An ECOPOTENTIAL Storyline: Changes in Leaf Coloration along an Elevational Gradient on the Oceanic Island La Réunion

Increasing elevation leads to harsher environmental conditions for plants, which in turn trigger plants to adapt their morphology and structure (e.g.Ehleringer,1988). Two of those environmental drivers which are known to increase with elevation are UV-radiation and wind speed (Lutz,1996). Potential adaptions to and protection against an increase in both UV-radiation and wind speed can be expressed by a change in leaf coloration: brighter surfaces have a higher albedo than dark surfaces, meaning that radiation is rather reflected than absorbed. Hairs or a pelt-like coating of a leaf surface, developed as a protection against higher evaporation due to wind speeds and the resulting increased water loss, also leads to a perceived brighter leaf colour. Therefore, the following hypothesis was made: With increasing elevation, perceived leaf colour will be brighter. To test this assumption, leaf colour data was gathered within the ECOPOTENTIAL project in the subalpine shrub land of the oceanic island La Réunion.

On the oceanic island of La Réunion leaf colours in the subalpine shrubland react to an elevation gradient as expected: Leaf brightness increases with increasing elevation. Important to mention is that the vegetation investigated here is mainly dominated by endemic species, which are usually highly adapted to specific small scale environmental conditions and usually appear in higher elevations.