Managing water evaporation and trace element accumulation using tree species at a red gypsum landfill

International audienceNowadays, the mining companies are increasingly confronted with problems related to manage contaminated sites and soils. The red gypsum landfill of Thann presents environmental and ecological context representative of the typology by-products storage of Ti extraction activity (high content of some Trace Element (TE): Fe, Mn … and low biodiversity). Moreover, this red gypsum is stored on a waterproof structure that requires appropriate management of the incoming and outgoing water masses. The aims of this study was to evaluate the impact of revegetation on the TE and the water status for red gypsum landfill. Our hypothesis is that the selection of tree species for TE accumulation capacity would not be antagonist of the selection of species with high transpiration rate. The opportunity of the 5 year-old demonstration plantation (18 tree species) was used to screen transpiration and TE accumulation in leaves (n=9 by species). For estimating the leaf area, we used remote-sensing airborne drone. A pot experiment with the anthroposol recovered from the study site, was initiated in the growth chamber at the laboratory for confirming the transpiration rate of the whole plant (by weighing lost method), and to measure Mn. In the field, there was a significant difference in maximum stomatal conductance between tree species, O. carpinifolia, M. pomifera, and R. copallina had the highest stomatal conductance. Regarding the Mn concentration in the leaves, O. carpinifolia and B. pendula had significantly higher levels than other tree species. The relationship between stomatal conductance and Mn content showed that tree especies that had a high Mn content, had high stomatal conductance (O. carpinifolia, B. pendula, S. aquatica grandis, S. alba) excepted R. copallina. The tree species with the lowest stomatal conductance have also low concentration of Mn. The results of the pot experiment reinforced the field results. O. carpinifolia transpiration rate was significantly higher than for other tree species tested. Although while B. pendula had intermediate transpiration, it accumulated the highest leave Mn content (1000 mg/kg DW). O. carpinifolia, S. aquatica grandis, M. pomifera, and U. pumula are the species that have the highest canopy volume. They showed higher growth performance than other tree species. The selection of tree species with hight transpiration capacity, would be therefore combining a high leaf surface area and a high maximum stomatal conductance