References of "Carnol, Monique"
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See detailElevated atmospheric CO2 influences ammonia oxidiser community structure and net nitrification
Carnol, Monique ULg; Malchair, Sandrine ULg

in International Symposium: Structure and Function of Soil Microbiota, Philipps-University Marburg, Germany, September 18-20, 2003 (2003)

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See detailImpacts of management strategies on nutrient fluxes in a temperate Picea abies (L. Karst) plantation
Carnol, Monique ULg

in Jansen, Jörg; Spiecker, Heinrich; von Teuffel, Konstantin (Eds.) Berichte Freiburger Forstliche Forschung, Heft 47, The question of conversion of coniferous forests, Abstracts, International Conference, 27 Septembre - 02 october, 2003, Freiburg im Breisgau, Germany (2003)

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See detailNitrosomonas europaea-like bacteria detected as the dominant beta-subclass Proteobacteria ammonia oxidisers in reference and limed acid forest soils
Carnol, Monique ULg; Kowalchuk, G. A.; De Boer, W.

in Soil Biology & Biochemistry (2002), 34

Net nitrification in intact soil cores and the community of ammonia-oxidising bacteria were studied in acid Norway spruce (Picea abies (L.) Karst) and sessile oak (Quercus petraea (Matt. Lieb.)) soils ... [more ▼]

Net nitrification in intact soil cores and the community of ammonia-oxidising bacteria were studied in acid Norway spruce (Picea abies (L.) Karst) and sessile oak (Quercus petraea (Matt. Lieb.)) soils (Haute Ardenne, east Belgium) 18 months after treatment with 5 t ha(-1) dolomite lime. Liming caused a significant increase in nitrification in the upper soil layers (0.15 m) of both stands. DGGE (denaturing gradient gel electrophoresis) profiling after P-subclass ammonia oxidiser-specific polymerase chain reaction (PCR), combined with hybridisation and sequencing of excised DGGE bands revealed a dominance of Nitrosomonas europaea-like sequences, independent of soil horizon, tree species and lime treatment. A minority Nitrosospira-like population was detected, which showed affinity to nitrosospiras previously detected in acid soil. These results contrast with several reports suggesting a dominance of Nitrosospira-like organisms among ammonia oxidiser communities in acid soils. (C) 2002 Elsevier Science Ltd. All rights reserved. [less ▲]

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See detailElevated atmospheric CO2 in open top chambers increases net nitrification and potential denitrification
Carnol, Monique ULg; Hogenboom, L.; Jach, M. E. et al

in Global Change Biology (2002), 8

The control of soil nitrogen (N) availability under elevated atmospheric CO2 is central to predicting changes in ecosystem carbon (C) storage and primary productivity. The effects of elevated CO2 on ... [more ▼]

The control of soil nitrogen (N) availability under elevated atmospheric CO2 is central to predicting changes in ecosystem carbon (C) storage and primary productivity. The effects of elevated CO2 on belowground processes have so far attracted limited research and they are assumed to be controlled by indirect effects through changes in plant physiology and chemistry. In this study, we investigated the effects of a 4-year exposure to elevated CO2 (ambient + 400 mumol mol(-1) ) in open top chambers under Scots pine (Pinus sylvestris L) seedlings on soil microbial processes of nitrification and denitrification. Potential denitrification (DP) and potential N-2 O emissions were significantly higher in soils from the elevated CO2 treatment, probably regulated indirectly by the changes in soil conditions (increased pH, C availability and NO3 (-) production). Net N mineralization was mainly accounted for by nitrate production. Nitrate production was significantly larger for soil from the elevated CO2 treatment in the field when incubated in the laboratory under elevated CO2 (increase of 100%), but there was no effect when incubated under ambient CO2 . Net nitrate production of the soil originating from the ambient CO2 treatment in the field was not influenced by laboratory incubation conditions. These results indicate that a direct effect of elevated atmospheric CO2 on soil microbial processes might take place. We hypothesize that physiological adaptation or selection of nitrifiers could occur under elevated CO2 through higher soil CO2 concentrations. Alternatively, lower microbial NH4 assimilation under elevated CO2 might explain the higher net nitrification. We conclude that elevated atmospheric CO2 has a major direct effect on the soil microbial processes of nitrification and denitrification despite generally higher soil CO2 concentrations compared to atmospheric concentrations. [less ▲]

