Fire disturbance is an integral process of rangeland ecosystems and landscapes. Wildfires, especial large ones with high burn severity, may have significant socio-ecological impacts. The vegetation recovery processes on rangeland are complicated as they can be affected by the both burn severity and postfire precipitation pattern. Studies on burn severity and vegetation recovery in rangeland ecosystems are limited and few explicitly explored the influence of postfire precipitation pattern. The objectives of this study were to 1) evaluate postfire vegetation recovery process using dense Landsat data, and 2) explore the effect of burn severity on vegetation recovery while factoring out the influence of precipitation pattern. Large rangeland wildfires in the Rolling Plains of Texas, recorded by Monitoring Trends in Burn Severity (MTBS), were used in this study. The Normalized Burn Ratios (NBR) were derived from Landsat long time series data to represent burn severity. The Normalized Difference Vegetation Index (NDVI), an index of “greenness” or photosynthetic activity, was used to assess vegetation recovery process after the fires. The PRISM data were used to represent precipitation pattern. Regression and correlation analysis were used to explore the relationship between burn severity and vegetation recovery.
Results/Conclusions
Results of preliminary analysis based on three large wildfires in 2011, Cooper mountain ranch, Dickens county complex, and Swenson, indicated that the NBR was sensitive to the fire events in these rangeland sites. The NBR time series was positive before fire and it decreased sharply when fire occurred. The NDVI decreased about 49.87% right after Swenson wildfire and about 24.70% right after the Dickens county complex wildfire. The Cooper mountain ranch and Swenson wildfires had similar burn severity (NBR=-0.24) which were greater than that happened in Dickens county complex (NBR=-0.15). The two areas with similar burn severity showed different vegetation recovery process when factoring out precipitation pattern, reflecting the importance of the precipitation pattern. The precipitation pattern had the largest impacts on vegetation recovery for the Dickens county complex wildfire (R2=0.44) which had the lowest burn severity, suggesting potentially negative impact of high burn severity on vegetation response to precipitation. These preliminary results suggest the importance to explore how the interactions of burn severity and precipitation pattern influence the recovery of rangeland vegetation and associated ecosystem services.