[en] The aim of the program was to determine if a modification of the forests management, can generate consequences on the soil carbon storage and reduce the carbon sinks function of the forestry. It aims also to prepare (by data providing) the validation of forestry parameters of the evolution model of carbonaceous soils reserves. Three impact type were considered: the trees age, the effect or fertilizer-enrichment and the effect of the forest treatment. (A.L.B.)

[en] The biogeochemical cycle of elements has been established in a spruce stand in the French Ardennes on a site with a poor acidic soil and a large input of nitrogen and sulphate from the atmosphere. This paper shows the interest of studying the seasonal N cycle instead of the global annual cycle, because part of the N input seems to be immobilized in the soil during the dormant season and is released afterwards and taken up during the growing season, and because of the important participation of N inputs in the N-uptake by trees during the growing season. The very large amount of NO₃-N leached towards the water table level should be reduced. Using the seasonal cycles, the relationship is discussed between the desirable reduction in the NO₃-N output and the N (NH₄-N + NO₃-N) input. A fertilization trial, including N and Ca, shows a decrease in the wood production after N fertilization. These models give us the opportunity to calculate the reduction of wood production in relation to the reduction of the N input in the ecosystem. 23 refs., 5 figs., 5 tabs

[en] Highlights: • Chronic toxicity of Pb varied 4-fold among three algae species. • The use of an organic P avoided Pb precipitation in the experiments. • pH and Dissolved Organic Carbon strongly affect Pb toxicity, Ca and Mg do not. • A bioavailability model was developed that accurately predicts toxicity. • Algae may become the most sensitive species to Pb above pH 7.4. - Abstract: Scientifically sound risk assessment and derivation of environmental quality standards for lead (Pb) in the freshwater environment are hampered by insufficient data on chronic toxicity and bioavailability to unicellular green algae. Here, we first performed comparative chronic (72-h) toxicity tests with three algal species in medium at pH 6, containing 4 mg fulvic acid (FA)/L and containing organic phosphorous (P), i.e. glycerol-2-phosphate, instead of PO_4"3"− to prevent lead-phosphate mineral precipitation. Pseudokirchneriella subcapitata was 4-fold more sensitive to Pb than Chlorella kesslerii, with Chlamydomonas reinhardtii in the middle. The influence of medium physico-chemistry was therefore investigated in detail with P. subcapitata. In synthetic test media, higher concentrations of fulvic acid or lower pH protected against toxicity of (filtered) Pb to P. subcapitata, while effects of increased Ca or Mg on Pb toxicity were less clear. When toxicity was expressed on a free Pb"2"+ ion activity basis, a log-linear, 260-fold increase of toxicity was observed between pH 6.0 and 7.6. Effects of fulvic acid were calculated to be much more limited (1.9-fold) and were probably even non-existent (depending on the affinity constant for Pb binding to fulvic acid that was used for calculating speciation). A relatively simple bioavailability model, consisting of a log-linear pH effect on Pb"2"+ ion toxicity linked to the geochemical speciation model Visual Minteq (with the default NICA-Donnan description of metal and proton binding to fulvic acid), provided relatively accurate toxicity predictions. While toxicity of (filtered) Pb varied 13.7-fold across 14 different test media (including four Pb-spiked natural waters) with widely varying physico-chemistry (72h-EC50s between 26.6 and 364 μg/L), this bioavailability model displayed mean and maximum prediction errors of only 1.4 and 2.2-fold, respectively, thus indicating the potential usefulness of this bioavailability model to reduce uncertainty in site-specific risk assessment. A model-based comparison with other species indicated that the sensitivity difference between P. subcapitata and two of the most chronically Pb-sensitive aquatic invertebrates (the crustacean Ceriodaphnia dubia and the snail Lymnaea stagnalis) is strongly pH dependent, with P. subcapitata becoming the most sensitive of the three at pH > 7.4. This indicates that inter-species differences in Pb bioavailability relationships should be accounted for in risk assessment and in the derivation of water quality criteria or environmental quality standards for Pb. The chronic toxicity data with three algae species and the bioavailability model presented here will help to provide a stronger scientific basis for evaluating ecological effects of Pb in the freshwater environment

