Thermal Resistance in Euphrates Poplar (Populus Euphratica) Provenances and Environmental Dependency in Bushehr Province

Despite the increase in heat waves and the sensitivity of forest ecosystems in desert areas, little information is available about the habitats of the Euphrates poplar in the southern parts of Iran. Characteristics of mother trees and geographical, climatic and soil characteristics of ten Euphrates poplar habitats in Bushehr province were recorded. In November, four trees from each habitat were selected and 14 cuttings were prepared from each mother tree. Seven months after planting, germination, sapling height, and branching were recorded and heat shock was applied at 70°C. Forty days later, traits of revival, sapling height, and resilience were measured. The results showed that, except for revival and resilience, there is a significant difference between the studied provenances. Branching decreased with increasing diameter of mother trees, germination increased with increasing height above sea level, and revival increased with increasing drought risk index. The resilience and height of seedlings showed a direct relationship with annual rainfall and latitude and an inverse relationship with evapotranspiration and latitude. The results of principal component analysis revealed that provenances that originated from relatively hot areas, with heavy soil, and high iron and low manganese contents had a lower germination and a higher revival rate. In addition, the resilience of provenances with high soil phosphorus and potassium contents was higher.