References of "Carnol, Monique"
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See detailFifty years of crop residue management have a limited impact on soil heterotrophic respiration.
Buysse, Pauline ULg; Schnepf-Kiss, Anne-Caroline; Carnol, Monique ULg et al

in Agricultural and Forest Meteorology (2013), 180

The impacts of crop residue management on soil microbial biomass, labile carbon and heterotrophic respiration (HR) were assessed at a long-term experimental site in the Hesbaye region in Belgium. Three ... [more ▼]

The impacts of crop residue management on soil microbial biomass, labile carbon and heterotrophic respiration (HR) were assessed at a long-term experimental site in the Hesbaye region in Belgium. Three treatments, residue export (RE), farmyard manure addition (FYM) and residue restitution after harvest (RR), have been applied continuously since 1959. The soil is a Eutric Cambisol with, in 2010, significantly different total soil organic carbon contents of 4.4, 5.1 and 5.9 kg C m-2 under the RE, RR and FYM treatments, respectively. Manual field HR measurements were carried out during the 2010 and 2012 crop seasons using a dynamic closed chamber system. Microbial biomass, labile C content and metabolic diversity of soil bacteria were assessed in spring 2012. Fifty-one years after the beginning of the treatments, residue management had a limited impact on HR. Based on daily averaged values, the treatment had a significant impact (α = 10%) in 2012 but not in 2010. Based on the individual measurement dates, the treatment impact was less obvious in 2012; with the observation of a significant impact (α = 10%) on HR in only 7% and 36.8% of the measurement dates in 2010 and 2012, respectively. Labile C and microbial biomass were significantly lower in the RE treatment than in FYM and RR. Residue management had no significant effect on cold-water extracted carbon and metabolic diversity of heterotrophic soil bacteria. The limited impact of residue management on HR could be explained by (i) the relatively low amounts of recent above-ground crop inputs, (ii) the large proportion of below-ground residues and other non-exportable above-ground residues reducing the potential differences between treatments and (iii) the relatively large spatial variability of HR. In conclusion, carbon losses due to heterotrophic respiration did not differ between RE, FYM and RR treatments in the studied soil. This contrasts with the different soil organic carbon contents observed in these three treatments after fifty years of experiment. Further investigations regarding the reduction of spatial variability and the potential roles played by organic matter protection within aggregates and biochemical composition of inputs are needed. [less ▲]

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See detailMetabolic diversity and microbial biomass in forest soils across climatic and tree species diversity gradients
Carnol, Monique ULg; Bosman, Bernard ULg; Vanoppen, Astrid et al

Poster (2013, August)

The biogeochemical cycling in forest ecosystems is highly dependent on the interactions between plants and soil. Tree species affect element cycling through deposition in throughfall, litterfall ... [more ▼]

The biogeochemical cycling in forest ecosystems is highly dependent on the interactions between plants and soil. Tree species affect element cycling through deposition in throughfall, litterfall, microbial activities in soil and rhizosphere processes. Tree species diversification has been suggested for maintaining forest ecosystem services and combining provisioning and supporting services within multifunctional and sustainable forestry. However, the understanding of the role of biodiversity in forests is unclear, in particular concerning the microbial diversity and activity in soils. Here we synthesize results from measurements of bacterial metabolic diversity and microbial biomass in soils sampled in the 209 plots of the Exploratory Platform of the FunDivEUROPE project (http://www.fundiveurope.eu/). This Exploratory Platform is a network of comparative plots of 1-5 tree species established in existing mature forest in 6 countries. These six focal regions represent important European forest types along the gradient from boreal forest to Mediterranean forest. We analysed the impact of tree species richness and the role of other controlling factors on the metabolic diversity of soil bacteria and on microbial biomass. [less ▲]

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See detailAOB community structure and richness under European beech, sessile oak, Norway spruce and Douglas-fir at three temperate forest sites
Malchair, Sandrine ULg; Carnol, Monique ULg

in Plant and Soil (2013), 366(1-2),

Abstract Background and aims The relations between tree species, microbial diversity and activity can alter ecosystem functioning. We investigated ammonia oxidizing bacteria (AOB) community structure and ... [more ▼]

