Relación entre la respuesta isotópica (δ13C) y las propiedades fisicoquímicas: Taxonomía de suelos del Valle de Monzón en la selva alta del Perú

Abstract

Identifying the carbon isotopic ratio is valuable for analyzing and understanding soil classification and dynamics. This study evaluated and related the soil isotopic ratio and its main properties (physicochemical) in the Monzón Valley. Fifteen pits were sampled within the strata of a toposequence. δ13C was determined using an isotope ratio mass spectrometry system coupled with an EA-IRMS elemental analyzer. To obtain accurate results, samples were categorized based on their depth. Between 500 and 600 µg of soil were weighed for samples <40 cm deep, and between 1500 and 2000 µg for samples deeper than 40 cm. The results provided information on the stable carbon content of the soil, separating each sample by its soil profile, depth, pH, color, Al, cultivar, carbon stock, taxonomic classification, among others. Differences in properties were found among the profiles studied, with quantitative variation in horizons, including the water table in some, and three soil orders. The δ13C ordering shows that Inceptisols exhibit mixtures of crops from C3 and C4 plants; this is likely due to historical human interference at certain depths. For Entisols, there is a lack of diagnostic horizon formation, with a predominance of C3 plants; however, in Alfisol the greatest uptake was in the surface horizon.