Assessing Ecosystem Isoprene Emissions by Hyperspectral Remote Sensing

Abstract

This study examined the relationship between foliar isoprene emissions, light use efficiency and photochemical reflectance index (PRI) throughout the canopy profile and explored the contribution of xanthophyll cycle pigments versus other carotenoid pigments to the isoprene/PRI relationship. Foliar isoprene emissions within the canopy profile were measured in a high-density poplar plantation in Flanders (Belgium) during the 2016 growing season. The results confirmed that PRI was a promising estimator of isoprene emissions at canopy level. Interestingly, xanthophyll cycle pigments contributed more to isoprene biosynthesis than chlorophyll and drove the isoprene/PRI relationship. The simple independent pigment index and novel defined indices, such as the hyperspectral isoprene index and simple hyperspectral isoprene index, showed promising results and could be suitable estimators of isoprene emissions due to their strong relationship with the xanthophyll pool.

Relation of Photochemical Reflectance Indices Based on Different Wavelengths to the Parameters of Light Reactions in Photosystems I and II in Pea Plants

“…It is important that intensities of the reflected light can be used for the calculation of reflectance indices, because analysis based on these indices has low errors in comparison with the analysis of absolute values of the reflected light [10]. It is known that reflectance indices permit to estimate different characteristics of plants, including the growth of biomass [21], the photosynthetic efficiency and photosynthetic stress responses [16][17][18][19][20]23,33,58,70,71], the changes in biochemical compositions [29][30][31][32][33][34][35][36], the transpiration [72,73], the isoprene emission [20,24,25], etc.…”

“…There are numerous investigations that analyze the relations of the modifications of reflectance with the responses of physiological processes (including photosynthesis and its regulation [16][17][18][19][20], growth [21], water exchange [14,22,23], isoprene emission [20,24,25], electrical activity [26][27][28], etc. ), the changes in biochemical content (including concentrations of chlorophylls [29][30][31], carotenoids [32][33][34], nitrogen compositions [35,36], etc.…”

Analysis of Light-Induced Changes in the Photochemical Reflectance Index (PRI) in Leaves of Pea, Wheat, and Pumpkin Using Pulses of Green-Yellow Measuring Light

“…The PRI is a widely used spectral index [2,4,5,7,8,30] which is connected with parameters of photosynthetic processes [9][10][11]14,15,36], the content of chlorophyll and xanthophyll cycle pigments [29,30,36,37], foliar isoprene emissions [38,39], etc. Measurements of PRI are noninvasive and can be performed at different spatial scales, including leaf, canopy, and ecosystem levels [5,31].…”

Influence of Local Burning on Difference Reflectance Indices Based on 400–700 nm Wavelengths in Leaves of Pea Seedlings

“…However, using only the current narrowband reflectance indices (RIs) can limit the search for new RIs that are sensitive to the ES-induced physiological changes, because the reflected light at most wavelengths is not analyzed in standard RIs. The limitation can be eliminated by using heat maps showing (i) the correlation coefficients of physiological parameters to all possible RIs calculated on the basis of measured spectra [80][81][82] or (ii) the significance of changes in these RIs under the action of stressors [83]. Considering these approaches, it can be expected that a similar analysis of RIs in the 400-700 nm spectral range, which is related to photosynthetic processes, could reveal new RIs that are sensitive to ES-induced photosynthetic changes.…”