[en] Forests contain most of the carbon stored in the earth's biomass (81 %) and could play a role in CO₂ mitigation to a certain extent. We estimate French forest carbon stocks in biomass to be 860 MtC on 14.5 million hectares of forests, and 1,140 MtC in forest soils. Total carbon in the 14.5 million hectares of French forests is estimated at 2,000 MtC. Average annual flux for the 1979/91 period is 10.5 MtC/y, i.e. 10 % of national fossil fuel emissions. The main causes of this net carbon uptake are the rapid increase of forest area, increasing productivity due to environmental changes, ageing or, in some localized areas, more intensive silviculture practices. These carbon sinks are not offset by the harvesting level which remains low on average (61 % of the annual volume growth). Forestry carbon mitigation options applicable in France are discussed. The need for global economic and ecological budgets (including carbon stocks, soil fertility and biodiversity) of the possible alternatives is stressed. (authors)

[en] This research aimed at determining whether forest ecosystems could store more carbon, which forestry can promote such a storage dynamics, and whether storage effects are sustainable. This lead to the development of a carbon model to assess the evolution of carbon storages under human and climatic constraints, and thus to model the building up of the organic storage. The authors report the study of the stand age effect, of the amendment/fertility effect, and of the effect of the silviculture process on carbon and soil nitrogen stock variations. Another report, related to the programme on the management and impacts of climate change, addresses the effects of forestry on the carbon storage in forest soils, and more particularly the validation of the parameters of the carbon stock evolution model. It provides data on the impact of silviculture management changes to support the validation of the model, and thus proposes an alternative presentation of issues addressed in the first report.

[en] Global environmental and climate conditions fluctuate on all kind of spatio-temporal scales. Some fluctuations or change/trends are not only anthropogenic, but have different regional and national signatures. While the frequency of extreme events on smaller scales is changing, the public sector and general opinion become more and more aware and concerned of local impacts from global environmental and climate changes. Indeed, negative effects and feedbacks, might occur on ecosystems, natural resources, buildings and grounds, superstructures, economies, food security, public health. This is how, during 1999, a concerted French initiative led to the research program 'Management and Impacts of Climate Change' (GICC). GICC is essentially managed by the Ministry of Ecology and Sustainable Development in close collaboration with the Inter-Ministerial Mission on Greenhouse Effect (MIES). GICC started in 1999. Its first phase (1999-2006) included four calls for proposal (1999, 2000, 2001, and 2002). In parallel and in 2003-2004, the MIES has been developing the so-called 'Climate Plan' based upon three principles : Insure that France follows agreements from the 'Kyoto Protocol'; Participate in ways and means leading to reduction of greenhouse gases by 75% in 2050; Allow for reduction of pollution from transportation means. Input from GICC Phase One final reports are contributing to 'Climate Plan'. The eight themes proposed by GICC-1 (1999-2002) are as follows: Theme 1: Evolution scenarios of the average and extreme features of the 21. Century climate; Theme 2: Interactions between climate, economy and society; related timescales; Theme 3: Role of carbon forest uptake and agricultural practices on climate policies; Theme 4: Links between national and international activities; Theme 5: Towards new inventories of GHG and aerosols (direct and indirect) emissions; Theme 6: Impacts on terrestrial biosphere; Theme 7: Impacts on hydro-systems; Theme 8: Impacts on public health. A symposium presenting the available results of the GICC first phase has taken place in MEDD, Paris, November 23-24, 2004. A final presentation workshop of the first phase took place in Paris, on May 11-12, 2006. This document is the proceedings of this scientific restitution seminar. It is organized in 9 sessions which follow the 8 themes listed above plus a round table for the status and perspectives of the GICC program. (J.S.)