The roles of climate change, land use, dispersal, masting, fire, and predation on the viability of Quercus engelmannii (Engelmann Oak)

Background/Question/Methods . A species' response to climate change depends on future habitat suitability, changes in ecological communities (predators, dispersal agents, etc.), changes in the species’ vital rates (of survival, growth, reproduction, etc.), and the species’ ability to migrate.  To explore these issues, we combine dynamic species distribution models, which predict current and future suitable habitat, with stochastic, stage-based, meta-population models, which use life history traits to predict population trajectory.  In particular, we estimate the effects of climate change, land use change, and altered fire frequency on Quercus engelmannii (Engelmann oak), emphasizing the roles of fire, masting, dispersal by jays, and acorn predation by insects, birds, and small mammals.   

Results/Conclusions . Our model predicts dramatic reduction in Q. engelmannii populations, especially under drier climates, increased fire frequency, and decreased masting frequency.  Current rates of dispersal are not likely to prevent these effects, although increased dispersal could mitigate population declines.  Less frequent masting is predicted to decrease Q. engelmannii populations, in part because masting events are associated with decreased relative predation (as a fraction of the acorn crop).  When predation and masting events are decoupled, the impact of less frequent masting is reduced, stressing the importance of predation.