Squirrels reduce postfire regeneration potential in pines
Most pines open their cones and disperse their seeds soon after the cone is mature. In serotinous pines, cones do not open when mature; they remain closed for several years [1]. Because cones are produced every year, the closed (serotinous) cones accumulate in a canopy seed bank. When a fire occurs, the heat opens the cones and stimulates dispersal in the open post‑fire environment, ensuring high post‑fire recruitment [1]. A disadvantage of maintaining a canopy seed bank is that seeds become a year‑round food source for seed predators, such as squirrels. These predators can thereby reduce the post‑fire regeneration capacity of serotinous pines.
In a recent paper, we tested the effect of squirrels on the canopy seed bank of Pinus halepensis, a Mediterranean serotinous pine [2]. Comparing stands with and without squirrels, we found that cones in stands with squirrels had reduced seed‑to‑cone mass and fewer seeds per cone, suggesting the acquisition of a defence strategy. Despite this defence, we estimate that squirrels reduce the canopy seed bank, and therefore the post‑fire regeneration potential, by 66% [3].
References
[1] Lamont BB, Pausas JG, He T, Witkowski, ETF, Hanley ME. 2020. Fire as a selective agent for both serotiny and nonserotiny over space and time. Crit. Rev. Plant Sci. 39(2):140-172. [doi | pdf | suppl.]
[2] Hernández-Serrano A., Verdú M., González-Martínez S.C., Pausas J.G. 2013. Fire structures pine serotiny at different scales. Am. J. Bot. 100 (12): 2349-2356. [doi | amjbot | pdf | supp.]
[3] Guiote C, Mezquida E.T, Pausas JG. 2026. Squirrels reduce post-fire regeneration potential in serotinous pines. Ann. Bot. [doi | data | pdf]