Spectral determination of concentrations of functionally diverse pigments in increasingly complex arctic tundra canopies

Abstract

As the Arctic warms, tundra vegetation is becoming taller and more structurally complex, as tall deciduous shrubs become increasingly dominant. Emerging studies reveal that shrubs exhibit photosynthetic resource partitioning, akin to forests, that may need accounting for in the "big leaf" net ecosystem exchange models. We conducted a lab experiment on sun and shade leaves from S. pulchra shrubs to determine the influence of both constitutive (slowly changing bulk carotenoid and chlorophyll pools) and facultative (rapidly changing xanthophyll cycle) pigment pools on a suite of spectral vegetation indices, to devise a rapid means of estimating within canopy resource partitioning. We found that: (1) the PRI of dark-adapted shade leaves (PRIo) was double that of sun leaves, and that PRIo was sensitive to variation among sun and shade leaves in both xanthophyll cycle pool size (V + A + Z) (r (2) = 0.59) and Chla/b (r (2) = 0.64); (2) A corrected PRI (difference between dark and illuminated leaves, ΔPRI) was more sensitive to variation among sun and shade leaves in changes to the epoxidation state of their xanthophyll cycle pigments (dEPS) (r (2) = 0.78, RMSE = 0.007) compared to the uncorrected PRI of illuminated leaves (PRI) (r (2) = 0.34, RMSE = 0.02); and (3) the SR680 index was correlated with each of (V + A + Z), lutein, bulk carotenoids, (V + A + Z)/(Chla + b), and Chla/b (r (2) range = 0.52-0.69). We suggest that ΔPRI be employed as a proxy for facultative pigment dynamics, and the SR680 for the estimation of constitutive pigment pools. We contribute the first Arctic-specific information on disentangling PRI-pigment relationships, and offer insight into how spectral indices can assess resource partitioning within shrub tundra canopies.

Detection and discrimination of various oil-contaminated soils using vegetation reflectance

“…Other carotenoids were sometimes involved, especially antheraxanthin and zeaxanthin. Total carotenoid estimation has been widely assessed using VI, but only few studies attempted to separate carotenes and xanthophylls (Boelman et al 2016, Stylinski et al 2002. Our study showed that it is of great importance for understanding the biochemical and spectral responses of vegetation to TPH and HM exposure.…”

When the sun never sets: daily changes in pigment composition in three subarctic woody plants during the summer solstice

“…Photosynthetic pigment composition and dynamics in arctic and sub-arctic plants has rarely been studied. To the best of our knowledge only one recent publication describes in detail carotenoid composition in leaves of Salix pulchra in northern Alaska tundra (68°63'N) (Boelman et al 2016) and, at a much higher latitude (Spitsbergen 78°04'N) bulk carotenoids and chlorophylls have been studied in a couple of bryophytes, lichens and vascular plants, but by non-resolutive spectrophotometric techniques (Shmakova 2010). In the three species analysed in our work, pigment composition (Fig.…”