Using hyperspectral leaf reflectance to estimate photosynthetic capacity and nitrogen content across eastern cottonwood and hybrid poplar taxa

Abstract

Eastern cottonwood (Populus deltoides W. Bartram ex Marshall) and hybrid poplars are well-known bioenergy crops. With advances in tree breeding, it is increasingly necessary to find economical ways to identify high-performing Populus genotypes that can be planted under different environmental conditions. Photosynthesis and leaf nitrogen content are critical parameters for plant growth, however, measuring them is an expensive and time-consuming process. Instead, these parameters can be quickly estimated from hyperspectral leaf reflectance if robust statistical models can be developed. To this end, we measured photosynthetic capacity parameters (Rubisco-limited carboxylation rate (Vcmax), electron transport-limited carboxylation rate (Jmax), and triose phosphate utilization-limited carboxylation rate (TPU)), nitrogen per unit leaf area (Narea), and leaf reflectance of seven taxa and 62 genotypes of Populus from two study plantations in Mississippi. For statistical modeling, we used least absolute shrinkage and selection operator (LASSO) and principal component analysis (PCA). Our results showed that the predictive ability of LASSO and PCA models was comparable, except for Narea in which LASSO was superior. In terms of model interpretability, LASSO outperformed PCA because the LASSO models needed 2 to 4 spectral reflectance wavelengths to estimate parameters. The LASSO models used reflectance values at 758 and 935 nm for estimating Vcmax (R2 = 0.51 and RMSPE = 31%) and Jmax (R2 = 0.54 and RMSPE = 32%); 687, 746, and 757 nm for estimating TPU (R2 = 0.56 and RMSPE = 31%); and 304, 712, 921, and 1021 nm for estimating Narea (R2 = 0.29 and RMSPE = 21%). The PCA model also identified 935 nm as a significant wavelength for estimating Vcmax and Jmax. Therefore, our results suggest that hyperspectral leaf reflectance modeling can be used as a cost-effective means for field phenotyping and rapid screening of Populus genotypes because of its capacity to estimate these physicochemical parameters.

Sentinel-2 Poplar Index for Operational Mapping of Poplar Plantations over Large Areas

“…Concerning the red edge, this spectral region (680-780 nm) proved to be highly sensitive to the chlorophyll content of the vegetation [81,82] and has been used to estimate structural features such as LAI [83,84], or nutritional status such as N concentration (e.g., [85]). Recently, Kyaw et al [86] showed that leaf reflectance of hybrid poplars at 712 nm (i.e., included in the B5 range) was a significant wavelength for predicting nitrogen content per unit leaf area (N area ), even if the observed correlation was weak (R 2 = 0.29 with a LASSO model). This relation was found using 105 leaf sample data of 62 Populus genotypes across seven taxa.…”

Research on the Detection Method of Organic Matter in Tea Garden Soil Based on Image Information and Hyperspectral Data Fusion

“…Machine vision and hyperspectral imaging are two nondestructive testing techniques that are widely utilized in many industries, including forestry [ 4 ], agriculture [ 5 ], animal husbandry [ 6 ], and fisheries [ 7 ]. Hyperspectral imaging technology is a technology based on image data in multiple narrow bands.…”