Increasing stocking rate provoked extensive degradation of grasslands in Inner Mongolia accompanied by increased soil erosion and desertification. By now China is one of the countries facing the most serious desertification problems in the world. The total area affected by desertification is approximately 2.6 million km2, covering 27.3 % of total territory of China. Since grasslands represent one of the largest stocks for organic carbon, its degradation has a significant feedback on the biosphere-atmosphere exchange for carbon and nitrogen. Hence grassland degradation leads to volatilization and dislocation by erosion of huge amounts of C and N previously stored in this ecosystems.
The MAGIM project compares five differently managed grasslands, which of two are ungrazed since 1999 and 1979, two are moderately grazed and one is heavily grazed. At these experimental sites and in the whole catchment area, respectively, we will study amount, composition, and turnover of organic matter pools in grassland soils (P1), limitation of grassland productivity by water and nitrogen (P2), mid term effects of grazing intensity on yield formation and forage quality (P3), Impact of grazing intensity on feed intake, feed quality and performance of sheep (P4), biosphere-atmosphere exchange of N- and C-trace gas fluxes (P5), water and carbon fluxes of grasslands (P6), regional water balance and matter flow (P7), Soil stability and water balance on the plot scale (P8), wind-driven matter fluxes (P9), carbon isotope composition (P10) and Surface and satellite based remote sensing to infer rain rate (P11).
The major objectives of the MAGIM project during during the second project phase can be summarized as follows:
- Demonstrating the positive effects of moderate grazing and of an improved grazing system on the sustainability of ecosystem grassland in Inner Mongolia steppe to define optimum grazing intensity within two different grazing systems related to individual animal performance, animal production per ha, grassland production, soil conditions, and nutrient fluxes,
- Test of the transferability of results of grazing effects from Leymus chinensis to Stipa grandis steppe type,
- Development, approval and application of indicator systems for assessing ecological effects of grazing pressure,
- Regionalisation of results on effects of grazing on C, N and water fluxes from the plot to the Xilin river catchment scale by regional experiments, model development and networking,
- Scenario analysis on the site and the regional scale for various grassland management systems.
The following main hypotheses will be tested:
- Grazing intensity significantly moderates water, nitrogen and carbon balances at local and regional scale by affecting micro-aggregation, pore functions, particulate organic matter formation and abundance, water and nitrogen availability, plant growth and plant species composition as well as biosphere-atmosphere exchange processes including wind erosion,
- Grazing even changes freezing and thawing and dew formation processes by altering the thermal properties, which again have a significant effect on water fluxes and biosphere-atmosphere exchange,
- The development of an ecological indicator system allows to identify grazing situations where overgrazing may occur and where a sustainable grassland management system is practised,
- Airborne measuring platforms can be used to determine spatial distribution of soil moisture, roughness length as well as CO2 and H2O fluxes in steppe ecosystems,
- Both long-term high animal productivity as well as the conservation of the sensitive ecological grassland system can be reached when certain ecological indicators are considered by the grazing management,
- Regionalisation of C, N and water fluxes can be achieved with an integrated model framework, which is again a suitable tool for scenario analysis.
The assessment of different land-use practices on regional water, carbon, and nitrogen budget as well as on soil erosion cannot solely be realised by and rely on the interpretation of experimental data from the field trials mentioned above (plot level). Large-scale modelling approaches allow to evaluate the potential impact of different management strategies on water and nutrient budgets on the regional scale. In this, models from various scientific disciplines and scales are networked to describe the assets and drawbacks of land-use changes (P5; P6; P7; P8; P9; see below). Remote sensing techniques (P6) – allow the quantification of water and C fluxes at a landscape level and, thus, represent a reliable approach to calibrate models on a regional scale.