Root-freezing damage in the containerized nursery: impact on plantation sites - A review

Root-freezing damage frequently occurs in forest nurseries operating in cold climates. This type of damage arises because: (i) environmental cues for root cold acclimation differ from those for shoot acclimation; (ii) the root growing season is longer than shoot growing season; (iii) strong differences in root cold tolerance exist among species and provenances; (iv) root tissues are less frost tolerant than those of shoots, and young roots are less tolerant than mature ones; and (v) cultural practices can adversely affect root cold hardiness. To quantify root-freezing damage, different techniques have been tested. Electrolyte leakage is the most widely used and provides a good correlation with survival and regrowth. The impact of root-freezing damage on seedling performance has been studied under controlled and field conditions. Seedlings with root-freezing damage showed a reduction in survival and growth. Survival was reduced when root-freezing damage are severe. Growth reduction is mainly explained by a reduction in water and nitrogen uptake. The identification of a threshold in root-freezing damage below which survival and regrowth would not be affected should be determined for species most commonly used in reforestation.