Range limits in tropical trees: the role of early life history stages

Background/Question/Methods

In the face of climate change, one option for tree species is to migrate, tracking changing climates. This creates the possibility for unprecedented changes in plant community composition. As opposed to temperate systems, species in tropical montane forests are expected to migrate to higher elevations rather than latitudinally. Tropical species may be particularly sensitive to increasing temperatures because they already experience high temperatures and therefore lack populations adapted to warmer temperatures, as well as populations that encounter little temperature variation. Different life history stage may respond to climate change differently, as juveniles may have narrower niches than adults and seedlings may experience mortality in conditions that do not affect conspecific adults.

We quantified the germination, survival, and growth of 5 species of native palms (Astrocaryum murumuru, Wettinia angustifolia, Socratea exorrhiza, Iriartea deltoidea, and Dictyocaryum lamarckianum) in a reciprocal transplant experiment along a 1500 m elevational gradient in the Kosñipata Valley, Peru.

Results/Conclusions

Germination was significantly different among species, and within select species, germination and survival were significantly different across elevation. For several species, seeds were able to germinate outside of the species’ elevation range. However, after 1.5 years, these germinants either died or did not transition to the seedling stage. This suggests that post germination mortality due to physiological or biotic factors maybe one limit to the upslope migration of tropical trees.