The major aims of this study were, firstly, to analyse the grazing-induced steppe degradation process and, secondly, to identify an efficient and sustainable grazing management system for the widely degraded Inner Mongolian typical steppe ecosystem. From 2005-2008 a grazing experiment was conducted to compare two grazing management systems, the Mixed System (MS) and the Traditional System (TS), along a gradient of seven grazing intensities, i.e. ungrazed (GI0), verylight (GI1), light (GI2), light-moderate (GI3), moderate (GI4), heavy (GI5), and very-heavy (GI6). Each grazing intensity treatment was considered a production unit comprising two adjacent plots, one for hay-making (single-cut system) and one for grazing. Hay-making and grazing alternated annually in the MS, while in the TS the same plots were used either for hay-making or for grazing. Effects of management system, grazing intensity, and year on end-of-season standing biomass (ESSB), aboveground net primary production (ANPP), relative difference in ANPP between 2005 and 2008 (ANPP Diff ), relative growth rate (RGR), and sward characteristics (litter accumulation, soil coverage) were analysed. Litter accumulation of production units was affected by grazing intensity (P<0.001) and decreased from GI0 to GI6 by 83%. Correspondingly, soil coverage decreased (P<0.001) from GI0 to GI6 by 43%, indicating an increased vulnerability to soil erosion. We found varying compensatory growth responses to grazing intensity among years, probably because of temporal variability in precipitation. The ability of plants to partially compensate for grazing damage was enhanced in years of greater seasonal precipitation. The ANPP of production units was negatively affected by grazing intensity and decreased from GI0 to GI6 by 37, 30, and 55% in 2006 (P< 0.01), 2007 (P<0.05), and 2008 (P<0.001), respectively. The effect of management system × grazing Plant Soil (2011) 340:103-115 intensity interaction on ANPP (P<0.05) and ANPP Diff (P<0.05) suggested greater grazing resilience of the MS as compared to the TS at GI3 to GI6.

Plant functional traits have been widely used to study the linkage between environmental drivers, trade-offs among different functions within a plant, and ecosystem structure and functioning. Here, the whole-plant traits, leaf morphological and physiological traits of two dominant species, Leymus chinensis (C 3 perennial rhizome grass) and Cleistogenes squarrosa (C 4 perennial bunchgrass), were studied in the Inner Mongolia grassland of China, with a grazing experiment including five stocking rates (0, 3.0, 4.5, 7.5, and 9.0 sheep/ha) in 2008 (wet year) and 2009 (dry year). Our results demonstrated that, for both species, the effects of stocking rate, year, and stocking rate×year on whole-plant traits and leaf morphological and physiological traits were highly significant in most cases. The differential responses of plant trait to variation in precipitation were caused by trait trade-offs between the wet and dry years. L. chinensis adopted the high N content and net photosynthetic rate (P n ) in the wet year but both the low N content and P n in the dry year under grazed conditions. The trait trade-offs of C. squarrosa were characterized by high specific leaf area (SLA) and P n in the dry year vs. low SLA and P n in the wet year. Our findings also indicate that C. squarrosa is more resistant to grazing than L. chinensis in terms of avoidance and tolerance traits, particularly under heavy grazing pressure and in the dry year.

who plan row crops and livestock around their grassland hectares are grassland farmers" (Barnes, 1995). Before Grassland agriculture is an important industry for livestock produc-World War II, agriculture in the USA was very diverse tion and land management throughout the world. We review the and integrated, agricultural markets were primarily loprinciples of nutrient cycling in grassland agriculture, discuss examples of grassland farming systems research, and demonstrate the usefulness cal, and nutrients were cycled mainly within farms and of whole-farm simulation for integrating economic and environmental among local farms. With the advent of mechanization, components. Comprehensive studies conducted at the Karkendamm chemical fertilizers, improved seeds, and agrichemicals, experimental farm in northern Germany and the De Marke experifarm size increased, agricultural markets became namental farm in the Netherlands have quantified nutrient flows and tional and international in scope, and nutrient cycles developed innovative strategies to reduce nutrient losses in grassland became more fragmented. Animal agriculture became farming systems. This research has focused on improving the utilizaspecialized and concentrated, relying on off-farm sources tion of manure nutrients on the farm by including grain crops in of feeds and fertilizers, which resulted in nutrient accucropping systems with grassland and by incorporating manure hanmulation on farms. dling techniques that reduce nitrogen losses. Although the information generated in experimental farms is not always directly applicable to Similar changes in farm structure occurred in northother climates and soils, it is being transferred to other regions through western Europe during the 1960s and 1970s (de Wit et computer simulation. A whole-farm model calibrated and verified al., 1987). Farms located in regions with good soils were with the experimental farm data is being used to evaluate and refine converted to crops like winter wheat (Triticum aestivum these strategies for commercial farms in other areas. Simulation of L.), oilseed rape (Brassica napus L.), potato (Solanum farms in northern Europe illustrate that on the sandy soils of this tuberosum L.), and sugarbeet (Beta vulgaris L.), whereas region, maize (Zea mays L.) silage can be used along with grasslands farms on poorer sandy soils specialized in milk producto increase farm profitability while maintaining or reducing nutrient tion with permanent grassland as the main crop. These loss to the environment. Use of cover crops, low emission barns,farms also intensified their use of purchased fertilizers covered manure storages, and direct injection of manure into soil and feed concentrates, and farm-scale nutrient budgets greatly reduces N losses from these farms, but their use creates a net cost to the producer. By integrating experimental farm data with became less balanced because of low conversion rates whole-farm simulation, more sustainable grassland production sys-of nutrients in milk and meat production...

