Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Accueil du site → Master → Israel → The Phosphorus nutrition of Quercus calliprinos under drier climate and elevated nitrogen deposition conditions

Ben-Gurion University of the Negev (2016)

The Phosphorus nutrition of Quercus calliprinos under drier climate and elevated nitrogen deposition conditions

Hila Gil

Titre : The Phosphorus nutrition of Quercus calliprinos under drier climate and elevated nitrogen deposition conditions

Auteur : Hila Gil

Etablissement de soutenance : Ben-Gurion University of the Negev

Grade : Master of Science (MS) 2016

Résumé
Enhanced nitrogen (N) deposition and extreme droughts have shown to alter the phosphorus (P) cycle in natural ecosystems. In Mediterranean forests, decreases in plant available P forms and in plant P content have been observed. P limitation in plants induces above- and belowground adaptations. Roots change to improve soil exploration and to increase the production and secretion of root exudation, in turn increasing the bioavailability of soil P. Therefore, plant responses and adaptations to dual moisture and P limitations are key to predict plant performance in natural ecosystems under change. Our research was done on the evergreen sclerophyllous tree Palestine oak (Quercus calliprinos), the dominant native tree in the Mediterranean woody vegetation in Israel . The effects of drought and N deposition on the P availability, P nutrition and P acquisition strategies of Q.calliprinos were studied on mature trees in a network of field sites, and on saplings in a controlled greenhouse experiment. The three field sites were located along a precipitation gradient (447 630 mm year–1) and were studied along one year. In the greenhouse, we exposed 6 months old Q.calliprinos saplings to five levels of soil P (0-5 mg kg-1) and one month of drought. P fertilization combined with drought in the greenhouse increased oak seedling drought tolerance, decreasing root carbohydrate exudation and P use efficiency by 3-fold. In the field, soil moisture and soil P were negatively related to root exudation, with cross-site minimum and maximum values of 0.3 and 1.5 µg cm-2 h-1 in winter and spring, respectively. The water status of mature trees in the field was positively related to foliar P content which was negatively correlated with soil N/P ratio. Our observations are the first to show the seasonal dynamic of root exudation in tree P deficiency under drought. These results show a high ability of Q.calliprinos to respond in the root level to limiting soil P environment under dry conditions with production and secretion of root exudates. Moreover, the results suggest that N deposition could have a negative effect on P uptake, especially under dry conditions, in turn affecting the tree water balance and drought tolerance. Since P is currently a limiting factor in many Mediterranean ecosystems, the negative effects of drought on P content in the ecosystem may well have additional indirect negative effects on plant drought tolerance.

Présentation (BGU)

Version intégrale

Page publiée le 16 décembre 2017, mise à jour le 26 novembre 2018