Impacts of predicted climate change on recruitment at the geographical limits of Scots pine

Ongoing changes in global climate are having a significant impact on the distribution of plant species, with effects particularly evident at range limits. We assessed the capacity of Pinus sylvestris L. populations at northernmost and southernmost limits of the distribution to cope with projected changes in climate. We investigated responses including seed germination and early seedling growth and survival, using seeds from northernmost (Kevo, Finland) and southernmost (Granada, Spain) populations. Seeds were grown under current climate conditions in each area and under temperatures increased by 5 °C, with changes in precipitation of +30% or -30% with reference to current values at northern and southern limits, respectively, in a fully factorial controlled-conditions experimental design. Increased temperatures reduced germination time and enhanced biomass gain at both range edges but reduced survival at the southern range edge. Higher precipitation also increased survival and biomass but only under a southern climate. Seeds from the southern origin emerged faster, produced bigger seedlings, allocated higher biomass to roots, and survived better than northern ones. These results indicate that recruitment will be reduced at the southernmost range of the species, whereas it will be enhanced at the northern limit, and that the southern seed sources are better adapted to survive under drier conditions. However, future climate will impose a trade-off between seedling growth and survival probabilities. At the southern range edge, higher growth may render individuals more susceptible to mortality where greater aboveground biomass results in greater water loss through evapotranspiration.