Recovery of soil quality after wildfire is essential for soil functioning such as nutrient cycling, resistance to biochemical degradation and sustainable plant growth. Post-fire soil quality is crucial for the maintenance of ecosystem sustainability. The objective of this study was to develop a soil quality index (SQI) for assessing post-fire soil quality in upland rangeland ecosystems of a semi-arid region in Central Iran. Soil samples were collected from burnt and unburnt plots at six rangeland sites two years after a wildfire event and analyzed for 22 soil properties. The soil microbial and biochemical properties indicated a greater magnitude of post-fire changes than soil chemical properties. The contribution of microbial respiration to soil quality, obtained using factor analysis, was the highest (36%) followed by particulate organic carbon (22%), microbial biomass carbon (15%), available phosphorus (15%) and alkaline phosphomonoesterase activity (12%). This indicates that microbial properties, labile carbon and phosphorus availability are the most important soil quality indicators to detect the wildfire effects in the study rangelands. The SQI value was, on average, 28% lower in burnt rangelands (0.39–0.55) than unburnt rangelands (0.56–0.75); indicating disturbance by wildfire would be accompanied by the loss of soil functioning. This illustrates that fire decreased soil quality, which did not recover two years after fire, probably due to the high grazing pressure and climatic conditions (i.e., longer drought periods and water limitation). Apparently, a longer period of time would be required for the complete recovery of soil quality in these semi-arid rangelands. In this study, we demonstrate that an integrated SQI would be more useful to assess post-fire soil functions than single soil properties in fire-affected rangelands of semi-arid climates.

野火后恢复土壤质量对于土壤功能至关重要，例如养分循环，抗生化降解和可持续植物生长。火灾后的土壤质量对于维持生态系统的可持续性至关重要。这项研究的目的是开发一种土壤质量指数（SQI），以评估伊朗中部半干旱地区的高地牧场生态系统的火后土壤质量。野火事件发生两年后，从六个牧场的烧毁土地和未烧毁土地上收集土壤样品，并分析了22种土壤特性。土壤微生物和生化特性表明，火灾后的变化幅度大于土壤化学特性。使用因子分析获得的微生物呼吸对土壤质量的贡献，最高（36％），其次是颗粒有机碳（22％），微生物生物量碳（15％），有效磷（15％）和碱性磷酸单酯酶活性（12％）。这表明微生物特性，不稳定的碳和磷的有效性是检测研究牧场中野火影响的最重要的土壤质量指标。烧过的牧场（0.39-0.55）的SQI值平均比未烧过的牧场（0.56-0.75）低28％；表明野火干扰会伴随土壤功能丧失。这说明火灾降低了土壤质量，火灾后两年没有恢复，这可能是由于高放牧压力和气候条件（即更长的干旱时期和水限制）造成的。显然，这些半干旱牧场的土壤质量完全恢复将需要更长的时间。在这项研究中，我们证明了在半干旱气候的受火灾影响的牧场中，综合的SQI比起单一土壤特性，更能评估火灾后的土壤功能。