Evaluating an attempt to restore summer fire in the Northern Great Plains.

There is growing interest in diversifying human-managed fire regimes. In many North American grasslands, late growing season burns re-introduce fire to periods most prone to lightning-driven fire prior to wildfire suppression policies. We report here on restoring summer fire in central North Dakota, USA, from a research project in which summer burns were only completed in two out of four years for which summer burns were planned. We use remotely-sensed imagery and local weather data to assess whether fuel or weather conditions limited burning in the summer, and to compare fire environmental conditions and subsequent burn severity across prescribed burns conducted in the spring and summer. Finally, we review historical data to determine if conditions have changed in either the spring or summer burn seasons over 42 years. Although burn severity generally declined with fuelbed greenness in the spring, summer burns could effect as high of severity as spring burns despite having greener fuelbeds. What little phenological change seems to have occurred at the study location over 42 years-slightly greener fuelbeds and slightly lower relative humidity in spring-likely offset each other to some degree. Overall, we found little evidence that being able to complete summer burns was anomalous, and conclude that it is reasonable for managers to incorporate late growing season fire into prescribed fire programs with the caveat that some summers will simply be too wet and/or too green to burn.