Physiological and Morphological Response of Argania spinosa (L.) Skeels to a Competing Liana: Case Study under Arid Climate

Lianas are woody climbing plants and are thought to impact the hosting trees negatively. Ephedra altissima is a liana rising on the Moroccan endemic tree Argania spinosa (L.) Skeels. In this study, our objective was to investigate the impact of the liana on the Argan tree’s physiology and leaf morphology. For that purpose, we compared gas exchange, relative water content, photosynthetic pigment content, and leaf dry mass per unit area of Argan trees associated and not associated with the liana. Our study on individual leaves does not give evidence of the existence or absence of aboveground competition between the liana and the hosting tree. Indeed, photosynthetic rates may suggest that no aboveground competition is occurring. In contrast, pigment content suggests a shading effect of the liana on the hosting tree during the winter season. Otherwise, Argan associated with the liana exhibited a high Chl a/b ratio at the beginning of the dry season, suggesting a belowground competition for nutrient resources. On the other hand, WUEi results indicate that the impact of the liana on the Argan tree may go through seasons with belowground competition for water during spring. The increased LMA values registered in trees associated with the lianasuggest the existence of belowground competition for nutrient resources that persist throughout the year.