Differential nutrient limitation and tree height control leaf physiology, supporting niche partitioning in tropical dipterocarp forests

David C. Bartholomew*, Lindsay F. Banin, Paulo R.L. Bittencourt, Mohd Aminur Faiz Suis, Lina M. Mercado, Reuben Nilus, David F.R.P. Burslem, Lucy Rowland

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)

Abstract

Revealing the mechanisms of environmental niche partitioning within lowland tropical forests is important for understanding the drivers of current species distributions and potential vulnerability to environmental change. Tropical forest structure and species composition change across edaphic gradients in Borneo over short distances. However, our understanding of how edaphic conditions affect tree physiology and whether these relationships drive niche partitioning within Bornean forests remains incomplete. This study evaluated how leaf physiological function changes with nutrient availability across a fine-scale edaphic gradient and whether these relationships vary according to tree height. Furthermore, we tested whether intraspecific leaf trait variation allows generalist species to populate a wider range of environments. We measured leaf traits of 218 trees ranging in height from 4 to 66 m from 13 dipterocarp species within four tropical forest types (alluvial, mudstone, sandstone and kerangas) occurring along an <5 km edaphic gradient in North Borneo. The traits measured included saturating photosynthesis (Asat), maximum photosynthetic capacity (Vcmax), leaf dark respiration (Rleaf), leaf mass per area (LMA), leaf thickness, minimum stomatal conductance (gdark) and leaf nutrient concentrations (N, P, Ca, K and Mg). Across all species, leaf traits varied consistently in response to soil nutrient availability across forest types except Rleaf_mass, [Mg]leaf and [Ca]leaf. Changes in photosynthesis and respiration rates were related to different leaf nutrients across forest types, with greater nutrient-use efficiency in more nutrient-poor environments. Generalist species partially or fully compensated reductions in mass-based photosynthesis through increasing LMA in more nutrient-poor environments. Leaf traits also varied with tree height, except Vcmax_mass, but only in response to height-related modifications of leaf morphology (LMA and leaf thickness). These height–trait relationships did not vary across the edaphic gradient, except for Asat, [N]leaf, [P]leaf and [K]leaf. Our results highlight that modification of leaf physiological function and morphology act as important adaptations for Bornean dipterocarps in response to edaphic and vertical environmental gradients. Meanwhile, multiple nutrients appear to contribute to niche partitioning and could drive species distributions and high biodiversity within Bornean forest landscapes. Read the free Plain Language Summary for this article on the Journal blog.

Original languageEnglish
Pages (from-to)2084-2103
Number of pages20
JournalFunctional Ecology
Volume36
Issue number8
Early online date29 Jun 2022
DOIs
Publication statusPublished - 3 Aug 2022

Bibliographical note

Funding Information:
This work is a product of a UK NERC studentship NE/L002434/1 to D.C.B. We also acknowledge a NERC-independent research fellowship to L.R.R. (NE/N014022/1) and the Royal Society for a Newton International Fellowship (NF170370) grant to P.R.L.B. We express gratitude for the support from our team of field assistants and tree climbers who helped with the collection of sample material. We also thank the assistance of local collaborators including Noreen Majalap, Eyen Khoo and Viviannye Paul and to the Sabah Forestry Department and Sabah State Government for permitting access to the forest. We thank Roland Robert, Sharveen Pillai and the Sepilok Forest Research Centre Chemistry Department for processing and analysing leaf and soil samples. We thank the Sepilok Orangutan Rehabilitation Centre for providing rangers to support fieldwork safety.

Publisher Copyright:
© 2022 British Ecological Society.

Keywords

  • Borneo
  • generalist
  • leaf respiration
  • leaf traits
  • ontogeny
  • photosynthetic capacity
  • rainforest
  • trait plasticity

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