Identifying earthworm's organic matter signatures by near infrared spectroscopy in different land-use systems in Tabasco, Mexico

In the state of Tabasco, South-eastern, Mexico, land-use changes such as the conversion of natural into agricultural systems, modify soil quality and the abundance of soil macrofauna, including earthworms. The aim of this study was to characterize by near-infrared spectroscopy (NIRS) the earthworms' fingerprint in soil, in six sites including natural and agricultural ecosystems with low and high earthworm biomass and low and high earthworm diversity, in order to identify specific wavelengths that discriminate the presence/abundance of earthworm species and functional groups. The spectral region of 1860-1870 nm was significantly correlated with total earthworm density, particularly at one of the sites (Cedar polyculture; r=0.8, p < 0.05). Earthworm biomass had a specific NIRS wavelength according to the earthworm species and feeding category: 1820 and 1860-1870 nm wavelengths were significantly correlated with Polypheretima elongata (r(2) = 0.7, p <0.05; mesohumic species) biomass and 2090 nm for biomass of all Lavellodrilus species (polyhumics). Two species had a much wider spectral range: L bonampakensis and Dichogaster saliens (an epigeic worm; 1690-2300 nm, r(2) = 0.7, p