Abstract Background and aims The relations between tree species, microbial diversity and activity can alter ecosystem functioning. We investigated ammonia oxidizing bacteria (AOB) community structure and richness, microbial/environmental factors related to AOB diversity and the relationship between AOB diversity and the nitrification process under several tree species. Methods Forest floor (Of, Oh) was sampled under European beech, sessile oak, Norway spruce and Douglas-fir at three sites. AOB community structure was assessed by PCR-DGGE and sequencing. Samples were analyzed for net N mineralization, potential nitrification, basal respiration, microbial biomass, microbial or metabolic quotient, pH, total nitrogen, extractable ammonium, organic matter content and exchangeable cations. Results AOB community structure and tree species effect on AOB diversity were site-specific. AOB richness was not related to nitrification. Factors regulating ammonium availability, i.e. net N mineralization or microbial biomass, were related to AOB community structure. Conclusion Our research shows that, at larger spatial scales, site specific characteristics may be more important than the nature of tree species in determining AOB diversity (richness and community structure). Within sites, tree species influence AOB diversity. The absence of a relation between AOB richness and nitrification points to a possibly role of AOB abundance, phenotypic plasticity or the implication of ammonia oxidizing archaea. [less ▲]

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See detailShort-term temperature impact on soil heterotrophic respiration in limed agricultural soil samples
Buysse, Pauline ULg; Goffin, Stéphanie ULg; Carnol, Monique ULg et al

in Biogeochemistry (2013), 112(1-3), 441-455

This study sought to investigate the hourly and daily timescale responses of soil CO2 fluxes to temperature in a limed agricultural soil. Observations from different incubation experiments were compared ... [more ▼]

This study sought to investigate the hourly and daily timescale responses of soil CO2 fluxes to temperature in a limed agricultural soil. Observations from different incubation experiments were compared with the results of a model combining biotic (heterotrophic respiration) and abiotic (carbonate weathering) components. Several samples were pre-incubated for 8-9 days at three temperatures (5, 15 and 25°C) and then submitted to short-term temperature cycles (where the temperature was increased from 5 to 35°C in 10°C stages, with each stage being 3 h long). During the temperature cycles (hourly timescale), the soil CO2 fluxes increased significantly with temperature under all pre-incubation temperature treatments. A hysteresis effect and negative fluxes during cooling phases were also systematically observed. At a given hourly timescale temperature, there was a negative relationship of the CO2 fluxes with the pre-incubation temperature. Using the combined model allowed the experimental results to be clearly described, including the negative fluxes and the hysteresis effect, showing the potentially large contribution of abiotic fluxes to total fluxes in limed soils, after short-term temperature changes. The fairly good agreement between the measured and simulated flux results also suggested that the biotic flux temperature sensitivity was probably unaffected by timescale (hourly or daily) or pre-incubation temperature. The negative relationship of the CO2 fluxes with the pre-incubation temperature probably derived from very labile soil carbon depletion, as shown in the simulations. This was not, however, confirmed by soil carbon measurements, which leaves open the possibility of adaptation within the microbial community. [less ▲]

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See detailA novel comparative research platform designed to determine the functional significance of tree species diversity in European forests
Baeten, Lander; Verheyen, Kris; Wirth, Christian et al

in Perspectives in Plant Ecology, Evolution & Systematics (2013), 15(5), 281-291

One of the current advances in functional biodiversity research is the move away from short-lived test systems towards the exploration of diversity-ecosystem functioning relationships in structurally more ... [more ▼]

