Many scientisst have expected that trees and tree line would migrate to higher elevations and latitudes as the climate warms. However, new research conducted by a team led by Lara Kueppers, research scientist in EESA’s Climate and Ecosystem Sciences Division and at UC Merced’s Sierra Nevada Research Institute, just published in the journal Global Change Biology, shows this didn’t hold true for two subalpine tree species in the Colorado Rockies. Unexpectedly, seedling survival in a five-year climate change experiment at University of Colorado’s Mountain Research Station at Niwot Ridge, Colorado, showed no benefit from warming at and above treeline and even reductions in Engelmann spruce recruitment. In lower elevation forest, warming had no net effect on limber pine but dramatically reduced Engelmann spruce recruitment, suggesting Engelmann spruce could lose ground at low elevations while not gaining ground up high. In addition, across all elevations, low elevation seed sources outperformed high elevation seed sources, indicating that the high elevation populations that are closest to new habitat are less suited to migrating upslope.
“Overall, our findings indicate that seedlings are highly vulnerable to climate variation, which should be taken into account as we predict what will happen to subalpine forests in a warming climate,” says research leader Lara Kueppers.
Kueppers, L. M., Conlisk, E., Castanha, C., Moyes, A. B., Germino, M. J., de Valpine, P., Torn, M. S. and Mitton, J. B. (2016), Warming and provenance limit tree recruitment across and beyond the elevation range of subalpine forest. Glob Change Biol. doi:10.1111/gcb.13561