Isotopic abundance of 13 C and contribution of eucalyptus biomass to soil organic matter conversion

Abstract

It has become possible to evaluate the conversion of soil organic matter (SOM) in pastures and arboreal crops due to the difference between the photosynthetic cycles of Eucalyptus (C3) and most grasses (C4). The auto analyzer method coupled to the IRMS (Isotope Ratio Mass Spectrometer) in the present study evaluated the 13C content in soil profiles of Eucalyptus plantations of different ages (2, 10 and 21 years), in natural regeneration areas and natural grazing fields, and estimated the SOM conversion of each crop type of. The initial management of all sampled areas was natural pasture. The following profile layers were evaluated: 0-5, 5-10, 10-20, 20-30, 30-40, 40-50, 50-70 and 70-90cm, and the contribution of Eucalyptus biomass over the years of farming was estimated in the SOM conversion process. After 2 years of planting Eucalyptus, the beginning of pasture carbon conversion process occurred in the surface layer (0-5cm). Ten years after planting, the process of converting organic matter by arboreal crops reached the layers up to 20cm. After 21 years of planting and in natural regeneration areas, the entire profile has already been changed by planting Eucalyptus and native tree species.

Consequences of removal of exotic species (eucalyptus) on carbon and nitrogen cycles in the soil-plant system in a secondary tropical Atlantic forest in Brazil with a dual-isotope approach

“…The superficial soil (0-10 cm) was collected from below the litter layer withdrawn, totalizing 75 samples with 400 cm 2 of soil. The 75 soil samples were dried at constant weight in an oven at 60 C for 48 h (Mayor et al, 2014;Severo et al, 2017, Camara et al, 2018. No decarbonation was performed once previous tests verified the absence of inorganic carbon in the soil (Camara et al, 2018).…”

Peer Review #1 of "Consequences of removal of exotic species (eucalyptus) on carbon and nitrogen cycles in the soil-plant system in a secondary tropical Atlantic forest in Brazil with a dual-isotope approach (v0.1)"

“…The superficial soil (0-10 cm) was collected from below the litter layer withdrawn, totalizing 75 samples with 400 cm 2 of soil. The 75 soil samples were dried at constant weight in an oven at 60 °C for 48 h (Mayor et al, 2014, Severo et al, 2017, Camara et al, 2018. No decarbonation was performed once previous tests verified the absence of inorganic carbon in the soil (Camara et al, 2018).…”

Propriedades físicas de um Argissolo após 17 anos de florestamento com Eucalyptus spp.

“…Segundo Gmach et al (2020) a qualidade e quantidade de material orgânico irão influenciar diretamente na disponibilidade de C. Em um Neossolo originalmente cultivado com pastagem natural observou-se que após 21 anos de cultivo com Eucalyptus spp. houve alteração na qualidade da matéria orgânica até 0,90 m de profundidade, foi observado que mais de 90% do C presente na matéria orgânica do solo é proveniente da floresta (Severo, 2017). O cultivo de Eucalyptus spp.…”

“…Como descrito anteriormente, ações antrópicas recentes sobre o sistema solo alteram as condições pedoambientais, principalmente na camada superficial dos solos (Schwertmann, 1991). Essas ações podem influenciar alterações (transformações ou dissoluções/neoformações) de minerais pedogênicos (Kämpf & Curi, 2000;Kämpf & Curi, 2003), dos teores de C e ASE do solo (Tomasi et al, 2012a, 2012b: Severo, 2017) e nas propriedades físico-hídricas do solo ( (Lopes et al, 2006;Sampietro et al, 2015). Neste contexto, o presente trabalho tem como objetivo investigar os efeitos da substituição de áreas de campo nativo por florestamentos de Eucalyptus spp.…”