Dynamics of frost tolerance during regeneration in a mixed (pine–oak–juniper) Mediterranean forest uri icon

abstract

  • The effect of frost events on natural regeneration of Mediterranean mixed forests under a scenario of climate change is not well known. The expected increase in mean annual temperature and the greater inter- and intra-annual variability in frosts occurrence can significantly damage natural regeneration leading to death, with a decisive effect on species composition and forest dynamics. We investigated seasonal variations in frost tolerance of three Mediterranean species (Pinus pinea, Quercus ilex and Juniperus oxycedrus) co-occurring in inland locations in Spain. Our aim was to assess seasonal inter-specific differences in frost sensitivity or tolerance. First, we applied the relative electrolyte leakage method (REL) to estimate the frost tolerance of these species every 3-4 weeks during the 9-month period in which frost events can occur in a year. Second, we explored the REL relationship with environmental variables impacting frost acclimation/deacclimation, i.e., absolute minimum and maximum temperatures and photoperiod. Third, we built a REL model to predict seasonal variations in REL performance of young trees. We simulated REL through a 2-year period, thus defining seasonal bottlenecks in which the dynamics of regeneration can be affected by frost events. Our results showed contrasting behaviors between species, highlighting a greater sensitivity to cold of P. pinea compared to the other two species. The three species are most vulnerable in autumn; however, the different strategies to cope with unfavorable conditions adopted by Q. ilex and J. oxycedrus (e.g., stress tolerance and/or resprouting ability) give these species a competitive advantage over P. pinea.
  • The effect of unexpected low temperature on coexisting species in inland locations was examined; frost tolerance simulation over a 2-year period was used to determine bottlenecks where competition can arise.

publication date

  • 2015
  • 2015