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See detailEffects of liming on forest soil algal communities
Kostinov, I.; Carnol, Monique ULg; Dulière, J.-F. et al

in Algological Studies (2001), 102

The effects of the application of dolomite lime (5 t ha-1) on soil algal communities were investigated in sessile oak (Quercus petraea (MATT.) LIEB.) and Norway spruce (Picea abies (L.) KARST.) plots ... [more ▼]

The effects of the application of dolomite lime (5 t ha-1) on soil algal communities were investigated in sessile oak (Quercus petraea (MATT.) LIEB.) and Norway spruce (Picea abies (L.) KARST.) plots situated in the Belgian Ardenne. Chlorophyta (60 taxa) were by far the most diverse group, followed by Xanthophyceae (10 taxa), Bacillariophyceae (3 taxa), Cyanophyceae (2 taxa) and Euglenophyceae (1 taxon). In both forest types, liming lead to a significant increase in soil pH, exchangeable magnesium and calcium. In the limed Quercus plots available phosphorus and soil solution nitrate concentrations were also increased. The soil algal diversity was similar in oak and spruce control plots and in limed spruce plots. However, in the limed oak plots a significantly higher algal diversity was observed. On the basis of a CCA analysis, three clusters of plots could be distinguished: a) Picea control plots, b) limed Picea and control Quercus plots, c) limed Quercus plots. Both soil pH and nutrient availability seem to be important in determining algal species composition in these forest soils. [less ▲]

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See detailElement removal in harvested tree biomass: scenarios for critical loads in Wallonia, south Belgium
Bosman, Bernard ULg; Remacle, Jean; Carnol, Monique ULg

in Water, Air & Soil Pollution : Focus (2001), 1

The critical load concept is now widely used as a tool for developing emission control policies in Europe. As a signatory country of the Convention of Long-Range Transboundary Air Pollution, critical ... [more ▼]

The critical load concept is now widely used as a tool for developing emission control policies in Europe. As a signatory country of the Convention of Long-Range Transboundary Air Pollution, critical loads for acidity, nutrient nitrogen, nitrogen and sulphur have been calculated for the Flemish and Walloon regions in Belgium. This paper describes the methodology used for estimating critical loads for forest soils in the Walloon region according to the Steady-State Mass Balance equations. As an example the methodology was applied to the catchment `Waroneu', situated in a sensitive area of the Haute Ardenne. Main input parameters to the equations were derived from precipitation and runoff data of the catchment study. Improved estimates of nitrogen uptake (Nu) and base cation uptake (BCu) were obtained by intensive sampling of Picea abies and Quercus robur trees. Nutrient contents (Ca, Mg, K, N) and nutrient to nitrogen ratios of Picea abies reflected the poor soil quality at a site with high N deposition. Quercus robur nutrient contents increased from stem to higher order branches with a high proportion of nutrients located in the bark. However the simulation of stem only harvesting had a minor effect on critical loads. Measured wood densities were lower than reported literature values with a main effect on Nu and BCu estimates. The use of recommended default values and/or data derived from the experimental site resulted in a wide range of critical loads, some of which were largely overestimated. Results demonstrated the importance of site specific data for critical load calculations. [less ▲]

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See detail'Dolomite lime effects on acid forest soils: traditional and molecular approaches
Carnol, Monique ULg

Conference (2000, November)

The study of biogeochemical processes in soil has long been restricted by the techniques available for investigating the micro-organisms concerned. In particular, isolated nitrifying bacteria are not ... [more ▼]

