Predicting leaf traits of herbaceous species from their spectral characteristics

• Published in: Ecology and evolution 2014-03, Vol.4 (6), p.706-719
• Main Authors: Roelofsen, Hans D., Bodegom, Peter M., Kooistra, Lammert, Witte, Jan‐Philip M.
• Format: Article
• Language: English
• Subjects: canopy structure; carbon gain; conifer needles; Dry matter; Ecosystems; Environmental conditions; Flowers & plants; Herbaceous species; Leaf area; leaf spectroscopy; leaf traits; Leaves; nitrogen; Nutrient content; Nutrients; optical-properties; Original Research; plant traits; Predictions; Reflectance; small width leaves; Species; Spectra; Spectrum analysis; squares regression; tropical forests; wide-range
• ISSN: 2045-7758; 2045-7758
• DOI: 10.1002/ece3.932

Trait predictions from leaf spectral properties are mainly applied to tree species, while herbaceous systems received little attention in this topic. Whether similar trait–spectrum relations can be derived for herbaceous plants that differ strongly in growing strategy and environmental constraints is therefore unknown. We used partial least squares regression to relate key traits to leaf spectra (reflectance, transmittance, and absorbance) for 35 herbaceous species, sampled from a wide range of environmental conditions. Specific Leaf Area and nutrient‐related traits (N and P content) were poorly predicted from any spectrum, although N prediction improved when expressed on a per area basis (mg/m2 leaf surface) instead of mass basis (mg/g dry matter). Leaf dry matter content was moderately to good correlated with spectra. We explain our results by the range of environmental constraints encountered by herbaceous species; both N and P limitations as well as a range of light and water availabilities occurred. This weakened the relation between the measured response traits and the leaf constituents that are truly responsible for leaf spectral behavior. Indeed, N predictions improve considering solely upper or under canopy species. Therefore, trait predictions in herbaceous systems should focus on traits relating to dry matter content and the true, underlying drivers of spectral properties. Leaf traits of herbaceous plant species were related to leaf spectral properties. The unexpected findings were attributed to plant strategies influencing leaf stoichiometry and decoupling the relation between the measured traits and the traits influencing spectral properties.