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 d iameter growth ( r = 0.53-0.73). With one exception (correlation between f oliar 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. Resume: Nous avons examine les relations entre la biomasse ou le taux de croissance et les caracteristiques des feuilles chez des arbres de deux ans appartenant a deux clones de Populus. Les caracteristiques des feuilles comprenaient la surface foliaire ou le poids des feuilles des plants au complet, la dimension moyenne (ou le poids) des feuilles terminales pleinement deployees ainsi que la concentration et le contenu en N, P, K, Ca, Mg, la chlorophylle totale et les hydrates de carbone totaux disponibles. Les arbres echantillonnes (n = 156) avaient ete soumis a deux regimes d'irrigation et a plusieurs traitements de fertilisation de telle sorte qu'ils representaient tine vaste gamme de conditions environnementales et de taux de croissance dans chaque clone. Le poids ou la surface foliaire des plants entiers etait fortement correle avec la biomasse epigee totale (r = 0,98-0,99). Cependant, la dimension moyenne (en surface ou en poids) des feuilles terminales pleinement deployees etait egalement fortement correlee avec la biomasse (r = 0,64-0,72),