A novel procedure for measuring functional traits of herbaceous species through field spectroscopy

Abstract

Collecting species‐level information on plant functional traits is highly relevant for understanding ecosystem functioning under global change. Measuring optical properties of plant species is a promising approach to retrieve such data, but standardized protocols are essential. Due to fine‐scale heterogeneity of many vegetation types, measuring the spectral response, as a proxy for functional traits, of individual plant species remains challenging using conventional approaches. Here we present a novel method for measuring the reflectance of individual species in situ. The procedure consists of measuring monospecific arrangements of plant individuals on a black, light absorbing table, preserving structural plant properties while avoiding the admixture of other species, soil or non‐photosynthetically active vegetation. To evaluate the feasibility of the approach, a case study was conducted on forbs, where we collected and compared the reflectance of 16 herbaceous species at different phenological stages, both using common field spectroscopy and by following our novel procedure. Our procedure accurately represented spectral and functional differences between species. Spectral shape, and to a lesser extent, amplitude differences between species were preserved (SAM: Mantel r = 0.69 and p = 0.001; Manhattan distance: Mantel r = 0.42 and p = 0.002). Moreover, the method was able to capture the pattern of functional traits present among the sampled species (Procrustes r = 0.81 and p = 0.001). The new method is promising for building databases of plant traits based on spectral libraries. It might, moreover, form a standardized procedure for field campaigns, especially in the context of mixed grasslands and forb systems where relatively small plants dominate the ecosystem.

Disentangling the effects of phosphorus, nitrogen and species identity on the vegetation reflectance spectrum

“…We then averaged these four measurements resulting in one reflectance spectrum for each pot. This protocol was based on Mutanga et al (2003), Ramoelo et al (2011), Bayat et al (2016) and Van Cleemput et al (2019).…”

Leaf reflectance can surrogate foliar economics better than physiological traits across macrophyte species

“…RS-based works have by a large majority focused on terrestrial plants, from forest and grassland biomes (e.g. [ 32 , 38 – 43 ], but some developments on wetland and aquatic vegetation have been recently documented [ 44 – 46 ]. As aquatic plants feature significant differences with respect to terrestrial ones in terms of morphology and physiology ([ 47 – 49 ], the relations between leaf optical properties and reflectance at the basis of functional traits modelling of terrestrial vegetation, such as the ones embedded into PROSPECT models [ 50 ], cannot be taken by granted, and to our best knowledge, a systematic check of those relations in current literature is still lacking.…”