One of the current advances in functional biodiversity research is the move away from short-lived test systems towards the exploration of diversity-ecosystem functioning relationships in structurally more complex ecosystems. In forests, assumptions about the functional significance of tree species diversity have only recently produced a new generation of research on ecosystem processes and services. Novel experimental designs have now replaced traditional forestry trials, but these comparatively young experimental plots suffer from specific difficulties that are mainly related to the tree size and longevity. Tree species diversity experiments therefore need to be complemented with observational studies in existing forests. Here we present the design and implementation of a new network of forest plots along tree species diversity gradients in six major European forest types: the FunDivEUROPE Exploratory Platform. Based on a review of the deficiencies of existing observational approaches and of unresolved research questions and hypotheses, we discuss the fundamental criteria that shaped the design of our platform. Key features include the extent of the species diversity gradient with mixtures up to five species, strict avoidance of a dilution gradient, special attention to community evenness and minimal covariation with other environmental factors. The new European research platform permits the most comprehensive assessment of tree species diversity effects on forest ecosystem functioning to date since it offers a common set of research plots to groups of researchers from very different disciplines and uses the same methodological approach in contrasting forest types along an extensive environmental gradient. [less ▲]

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See detailNutrient return to the forest floor through litter and throughfall under 7 forest species after conversion from Norway spruce
Carnol, Monique ULg; Bazgir, Masoud

in Forest Ecology & Management (2013), 309(0), 66-75

Tree species can influence nutrient return to the forest floor and nutrient cycling through the amount and chemical composition of throughfall and litter. We compared foliar nutrient concentrations ... [more ▼]

Tree species can influence nutrient return to the forest floor and nutrient cycling through the amount and chemical composition of throughfall and litter. We compared foliar nutrient concentrations, litter production, nutrient return and soil chemistry under 7 tree species planted on the same site after two generations of a Norway spruce (Picea abies (L.) Karst.) monoculture. Common alder (Alnus glutinosa (L.) Gaertn.), european beech (Fagus sylvatica L.), pedunculate oak (Quercus robur L.), silver birch (Betula pendula Roth.), goat willow (Salix caprea L.) and rowan (Sorbus aucuparia L.) were planted within an experimental catchment on poor acid soil in south-eastern Belgium. Measurements were performed during one year, 11 years after planting. This study demonstrated that Ca, Mg, K and N concentrations in foliage and leaf litter are tree-species specific. Fresh foliage and foliar litter N concentrations were highest in alder and willow, while Ca, Mg and K concentrations were highest in rowan. Litter Ca concentrations were approximately twice in rowan than those of all other species. Differences in nutrient concentrations between foliage and leaf litter depended both on the element concerned and on tree species. The total average litterfall biomass ranged from 615 kg ha−1 year−1 under oak to 3122 kg ha−1 year−1 under rowan. Foliar litterfall represented above 85% for beech, spruce and oak, 70% for alder and willow and ca. 55% for birch and rowan. Reproductive parts formed 44% of total litterfall biomass under rowan. Ca, Mg, K and N return via throughfall, foliar litter and reproductive parts were higher under accompanying tree species (alder, birch, willow, rowan) than under the main commercial tree species (oak, beech, spruce). Total N return was in the order of 50 kg ha−1 year−1 under accompanying species, 33 kg ha−1 year−1 under spruce and near 20 kg ha−1 year−1 under beech and oak. Under rowan, total Ca, Mg, and K return to the forest floor through throughfall deposition, litterfall of leaves and reproductive parts amounted to 47, 9 and 66 kg ha−1 year−1, respectively. Compared to spruce, forest floor pHH20 has increased by 0.4 unit under birch and rowan, and exchangeable Ca2+, Mg2+, K+ have increased about threefold under rowan. Planting rowan as accompanying species may therefore represent an interesting management option for improving forest floor chemistry on nutrient poor sites through Ca, Mg, and K nutrient return. [less ▲]

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See detailCurrent net ecosystem exchange of CO2 in a young mixed forest: any heritage from the previous ecosystem?
Violette, Aurélie ULg; Heinesch, Bernard ULg; Erpicum, Michel ULg et al

Poster (2013)

For 15 years, networks of flux towers have been developed to determine accurate carbon balance with the eddy-covariance method and determine if forests are sink or source of carbon. However, for ... [more ▼]

