Effect of High pH on Foliar Chlorosis and Growth of Five Betula Species

Abstract The relative alkalinity tolerances of yellow birch, sweet birch, river birch, paper birch, and Japanese white birch were evaluated by comparing foliar chlorosis and growth of seedlings irrigated for 56 days with either a pH 6.0 nutrient solution (control) or K2CO3-amended solutions adjusted to pH 7.3 or 8.3. Both visual ratings and SPAD-502 chlorophyll meter measurements were effective methods of quantifying the severity of alkalinity-induced foliar chlorosis. Eight weeks of the pH 8.3 treatment was more effective than 4 weeks of the same treatment or 4 or 8 weeks of the pH 7.3 treatment for detecting differences in alkalinity tolerance among the species. Treatment for 8 weeks with either pH 7.3 or 8.3 solutions increased foliar chlorosis of sweet, river, paper, and Japanese white birch seedlings relative to the control treatment, whereas yellow birch seedlings exhibited mild chlorosis only in the pH 8.3 treatment. Based upon severity of chlorosis, yellow birch was most tolerant of soil alkalinity, sweet birch was least tolerant, and river, paper and Japanese white birch were intermediate in tolerance. Stem relative growth rates and shoot and root cumulative dry mass values did not consistently corroborate the relative alkalinity tolerances of the birch species indicated by the chlorosis and chlorophyll data, possibly because of container restriction of root growth of the more rapidly growing species. Results of this study indicate that yellow birch may be valuable for developing new birch cultivars adapted to alkaline soils.