Changes in leaf functional traits of rainforest canopy trees associated with an El Niño event in Borneo

Matheus Henrique Nunes, Sabine Both, Boris Bongalov, Craig Brelsford, Sacha Khoury, David F. R. P. Burslem, Christopher D. Philipson, Noreen Majalap, Terhi Riutta, David A. Coomes (Corresponding Author), Mark E. J. Cutler (Corresponding Author)

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Abstract

El Niño events generate periods of relatively low precipitation, low cloud cover and high temperature over the rainforests of Southeast Asia, but their impact on tree physiology remains poorly understood. Here we use remote sensing and functional trait approaches - commonly used to understand plant acclimation to environmental fluctuations - to evaluate rainforest responses to an El Niño event at a site in northern Borneo. Spaceborne measurements (i.e. NDVI calculated from MODIS data) show the rainforest canopy greened throughout 2015, coinciding with a strengthening of the El Niño event in Sabah, Malaysia, then lost greenness in early 2016, when the El Niño was at its peak. Leaf chemical and structural traits measured for mature leaves of 65 species (104 branches from 99 tree canopies), during and after this El Niño event revealed that chlorophyll and carotenoid concentrations were 35% higher in mid 2015 than in mid 2016. Foliar concentrations of the nutrients N, P, K and Mg did not vary, suggesting the mineralisation and transportation processes were unaffected by the El Niño event. Leaves contained more phenolics, tannins and cellulose but less Ca and lignin during the El Niño event, with concentration shifts varying strongly among species. These changes in functional traits were also apparent in hyperspectral reflectance data collected using a field spectrometer, particularly in the shortwave infrared region. Leaf-level acclimation and leaf turnover could have driven the trait changes observed. We argue that trees were not water limited in the initial phase of the El Niño event, and responded by flushing new leaves, seen in the canopy greening trend and higher pigment concentrations (associated with young leaves); we argue that high evaporative demand and depleted soil water eventually caused leaves to drop in 2016. However, further studies are needed to confirm these ideas. Time-series of vegetation dynamics obtained from space can only be understood if changes in functional traits, as well as the quantity of leaves in canopies, are monitored on the ground.
Original languageEnglish
Article number085005
JournalEnvironmental Research Letters
Volume14
Issue number8
Early online date2 Jul 2019
DOIs
Publication statusPublished - 29 Jul 2019

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Borneo
rainforest
Acclimatization
Malaysia
canopy
Tannins
Physiology
Chlorophyll
Lignin
Pigments
Nutrients
Spectrometers
Water
Time series
Remote sensing
Cellulose
Southeastern Asia
Carotenoids
Infrared radiation
Soils

Keywords

  • El Nino
  • leaf greening
  • leaf trait dynamics
  • ground-based reflectance
  • tropical forests
  • DIE-OFF
  • PHOTOSYNTHETIC SEASONALITY
  • IMAGING SPECTROSCOPY
  • TROPICAL FORESTS
  • AREA LMA
  • DROUGHT
  • AMAZON
  • REFLECTANCE
  • DIVERSITY
  • LEAVES

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Changes in leaf functional traits of rainforest canopy trees associated with an El Niño event in Borneo. / Nunes, Matheus Henrique; Both, Sabine; Bongalov, Boris; Brelsford, Craig; Khoury, Sacha; Burslem, David F. R. P.; Philipson, Christopher D.; Majalap, Noreen ; Riutta, Terhi; Coomes, David A. (Corresponding Author); Cutler, Mark E. J. (Corresponding Author).

In: Environmental Research Letters, Vol. 14, No. 8, 085005, 29.07.2019.