For 15 years, networks of flux towers have been developed to determine accurate carbon balance with the eddy-covariance method and determine if forests are sink or source of carbon. However, for prediction of the evolution of carbon cycle and climate, major uncertainties remain on the ecosystem respiration (Reco, which includes the respiration of above ground part of trees, roots respiration and mineralization of the soil organic matter), the gross primary productivity (GPP) and their difference, the net ecosystem exchange (NEE) of forests. These uncertainties are consequences of spatial and inter-annual variability, driven by previous and current climatic conditions, as well as by the particular history of the site (management, diseases, etc.). In this study we focus on the carbon cycle in two mixed forests in the Belgian Ardennes. The first site, Vielsalm, is a mature stand mostly composed of beeches (Fagus sylvatica) and douglas fir (Pseudotsuga menziesii) from 80 to 100 years old. The second site, La Robinette, was covered before 1995 with spruces. After an important windfall and a clear cutting, the site was replanted, between 1995 and 2000, with spruces (Piceas abies) and deciduous species (mostly Betula pendula, Aulnus glutinosa and Salix aurita). The challenge here is to highlight how initial conditions can influence the current behavior of the carbon cycle in a growing stand compared to a mature one, where initial conditions are supposed to be forgotten. A modeling approach suits particularly well for sensitivity tests and estimation of the temporal lag between an event and the ecosystem response. We use the forest ecosystem model ASPECTS (Rasse et al., Ecological Modelling 141, 35-52, 2001). This model predicts long-term forest growth by calculating, over time, hourly NEE. It was developed and already validated on the Vielsalm forest. Modelling results are confronted to eddy-covariance data on both sites from 2006 to 2011. The main difference between both sites seems to rely on soil respiration, which is probably partly a heritage of the previous ecosystem at the young forest site. [less ▲]

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See detailAssessment of the functional role of tree diversity: the multi-site FORBIO experiment
Verheyen, Kris; Ceunen, Kris; Ampoorter, Evy et al

in Plant Ecology and Evolution (2013), 146(1), 26-35

Context – During the last two decades, functional biodiversity research has provided strong support for the hypothesis that more biodiverse ecosystems have the potential to deliver more and better ... [more ▼]

Context – During the last two decades, functional biodiversity research has provided strong support for the hypothesis that more biodiverse ecosystems have the potential to deliver more and better services. However, most empirical support for this hypothesis comes from simple structured communities that are relatively easy to manipulate. The impact of forest biodiversity on forest ecosystem functioning has been far less studied. Experiment design – In this paper, we present the recently established, large-scale FORBIO experiment (FORest BIOdiversity and Ecosystem Functioning), specifically designed to test the effects of tree species diversity on forest ecosystem functioning. FORBIO’s design matches with that of the few other tree diversity experiments worldwide, but at the same time, the FORBIO experiment is unique as it consists of a similar experimental set-up at three sites in Belgium (Zedelgem, Hechtel-Eksel and Gedinne) with contrasting edaphic and climatological c haracteristics. This design will help to provide answers to one of the most interesting unresolved questions in functional biodiversity research, notably whether the effects of complementarity on ecosystem functioning decrease in less stressful and more productive environments. At each site, FORBIO consists of 41 to 44 plots (127 plots in total) planted with monocultures and mixtures up to four species, selected from a pool of five site-adapted, functionally different tree species. When allocating the treatments to the plots, we maximally avoided any possible covariation between environmental factors. Monitoring of ecosystem functioning already started at the Zedelgem and Gedinne sites and will start soon in Hechtel-Eksel. Multiple processes are being measured and as the trees grow older, we plan to add even more processes. Expected results – Not only basic science, but also forest management will benefit from the results coming from the FORBIO experiment, as FORBIO is, for instance, also a test case for uncommon, not well-known tree species mixtures. To conclude, FORBIO is an important ecosystem experiment that has the potential to deliver badly needed insights into the multiple relationships between biodiversity and ecosystem functioning, which will be valuable for both science and practice. [less ▲]

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See detailEffects of tree species diversity on earthworm communities in European forests
de Wandeler, Hans; Ottoy, Sam; Hermy, Martin et al

Poster (2012, July)

The belowground food web holds a big part of the associated biodiversity in forest ecosystems and plays a major role in essential ecosystem processes, e.g. litter decomposition and nutrient turnover. So ... [more ▼]

