EFFECT OF LIGHT INTENSITY ON GROWTH, LEAF PRODUCTION, LEAF LIFESPAN AND LEAF NUTRIENT BUDGETS OF <em>ACACIA</em> <em>MANGIUM</em>, <em>CINNAMOMUM</em> <em>INERS</em>, <em>DYERA</em> <em>COSTULATA</em>, <em>EUSIDEROXYLON</em> <em>ZWAGERI</em> AND <em>SHOREA</em> <em>ROXBURGHII</em>

Authors

  • F. S. P. Ng

Keywords:

Nutrient cycling, nutrient uptake, senescence, phenology, growth modelling

Abstract

TONG, P. S. & NG, F. S. P. 2008. Effect of light intensity on growth, leaf production, leaf lifespan and leaf
nutrient budgets of Acacia mangium, Cinnamomum iners, Dyera costulata, Eusideroxylon zwageri and Shorea
roxburghii. Saplings of Acacia mangium, Cinnamomum iners, Dyera costulata, Eusideroxylon zwageri and Shorea
roxburghii were grown side by side at 4, 7, 25, 50 and 100% relative light intensities (RLIs) to facilitate
comparison under identical soil and climate conditions. The comparisons cover height increment, diameter
increment, rate of production of new leaves, leaf lifespan and leaf nutrient content. The study was carried
out in just under two years and the best plants grew from 30 cm to over 300 cm tall. Acacia mangium and
S. roxburghii grew fastest at 100% RLI. The other three species grew fastest at 25% RLI. In height, A. mangium
at 100% RLI grew four times faster than the second best species, S. roxburghii, and 21 times faster than the
slowest species, E. zwageri. Leaf lifespan, found to be maximum at 4% RLI, was shortened by a constant
amount by each doubling of light intensity. For example, each doubling of light intensity shortened the
leaf lifespan of S. roxburghii by 70 days, and that of A. mangium by 40 days. Photo-senescence of leaves is
proposed as a mechanism driving phenological events in the non-seasonal humid tropics. Old leaves at
the point of shedding had lower NPK contents than newly expanded leaves. The difference is a measure
of internal nutrient recycling of NPK. Mg was sometimes internally recycled, sometimes not, while Ca was
usually accumulated. In the two fastest-growing species, A. mangium and S. roxburghii, the NPK content in
new leaves tended to peak at about 25% RLI while the growth rate reached its maximum at 100%. Leaf
nutrient content did not mirror the rate of growth. Acacia mangium had the highest rate of nutrient uptake
per growing shoot—10 to 16 times that of S. roxburghii. At 100% RLI it grew fastest, had the shortest leaf
lifespan and the highest leaf turnover rate.

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Published

2022-06-22

How to Cite

F. S. P. Ng. (2022). EFFECT OF LIGHT INTENSITY ON GROWTH, LEAF PRODUCTION, LEAF LIFESPAN AND LEAF NUTRIENT BUDGETS OF <em>ACACIA</em> <em>MANGIUM</em>, <em>CINNAMOMUM</em> <em>INERS</em>, <em>DYERA</em> <em>COSTULATA</em>, <em>EUSIDEROXYLON</em> <em>ZWAGERI</em> AND <em>SHOREA</em> <em>ROXBURGHII</em>. Journal of Tropical Forest Science (JTFS), 20(3), 218–234. Retrieved from https://jtfs.frim.gov.my/jtfs/article/view/773

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