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Post‐fire forest regeneration shows limited climate tracking and potential for drought‐induced type conversion

Author(s): Derek J. N. Young, Chhaya M. Werner, Kevin R. Welch, Truman P. Young, Hugh Safford, Andrew Latimer
Year Published: 2019

Disturbance such as wildfire may create opportunities for plant communities to reorganize in response to climate change. The interaction between climate change and distur- bance may be particularly important in forests, where many of the foundational plant species (trees) are long-lived and where poor initial tree establishment can result in conversion to shrub- or graminoid-dominated systems. The response of post-disturbance vegetation establishment to post-disturbance weather conditions, particularly to extreme weather, could therefore provide useful information about how forest communities will respond to climate change. We examined the effect of post-fire weather conditions on post-fire tree, shrub, and graminoid recruitment in fire-adapted forests in northern California, USA, by surveying regenerating vegetation in severely burned areas 4–5 yr after 14 different wildfires that burned between 2004 and 2012. This time period (2004–2016) encompassed a wide range of post-fire weather conditions, including a period of extreme drought. For the most common tree species, we observed little evidence of dis- turbance-mediated community reorganization or range shifts but instead either (1) low sensitiv- ity of recruitment to post-fire weather or (2) weak but widespread decreases in recruitment under unusually dry post-fire conditions, depending on the species. The occurrence of a single strong drought year following fire was more important than a series of moderately dry years in explaining tree recruitment declines. Overall, however, post-fire tree recruitment patterns were explained more strongly by long-term climate and topography and local adult tree species abun- dance than by post-fire weather conditions. This observation suggests that surviving adult trees can contribute to a “biological inertia” that restricts the extent to which tree community compo- sition will track changes in climate through post-disturbance recruitment. In contrast to our observations in trees, we observed substantial increases in shrub and graminoid establishment under post-fire drought, suggesting that shifts in dominance between functional groups may become more likely in a future with more frequent and intense drought.

Citation: Young DJN, Chhaya M, Werner CM, Welch KR, Young TP, Safford HD, Latimer AM. 2019. Post‐fire forest regeneration shows limited climate tracking and potential for drought‐induced type conversion. Ecology 100 (2): e02571. https://doi.org/10.1002/ecy.2571
Topic(s): Fire Behavior, Weather, Fire Ecology, Ecosystem Changes, Fire & Climate
Ecosystem(s): None
Document Type: Book or Chapter or Journal Article
NRFSN number: 19037
Record updated: Mar 14, 2019