The study of biogeochemical processes in soil has long been restricted by the techniques available for investigating the micro-organisms concerned. In particular, isolated nitrifying bacteria are not active in culture media below pH 5.5-6.0, and it is not clear to what extent these strains, if at all, are active in the acid soils of temperate forests. Since DNA/RNA based microbiological techniques do not require isolation of bacterial strains, they provide a new, powerful approach to gain insight into the nitrification process. We therefore combined the use of a large scale field experiment and laboratory soil incubations with molecular analysis of the nitrifying bacterial community to investigate the effect of dolomite lime on the nitrification process in the soil of the Belgian Ardenne. In this area, soils are naturally poor in magnesium and liming at moderate doses has been suggested to alleviate soil acidification and nutritional deficiencies. However, possible side effects needed to be evaluated, in particular on the nitrification process. As nitrification may be linked to soil acidification, cation leaching, aluminium mobilisation and N2O emission, increased knowledge is essential when evaluating effects of global environmental change and management strategies on forest ecosystems. The effects of dolomite lime (3-5 T/ha) were investigated at the watershed (80 ha, mainly Picea abies), plot (Quercus petraea and Picea abies stands) and laboratory level. Runoff chemistry, soil solution, net nitrate production in the laboratory and the community structure of ammonium oxidising bacteria (by PCR amplification of 16S-RNA genes, Denaturing Gradient Gel Electrophoresis - DGGE, sequence analysis and hybridisation) were analysed. In the watersheds, consequences on runoff water chemistry were minor. However, in the plot study, soil solution nitrate concentrations were significantly increased through liming in the Quercus plots. Increased net nitrification in the Quercus stand was confirmed by potential net nitrification measurements in the laboratory, whereas soil pH rose in both stands. The impact of liming on potential net nitrification was not related to a shift in the 16S rDNA DGGE community profile of ammonia-oxidising bacteria. The DDGE profile, combined with hybridisation and sequencing of cut out bands revealed a dominance of Nitrosomonas europea-like sequences and a minor presence of Nitrosospira cluster 2-like sequences. These results contrast with several reports suggesting a dominance of Nitrosospira-like organisms among ammonia oxidiser communities in acid soils. Our study reflects the great potential of combining new molecular techniques with conventional methods for improving our knowledge on the ecology of biogeochemical processes. [less ▲]

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See detailEffects of dolomite lime and clearcut on nitrate leaching from acid forest soils
Carnol, Monique ULg

Conference (1999, May)

Forest liming has received increased attention since the 1980s, when unusual needle yellowing and fall were observed in large parts of Europe and North America. This ‘new forest decline’ has been ... [more ▼]

Forest liming has received increased attention since the 1980s, when unusual needle yellowing and fall were observed in large parts of Europe and North America. This ‘new forest decline’ has been attributed to several causes acting individually or in synergy, amongst which were 'acid rain', nitrogen saturation and nutritional imbalances. Liming at moderate doses was suggested as a counteracting measure against soil acidification and to remove nutritional deficiencies. Another major forest management operation is whole tree harvesting. Both liming and clearcut may however affect the water quality leaving the treated areas. In particular, nitrate leaching is of major concern, as nitrate leaching may be linked to soil acidification, associated cation and/or aluminium release, and nitrate contamination of surface and groundwater. In this paper, I summarise main results of studies performed in the Belgian Ardennes. In this area, the acid brown soils are naturally poor in magnesium and the observed forest dieback symptoms were supposed to be the consequence of increased pollution exacerbating magnesium deficiency. Liming was suggested for prevention and correction. However, possible side effects, in particular on soil solution and stream water chemistry needed to be evaluated. Another major concern was the effects of clearcut operations on the streamwater quality in this area important for drinking water collection. The effects of dolomite lime were investigated at the watershed, plot and laboratory level. Paired watersheds of approximately 80 ha were mainly covered with Picea abies. One watershed of each pair was limed with 3 T/ha of fine ground dolomite and 200 kg/ha K2SO4. Runoff chemistry was analysed for major cations and anions and time series intervention analysis was used to detect statistically significant changes in stream water chemistry. Results showed increased magnesium concentrations immediately after liming, but a major part of the lime was retained by the soil system, and consequences on water chemistry were minor. However, in the plot study, where 5 T ha-1 of a dolomite lime suspension were applied to adjacent Quercus petraea and Picea abies stands, soil solution nitrate concentrations were significantly increased through liming in the Quercus plots. Increased net nitrification in the Quercus stand was confirmed by potential net nitrification measurements in the laboratory. The effects of tree harvesting on streamwater ion concentrations were investigated by clear felling 22 ha (9650 m3 wood) of a 81 ha watershed. This area represented one third of the forested area, the remaining area being covered equally with young plantations and 70-100 year old Picea abies. First data indicate increased potassium, iron, lead and organic carbon concentrations, but no major change in streamwater nitrate concentrations. Results will be discussed in relation to literature data and known controlling factors of the nitrification process. This analysis reveals that the speed, extent and duration of a perturbation in nitrate leaching after liming or felling vary at different sites. Risks assessment for nitrate leaching is therefore difficult and prediction of nitrate leaching in response to a perturbation remains an important challenge for further studies. In particular, basic controls of the nitrification process and relation nitrification/immobilisation need further investigation. [less ▲]

