Eco-physiological mechanisms of gypsum plants to survive drought
Soils with high gypsum (CaSO4·2H2O) content are present in arid and semi-arid areas around the world. The adaptation of plants to gypsum soils results in communities composed of species that live exclusively on gypsum soils (gypsophyles) and other species, more generalist, that can live inside and outside these soils (gypsovags). Both groups of plants must deal with physical and chemical limitations inherent to these atypical soils, in addition to dealing with water scarcity, the most limiting factor for life in gypsum ecosystems. However, water use at the community and species level is still poorly explored in gypsum ecosystems. Gypsum crystallization water could be a critical water source for some plants to survive the dry season, but the factors that enable its utilization are still unknown. Hydroecological niche segregation, by which coexisting species partition water resources, could play a fundamental role in the maintenance of diversity in gypsum communities, and its understanding would bring us closer to the knowledge of adaptation to this atypical substrate. On the other hand, the association with soil microorganisms and the exudation of different compounds by roots could have a fundamental role for the survival and the acquisition of water and nutrients by plants dwelling in these alkaline and nutrient-poor soils.
This PhD Thesis aims to define the water sources used by gypsum plant species in two different communities (one in NE Spain and another in Iran), considering gypsum crystallization water as a potential source in addition to free water at different soil depths. Further, it aims to explain the below and above-ground strategies of two gypsophyles to survive water and nutrient limitations, including tracing gypsum crystallization water use by a labelling treatment in Helianthemum squamatum plants, and the in situ observation of rhizosphere pH during growth of Ononis tridentata on gypsum soils with modified fungal presence.
Soils with high gypsum (CaSO4·2H2O) content are present in arid and semi-arid areas around the world. The adaptation of plants to gypsum soils results in communities composed of species that live exclusively on gypsum soils (gypsophyles) and other species, more generalist, that can live inside and outside these soils (gypsovags). Both groups of plants must deal with physical and chemical limitations inherent to these atypical soils, in addition to dealing with water scarcity, the most limiting factor for life in gypsum ecosystems. However, water use at the community and species level is still poorly explored in gypsum ecosystems. Gypsum crystallization water could be a critical water source for some plants to survive the dry season, but the factors that enable its utilization are still unknown. Hydroecological niche segregation, by which coexisting species partition water resources, could play a fundamental role in the maintenance of diversity in gypsum communities, and its understanding would bring us closer to the knowledge of adaptation to this atypical substrate. On the other hand, the association with soil microorganisms and the exudation of different compounds by roots could have a fundamental role for the survival and the acquisition of water and nutrients by plants dwelling in these alkaline and nutrient-poor soils.
This PhD Thesis aims to define the water sources used by gypsum plant species in two different communities (one in NE Spain and another in Iran), considering gypsum crystallization water as a potential source in addition to free water at different soil depths. Further, it aims to explain the below and above-ground strategies of two gypsophyles to survive water and nutrient limitations, including tracing gypsum crystallization water use by a labelling treatment in Helianthemum squamatum plants, and the in situ observation of rhizosphere pH during growth of Ononis tridentata on gypsum soils with modified fungal presence.