title: Convergence in relationships between leaf traits, spectra and age across diverse canopy environments and two contrasting tropical forests.
abstract: Leaf age structures the phenology and development of plants, as well as the evolution of leaf traits over life histories. However, a general method for efficiently estimating leaf age across forests and canopy environments is lacking. Here, we explored the potential for a statistical model, previously developed for Peruvian sunlit leaves, to consistently predict leaf ages from leaf reflectance spectra across two contrasting forests in Peru and Brazil and across diverse canopy environments. The model performed well for independent Brazilian sunlit and shade canopy leaves (R2= 0.75-0.78), suggesting that canopy leaves (and their associated spectra) follow constrained developmental trajectories even in contrasting forests. The model did not perform as well for mid-canopy and understory leaves (R2= 0.27-0.29), because leaves in different environments have distinct traits and trait developmental trajectories. When we accounted for distinct environment-trait linkages - either by explicitly including traits and environments in the model, or, even better, by re-parameterizing the spectra-only model to implicitly capture distinct trait-trajectories in different environments - we achieved a more general model that well-predicted leaf age across forests and environments (R2= 0.79). Fundamental rules, linked to leaf environments, constrain the development of leaf traits and allow for general prediction of leaf age from spectra across species, sites and canopy environments.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, 85721, USA.
authors.forename: Jin
authors.initials: J
authors.lastname: Wu
authors.affiliation: Environmental Change Institute, School of Geography and the Environment, University of Oxford, Oxford, OX1 3QY, UK.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Chavana-Bryant
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, 85721, USA.
authors.forename: Neill
authors.initials: N
authors.lastname: Prohaska
authors.affiliation: Biological, Environmental & Climate Sciences Department, Brookhaven National Lab, Upton, New York, NY, 11973, USA.
authors.forename: Shawn P
authors.initials: SP
authors.lastname: Serbin
authors.affiliation: Department of Natural Resources and Environmental Sciences, University of Illinois at Urbana Champaign, Urbana, IL, 61801, USA.
authors.forename: Kaiyu
authors.initials: K
authors.lastname: Guan
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, 85721, USA.
authors.forename: Loren P
authors.initials: LP
authors.lastname: Albert
authors.affiliation: Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI, 02912, USA.
authors.forename: Xi
authors.identifier: http://orcid.org/0000-0002-5095-6735
authors.initials: X
authors.lastname: Yang
authors.affiliation: School of Natural Resources and the Environment, University of Arizona, Tucson, AZ, 85721, USA.
authors.forename: Willem J D
authors.initials: WJ
authors.lastname: van Leeuwen
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, 85721, USA.
authors.forename: Anthony John
authors.initials: AJ
authors.lastname: Garnello
authors.affiliation: Brazil's National Institute for Amazon Research (INPA), Manaus, AM, 69067-375, Brasil.
authors.forename: Giordane
authors.initials: G
authors.lastname: Martins
authors.affiliation: Environmental Change Institute, School of Geography and the Environment, University of Oxford, Oxford, OX1 3QY, UK.
authors.forename: Yadvinder
authors.initials: Y
authors.lastname: Malhi
authors.affiliation: Centre for Ecology and Hydrology (CEH), Wallingford, OX10 8BB, UK.
authors.forename: France
authors.initials: F
authors.lastname: Gerard
authors.affiliation: Embrapa Amazônia Oriental, Santarém, PA, 68035-110, Brasil.
authors.forename: Raimundo Cosme
authors.initials: RC
authors.lastname: Oliviera
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, 85721, USA.
authors.forename: Scott R
authors.initials: SR
authors.lastname: Saleska
mesh_terms: D001938:Brazil; D065928:Forests; D005843:Geography; D008027:Light; D008962:Models, Theoretical; D010568:Peru; D018515:Plant Leaves / Q000254:growth & development* / Q000502:physiology*; D019655:Quantitative Trait, Heritable; D012044:Regression Analysis; D014197:Trees / Q000033:anatomy & histology / Q000254:growth & development; D014329:Tropical Climate
keywords: leaf mass per area (LMA); leaf water content (LWC); partial least-squares regression (PLSR); spectroscopy; understory; vegetation indices; vertical canopy profiles