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See detailImpact of dolomite lime on the ground vegetation and on potential net N transformations in Norway spruce (Picea Abies (L.) Karst.) and sessile oak (Quercus Petraea (Matt.) Lieb.) stands in the Belgian Ardenne
Duliere, J.-F.; Carnol, Monique ULg; Dalem, S. et al

in Annals of Forest Science : a Multidisciplinary and International Journal (1999), 56

The impact of dolomite lime (5 T·ha-1) on the ground vegetation and on potential net nitrogen (N) transformations was investigated in two Belgian forest ecosystems. Norway spruce (Picea abies (L.) Karst ... [more ▼]

The impact of dolomite lime (5 T·ha-1) on the ground vegetation and on potential net nitrogen (N) transformations was investigated in two Belgian forest ecosystems. Norway spruce (Picea abies (L.) Karst.) and sessile oak (Quercus petraea (Matt.) Lieb.) stands were situated in the Haute Ardenne (east Belgium) on acid-brown soil. The herb-layer floristic richness increased during the 2 years following liming, with the appearance of light and N-demanding species, which are also found in clear-cut areas or on road verges. Mosses reacted rapidly, showing a decrease acidophilous-dominant species and the establishment of some ruderal species. Six months after liming, the pH was significantly increased in the organic horizon of both stands and in the organomineral horizon of the oak stand. Soils originating from the two stands showed distinct responses in net NO3- production to the dolomite lime treatment. In the organic layer of the Quercus soil, net NH4+ production was decreased, NO3- production increased, and total N mineralisation remained unchanged. In the organomineral layer, NO3 - production was increased. In the Picea soil, NO3 - production was decreased in the organomineral soil layer. These results indicate the possibility of differences in the control of the N transformation processes occurring in the two sites. [less ▲]

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See detailAbiotic factors controlling nitrification in acid forest soils
Carnol, Monique ULg

in Rastin, N.; Bauhus (Eds.) Going underground - Ecological studies in forest soils (1999)

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See detailImpacts of (NH4)2SO4 deposition on Norway spruce (Picea abies [L.] Karst) roots
Carnol, Monique ULg; Cudlin, Pavel; Ineson, Phil

in Water, Air & Soil Pollution (1999), 116

The effects of enhanced (NH4)(2)SO4 (NS) deposition on Norway spruce (Picea abies [L.] Karst) fine root biomass, vitality and chemistry were investigated using root-free in-growth cores reproducing native ... [more ▼]

The effects of enhanced (NH4)(2)SO4 (NS) deposition on Norway spruce (Picea abies [L.] Karst) fine root biomass, vitality and chemistry were investigated using root-free in-growth cores reproducing native organic and mineral soil horizons. The cores were covered and watered every 2 weeks with native throughfall or throughfall supplemented with NS to increase deposition by 75 kg ha(-1) a(-1) NH4+-N (86 kg ha(-1) a(-1) SO42--S). The in-growth cores were sampled after 19 months and assessed for root biomass, necromass, length, tip number, tip vitality and fine root chemistry. Root biomass and fine root aluminium (Al) concentration were negatively correlated, but NS deposition had no effect on root growth or root tip vitality. NS deposition caused increased fine root nitrogen (N) concentrations in the organic horizon and increased Calcium (Ca) concentrations in the mineral horizon. Fine root biomass was higher in the organic horizon, where fine root Al and potassium (K) concentrations were lower and Ca concentrations higher than in the mineral horizon. Results highlighted the importance of soil stratification on fine root growth and chemical composition. [less ▲]

