SOIL MICROBIAL COMMUNITY PHYSIOLOGICAL PROFILING AS RELATED TO CARBON AND NITROGEN AVAILABILITY UNDER DIFFERENT LAND USES

GARLAND, JAY L.; ZABALOY, MARÍA CELINA; GOMEZ, ELENA V; ALLEGRINI, MARCO

PEDOSPHERE

SCIENCE PRESS

Lugar: Marrickville NSW; Año: 2016 vol. 26 p. 216 - 225

1002-0160

The goal of this work was to assess soil respiration in response to endogenous C and separate amendment of several individual C sources (i.e., community level physiological profiling in an oxygen-sensitive microplate, or O2-CLPP), in soils with different organic C content (as a function of soil type and management practice). We also used the O2-CLPP to determine the respiratory response of these soils to endogenous C and amended substrates with N addition. A respiratory quotient (qR) was calculated based on the ratio of the response to endogenous soil C vs. each C-only source, and was related to total organic carbon (TOC). For assessing N availability for microbial activity, an Nratio was calculated based on the response of several substrates to N addition relative to the response without N. Soils clustered in four groups after a Principal Component Analysis (PCA), based on their respiratory response to substrates and endogenous C, and TOC. These groups reflected differences among soils in their geographic origin, land use and C content. Calculated qR values were significantly lower in natural forest soils than in managed soils for most C-only sources. TOC was negatively correlated with qR (R2>0.42), indicating that soils with higher organic matter have increased respiratory efficiency. Nitrogen addition in the assay in the absence of C amendment (i.e., only endogenous soil C present) had no effect on microbial respiration in any soil, indicating that these soils were not intrinsically N-limited, but substrate-dependent variation in Nratio within soil groups was observed.