Research output: Contribution to journalArticle

Nunes, MH, Both, S, Bongalov, B, Brelsford, C, Khoury, S, Burslem, DFRP, Philipson, CD, Majalap, N, Riutta, T, Coomes, DA & Cutler, MEJ 2019, 'Changes in leaf functional traits of rainforest canopy trees associated with an El Niño event in Borneo' Environmental Research Letters, vol. 14, no. 8, 085005. https://doi.org/10.1088/1748-9326/ab2eae
Nunes, Matheus Henrique ; Both, Sabine ; Bongalov, Boris ; Brelsford, Craig ; Khoury, Sacha ; Burslem, David F. R. P. ; Philipson, Christopher D. ; Majalap, Noreen ; Riutta, Terhi ; Coomes, David A. ; Cutler, Mark E. J. / Changes in leaf functional traits of rainforest canopy trees associated with an El Niño event in Borneo. In: Environmental Research Letters. 2019 ; Vol. 14, No. 8.
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title = "Changes in leaf functional traits of rainforest canopy trees associated with an El Ni{\~n}o event in Borneo",
abstract = "El Ni{\~n}o events generate periods of relatively low precipitation, low cloud cover and high temperature over the rainforests of Southeast Asia, but their impact on tree physiology remains poorly understood. Here we use remote sensing and functional trait approaches - commonly used to understand plant acclimation to environmental fluctuations - to evaluate rainforest responses to an El Ni{\~n}o event at a site in northern Borneo. Spaceborne measurements (i.e. NDVI calculated from MODIS data) show the rainforest canopy greened throughout 2015, coinciding with a strengthening of the El Ni{\~n}o event in Sabah, Malaysia, then lost greenness in early 2016, when the El Ni{\~n}o was at its peak. Leaf chemical and structural traits measured for mature leaves of 65 species (104 branches from 99 tree canopies), during and after this El Ni{\~n}o event revealed that chlorophyll and carotenoid concentrations were 35{\%} higher in mid 2015 than in mid 2016. Foliar concentrations of the nutrients N, P, K and Mg did not vary, suggesting the mineralisation and transportation processes were unaffected by the El Ni{\~n}o event. Leaves contained more phenolics, tannins and cellulose but less Ca and lignin during the El Ni{\~n}o event, with concentration shifts varying strongly among species. These changes in functional traits were also apparent in hyperspectral reflectance data collected using a field spectrometer, particularly in the shortwave infrared region. Leaf-level acclimation and leaf turnover could have driven the trait changes observed. We argue that trees were not water limited in the initial phase of the El Ni{\~n}o event, and responded by flushing new leaves, seen in the canopy greening trend and higher pigment concentrations (associated with young leaves); we argue that high evaporative demand and depleted soil water eventually caused leaves to drop in 2016. However, further studies are needed to confirm these ideas. Time-series of vegetation dynamics obtained from space can only be understood if changes in functional traits, as well as the quantity of leaves in canopies, are monitored on the ground.",
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note = "Field data were acquired through the DfID / NERC project Spatio-Temporal Dynamics of Forest Response to ENSO Drought (STEED) (NE/P004806/1) and NERC's Human Modified Tropical Forests research programme (grant number NE/K016377/1 awarded to the BALI consortium). We thank the NERC Field Spectroscopy Facility for loaning the ASD spectrometer used in the first campaign, and Doreen Boyd (University of Nottingham) for loaning the one used in the second campaign. M.H.N was supported by a PhD scholarship from the Conselho Nacional de Pesquisa e Desenvolvimento (CNPq). We thank the Sabah Biodiversity Council and the Danum Valley Management Committee for permission to conduct this work.We acknowledge the assistance and support from the South East Asia Rainforest Research Partnership (SEARRP), Laura Kruitbos, Unding Jami, research assistants and the Sabah Forestry Department.",
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AU - Both, Sabine

