Soil organic carbon stock in the Belgian Ardennes as affected by afforestation and deforestation from 1868 to 2005

The effects of historical land use changes on the global C cycle have mainly been studied by means of bookkeeping models. Here, we investigate with such models the impact of afforestation and deforestation on soil organic carbon (SOC) stocks. This approach, using field-based estimates of the response of SOC upon land use changes, is applied to a pilot area in the Belgian Ardennes over one and a half century (1868–2005). After a small initial decline during the 1868–1888 period due to deforestation for agricultural use, mean SOC stocks increased steadily up to 1990, due essentially to the conversion of deciduous to coniferous forests (in the study area, deciduous forests stored less SOC than coniferous) and the reclamation of heathland, which occurred both at the turn of the 19th and 20th centuries. Simulations showed that SOC stocks decreased recently (1990–2005) because of the slow down of sequestration in coniferous forests and a reversion of some of the coniferous plantations to deciduous forests. Over the entire period, afforestation resulted in a net sequestration of carbon (0.16 t C ha⁻¹ year⁻¹). Monte Carlo simulations demonstrated that the model was highly sensitive to its inputs (initial SOC stocks for each land use) both in term of predicted SOC stocks and rates of SOC stocks change. However, the sensitivity of the model was not large enough to revert the main trends of SOC changes observed. Compared to the amount of carbon sequestered in the biomass, the contribution of soils to the C sink in forest is small. Despite several sources of errors, a detailed reconstruction of land use changes combined with realistic SOC response curves upon land use conversion are required to be able to quantify the contribution of soils to terrestrial carbon fluxes.     

Soil factors influencing the growth response of <Emphasis Type="Italic">Acacia holosericea</Emphasis> A. Cunn. ex G. Don to ectomycorrhizal inoculation

Australian acacias like Acacia holosericea are excellent candidates for the revegetation of arid zones in Africa. Their high ability to develop multiple symbioses with soil microorganisms is crucial to their rapid development in adverse climatic and edaphic conditions. These symbioses include nitrogen fixation with rhizobia, vesicular arbuscular mycorrhization and ectomycorrhization. We set up an experiment to test the growth response of A. holosericea to ectomycorrhizal inoculation in 13 different soils from Senegal. After autoclaving the soil, the experiment was conducted in a greenhouse for four weeks. Plants were inoculated with Pisolithus albus strain IR100. The following parameters were measured: plant biomass, N, P, K and Ca foliar composition, spontaneous nodulation rate, and ectomycorrhizal colonization. Data were analyzed in light of the physical, chemical and total microbial characteristics of the soil. The results demonstrated a global promoting effect of P. albus inoculation on plant (shoot and root) growth and on foliar P and K, together with a depressive effect on N, while Ca rates were barely affected. Interestingly, spontaneous nodulation with putative water- or airborne rhizobia was stimulated after P. albus inoculation. However, these nodules seemed poorly effective, as they failed to cause any change in plant growth or in foliar N composition within the nodulated and nonnodulated control plants. These results show that plant growth response to ectomycorrhizal inoculation is greatly dependent on soil characteristics, and that root ectomycorrhizal colonization is influenced by biotic factors such as soil microbiota. From a practical point of view, data from the present study demonstrate that it is possible to optimize the effect of fungi on plant growth by screening soils under nursery conditions.     

Litter decomposition can detect effects of high and moderate levels of forest disturbance on stream condition