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See detailEnvironmental factors controlling NO3- leaching, N2O emissions and numbers of NH4+ oxidisers in a coniferous forest soil
Carnol, Monique ULg; Ineson, Phil

in Soil Biology & Biochemistry (1999), 31

Main and interactive effects of temperature, throughfall volume and NH4+ deposition on soil solution NO3- concentrations, N2O emissions and numbers of NH4+ oxidisers were investigated in a controlled ... [more ▼]

Main and interactive effects of temperature, throughfall volume and NH4+ deposition on soil solution NO3- concentrations, N2O emissions and numbers of NH4+ oxidisers were investigated in a controlled laboratory experiment. Large intact soil cores from a Picea abies (L.) Karat. stand were incubated according to an 'incomplete factorial design' at 4, 12 or 20 degrees C and watered every 2 weeks with 300, 500 or 700 ml (442, 737 and 1032 mm yr(-1)) of a natural throughfall solution enriched with 0, 37.5 or 75 kg NH4+-N ha(-1) yr(-1). Watering and sampling were performed every 2 weeks, during a 112 d period. At d 112, a temperature optimum for NO3--N concentrations in the leachate, NO3--N fluxes and numbers of NH4+ oxidisers in the mineral soil layer was determined at ca. 11 degrees C. NO3--N concentrations also decreased with throughfall volume, towards a minimum at 590 ml, with temperature however contributing most to modelling NO3--N concentrations and the two factors acting independently. The model explained 59% of the variability in the data, and the regression between observed and predicted concentrations was highly significant (P < 0.0001, r(2) = 0.93). NO3--N fluxes increased quadratically with throughfall volume, and throughfall volume and NH4+ deposition interacted significantly in determining the numbers of NH4+ oxidisers in the mineral soil layer. Numbers of NH4+ oxidisers were higher in the humus layer and decreased with increasing temperatures. N2O fluxes increased quadratically with temperature, and the linear and quadratic effects of throughfall volume (maximum at 500 ml). Results suggest that optimum temperatures for net nitrification may have been overestimated in previous studies by the use of disturbed soils. [less ▲]

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See detailImpacts of (NH4)2SO4 deposition on Norway spruce (Picea abies [L.] Karst) and Scots pine (Pinus sylvestris L.) fine roots
Carnol, Monique ULg; Zoomer, Rik; Berg, Matty et al

Conference (1998, September)

The increased inorganic nitrogen (N) deposition in the last decades has become a major concern for the health of forests. In forest ecosystem, where N might no longer be limiting to primary production ... [more ▼]

