Saline Water Stress in Caatinga Species with Potential for Reforestation in the Face of Advancing Desertification in the Brazilian Semiarid Region

The advance of the soil desertification process and water salinisation hinders reforestation actions in the Brazilian semiarid region due to the negative effects on the initial establishment of seedlings. Knowledge of potential species for overcoming the problems of soil and water salinity is of broad interest. This study evaluated the growth of seedlings of the species Handroanthus impetiginosus and Handroanthus spongiosus subjected to the combined stresses of salinity and water deficit. The species were subjected to three water depths (WDs): WD1—50%, WD2—75% and WD3—100% of reference evapotranspiration, and four salinity levels (SL): SL1—0.27 dS m⁻¹, SL2—2.52 dS m⁻¹, SL3—6.35 dS m⁻¹ and SL4—7.38 dS m⁻¹. Biometric data, including plant height, number of leaves, collar diameter and biomass, was obtained. The results showed that H. impetiginosus was more tolerant of the conditions analysed. The species showed greater sensitivity to salt stress, which reduced growth and dry biomass accumulation by up to 98%. Increased water deficit reduced height, collar diameter, number of leaves, root biomass and total biomass. We propose that the optimal water depth for both species is 100% of the reference evapotranspiration.