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Tree species differentiation in growth, recruitment and allometry in relation to maximum height in a Bornean mixed dipterocarp forest

Authors

  • Takashi Kohyama,

    Corresponding author
    1. Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060–0810, Japan,
      T. Kohyama, Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060–0810, Japan (fax + 81 11 706 4954; e-mail kohyama@ees.hokudai.ac.jp).
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  • EizI Suzuki,

    1. Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060–0810, Japan,
    2. Faculty of Science, Kagoshima University, Kagoshima 890–0065, Japan,
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  • Tukirin Partomihardjo,

    1. Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060–0810, Japan,
    2. Research Centre for Biology, Indonesian Institute of Sciences, Bogor 16122, Indonesia, and
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  • Toshihiko Yamada,

    1. Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060–0810, Japan,
    2. Faculty of Environmental and Symbiotic Sciences, Prefectural University of Kumamoto, Kumamoto 862–8502, Japan
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  • Takuya Kubo

    1. Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060–0810, Japan,
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T. Kohyama, Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060–0810, Japan (fax + 81 11 706 4954; e-mail kohyama@ees.hokudai.ac.jp).

Summary

  • 1Maximum attainable height varies greatly between tree species in tropical rain forests and covaries with demographic and allometric traits. We examined these relationships in 27 abundant tree species in a mixed dipterocarp forest. These species were monitored over 3 years in two 1-ha plots in western Borneo. A 95-percentile upper height limit was used to represent maximum height, to avoid sample size differences among populations.
  • 2Average growth rate in trunk diameter was regressed against trunk diameter using a maximum likelihood model and assuming that growth rates were exponentially distributed around the average. Estimated average growth rate at small trunk diameters (up to 11 cm) was independent of maximum height among the 27 species, while the degree of growth reduction at larger diameters was larger for species with smaller maximum height.
  • 3The recruitment rate efficiency of saplings was negatively correlated with maximum height, regardless of the measure used to assess species abundance. In particular, sapling recruitment per unit basal area declined greatly with increasing maximum height, consistent with model predictions of the traits required for the stable coexistence of species at different heights within the canopy.
  • 4Allometric analyses showed that understorey species had shorter heights at the same trunk diameter, and deeper crowns at the same tree height, than canopy species. Therefore, understorey species showed adaptive morphology to deep shade.
  • 5The regressed size-dependent pattern of average growth rate and an assumption that the population was in a steady state readily explained the observed trunk diameter distributions for 21 species among 27 examined. These species, for which the projected size distribution hardly changed when the natural increase or decrease of the population was set at γ = ±0.005 year−1, had mortality rates of more than four times the value of γ.

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