The increased inorganic nitrogen (N) deposition in the last decades has become a major concern for the health of forests. In forest ecosystem, where N might no longer be limiting to primary production, the excess N is thought to be related to forest decline and a concept of ‘N saturation ‘ has been developed. In particular, N, in the form of NH4, in excess to plant and microbial demands could lead to soil acidification if nitrified in the soil and leached, causing loss of base cations or mobilisation of phytotoxic aluminium. As part of the CORE project (CEC), investigating nutrient dynamics in European coniferous forest soils, we studied the effects of continuously increased (NH4)2SO4 deposition and soil characteristics on Norway spruce (Picea abies [L.] Karst) and Scots pine (Pinus sylvestris L.) fine root biomass, vitality and chemistry with an ingrowth core technique. The same experiment was performed in a Norway spruce stand on clay soil (Grizedale, UK) and a Scots pine stand on sandy soil (Wekerom, NL), using soil from each of the two sites. Root-free ingrowth cores reproduced organic and mineral soil horizons to 15 cm depth. They were covered to exclude native throughfall and watered every 2 weeks with throughfall or throughfall with (NH4)2SO4 added to increase deposition by 75 kg ha-1 a-1 NH4+-N. The ingrowth cores were sampled after 19 months, divided into layers, roots washed and analysed for biomass, necromass, root length, root tip number (RTN), root tip vitality and fine root chemistry. A previous field experiment had shown high soil solution Al concentrations at both sites, and an increase in NO3- and Al concentrations in response to increased (NH4)2SO4 deposition at the Grizedale site. The effects of high (NH4)2SO4 deposition depended on tree species, soil type and soil horizon. For Norway spruce, (NH4)2SO4 deposition did not result in any significant changes in root growth or vitality when growing into the native clay soil. However, when growing into the sandy soil, RTN and the proportion of dead roots were increased by N deposition. Norway spruce fine root N content was also increased in the organic horizon of both soil types. For Scots pine, (NH4)2SO4 treatment caused increased fine root Al content and a decreased Mg/Al ratio in the mineral layer of the sandy soil, with opposite effects in the clay soil. This (NH4)2SO4 treatment effect in the sandy soil for Scots pine was the only indication of a potential adverse effect of (NH4)2SO4 deposition on fine roots. Further results demonstrated the dominant importance of inherent soil characteristics and the stratification into soil horizons on fine root growth and chemical composition. For example, a negative correlation between root biomass and fine root Al content was established for Norway spruce. [less ▲]

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See detailAmendement de bassins versants dans les Ardennes belges: effets sur l'eau de percolation et l'eau à l'exutoire
Carnol, Monique ULg; Piret, André ULg; Requier, Marie-Christine ULg et al

in Santé et Biodiversité en Forêt Wallonne - Acte des Colloques (1998)

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See detailComparaison des peuplements de diatomées épilithiques de ruisseaux acides en milieu forestier soumis à un amendement de dolomie (Massif Ardennais, Belgique)
Loncin, Anne; Leclercq, Louis ULg; Carnol, Monique ULg et al

in Annales de Limnologie (1998), 34(1), 13-22

Three to five years following application of dolomite (calcium magnesium carbonate) on some forest catchments in the belgian area of the Ardenne, epilithic diatoms were sampled in two streams running on ... [more ▼]

Three to five years following application of dolomite (calcium magnesium carbonate) on some forest catchments in the belgian area of the Ardenne, epilithic diatoms were sampled in two streams running on treated sites and in two streams running on untreated sites in order to evaluate the possible changes in the algal population. Typical acid water assemblages with Eunotia were observed. The dominant species was Eunotia exigua often found with E. rhomboidea or E. bilunaris. In the present study, no influence of the treatment can be demonstrated using these bioindicators. [less ▲]

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See detailAmendements de bassins versants dans les Ardennes belges : effets sur l’eau de percolation et l’eau à l’exutoire
Carnol, Monique ULg

Conference given outside the academic context (1997)

Alors que des essais d’amendements en forêt se sont révélés peu rentables, un nouvel intérêt s’est manifesté pour ce type de traitement dans les années 1980, après les observations de jaunissement et de ... [more ▼]

