Leaf functional traits in relation to growth performance in Malaysian teak ( Tectona grandis L.f.)

Leaf functional traits such as leaf mass per area (LMA) and nitrogen and chlorophyll content are potential indicators of tree growth performance because they reflect leaf physiological traits including photosynthetic capacity and are influenced by environmental stress. However, our knowledge of the leaf traits associated with growth is limited in teak ( Tectona grandis). We investigated the relationship between leaf functional traits and growth rate in four Malaysian teak stands varying from 14 to 46 years of age. We measured the height and diameter of 11-13 teak individuals in each stand. Sun-exposed leaves from each tree were collected and assessed for nitrogen content, LMA, single leaf area, and SPAD value, which is an indicator of chlorophyll content. SPAD values were positively correlated with diameter growth in all stands, with height increases found in three of four stands. Nitrogen content and single leaf area were positively correlated with height and diameter growth in one forest stand each, whereas LMA did not exhibit a significant relationship. After pooling the data for all stands, we examined the relationship between leaf functional traits and stand age, diameter and height via multiple regression analysis and found a significant positive correlation with SPAD value, but weaker correlations with the other three leaf traits. Because leaf chlorophyll content decreases with environmental stresses such as reduced soil nutrient availability and drought, trees with lower SPAD values may decrease their photosynthetic production and thus grow more slowly. Our results suggest that the SPAD value is a simple growth indicator of teak, regardless of their age and size.