Influence of soil organisms on accuracy predicting leaf litter decomposition by near infrared spectroscopy

Abstract

To use Near Infrared Spectroscopy (NIRS) in the study of litter decomposition in field conditions, it's essential to know the relative role of different environmental factors that may affect its accuracy. This study attempts to determine the effects of soil organisms on direct predicting by NIRS, the stage of litter decomposition, expressed as the percentage of ash-free litter mass remaining (LMR). An experiment was carried out on 10 species and at different stages of litter decomposition produced by laboratory incubations. The LMR calibration was carried out on about two third of the set (267) of samples of the 10 species including grasses, shrubs, deciduous trees and evergreen trees. The standard error of calibration was 2.81. Predictions were carried out on the remaining third of the set of the samples and on samples of other species (Aleppo pine, beech, downy oak, holm oak and sweet chestnut) decomposed in laboratory in the same previous experimental conditions. The standard error of prediction varied between 2.93 and 3.41, with similar coefficients of determination (r2) of 0.94. The calibration equation obtained from the laboratory samples, was applied to samples of four species (Aleppo pine, downy oak, holm oak and sweet chestnut) that had decomposed in litter-bags on four sites (Cambo, Liouc, Montpellier and Pech-Rouge). The standard error of prediction was of 7.29, with r2 of 0.82 and a bias of -2.59. This precision, although lower than that obtained with laboratory samples, permits the use of NIRS in studies of litter decomposition in order to complete the classical methods. The role of earthworms and that of micro-organisms are also discussed.

Keywords: NIRS, Litter decomposition, Earthworms, Mediterranean plant species

CaJEB Vol. 3 (2) 2007: pp. 88-96