Assessing wildfire burn severity in western United States rangelands from 1984 to 2017

Abstract:

Fire is a natural and significant component of many rangeland ecosystems, which can help restore key ecosystem services and reduce woody plant encroachment. Wildfires have become more frequent and larger across the western United States during the last few decades, and burn severity, which is the scaled index gauging the magnitude of ecological change caused by fire, can provide insights on ecological implications of fire regimes. Previous studies mainly focused on the trends of high burn severity in forest ecosystems, while little is known about rangeland ecosystems. Furthermore, besides high burn severity, information on effects of low and moderate burn severity are also important to better understand ecological impacts of fires in different ecosystems. This study combined the fire perimeters and burn severity mosaics from the Monitoring Trends in Burn Severity (MTBS) product with the existing vegetation type (EVT) derived from the LANDFIRE program to examine the impacts of wildfires on rangeland ecosystems. The objective of this study is to evaluate temporal trends of different levels of rangeland burn severity using Autoregressive Integrated Moving Average (ARIMA) analysis in Western United States rangelands and three categorical rangeland ecosystems including herbaceous-dominated, shrub-dominated and tree-dominated rangelands from 1984 to 2017. The preliminary results indicated that the rangeland burned areas had increased significantly in western United States. The herbaceous-dominated and tree-dominated rangeland burned areas had significant increasing trends, while the shrub-dominated rangeland burned areas had no evident trend from 1984 to 2017. The trends for low, moderate and high burn severity in western United States rangelands all increased, and those for low and moderate burn severity were statistically significant (p<0.05). These findings can contribute to our understanding of the patterns of wildfire effects on rangeland ecosystems and aid the development of management strategies for rangeland conservation and sustainability.