Abstract
Understanding the vertical pattern of leaf traits across plant canopies provide critical information on plant physiology, ecosystem functioning and structure and vegetation response to climate change. However, the impact of vertical canopy position on leaf spectral properties and subsequently leaf traits across the entire spectrum for multiple species is poorly understood. In this study, we examined the ability of leaf optical properties to track variability in leaf traits across the vertical canopy profile using Partial Least Square Discriminatory Analysis (PLS-DA). Leaf spectral measurements together with leaf traits (nitrogen, carbon, chlorophyll, equivalent water thickness and specific leaf area) were studied at three vertical canopy positions along the plant stem: lower, middle and upper. We observed that foliar nitrogen (N), chlorophyll (Cab), carbon (C), and equivalent water thickness (EWT) were higher in the upper canopy leaves compared with lower shaded leaves, while specific leaf area (SLA) increased from upper to lower canopy leaves. We found that leaf spectral reflectance significantly (P ≤ 0.05) shifted to longer wavelengths in the ‘red edge’ spectrum (685–701 nm) in the order of lower > middle > upper for the pooled dataset. We report that spectral bands that are influential in the discrimination of leaf samples into the three groups of canopy position, based on the PLS-DA variable importance projection (VIP) score, match with wavelength regions of foliar traits observed to vary across the canopy vertical profile. This observation demonstrated that both leaf traits and leaf reflectance co-vary across the vertical canopy profile in multiple species. We conclude that canopy vertical position has a significant impact on leaf spectral properties of an individual plant’s traits, and this finding holds for multiple species. These findings have important implications on field sampling protocols, upscaling leaf traits to canopy level, canopy reflectance modelling, and subsequent leaf trait retrieval, especially for studies that aimed to integrate hyperspectral measurements and LiDAR data.
Highlights
Leaf traits play a key role in ecosystem structure, functioning and resilience [1] and ecophysiology [2]
Results from our study demonstrated that only C. elegans leaf spectral reflectance (Figure 4D) increased concomitantly with its specific leaf area (SLA) (Figure 6) which may be explained by the species ability to adjust traits content across their vertical canopy profile [53]
We examined the effect of vertical canopy position on leaf traits and leaf spectral properties across multiple species
Summary
Leaf traits play a key role in ecosystem structure, functioning and resilience [1] and ecophysiology [2]. Physical models on the other hand, rigorously simulate light absorption and scattering inside vegetation canopies accounting for leaf traits composition, canopy structural properties and soil background based on radiation transfer theory [15]. These spectroscopic approaches for studying plant traits are promising, many efforts have been placed on the spectra-trait relationship for mature, sunlit leaves at the top of canopy [16]. The distribution of leaf traits within vegetation canopies is complex and often varies across the canopy vertical profile especially in resource constrained ecosystems [17]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
