Habitat constraints on the functional significance of soil microbial communities

Habitat constraints on the functional significance of soil microbial communities. EGU 2017, European Geophysical Union General Assembly 201

Does pore scale biogeography exist in different soil types?

Microbial activity is largely controlled by the abiotic conditions prevailing in their habitats, which are very heterogeneous at the microscopic scale. A few studies have demonstrated a microbial biogeography at the pore scale. Different regions in the soil pore network can be considered to be different microbial habitats and these different regions have been shown to be well correlated with organic carbon mineralization rates. We aimed to test whether such a functional biogeography exists for different soil types and whether it is consistent across soils. We selected six topsoils with contrasted texture, soil organic matter content and pH (2 cambisols, 3 luvisols and 1 podzol under different managements). We added a 13C labelled, easily mineralisable organic substrate, pyruvate, to soil samples previously equilibrated at different matric potentials, in order to place the substrate preferentially in soil pores with neck diameters of 3 to 10 μm or 30 to 10μm, according to the Jurin- Laplace law. The soil samples were then incubated at pF 1.5 for 3 weeks and CO2 and 13C-CO2 were monitored. At the end of incubation, total and 13C-PLFA were extracted and analysed. Basal mineralisation, expressed as % total organic C was affected by soil type, mainly related soil pH and the quality[NN1] of the organic matter. The 6 soils exhibited contrasted microbial community composition, as shown by their PLFA profiles. The addition of pyruvate did not induce any priming effect in soils, except in the long term bare fallow soil, where the mineralization of SOM was presumably limited by energy. In the long term bare fallow soil, pyruvate mineralization was the same whatever the region it was placed in, suggesting other controls of its mineralization than the characteristics of pore scale habitats. In four soils out of six, the mineralization of pyruvate was more rapid when it was initially placed in large pores (30 to 100μm) than in small pores (3 to 10 μm), suggesting that pore scale biogeography may be a general feature in soils and that coarser pores are more favourable habitats for soil organic matter mineralization

Does pore scale biogeography exist in different soil types

Does pore scale biogeography exist in different soil types. EGU 2018, European Geophysical Union General Assembly 201

Does pore scale biogeography exist in different soil types

Does pore scale biogeography exist in different soil types. EGU 2018, European Geophysical Union General Assembly 201

Does pore scale biogeography exist in different soil types?

Microbial activity is largely controlled by the abiotic conditions prevailing in their habitats, which are veryheterogeneous at the microscopic scale. A few studies have demonstrated a microbial biogeography at thepore scale. Different regions in the soil pore network can be considered to be different microbial habitats andthese different regions have been shown to be well correlated with organic carbon mineralization rates. Weaimed to test whether such a functional biogeography exists for different soil types and whether it is consistentacross soils. We selected six topsoils with contrasted texture, soil organic matter content and pH (2 cambisols,3 luvisols and 1 podzol under different managements). We added a 13C labelled, easily mineralisable organicsubstrate, pyruvate, to soil samples previously equilibrated at different matric potentials, in order to place thesubstrate preferentially in soil pores with neck diameters of 3 to 10 μm or 30 to 10μm, according to the Jurin-Laplace law. The soil samples were then incubated at pF 1.5 for 3 weeks and CO2 and 13C-CO2 weremonitored. At the end of incubation, total and 13C-PLFA were extracted and analysed. Basal mineralisation,expressed as % total organic C was affected by soil type, mainly related soil pH and the quality[NN1] of theorganic matter. The 6 soils exhibited contrasted microbial community composition, as shown by their PLFAprofiles. The addition of pyruvate did not induce any priming effect in soils, except in the long term bare fallowsoil, where the mineralization of SOM was presumably limited by energy. In the long term bare fallow soil,pyruvate mineralization was the same whatever the region it was placed in, suggesting other controls of itsmineralization than the characteristics of pore scale habitats. In four soils out of six, the mineralization ofpyruvate was more rapid when it was initially placed in large pores (30 to 100μm) than in small pores (3 to 10μm), suggesting that pore scale biogeography may be a general feature in soils and that coarser pores are morefavourable habitats for soil organic matter mineralization

Diversification of photoperiodic response patterns in a collection of early-flowering mutants of arabidopsis

Many plant species exhibit seasonal variation of flowering time in response to daylength. Arabidopsis (Arabidopsis thaliana) flowers earlier under long days (LDs) than under short days (SDs). This quantitative response to photoperiod is characterized by two parameters, the critical photoperiod (Pc), below which there is a delay in flowering, and the ceiling photoperiod (Pce), below which there is no further delay. Thus Pc and Pce define the thresholds beyond which maximum LD and SD responses are observed, respectively. We studied the quantitative response to photoperiod in 49 mutants selected for early flowering in SDs. Nine of these mutants exhibited normal Pce and Pc, showing that their precocious phenotype was not linked to abnormal measurement of daylength. However, we observed broad diversification in the patterns of quantitative responses in the other mutants. To identify factors involved in abnormal measurement of daylength, we analyzed the association of these various patterns with morphogenetic and rhythmic defects. A high proportion of mutants with altered Pce exhibited abnormal hypocotyl elongation in the dark and altered circadian periods of leaf movements. This suggested that the circadian clock and negative regulators of photomorphogenesis may contribute to the specification of SD responses. In contrast, altered Pc correlated with abnormal hypocotyl elongation in the light and reduced photosynthetic light-input requirements for bolting. This indicated that LD responses may be specified by positive elements of light signal transduction pathways and by regulators of resource allocation. Furthermore, the frequency of circadian defects in mutants with normal photoperiodic responses suggested that the circadian clock may regulate the number of leaves independently of its effect on daylength perception

Hierarchy of two drivers of soil organic matter biodegradation. Habitat properties versus habitat community structure

Hierarchy of two drivers of soil organic matter biodegradation. Habitat properties versus habitat community structure. 20. World Congress of Soil Scienc

Similar mineralization rates of soil organic carbon and nitrogen in different alternative arable cropping systems

Similar mineralization rates of soil organic carbon and nitrogen in different alternative arable cropping systems. EGU 2018, European Geophysical Union General Assembly 201

Pore scale microbial biogeography

Pore scale microbial biogeography. 4. International Congress EUROSOIL 201

Soil organic mater decompositon – the roles of microbial habitats and of microbial communites

Soil organic mater decompositon – the roles of microbial habitats and of microbial communites. International symposium on biogeochemical interfaces in soil – toward a comprehensive and mechanistic understanding of soil function