The belowground food web holds a big part of the associated biodiversity in forest ecosystems and plays a major role in essential ecosystem processes, e.g. litter decomposition and nutrient turnover. So far, important interactions between diversity and composition of above-and belowground food webs have been observed. However the effects of tree species diversity on the belowground food web are so far not conclusive. This study aims at elucidating the effect of tree species mixtures, species diversity and trait diversity on the composition of the earthworm communities in European forests. Experimental platforms of planted tree species diversity assemblages in Finland (Satakunta) and Germany (Biotree) are therefore intensively sampled for earthworms using the combined mustard extraction/hand sorting method. First results are reported and discussed and diversity effects are evaluated with overyielding tests. [less ▲]

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See detailLitterfall quantity and quality and nutrient status in a young stand under Norway spruce and broadleaved species
Bazgir, Masoud; Carnol, Monique ULg

Poster (2012, July)

In Europe, because of previous intense forest use in the past centuries, the plantation of coniferous stands, especially Norway spruce with high production potential has been a common strategy. However ... [more ▼]

In Europe, because of previous intense forest use in the past centuries, the plantation of coniferous stands, especially Norway spruce with high production potential has been a common strategy. However, the characteristics of Norway spruce such a s susceptibility to windfall, forest dieback and soil acidification have caused negative ecological impacts at many sites. Conversion of conifers into deciduous or mixed stands has been suggested in order to improve ecological conditions and biodiversity o f forest ecosystems. In this study, six broadleaved species were planted at the same site, thus being subjected to similar condition in terms of soil type, land use history and climate. The aim of this research was to study of foliar nutrient status and nu trient return to the forest floor through litterfall 11 years after conversion of Norway spruce (Picea abie s (L.) KARST.) into a mixed stand with common alder (Alnus glutinosa (L.) GAERTN.), european beech (Fagus sylvatica L.), pedunculate oak (Quercus rob ur L.), silver birch (Betula pendula ROTH.), goat willow (Salix caprea L.) and rowan (Sorbus aucuparia L.). Our results revealed that tree species had a different foliar nutrient status and an effect on nutrient input fluxes through litterfall. For example , litter nutrient contents (N, Ca, Mg, K) were highest under alder, rowan and willow. Total litterfall and nutrient fluxes from leaf litter were highest under rowan. Our results demonstrate that, on poor sites, plantation of pioneer species, especially row an, may improve the nutrient status of the forest floor through higher input in litterfall. [less ▲]

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See detailNutrient fluxes and soil microbial processes under tree species after conversion from Norway spruce
Carnol, Monique ULg; Bazgir, Masoud

Conference (2012, July)

The biogeochemical cycling in forest ecosystems is highly dependent on the interactions between plants and soil. Tree species affect element cycling through deposition in throughfall, litter composition ... [more ▼]

The biogeochemical cycling in forest ecosystems is highly dependent on the interactions between plants and soil. Tree species affect element cycling through deposition in throughfall, litter composition, microbial activities in soil and rhizosphere processes. Species diversification has been suggested for maintaining forest ecosystem services and uniting provisioning and supporting services within multifunctional and sustainable forestry. However, most information on species impacts has been derived from studies performed at different sites, where the influence of cofactors cannot be accounted for. Here we synthesize results from a study performed 11 years after conversion of a Norway spruce stand (Picea abies (L.) KARST.) to a mixed stand composed of Norway spruce, common alder (Alnus glutinosa (L.) GAERTN.), european beech (Fagus sylvatica L.), pedunculate oak (Quercus robur L.), silver birch (Betula pendula ROTH.), goat willow (Salix caprea L.) and rowan (Sorbus aucuparia L.). As stand closure was not achieved yet, the impact of individual species could be evaluated. We measured fresh leaf element composition, element return to the soil via throughfall and litterfall (leaves, twigs, reproductive parts), forest floor chemical characteristics, microbial biomass and microbial activities (N mineralization, potential nitrification, respiration) in the forest floor under the different tree species. Our results suggested that (1) foliar element concentrations differed between species and were highest for rowan, (2) high base cation litterfall and throughfall fluxes under rowan lead to better soil quality, (3) input of acidifying cations was reduced under broadleaves, (4) potential nitrification increased under the N2 fixing alder. [less ▲]

