Effects of salinity, watering regimes and soil types on growth of Cupressus sempervirens, Thuja orientalis, and Casuarina equisetifolia seedlings

Abstract

Effects of three levels of irrigation frequency; five levels of increasing NaCl (max 8000 ppm) in the irrigation water; and, two different soil types on the growth and survival of Italian Cypress Cupressus sempervirens, Oriental Arborvitae Thuja orientalis, and She-Oak Casuarina equisetifolia tree seedings were studied under greenhouse conditions. There were significant differences between the species throughout the stress period with regard to the evaluated parameters. Height, diameter growth, and leaf water potential in all species were reduced by increasing water and salt stress throughout the stress period. Reductions in total, shoot and root dry weight by water and salt stress were significant. Higher reductions were associated with higher water or salinity stress level. However, the species differed in their response to the stress treatments. Thuja had the lowest reductions in all measured growth parameters, followed by Casuarina and Cupressus. Water and salt stress treatments affected foliage tissue ion concentrations in all seedlings. N, P, K, Ca, Mg, Na, and Cl decreased as water stress level increased (except for, Na and Cl in Brazito soil). However, Ca, Mg, Na and Cl ion concentrations increased as the salinity level in the irrigation water increased. N and P decreased with increasing salinity and K was selectively accumulated. The seedlings' health declined with increasing stress treatment level. NaCl treatments caused foliar injury, which increased as the concentration of NaCl in the irrigation water increased. Thuja showed the least injury followed by Casuarina. Mortality was limited to Cupressus seedlings on both soil types. More mortality was noted with the increase in irrigation frequency and salinity level of the irrigation water. Thuja and Casuarina seedlings survived to the highest salinity level (8000 ppm NaCl), but with visible injury. Soil types affected all seedlings morphological parameters, total water potential, and foliage ion concentrations, except for P and Ca. All seedlings (except for Casuarina root dry weight) planted in Pima soil maintained higher growth and better overall health condition than on Brazito soil. Also, total water potential reached lower values in all species planted in Brazito soil rather than on Pima soil. Foliage Na and Cl concentrations on Brazito soil exceeded those on Pima soil. Survival of Cupressus seedlings was less on Brazito soil than on Pima soil. Overall, Cupressus growth was reduced the most on Brazito soil as compared with Pima soil. Growth of Casuarina was the least adversely affected on Brazito soil.