Considerable research efforts have been devoted to determining what forest management practices most affect stream ecosystems, and how those impacts might be mitigated. Recent studies have stressed the relevance of litter decomposition to assess the conditions of headwater streams affected by riparian and upland forest harvest. Here we specifically examined whether litter decomposition can detect ecological effects of clearcutting to stream edges on headwater streams eight years after logging and if large (30 m) and narrow (10 m) riparian reserves (8-year post-harvest), and selection logging at 50% removal of basal area of riparian trees (1-year post-harvest), are effective protection measures for streams. We measured decomposition rates of red alder (Alnus rubra) leaf litter in sixteen stream reaches, including reference reaches in a 70-year-old forest. We further examined assemblages of two main litter consumer groups, shredder invertebrates in riffles and aquatic hyphomycete fungi developing on decaying alder leaves. Alder decay rate was significantly lower in clearcut reaches than in reference reaches, and we found no evidence that any alternative riparian management practices examined in this study were able to mitigate against such an effect of logging. In unlogged reaches, rapid litter decomposition (0.0050–0.0118 day⁻¹) was associated with high density and diversity of shredders (up to ten taxa). Slower litter decomposition in wide and narrow reserve reaches (0.0019–0.0054 day⁻¹) and clearcut reaches (0.0024–0.0054 day⁻¹) was attributed to lower density and richness of shredders. By contrast, the low decay rate in recently established thinned reaches (0.0031–0.0049 day⁻¹) was not associated with a numerical response of shredders. Smothering of submerged leaves by sediments may have caused the reduction in alder decay rate in thinned reaches. Across all forest treatments fungal biomass or diversity remained fairly similar. Our findings suggest that stream ecosystems are extremely sensitive to small changes in riparian and upland forest cover. We propose that litter decomposition as a key ecosystem function in streams could be incorporated into further efforts to evaluate and improve forestry best management practices.     

Fertilizing Properties of Potassium Feldspar Altered Hydrothermally

The material obtained through hydrothermal alteration of K-feldspar rock in alkaline conditions is a potential source of soluble potassium (K), but agronomic testing is needed to verify its capacity to supply K to crops. A (NH₄)₂SO₄-based bioassay was used to test the capacity of the material to supply K to tomato plants (Lycopersicon esculentum Mill.) growing in a mixture of silt loam, peat moss, and sand. Potassium chloride (KCl) and unaltered K-feldspar rock powder also were tested for comparison. The fresh weight and K composition of the plants increased as doses of KCl or hydrothermal material increased, but not with increases in K-feldspar rock. Development of stem lesions, which develop as symptoms of K deficiency in the presence of (NH₄)₂SO₄, were eliminated by KCl or hydrothermal material but not by feldspar rock. A beneficial effect may occur due to the calcium (Ca) supplied or with adjustment of soil acidity by the hydrothermal material. The hydrothermal material is a K fertilizer at least as effective as KCl since it yields the same or better plant weight.     

Detection of rotavirus in faecal specimens with a monoclonal antibody enzyme-linked immunosorbent assay: Comparison with polyclonal antibody enzyme immuno-assays and a latex agglutination test

Monoclonal antibodies have been produced against the 81/36F strain of rotavirus. One of them, was chosen as diagnostic reagent: it showed high ELISA reactivity with all the bovine, human and porcine rotavirus strains tested and reacted with VP6, structural protein product known to support the common rotavirus antigen.

A sandwich ELISA procedure using the chosen monoclonal as “capture and detecting” antibody was performed to detect rotavirus in faecal samples from experimentally inoculated newborn calves: it always gave a negative response with meconium and a positive response for the stool specimens which rotavirus have been isolated. This assay was compared with Enzygnost and Slidex Rota Kit tests and with a non-commercial sandwich ELISA test using polyclonal antibodies: it showed more sensitivity than the agglutination test and was as sensitive as the other two tests to detect rotavirus in routine diagnostic material. The test evaluated showed no equivocal results.     

Current status of medical and veterinary entomology in France: endangered discipline or promising science?

Following alarming statements (French Senate, Académie des Sciences) on the present situation concerning entomology and systematics in France, the Conseil Général Vétérinaire designated one of us (D.C.) to carry out a survey on the status of medical and veterinary entomology (MVE) with respect to research orientations and university curricula. Around 100 participants, including scientists, teachers and several directors of research and educational bodies, were interviewed and filled in questionnaires for this survey. On the basis of the results, it was concluded that the deterioration of MVE in France is associated with: (1) the hasty reorganisation of training and research in the life sciences, leading to the disappearance of several disciplines. Hence, the postgraduate DEA degree in entomology was eliminated, and even the name 'entomology' no longer appears in teaching programmes or on research contracts; (2) France's withdrawal from action research programmes in developing countries. Although these programmes were efficient in controlling outbreaks of major endemic diseases, integrated pest and vector management programmes have been replaced by basic health care ('Health for everyone in 2000') and vaccination programmes; (3) the general shift from field to laboratory research, focused mainly on molecular mechanisms. The survey results confirmed generally acknowledged trends concerning many points and highlighted several specific problems, such as the disappearance of systematics experts. Several potential solutions are proposed.