Is there potential in elevational assisted migration for the endangered Magnolia vovidesii?

Abstract

Faced with global climate change, biodiversity management and conservation strategies must consider both the current and potential distribution of tree species in response to rising temperatures. Assisted migration is a climate change mitigation strategy to overcome the uncoupling between species populations and the climate. However, limited field information exists regarding the responses of tree species to such movement along elevation gradients. We analysed the performance of Magnolia vovidesii saplings planted along an elevation gradient (1250–2517 m a.s.l.) in Mexico. This is a native cloud forest tree species that is endangered throughout its restricted distribution. Saplings were planted in nine forest sites, one site at the same elevation as the M. vovidesii population seed source, five sites at higher elevation and with lower temperatures, testing the potential for assisted population migration, as well as three sites at lower elevation in order to mimic the effects of increased temperature. In each site, 30 saplings were planted under the forest canopy and their survival and relative growth rate in height (RGRh) recorded over three years. Sapling survival ranged from 53 % to 97 % and survival increased with elevation, followed by a decrease at the two highest elevations studied. RGRh also increased with elevation, followed by a decrease at the highest sites. Saplings displayed higher RGRh at intermediate levels of canopy cover. Our results indicate that the transfer of M. vovidesii saplings up to ∼2300 m a.s.l, which is 600 m above the elevation limit of its current reported distribution, has potential as a conservation strategy to mitigate climate change effects.