Alors que des essais d’amendements en forêt se sont révélés peu rentables, un nouvel intérêt s’est manifesté pour ce type de traitement dans les années 1980, après les observations de jaunissement et de chutes d’aiguilles inhabituelles, notamment chez l’épicéa. Les causes de ce ‘nouveau dépérissement forestier’, parmi lesquelles citons, l’acidification des sols, la saturation de l’écosystème en azote et les déséquilibres nutritionnels, sont supposées agir de manière synergique. Les forêts ardennaises n’ont pas été épargnées par ce phénomène, et des symptômes de dépérissement forestier ont été rapportés en 1983 par Weissen (Weissen et al., 1983). Ce dépérissement serait dû à une augmentation de la pollution atmosphérique exacerbant la déficience en magnésium des arbres, qui se développent sur les sols ardennais naturellement pauvres en magnésium (Weissen et al., 1990). L’amendement a donc été conseillé comme mesure de protection et de correction de l’acidification des sols et des déséquilibres nutritionnels chez les arbres. Cependant, des effets secondaires potentiels, en particulier sur l’eau à l’exutoire (nappes et eau potable) et sur la solution du sol (nutrition des arbres) doivent être évalués. Dans cette présentation, je résumerai les résultats d’une étude poursuivie dans 4 bassins versants boisés, en majorité, par l’épicéa commun (Picea abies [L.] Karst.). Les deux couples de bassins versants d’une taille d’environ 80 ha sont situées à la Croix Scaille (commune de Gedinne) et dans l’Hertogenwald (Hautes Fagnes), sur sol brun acide. Un bassin versant de chaque couple a été amendé par 3 T/ha de dolomie ((Ca, Mg)CO3 55/40) et de 200 kg/ha de K2SO4 en 1992 et 1993, respectivement. La pluie à découvert, les pluviolessivats (pluie interceptée par les arbres) et la solution du sol ont été analysés mensuellement, l’eau à l’exutoire toutes les 2 semaines. L’analyse en séries temporelles a été utilisée pour détecter des changements significatifs qui surviendraient dans les concentrations en éléments minéraux dans l’eau à l’exutoire et qui seraient dus à l’amendement. Par ailleurs, les flux entrants et sortants du bassin versant ont été calculés de manière à établir le bilan entrée-sortie des éléments dans la forêt et ainsi pouvoir évaluer les pertes de l’amendement vers le ruisseau. Dans le bassin des Hautes Fagnes, la dissolution de la dolomie a influencé de manière significative les concentrations à l’exutoire. Les concentrations en magnésium ont augmenté immédiatement après l’amendement (Fig. 1), probablement à cause de l’écoulement de l’eau de pluie dans les couches supérieures du sol. Quatre années après le traitement, elles restent toujours supérieures aux concentrations observées avant l’amendement. Néanmoins, les quantités de magnésium perdues à l’exutoire sont faibles par rapport aux doses apportées par l’amendement. Dans les 2 bassins amendés, les concentrations du calcium et des autres cations et anions majeurs de la solution du sol n’ont pas été influencées significativement par le traitement. Les concentrations en magnésium dans la solution du sol ont augmenté immédiatement et un an après l’amendement respectivement à environ 5 et 15 cm de profondeur. Les concentrations en calcium dans la solution du sol ont augmenté 3 ans après l’amendement. Ces résultats indiquent que, pour les sols étudiées et la dose d’amendement apportée, une grande partie de l’amendement est retenue dans les sols, et que, jusqu’à présent, les conséquences pour l’eau à l’exutoire sont peu importantes. En effet, seule la concentration en magnésium a augmenté de manière significative alors qu’aucun changement significatif n’a été détecté, jusqu'à présent, dans les teneurs en nitrates (Fig. 2) et en métaux lourds (Cd, Pb, Zn). On peut donc conclure que, sur base de nos analyses et dans la situation actuelle, l’eau de l’exutoire qui alimente le barrage-réservoir de la Gileppe n’a pas subi de modifications importantes à la suite de l’amendement. Il faut cependant souligner que la dissolution de l’amendement peut être lente dans les sols acides, et que des effets ‘à retardement’ sont possibles. De plus, une étude récente, comparant, « in situ », l’effet d’un amendement sur la solution du sol d’une chênaie et d’une pessière de même âge a montré une augmentation de la concentration en nitrates dans la solution de sol de la chênaie. Il faut donc rester prudent lors de l’extrapolation de ces résultats vers d’autres sites. Figure 1. Influence d’un amendement dolomitique (3 T/ha) sur les concentrations en magnésium à l’exutoire d’un bassin versant. Figure 2. Influence d’un amendement dolomitique (3 T/ha) sur les concentrations en nitrate à l’exutoire d’un bassin versant. Références Weissen, F., Letocart, H. & Van Praag, H.J., Bull. Soc. Roy. Bot. Belg. 2, 1-13 (1983) Weissen, F., Hambuckers, A., Van Praag, H.J. and Remacle, J., Plant Soil 128, 59-66 (1990). [less ▲]

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