Microbial diversity and soil functions

Abstract

Summary Soil is a complex and dynamic biological system, and still in 2003 it is difficult to determine the composition of microbial communities in soil. We are also limited in the determination of microbially mediated reactions because present assays for determining the overall rate of entire metabolic processes (such as respiration) or specific enzyme activities (such as urease, protease and phosphomonoesterase activity) do not allow any identification of the microbial species directly involved in the measured processes. The central problem posed by the link between microbial diversity and soil function is to understand the relations between genetic diversity and community structure and between community structure and function. A better understanding of the relations between microbial diversity and soil functions requires not only the use of more accurate assays for taxonomically and functionally characterizing DNA and RNA extracted from soil, but also high‐resolution techniques with which to detect inactive and active microbial cells in the soil matrix. Soil seems to be characterized by a redundancy of functions; for example, no relationship has been shown to exist between microbial diversity and decomposition of organic matter. Generally, a reduction in any group of species has little effect on overall processes in soil because other microorganisms can take on its function. The determination of the composition of microbial communities in soil is not necessary for a better quantification of nutrient transformations. The holistic approach, based on the division of the systems in pools and the measurement of fluxes linking these pools, is the most efficient. The determination of microbial C, N, P and S contents by fumigation techniques has allowed a better quantification of nutrient dynamics in soil. However, further advances require determining new pools, such as active microbial biomass, also with molecular techniques. Recently investigators have separated 13C‐ and 12C‐DNA, both extracted from soil treated with a 13C source, by density‐gradient centrifugation. This technique should allow us to calculate the active microbial C pool by multiplying the ratio between labelled and total DNA by the microbial biomass C content of soil. In addition, the taxonomic and functional characterization of 13C‐DNA allows us to understand more precisely the changes in the composition of microbial communities affected by the C‐substrate added to soil.

Species-specific effects of plant invasions on activity, biomass, and composition of soil microbial communities

“…They exert negative influence on the biodiversity of valuable natural and extensively managed habitats (Zelnik 2012). These species are considered transformers (Tokarska-Guzik et al 2010), i.e., invasive species that Bchange the character, condition, form, or nature of ecosystems over a substantial area^ (Pyšek et al 2004); therefore, their effects on soil microbial processes and thus soil functioning (Nannipieri et al 2003) require detailed investigations. Previous research has been often conducted using either one or a small number of study sites, a single invasive species/ genus, and/or measuring few microbial properties, making generalizations on the impact of the invasion on soil functioning problematic Herr et al 2007;Scharfy et al 2009Scharfy et al , 2010Aguilera et al 2010;Dassonville et al 2011;Tharayil et al 2013;Mincheva et al 2014).…”

Effect of Nitrogen Fertilization Types on the Soil Microbial Biomass and Greenhouse Gases Emission

“…1) (100 g) -1 ). Due to the role of microorganisms in soil processes, their presence and biomass significantly affect the level of CO 2 emission from soils (Nannipieri et al, 2003), which is the result of root respiration and physiological processes of the microorganisms involved in the decomposition of organic material. Emissions of CO 2 from soils appear to be highly variable in heterogeneous soil micro-sites, and they are influenced by the activity of roots, microbial processes, crop residue and litter content, microclimate and catalytic properties of clay colloids (Matteucci et al, 2000).…”

“…Many papers suggested, that soil moisture and type of fertilization are key determinants of the microbial processes (Natywa et al, 2014), that determine the fluxes of GHG from soil (Nannipieri et al, 2003;Skiba et al, 2013).…”

Influence of Application of Different Formulations of Phosphate Solubilizing Biofertilizers on Soil Enzymes in Maize Crop

“…Thus it is inferred that higher rates of N, P and K fertilization with organic carbon enhanced the activities of soil dehydrogenase activity. Nannipieri et al, (2003) reported that dehydrogenase activity reflects the oxidative activity or intensity of the metabolism of soil micro flora and can be used as an indicator of microbial activity.…”