Integrating phenology and demography to understand the consequences of phenological shifts for plant population dynamics

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The Earth’s changing climate is disrupting many aspects of the natural world. Timing of flowering and when birds lay eggs have shifted, and this can disrupt other natural processes. Little is known about whether these changes in reproductive timing affect the ability of populations to persist, grow, or vanish into extinction. A large gap in scientific understanding exists because few studies have directly linked changes in plant timing to consequences for plant populations. This research will address this scientific gap by using a field experiment where plants are forced to leaf out and flower earlier, and compared to unmanipulated ‘control’ plants, followed by simulations of how the populations will fare in these different scenarios. This project provides many training and career opportunities, including research positions, science communication workshops for college students, K–12 public school teacher training workshops, and K–12 curriculum that will be made publicly available to teachers. This project provides societal benefits because it assesses the risk of a changing climate to plant populations and therefore to all of the benefits that plants provide: clean air, food, recreation, ecosystem services like pollination and pest control, and benefits for human health. This research will link climate change-induced shifts in plant phenology – the timing of life-cycle events ¬– to plant population dynamics. It has been widely hypothesized that shifts in phenology will affect population persistence because phenology influences the survival and reproduction of organisms, and survival and reproduction in turn determine population growth. To address this hypothesis, the researchers will conduct an experimental demography project in which the phenology of four plant species will be advanced via experimental manipulation of the timing of spring snowmelt in a subalpine ecosystem. Advanced phenology will then be associated with changes in vital rates: survival, vegetative growth, reproduction, and recruitment. Specifically, earlier leaf expansion is expected to affect survival and vegetative growth, earlier flowering is expected to affect reproduction, and earlier germination is expected to affect recruitment. The demographic data will parameterize integral projection models (IPMs) for each species, and Life Table Response Experiments will determine which vital rate, if any, these advanced reproductive events affects population growth rates. The researchers will additionally use Structural Equation Modeling to investigate the abiotic and biotic factors through which advanced life-cycle events affect vital rates: longer drought periods, longer growing seasons, and herbivory under earlier leaf-out or germination and interactions with pollinators under earlier flowering.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.