Functional structure of plant communities along salinity gradients in Iranian salt marshes

Salt marshes are unique habitats between sea or saline lakes and land that need to be conserved from the effects of global change. Understanding the variation in functional structure of plant community along environmental gradients is critical to predict the response of plant communities to ongoing environmental changes. We evaluated the changes in the functional structure of halophytic communities along soil gradients including salinity, in Iranian salt marshes; Lake Urmia, Lake Meyghan, Musa estuary, and Nayband Bay (Iran). We established 48 plots from 16 sites in four salt marshes and sampled 10 leaves per species to measure leaf functional traits. Five soil samples were sampled from each plot and 30 variables were analyzed. We examined the changes in the functional structure of plant communities (i.e., functional diversity [FD] and community weighted mean [CWM]) along local soil gradients using linear mixed effect models. Our results showed that FD and CWM of leaf thickness tended to increase with salinity, while those indices related to leaf shape decreased following soil potassium content. Our results suggest that the variations in functional structure of plant communities along local soil gradients reveal the effect of different ecological processes (e.g., niche differentiation related to the habitat heterogeneity) that drive the assembly of halophytic plant communities in SW Asian salt marshes

The hydrogeochemistry of shallow groundwater from Lut Desert, Iran: The hottest place on Earth

International audienceThis paper presents the first shallow groundwater geochemical data from the Lut Desert (Dasht-e-Lut), one of the hottest places on the planet. The waters are Na-Cl brines that have undergone extensive evaporation, but they are unlike seawater derived brines in that the K + is low and the Ca 2+ > Mg 2+ and HCO 3 − > SO 4 2−. In addition to evapo-concentration, the most saline samples indicate that the dissolution of previously deposited salt also acts as a major control on the geochemistry of these waters. High concentrations of gypsum in surface soils along with the water geochemistry indicate the dissolution, precipitation, and reprecipitation of evaporite salts are very important to the overall chemistry of the near surface environment. As demonstrated by the high H 4 SiO 4 concentrations, the weathering of aluminosilicate minerals also contributes to the solutes present. Fixed nitrogen (NO 3 − + NO 2 −) concentrations suggest little to no denitrification is occurring in these waters. The processes controlling the geochemistry of the Lut waters are similar to those in other hyperarid regions of the Earth

Iconic relationships in some halophytic Iranian Chenopodiaceae and their rhizospheres

Matinzadeh Z, Breckle S-W, Mirmassoumi M, Akhani H. Iconic relationships in some halophytic Iranian Chenopodiaceae and their rhizospheres. Plant And Soil. 2013;372(1-2):523-539.Previous studies on the identification of ion relations in halophytes have revealed that many members of Chenopodiaceae accumulate high amounts of sodium and chloride even in soils with low salinity, indicating a typical pattern which is genetically fixed. In this study, we followed up with the question of ion relations in different halophyte species with different photosynthetic pathways and different salt tolerance strategies over a complete growing season. Soil and plant samples from five species Climacoptera turcomanica (Litv.) Botsch. (leaf succulent-C-4), Salicornia persica Akhani subsp. rudshurensis Akhani (stem succulent-C-3), Halimocnemis pilifera Moq. (leaf succulent-C-4), Petrosimonia glauca (Pall.) Bunge (leaf succulent-C-4) and Atriplex verrucifera M. Bieb. (recreto-halophyte-C-3) were collected over a complete growing season from a salt flat 60 km W of Tehran. The contents of main cations (Na+, K+, Ca2+, and Mg2+) and chloride were determined in plant and soil samples. Na+ and Cl- concentration in the shoots of two hygro-halophytes Climacoptera turcomanica and Salicornia persica subsp. rudshurensis were constant over the period of the growing season. In contrast, sodium and chloride in the shoots of Halimocnemis pilifera and Petrosimonia glauca showed respectively an increasing and, in the shoots of Atriplex verrucifera, a decreasing, trend. We did not notice any decreasing trend of K+ together with increasing trend of Na+ in the shoots of the studied species; however K+ in the shoots of all examined species was considerably lower than Na+ and Cl-. It was observed that Climacoptera and Salicornia could absorb and retain calcium even in high salinity conditions, while Halimocnemis and Petrosimonia could not. Na+, K+, Cl-, Ca2+, and Mg2+ contents in the shoots of different types of halophytes (stem-succulent, leaf-succulent and excreting halophyte) or different type of photosynthesis (C-3, C-4) are independent of those in their rhizosphere. We concluded that it is controlled by the genetic characteristic of the specific taxon rather than by the environment