Leaf characteristics reflect growth rates of 2-year-old Populus trees

We examined the relationships between biomass or growth rates and leaf characteristics of 2-year-old trees of two clones of Populus. Leaf characteristics were total plant leaf area or leaf weight, mean size (or weight) of fully expanded terminal leaves, and foliar concentrations and contents of N, P, K, Ca, Mg, total chlorophyll, and total available carbohydrates. Sample trees (n = 156) were chosen from two irrigation regimes and several fertilization treatments to provide a wide range of environmental conditions and growth rates for each clone. Total plant leaf area or weight was strongly correlated with total aboveground biomass (r = 0.98-0.99); however, mean size (area or weight) of the fully expanded terminal leaves was also quite strongly correlated with biomass (r = 0.64-0.72), height growth (r = 0.54-0.72), and diameter growth (r = 0.53-0.73). With one exception (correlation between foliar K concentration and height growth of one clone, r = 0.67), leaf size characteristics were more strongly correlated with biomass or growth than were concentrations or contents of foliar chemicals. Since size of the terminal leaves is easy to measure, it may be useful as a simple indicator of potential productivity.