Results
Variation in leaf ecophysiological traits along with the leaf and tree age
Though the influence of tree age and leaf age manifested in significant physiological trait differences in A. nepalensis . The fully expended leaf have highest values of all the physiological traits than leaf bud burst and leaf senescence stage significantly, regardless of the tree age gradient (Fig. 1). The effect of leaf and tree age was significant and evident for most of the leaf traits. Most of the leaf physiological trait values were highest in the young stage than in the mature and old stages (Fig. 1 and Table 2). Leaf age recorded patterns of most of the leaf trait values were in the descending order of summer (fully expended stage) > spring (leaf bud burst stage) > autumn (leaf senescence stage). Fully expanded leaves had a greater capacity for photosynthesis compared to either young (leaf bud burst stage) or old leaves (senescence stage). Like the physiological traits, SLA, total chlorophyll concentrations, N and P concentration per unit leaf mass followed a similar leaf age-related pattern (higher for the fully expended stage than leaf bud burst stage and senescence stage subsequently) (Fig.2 and Table 2).
Aarea and Amass, Eareaand Emass, gswarea and gswmass, PNUE and PPUE tend to decrease with tree age. WUEi and WUE tend to increase with tree age. Despite high physiological traits in the fully expended stage (summer leaf age), predawn (Ψpd) and midday (Ψmd) water potential were more negative (indicating higher potential stress) during the fully expended stage and leaf senescence stage in the old stage (Fig.3 and Table 2). However, SLA, N, and P per unit area did not change significantly with tree age. The total chlorophyll concentrations peaked when the leaf was fully expended stage and decreased with tree age.