Ratio of microbial biomass carbon to soil organic carbon as a sensitive indicator of changes in soil organic matter

Abstract

The sensitivity of soil organic carbon (Corg) and microbial carbon (Cmic) measurements, and the Cm~,/Co,, ratio, to reflect climatic, vegetation, cropping and management history was investigated using a range of topsoils in New Zealand. The Cmic generally comprised 1-4% of Corg, with the proportion being consistently greater under pastures, than the equivalent soil under native forest, exotic forest or arable cropping. However, absolute values differed markedly between soils and were greatly influenced by texture, mineralogy and the Corg content. The Cmic recovered more rapidly than Corg on returning to pasture following cropping. There was a generally greater Corg content in those soils from the areas with higher precipitation, but the precipitation-evaporation quotient proposed by Insam et al. (Soil Biol. Biochem. 1989, 21, 211-21) to predict the relationship between Cmic and Corg, greatly underestimated the Cmic content of New Zealand soils and there was too great a scatter in the data to derive a revised regression formula. The Cmic and the Cmic/Cor, ratio are useful measures to monitor soil organic matter and both provide a more sensitive index than COrg measured alone. However, under typical climatic and land use conditions in New Zealand, the values do not appear readily transferrable between soils. To ascertain whether a soil has achieved equilibrium in organic matter status, it will be necessary to establish reference values to which a tested soil can be compared.

Carbono da biomassa microbiana em solo cultivado com soja sob diferentes sistemas de manejo nos Cerrados

“…O tipo de vegetação e as condições ambientais são fatores que determinam a quantidade e a qualidade do material que se deposita no solo, influenciando a heterogeneidade e a taxa de decomposição do material depositado a superfície (Moreira & Siqueira, 2002). A decomposição destes materiais depende dos processos de transformação da matéria orgânica pelos microrganismos do solo, por meio dos quais pode-se mensurar a qualidade do solo, determinando-se os valores do carbono da biomassa microbiana (Sparling, 1992). Na região do Cerrado, grande parte da vegetação natural está sendo substituída por culturas anuais e pastagens.…”

“…A razão carbono microbiano e carbono orgânico indica a qualidade da matéria orgânica (Wardle, 1994). De acordo com Sparling (1992), pode-se monitorar a dinâmica da matéria orgânica do solo usando-se a razão carbono microbiano (C mic ):carbono orgânico (C org ).…”

Alterações na biomassa e na atividade microbiana da serapilheira e do solo, em decorrência da substituição de cobertura florestal nativa por plantações de eucalipto, em diferentes sítios da Região Sudeste do Brasil

“…Calcularam-se os seguintes índices microbiológicos: relações C da biomassa microbiana/ C orgânico (CBM:C), N da biomassa microbiana/ N total (NBM:N) (Sparling, 1992) e o quociente metabólico (qCO 2 ), calculado pela relação entre a respiração acumulada e o C da biomassa microbiana (Anderson & Domsch, 1993), sendo expresso em mg CO 2 g -1 dia -1 CBM. Os dados referentes aos atributos microbiológicos dos solos sob eucalipto (CBMS, NBMS e RAS) foram extraídos de Gama-Rodrigues et al (2005).…”

Collembola Community Structure as a Tool to Assess Land Use Effects on Soil Quality

“…Basal respiration (BR; CO 2 -C) was estimated using 50 g of soil (Alef and Nannipieri, 1995), by quantifying the CO 2 released from the microbial respiration process in a period of 10 days of incubation at 28 °C. Eco-physiological parameters, such as metabolic quotient (qCO 2 ) (Anderson and Domsch, 1993) and microbial quotient (qMic) (Sparling, 1992), were calculated by dividing basal respiration by MBC, and by the expression (MBC/Corg)/10, respectively.…”