Climate effects on fire regimes and tree recruitment in Black Hills ponderosa pine forests
The authors examined long-term, historic fire and post-fire recruitment chronologies of ponderosa pine in the Black Hills to evaluate the relationship between climate, fire years, and tree recruitment patterns and their effects on forest structure over time.
The authors found that regional fire years were highly associated with drought with no prior lag years of moisture required. They suggest that because fire return intervals were generally longer in the Black Hills than in ponderosa pine forests of the Southwest, so that fuels had adequate time to build up between fire years. Fire years in the Black Hills were also related to La Niña years (summer-dry conditions) and cool phases of PDO, which magnifies the effects of the La Niña drought. Finally, episodes of synchronous tree recruitment and growth were highly associated with periods of increased moisture. These pluvial periods limited fire frequency and likely contributed to the increased establishment and survivorship of seedlings. The authors propose that variations in fire frequency and timing were more important in shaping forest structure than variations in fire severity.