An ancient forest on the move: Range shifts in bristlecone pines

Abstract

Recent changes in global climate are causing many species to shift their ranges towards higher elevations. The rate at which species can shift their ranges may determine whether or not they will be able to persist in light of such rapid environmental change. In this study, we examined the effect of elevation on recruitment, mortality, and intraspecific competition in Great Basin bristlecone pines (Pinus longaeva, BC), a long-lived subalpine species whose upper limit is often at the alpine treeline. We measured recruitment, mortality, and neighbor abundance at ten predominantly BC groves across an elevational gradient in the White Mountains of California. We found proportionally more small BC and fewer large and dead BC at higher elevations, indicating recruitment increased and mortality decreased at higher elevation. Larger trees had fewer small and medium neighbors which suggests intraspecific competition may limit recruitment. Overall, increasing recruitment of Great Basin bristlecone pines at higher elevations may signal an expanding climatic range.