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See detailMicroorganisms in Karsts: a case study in St Anne cave, Belgium
Carnol, Monique ULg; Willems, Luc ULg; Malchair, Sandrine ULg

Poster (2011, September 30)

Despite the importance of microorganisms as geochemical agents over geological times, their extended metabolic diversity and their essential role in element cycles (i.e. mineral dissolution, precipitation ... [more ▼]

Despite the importance of microorganisms as geochemical agents over geological times, their extended metabolic diversity and their essential role in element cycles (i.e. mineral dissolution, precipitation, oxido-reduction processes), microbial community composition and processes as well as their ecological role in karst environments are poorly known. While little was published on cave-dwelling microorganisms until the early 1990s, it is now recognized that microorganisms may mediate many important mineral transformations, originally considered to be inorganic in nature. Indeed, recent evidence (Northup & Lavoie, 2001) proved the implication of microorganisms in karstification through precipitation and dissolution processes, resulting in the deposition of carbonate speleothems, silicates, iron or manganese oxides, sulphur compounds and nitrates and in the breakdown of limestone walls. In this poster, we review some potential processes and signs of microbial activity in caves. We present results of a study on the microbial diversity in the ‘St Anne’ cave, Belgium. We focused on ammonia-oxidizing bacteria (AOB), which are responsible for the first, acidifying step of the nitrification process. Chemical composition of the water, numbers of cultivable bacteria (free and particle-associated bacteria) and the diversity of AOB were studied in waters and sediments of the ‘Chawresse’ (underground river in St Anne), on the cave wall and in the soil aboveground. The use of molecular techniques, based on direct ADN extractions, provide more detailed information on the microbial diversity of an environment, as culture-based techniques retrieve only about 1% of bacterial species present in the environment. Bacterial counts showed that most cultivable bacteria were associated with suspended particles and that their numbers decreased underground. Molecular analyses revealed the presence of AOB in the karst system. Comparison of aboveground and belowground diversity also indicated the possibility of a specific endokarst AOB community. Further research perspectives will be discussed. <br /> <br /> <br />Northup, D.E. and Lavoie, K.H. 2001. Geomicrobiology of caves: A review. Geomicrobiology Journal, 18(3):199-220. [less ▲]

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See detailMicrobiological and chemical characterisation of St Anne cave, Belgium
Carnol, Monique ULg; Malchair, Sandrine ULg

Poster (2011, September)

In Belgium, most drinking water is provided by calcareous karst aquifers. Chemical and microbiological characterisation of these systems focalises mainly on the transfer of pollutants and microbial ... [more ▼]

In Belgium, most drinking water is provided by calcareous karst aquifers. Chemical and microbiological characterisation of these systems focalises mainly on the transfer of pollutants and microbial contaminants, major sources of sanitary risks. These studies are generally based on bacterial cultures, representing however only 1% of bacterial species present in the environment. Molecular techniques allow the study of the global microbial diversity of an environment, as they are based on direct ADN extractions, without previous culturing steps. The objective of this research was the study of the microbial diversity in the ‘St Anne’ cave, Belgium. Chemical composition of the water, cultivable bacteria and the diversity of ammonia-oxydizing bacteria (AOB) were studied in waters and sediments of the ‘Chawresse’ (underground river in St Anne), on the cave’s wall and in soils aboveground. Bacterial counts revealed that most cultivable bacteria were associated with suspended particles and that their numbers decreased underground. Molecular analyses revealed the presence of AOB in the karst system. AOB are responsible for the first, acidifying step of the nitrification process. Further studies will specify and quantify their activity in this karst system. [less ▲]

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See detailEffects of long term soil organic matter restitution mode on soil heterotrophic respiration and soil biological properties.
Buysse, Pauline ULg; Carnol, Monique ULg; Malchair, Sandrine ULg et al

Poster (2011, July)

Soil heterotrophic respiration (SHR) is the process by which CO2 is released during organic matter decomposition. It is generally expected that SHR can act as a positive feedback to global warming ... [more ▼]

