Desert plant species can be pretty weird. They have adapted to aridness in different ways and manage to survive some of the hardest environments on Earth. A common adaptation among desert plants is solar tracking, which is the ability of some plants to move their leaves to avoid facing direct sun light (pareheliotropism). This way, leaves protect themselves from getting burned in the desert. Although most of the ecosystems in the world are currently being monitored using satellites, the usefulness of this technology for desert ecosystems still needs to be explored.
In his PhD, Roberto discovered that leaf solar tracking has an enormous effect on estimations of the water status of desert vegetation using satellites. Common satellite derived metrics of vegetation health, such as the normalized difference vegetation index (NDVI), change in solar tracking vegetation as solar radiation changes from morning to midday and from summer to winter. Not knowing this behaviour can lead to serious errors when interpreting satellite images. Nevertheless, Roberto’s research also showed that leaf solar tracking is limited by water stress, and therefore, the normal diurnal and seasonal variation of NDVI decline as foliage runs out of water. This was successfully used to map early water stress of desert vegetation over a whole watershed in the Atacama Desert (Northern Chile).