Search results for "soil biology"

Soil processes are not influenced by the functional complexity of soil decomposer food webs under disturbance

2002

Abstract A 3 yr experiment, using field lysimeters with seedlings of Scots pine (Pinus sylvestris) growing in raw humus, was established to study how functional complexity of the soil decomposer food web affects ecosystem functioning. The functional complexity of decomposer system was manipulated by (1) allowing either microfauna (fine mesh) or microfauna+mesofauna (coarse mesh) to enter the initially defaunated systems, and (2) treating half of the lysimeters with wood ash. To test whether altering functional complexity of the decomposer community is related to the system's ability to resist disturbance, the lysimeters were later on disturbed with drought. Ecosystem function, measured as l…

Plant removal disturbance and replant mitigation effects on the abundance and diversity of low-arctic soil biota

2014

Abstract Due to the dependence of soil organisms on plant derived carbon, disturbances in plant cover are thought to be detrimental for the persistence of soil biota. In this work, we studied the disturbance effects of plant removal and soil mixing and the mitigation effects of replanting on soil biota in a low-arctic meadow ecosystem. We set up altogether six replicate blocks, each including three randomized treatment plots, at two distinct fells at Kilpisjarvi, northern Finland. Vegetation was removed in two thirds of the plots: one third was then kept barren (the plant-removal treatment), while the other third was replanted with a local herb Solidago virgaurea. The remaining plots of int…

Response to reindeer grazing removal depends on soil characteristics in low Arctic meadows

2014

In Arctic tundra, grazing is expected to exert a positive influence on microbial activity thus enhancing nutrient cycling and promoting the presence of high productive graminoids. We investigated the changes occurring in two low Arctic meadow sites after 10 years exclusion from grazing. We compared plant, soil fauna and microbial community composition, extracellular enzymes activities, and soil nutrients in ungrazed and adjacent grazed area in two low Arctic meadows. The two closely located experimental sites were both dominated by the common grass Deschampsia flexuosa which covered more than 50% of the meadows. Plant community was affected significantly by site and grazing, but the effect …

Ecological fitness of the biocontrol agent Fusarium oxysporum Fo47 in soil and its impact on the soil microbial communities

2009

Some nonpathogenic strains of Fusarium oxysporum can control Fusarium diseases responsible for severe damages in many crops. Success of biological control provided by protective strains requires their establishment in the soil. The strain Fo47 has proved its efficacy under experimental conditions, but its ecological fitness has not been carefully studied. In a series of microcosm studies, the ability of a benomyl-resistant mutant Fo47b10 to establish in two different soils was demonstrated. One year after its introduction at two concentrations in the disinfected soils, the biocontrol agent (BCA) established at similar high population densities, whereas in the nondisinfected soils it survive…

Water-extractable organic matter linked to soil physico-chemistry and microbiology at the regional scale

2015

10 pages; International audience; A better understanding of the links between dissolved organic matter and biogeochemical processes in soil could help in evaluating global soil dynamics. To assess the effects of land cover and parental material on soil biogeochemistry, we studied 120 soil samples collected from various ecosystems in Burgundy, France. The potential solubility and aromaticity of dissolved organic matter was characterised by pressurised hot-water extraction of organic carbon (PH-WEOC). Soil physico-chemical characteristics (pH, texture, soil carbon and nitrogen) were measured, as was the δ13C signature both in soils and in PH-WEOC. We also determined bacterial and fungal abund…

Agricultural management affects the response of soil bacterial community structure and respiration to water-stress

2013

International audience; Soil microorganisms are responsible for organic matter decomposition processes that regulate soil carbon storage and mineralisation to CO2. Climate change is predicted to increase the frequency of drought events, with uncertain consequences for soil microbial communities. In this study we tested the hypothesis that agricultural management used to enhance soil carbon stocks would increase the stability of microbial community structure and activity in response to water-stress. Soil was sampled from a long-term field trial with three soil carbon management systems and was used in a laboratory study of the effect of a dry wet cycle on organic C mineralisation and microbi…

2017

Arbuscular mycorrhizal fungi positively affect growth of Ailanthus altissima (Mill.) Swingle seedlings and show a strong association with this invasi…

2015

Arbuscular mycorrhizal fungi (AMF) may promote plant invasion by enhancing plant performance and competitiveness. However, only a small number of studies have considered the interactions between local soil microbial communities and invasive plants, and even fewer have focused on alien trees. Ailanthus altissima is a serious problem in the Mediterranean Basin, where it has invaded many habitats. We investigated the symbiosis between A. altissima and indigenous AMF in two invaded, ecologically different Mediterranean woodlands. Mycorrhizal infection was high at both sites (> 60% of the root fragments were mycorrhizal), indicating that A. altissima roots may be infected by AMF under different …

Interplay of omnivory, energy channels and C availability in a microbial-based soil food web

1998

To study the effects of omnivory on the structure and function of soil food webs and on the control of trophic-level biomasses in soil, two food webs were established in microcosms. The first one contained fungi, bacteria, a fungivorous nematode (Aphelenchoides saprophilus) and a bacterivorous nematode (Caenorhabditis elegans), and the second one fungi, bacteria, the fungivore and an omnivorous nematode (Mesodiplogaster sp.) feeding on both bacteria and the fungivore. Half of the replicates of each food web received additional glucose. The microcosms were sampled destructively at 5, 9, 13 and 19 weeks to estimate the biomass of microbes and nematodes and the soil NH4+-N concentration. The e…

Shifts in size, genetic structure and activity of the soil denitrifier community by nematode grazing

2010

International audience; Bacterial-feeding nematodes represent an important driver of the soil microbial activity and diversity. This study aimed at characterizing the impact of nematode grazing on a model functional bacterial guild involved in N-cycling, the denitrifiers. Bacterial-feeding nematodes (Cephalobus pseudoparvus) were inoculated into soil microcosms whose indigenous nematofauna had previously been removed. The size, genetic structure and activity of the soil denitrifier community were characterized 15 and 45 days after nematodes inoculation using quantitative PCR of the nirK, nirS and nosZ denitrification genes, fingerprinting of the nirK and nirS genes and denitrification enzym…