Soil heterotrophic respiration (SHR) is the process by which CO2 is released during organic matter decomposition. It is generally expected that SHR can act as a positive feedback to global warming, therefore leading to more CO2 release into the atmosphere. It is thus important to better understand this process. Particularly, agricultural soils may behave as important CO2 sources that are strongly influenced by soil and crop management (e.g. organic matter restitution modes, hereafter “OM-RM”). The present study aimed at determining if, after more than 50 years of application of different OM-RM, (1) significant differences of SHR fluxes can be observed between treatments, (2) SHR responses to temperature and soil moisture content can be affected by the OM-RM and (3) the experimental design is suitable to assess potential differences between treatments. The experimental field is situated in Liroux, near Gembloux in Belgium. At that site, a long term experiment with different OM-RM runs from 1959 onwards. For the present study, three contrasted treatments were considered: (1) exportation of all residues after harvest, (2) addition of manure once every three to four years and (3) restitution of residues after harvest. SHR flux measurements were carried out manually on fourteen occasions from 2 April to 30 July 2010, using a dynamic closed chamber system. Temperature and soil moisture content at 5 cm depth were also measured manually. Results showed that after more than 50 years of OM-RM application, no significant differences could be observed between the three treatments in terms of SHR fluxes and SHR responses to temperature or soil moisture, while the soil organic carbon content did vary significantly between them. The sensitivity to temperature was quite low in all treatments, with a mean Q10 value of 1,36. Besides, SHR fluxes were seen to be more responsive to increases in soil water content than to absolute soil moisture content values. Indeed, when soil moisture content increased between two consecutive measurement dates, the ratio of the corresponding SHR fluxes was larger than 1. Particularly dry conditions in 2010 may actually have caused the fluxes to be very low, making the assessment of differences between treatments more difficult. Moreover, soil dryness is likely to be responsible for the SHR flux increases after rain events, as caused by re-solubilization of organic compounds. Also, an important spatial variability was observed, which may have obscured the assessment of potential differences between treatments. Further investigations will consist in performing a new flux measurement campaign in 2011 that will take the spatial variability issue into account, and in monitoring microbial and soil properties in the different treatments, such as microbial biomass, metabolic activity and labile carbon. [less ▲]

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See detailDo we need to standardize extraction procedures for community level physiological profiling?
Carnol, Monique ULg; Bosman, Bernard ULg; Malchair, Sandrine ULg

Poster (2011, July)

Microorganisms are essential regulators of soil functioning, as they are involved in many crucial processes such as organic matter decomposition, nutrient cycling, soil structure and fertility. Currently ... [more ▼]

Microorganisms are essential regulators of soil functioning, as they are involved in many crucial processes such as organic matter decomposition, nutrient cycling, soil structure and fertility. Currently, there is a growing interest in functional diversity, such as the number and type of substrates used for energy metabolism (CLPP-community level physiological profiling). Such metabolic diversity of heterotroph soil bacteria is frequently investigated through Biolog Ecoplates, containing 31 of the most useful carbon sources for the soil community. The metabolic diversity of soil bacteria might be an interesting biological indicator of soil quality, and also a useful tool for investigating the link between land use change, climate warming, soil carbon, microbial diversity and activity. Methods related to Biolog-CLPP reported in the literature differ in the suspension medium and extraction method, the type and density of inoculums, the inoculation procedures and conditions of incubations. For example, various combinations of extraction methods and suspension media are being used for the first bacterial extraction step. Despite such methodological differences, Biolog-CLPP data are often compared across studies. The development of a standardised method for Biolog-CLPP is however essential improving the relevance and significance of results across studies. In this work, we investigated the influence of extraction procedures on microbial extraction efficiency for further use in CLPP. The microbial extraction efficiency was tested by plate counts for a total of twelve combinations of three suspension media and four extraction methods. The experiment was performed on four soils differing in organic matter content. The aims of this study were to: • Synthesize extraction procedures used for Biolog-CLPP • Measure the effect of extraction procedures on microbial extraction efficiency (plate counts) in four soil types • Investigate a possible interaction between the suspension media and the extraction method used • Evaluate whether a standardized extraction procedure can be recommended across soil types [less ▲]

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