Ciências Agrárias
URI permanente desta comunidadehttps://locus.ufv.br/handle/123456789/2
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Resultados da Pesquisa
Item Plant material controls soil organic matter formation and the magnitude of priming effect(Universidade Federal de Viçosa, 2020-03-31) Almeida, Luís Fernando Januário; Silva, Ivo Ribeiro da; http://lattes.cnpq.br/1430037122937567Soil organic matter (SOM) has the capacity to store large amounts of carbon (C). In this context, SOM is a potential sink of atmospheric C and an alternative for global warming mitigation. Although SOM is widely investigated, the processes governing its formation and retention in soils are not completely understood. Thus, we aimed in the present study to understand how the chemical composition of plant litter drives the formation of new SOM and the mineralization of “native” SOM. The research was divided in two parts that originated two chapters: I) Quantitative parametrization of molecular diversity and microbial respiration of biochemical fractions of eucalypt plant tissues; and II) Forest litter constraints on the pathways controlling soil organic matter formation. For the chapter I we fractionated eucalypt plant components through proximate analysis (PA), which has been widely used to determine litter chemistry in decomposition studies. The fractions obtained had their biochemical composition characterized by 13 C-NMR spectroscopy and thermochemolysis coupled to gas chromatography-mass spectrometry. After this characterization, artificial plant organs were “reconstructed” and incubated in soil samples for 200-days under controlled conditions. Our results showed that the chemical composition of substrate drives the respiration of plant material at the early stages of decomposition. Conversely, at the late stages of decomposition substrate properties had no significant influence on C- CO 2 release. For the chapter II we incubated soil samples with different eucalypt plant organs for 200 days. These plant organs represented forest litter fractions with distinct chemical composition and usual input location in soil (above and belowground). For each treatment, we determined the amount of litter-derived C incorporated into different SOM fractions as well as the priming effect caused by the fresh litter amendments. Our results indicate that the aboveground litter were respired at higher rates but caused less native SOM degradation as compared to root litter. Additionally, aboveground litter contributed to net gains in both POM and MAOM, while root litter only led to net gains in POM. Generally, SOM formation via microbial incorporation of aboveground litter through in vivo pathways appears to be more efficient and causes less degradation of “native” MAOM than roots. Keywords: Substrate biochemistry. Microbial respiration. In vivo pathway. Ex vivo pathway. Priming effect. 13 C-CP/MAS-NMR spectroscopy. Aboveground litter. Root litter. Particulate organic matter. Mineral-associated organic matter.