Seasonal timing determines how warming affects mast-driven food webs

Research Highlight: Keesing, F., LaDeau, S., Canham, C., Oggenfuss, K., & Ostfeld, R. Climate warming, acorn masting and the dynamics of rodent populations: Comparing long-term studies. Journal of Animal Ecology. https://doi.org/10.1111/1365-2656.70257. Mast seeding by forest trees drives consumer outbreaks and wider food-web dynamics, so climate-driven shifts in seed production are expected to cascade through ecosystems. Yet, long-term datasets that track both seed production and consumer responses remain rare. In a recent study, Keesing et al. combined two long-term datasets of acorn and rodent data, their 33-year-long study from New York and a 39-year Maine study by Dri et al., creating a rare opportunity to assess the generality of climate effects on mast-driven food webs. Despite warming and forest growth in both systems, acorn production, mouse abundance and mouse body mass increased only in Maine, whereas New York acorn production showed no directional increase, and mouse abundance remained tied to interannual variation in seed production. This contrast suggests that climate effects depend on the stage of reproduction during which warming occurs. These studies show that the acorn-mouse interaction is robust, but that the pathway from warming to seed production depends on seasonal climate change and species-specific reproductive mechanisms.