran

Abstract

Fire is a frequent phenomenon in rangelands and because of its complicated and different effects on natural ecosystems, it has great importance. Awareness of such fire effects on vegetation cover in point of rangeland management after fire is important and helps better understanding and sustainable management of rangelands. Fire effects on soil seed bank (SSB) is a fundamental subject in ecology and phytosociology. These seeds have a vital role in the maintenance and reclamation of deteriorated rangelands and also in plant composition improvement in plant communities. This study was conducted to evaluate the effect of fire on vegetation, SSB, and soil properties in Sarkhalaj rangelands of Kangavar, Kermanshah province. One year after the prescribed fire, in two areas of the control (grazing exclosure) and prescribed fire, the percentage of canopy cover and soil properties were sampled on transects with a systematic random approach. Seed bank samples were sampled on these transects in two depths of 0–5 and 5–10 cm. The sampling was repeated after burning the canopy. After greenhouse cultivation, germinated seedlings were identified and the composition and density of SSB and soil properties were determined. The results indicated that compared to before the prescribed fire, the diversity, richness, and evenness indices were significantly reduced. The results of SSB in the depth of 0–5 cm showed that prescribed fire decreased the diversity and species richness indices. Moreover, at 5- to 10-cm depth, prescribed fire had no significant effect on diversity indices. At 0- to 5-cm depth, the prescribed fire increased the pH, carbon/nitrogen (C/N) ratio, electrical conductivity, and Mg and decreased the organic matter%, and N%. However, at 5- to 10-cm depth, the prescribed fire had no significant effect on the soil's physiochemical properties. Overall, it could be said that by changing the site conditions, both in terms of the space required for the establishment of new species and by changing the soil properties, the prescribed fire caused a change in SSBs in the area. This study indicated that seeds stored within the soil under certain shrub species are at a high risk of mortality during prescribed fire. Thus, successful post-fire recovery does not rely on the seed bank reservoir under these shrubs.