Accuracy and limitations for spectroscopic prediction of leaf traits in seasonally dry tropical environments

Autor(es)

Streher, Annia Susin ^[1] ; Torres, Ricardo da Silva ^[2] ; Cerdeira Morellato, Leonor Patricia ^[3] ; Freire Silva, Thiago Sanna ^[4]

Afiliação do(s) autor(es)

^[1] Univ Estadual Paulista, Inst Biociencias, Dept Biodiversidade, UNESP, Rio Claro, SP - Brazil

^[2] NTNU Norwegian Univ Sci & Technol, Dept ICT & Nat Sci, Alesund - Norway

^[3] Univ Estadual Paulista, Inst Biociencias, Dept Biodiversidade, Phenol Lab, UNESP, Rio Claro, SP - Brazil

^[4] Univ Stirling, Fac Nat Resources, Biol & Environm Sci, Stirling FK9 4LA - Scotland

• Tipo de documento: Artigo Científico
• Fonte: REMOTE SENSING OF ENVIRONMENT; v. 244, JUL 2020.
• Citações Web of Science: 0

Resumo

Generalized assessments of the accuracy of spectroscopic estimates of ecologically important leaf traits such as leaf mass per area (LMA) and leaf dry matter content (LDMC) are still lacking for most ecosystems, and particularly for non-forested and/or seasonally dry tropical vegetation. Here, we tested the ability of using leaf reflectance spectra to estimate LMA and LDMC and classify plant growth forms within the cerrado and campo rupestre seasonally dry non-forest vegetation types of Southeastern Brazil, filling an existing gap in published assessments of leaf optical properties and plant traits in such environments. We measured leaf reflectance spectra from 1648 individual plants comprising grasses, herbs, shrubs, and trees, developed partial least squares regression (PLSR) models linking LMA and LDMC to leaf spectra (400-2500 nm), and identified the spectral regions with the greatest discriminatory power among growth forms using Bhattacharyya distances. We accurately predicted leaf functional traits and identified different growth forms. LMA was overall more accurately predicted (RMSE = 8.58%) than LDMC (RMSE = 9.75%). Our model including all sampled plants was not biased towards any particular growth form, but growth-form specific models yielded higher accuracies and showed that leaf traits from woody plants can be more accurately estimated than for grasses and forbs, independently of the trait measured. We observed a large range of LMA values (31.80-620.81 g/m(2)) rarely observed in tropical or temperate forests, and demonstrated that values above 300 g/m(2) could not be accurately estimated. Our results suggest that spectroscopy may have an intrinsic saturation point, and/or that PLSR, the current approach of choice for estimating traits from plant spectra, is not able to model the entire range of LMA values. This finding has very important implications to our ability to use field, airborne, and orbital spectroscopic methods to derive generalizable functional information. We thus highlight the need for increasing spectroscopic sampling and research efforts in drier non-forested environments, where environmental pressures lead to leaf adaptations and allocation strategies that are very different from forested ecosystems. Our findings also confirm that leaf reflectance spectra can provide important information regarding differences in leaf metabolism, structure, and chemical composition. Such information enabled us to accurately discriminate plant growth forms in these environments regardless of lack of variation in leaf economic traits, encouraging further adoption of remote sensing methods by ecologists and allowing a more comprehensive assessment of plant functional diversity. (AU)

• Processo FAPESP: 16/00757-2 - Entendendo montagem de comunidades ao longo de gradientes altitudinais nos trópicos: variação em atributos funcionais conseguem explicar mecanismos de diversidade?
• Beneficiário: Annia Susin Streher
• Modalidade de apoio: Bolsas no Exterior - Estágio de Pesquisa - Doutorado
• Processo FAPESP: 13/50155-0 - Combining new technologies to monitor phenology from leaves to ecosystems
• Beneficiário: Leonor Patricia Cerdeira Morellato
• Modalidade de apoio: Auxílio à Pesquisa - Programa de Pesquisa sobre Mudanças Climáticas Globais - PITE
• Processo FAPESP: 17/01912-4 - Utilização de atributos ópticos para testar teorias ecológicas de distribuição de espécies
• Beneficiário: Annia Susin Streher
• Modalidade de apoio: Bolsas no Exterior - Estágio de Pesquisa - Doutorado
• Processo FAPESP: 09/54208-6 - EMU: Laboratório Multiusuário Centralizado do Núcleo de Estudos em Biodiversidade da UNESP
• Beneficiário: Célio Fernando Baptista Haddad
• Modalidade de apoio: Auxílio à Pesquisa - Programa Equipamentos Multiusuários
• Processo FAPESP: 15/17534-3 - Controles bióticos e abióticos sobre a diversidade de espécies em um gradiente altitudinal: testando teorias ecológicas através de atributos óticos
• Beneficiário: Annia Susin Streher
• Modalidade de apoio: Bolsas no Brasil - Doutorado