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.