Degradation and decreasing productivity increasingly demand sustainable grazing management practices within Inner Mongolian steppe ecosystems. This study focuses on grazing-induced degradation processes over a wide range of stocking rates and aims to identify short-term sensitive indicators and alternative management practices. Short-term effects of 2 grazing management systems (Mixed System and Traditional System) and 7 stocking rates (SR0, SR1.5, SR3, SR4.5, SR6, SR7.5, and SR9 for 0,1.5, 3, 4.5, 6, 7.5, and 9 sheep/ha, respectively) on yielding performance and herbage quality were measured on experimental plots in which moveable exclosures were used on areas chronically grazed by sheep. The experiment was conducted in a typical steppe ecosystem in Inner Mongolia, P. R. China. Results are presented for 2005 and 2006. Sampling time was the main factor affecting yield and quality. Stocking rate also showed considerable effects on yield. Herbage mass decreased linearly from SR0 to SR9, by 85% and 82% in 2005 and 2006, respectively. Herbage accumulation was also affected by stocking rate, and was highest at SR1.5 and clearly reduced at SR9. Grazing effects on relative growth rate indicated grazing tolerance of plants in the short-term, since up to high stocking rates, relative growth rates remained stable. Precipitation also determined plant responses to increasing levels of grazing. The year of higher rainfall generated higher grazing tolerance of plants and higher herbage growth than the drought year. Despite considerable reduction of herbage mass, consistent short-term responses of herbage quality to grazing in 2005 and 2006 were reflected only in terms of crude protein and acid detergent lignin. Herbage crude protein content was highest at SR7.5 and SR9, while lignin was lowest at SR7.5 and SR9. Neither productivity nor herbage quality was affected by the management system, suggesting that both systems may be applicable on typical steppe in the short-term.

While water availability determines grassland productivity in semiarid regions, nutrient availability is the main limiting factor under wet conditions. An experiment was conducted in 2008 at two sites in Inner Mongolia with histories of heavy grazing (HG) and moderate grazing (MG) to study the interactive effects of water and nitrogen on aboveand belowground net primary productivity (ANPP and BNPP), biomass partitioning, and plant species composition. The study comprises two water treatments (no irrigation and irrigated when soil water content was below 70% of the field capacity), and two nitrogen (N) levels (0 and 100 kg N ha −1 ). Mean values of ANPP at the peak biomass time reached 1,028±95 SD g m −2 at the HG site and 568±32 SD g m −2 at the MG site in irrigated and fertilized treatment. Nitrogen use efficiency (NUE) was significantly higher at irrigated plots compared to rain-fed plots at both HG and MG sites. Water use efficiency (WUEt) based on total water input and ANPP decreased with irrigation at the HG site. Meanwhile, N application significantly increased WUEt, WUEp (based on precipitation), and WUEi (based on irrigation water) at both sites. BNPP was significantly higher at irrigated plots compared to rain-fed plots at both HG and MG sites, and it tended to decrease with N addition. However, the fraction of belowground to total biomass (f BNPP = BNPP/(ANPP+BNPP) decreased with the addition of supplemental resources and exhibited a negative correlation with ANPP. Species diversity remained lower at the HG site compared to the MG site; it decreased with the addition of supplemental resources at the latter site. The annual Salsola collina contributed the most to the total biomass under irrigation. Based on global climate models, more frequent extreme climates are predicted in the future, which can result in changes in resource availabilities. Therefore, our research results have important implications for predicting the production and other properties of grassland ecosystems.