Although climate change induced disturbance and drought are causing widespread mortality in Pinyon-Juniper woodlands across the western US, the long-term resilience and viability of Pinyon-Juniper woodlands are generally unknown because we lack an understanding of other key demographic processes. In particular, we lack information on recruitment and individual growth rates that determine where, and over what time scales, Pinyon-Juniper can recover from mortality events. Using data from >5,000 re-censused Forest Inventory and Analysis (FIA) plot across the western US, we developed spatially-explicit, size structured demographic models of survival, growth, and recruitment of 7 Pinyon and Juniper species across their ranges. These structured population models allowed us to estimate resilience and long-term population growth.
Results/Conclusions
Preliminary results indicate that while the majority of populations, ~90%, are nearly stable (10 yr. λ>0.9), rapid population decline (λ<0.9) is more common than rapid growth (λ>1.1). In some species, vital rates and population growth rates vary systematically across the species’ range. For example, two-needle pinyon (Pinus edulis) growth and survival decline with latitude, leading to a lower population growth rates, on average, at its southern range limit. In contrast, Utah juniper (Juniperus osteosperma), individual growth rates and population growth rates decline at more northern latitudes and low elevations. Our results highlight that the vulnerability of Pinyon-Juniper woodlands is likely to be idiosyncratic and species-specific, but landscape-scale demographic models will be valuable tools to anticipate future vulnerabilities of forests to climate change.