AU - Bongalov, Boris

AU - Brelsford, Craig

AU - Khoury, Sacha

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AU - Riutta, Terhi

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N2 - El Niño events generate periods of relatively low precipitation, low cloud cover and high temperature over the rainforests of Southeast Asia, but their impact on tree physiology remains poorly understood. Here we use remote sensing and functional trait approaches - commonly used to understand plant acclimation to environmental fluctuations - to evaluate rainforest responses to an El Niño event at a site in northern Borneo. Spaceborne measurements (i.e. NDVI calculated from MODIS data) show the rainforest canopy greened throughout 2015, coinciding with a strengthening of the El Niño event in Sabah, Malaysia, then lost greenness in early 2016, when the El Niño was at its peak. Leaf chemical and structural traits measured for mature leaves of 65 species (104 branches from 99 tree canopies), during and after this El Niño event revealed that chlorophyll and carotenoid concentrations were 35% higher in mid 2015 than in mid 2016. Foliar concentrations of the nutrients N, P, K and Mg did not vary, suggesting the mineralisation and transportation processes were unaffected by the El Niño event. Leaves contained more phenolics, tannins and cellulose but less Ca and lignin during the El Niño event, with concentration shifts varying strongly among species. These changes in functional traits were also apparent in hyperspectral reflectance data collected using a field spectrometer, particularly in the shortwave infrared region. Leaf-level acclimation and leaf turnover could have driven the trait changes observed. We argue that trees were not water limited in the initial phase of the El Niño event, and responded by flushing new leaves, seen in the canopy greening trend and higher pigment concentrations (associated with young leaves); we argue that high evaporative demand and depleted soil water eventually caused leaves to drop in 2016. However, further studies are needed to confirm these ideas. Time-series of vegetation dynamics obtained from space can only be understood if changes in functional traits, as well as the quantity of leaves in canopies, are monitored on the ground.

AB - El Niño events generate periods of relatively low precipitation, low cloud cover and high temperature over the rainforests of Southeast Asia, but their impact on tree physiology remains poorly understood. Here we use remote sensing and functional trait approaches - commonly used to understand plant acclimation to environmental fluctuations - to evaluate rainforest responses to an El Niño event at a site in northern Borneo. Spaceborne measurements (i.e. NDVI calculated from MODIS data) show the rainforest canopy greened throughout 2015, coinciding with a strengthening of the El Niño event in Sabah, Malaysia, then lost greenness in early 2016, when the El Niño was at its peak. Leaf chemical and structural traits measured for mature leaves of 65 species (104 branches from 99 tree canopies), during and after this El Niño event revealed that chlorophyll and carotenoid concentrations were 35% higher in mid 2015 than in mid 2016. Foliar concentrations of the nutrients N, P, K and Mg did not vary, suggesting the mineralisation and transportation processes were unaffected by the El Niño event. Leaves contained more phenolics, tannins and cellulose but less Ca and lignin during the El Niño event, with concentration shifts varying strongly among species. These changes in functional traits were also apparent in hyperspectral reflectance data collected using a field spectrometer, particularly in the shortwave infrared region. Leaf-level acclimation and leaf turnover could have driven the trait changes observed. We argue that trees were not water limited in the initial phase of the El Niño event, and responded by flushing new leaves, seen in the canopy greening trend and higher pigment concentrations (associated with young leaves); we argue that high evaporative demand and depleted soil water eventually caused leaves to drop in 2016. However, further studies are needed to confirm these ideas. Time-series of vegetation dynamics obtained from space can only be understood if changes in functional traits, as well as the quantity of leaves in canopies, are monitored on the ground.

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KW - leaf trait dynamics

KW - ground-based reflectance

KW - tropical forests

KW - DIE-OFF

KW - PHOTOSYNTHETIC SEASONALITY

KW - IMAGING SPECTROSCOPY

KW - TROPICAL FORESTS

KW - AREA LMA

KW - DROUGHT

KW - AMAZON

KW - REFLECTANCE

KW - DIVERSITY

KW - LEAVES

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DO - 10.1088/1748-9326/ab2eae

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VL - 14

JO - Environmental Research Letters

JF - Environmental Research Letters

SN - 1748-9326

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