Use of remote sensing and anatomical evidence at contrasting elevations to infer climate change sensitivity: Preliminary results in Pinus Patula

Background: Indicators of productivity could be useful to identify vulnerable species to climate change, stress and safeguarding sites, and early detection of climate change effects, but require to be developed and tested. Species study: Pinus patula is a tropical Mexican mountain pine on which divergent opinions are available regarding its sensitivity to global warming. Local anecdotes indicate upslope shifts. Methods: We use a space-for-time substitution to infer climate change sensitivity in Pinus patula, testing putative productivity indicators at different elevations: the normalized difference vegetation index (NDVI) and leaf anatomical traits, after following standardization protocols. Results: As elevation increases, the NDVI, leaf thickness, and the mesophyll width increased, while the xylem-to-mesophyll ratio decreased, probably as different plant manifestations to higher productivity towards the mountain tops. These results concur with other studies showing evidence of more productivity toward higher elevations on the leeward side of the southern Mexico mountains based on NDVI, small mammal abundance, soil macrofungi carpophore cover, and tree basal area. Under global warming, high elevations in south Mexico appear to become more favorable because of their less extreme cold temperatures and higher rainfall. Conclusions: Our results provide an explanation of previous findings suggesting that global warming could reduce the population size and the habitable area of Pinus patula, and the observed upslope shifts. After following standardization protocols, the NDVI, mesophyll width, and xylem-to-mesophyll ratio could be promising tools to assess climate change sensitivity in terrestrial plants and deserve further studies to test their validity in other situations and species.