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 ch aracteristics 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 availabl e carbohydrates. Sample trees (n = 156) were chosen from two irrigatio n regimes and several fertilization treatments to provide a wide range of environmental conditions and growth rates for each clone. Total pl ant leaf area or weight was strongly correlated with total aboveground biomass (r = 0.98-0.99); however, mean size (area or weight) of the f ully expanded terminal leaves was also quite strongly correlated with biomass (r = 0.64-0.72), height growth (r = 0.54-0.72), and diameter g rowth (r = 0.53-0.73). With one exception (correlation between foliar K concentration and height growth of one clone, r = 0.67), leaf size c haracteristics were more strongly correlated with biomass or growth th an were concentrations or contents of foliar chemicals. Since size of the terminal leaves is easy to measure, it may be useful as a simple i ndicator of potential productivity.