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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.

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.

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The positive relationship between fecal CP concentration and diet OM digestibility in cattle, which is based on increasing undigested microbial CP and decreasing fecal OM as OM digestibility increases, may be used as an indirect method for estimating diet OM digestibility from fecal CP concentration. Results of digestibility trials (445 individual observations) conducted at Hohenheim and Braunschweig, Germany, and at Gumpenstein, Austria, were used to study the relationship between CP concentration in feces (x, g/kg OM) and OM digestibility (y, %). The best fit was obtained with the curvilinear relationship y = ai -107.7e(-0.01515 x x), with a1 = 79.76 and a2 = 72.86 (R2 = 0.82; residual SD = 2.7; SE = 0.13), which takes into account the effects of location (i = 1 for Braunschweig and Hohenheim, and i = 2 for Gumpenstein). Dietary CP and crude fat concentration, and DMI had no effect on fecal CP content, whereas crude fiber content, proportion of concentrate in the diet, and forage type significantly affected CP concentration in feces; however, the magnitude of these effects was less than 2 percentage units, and the direction of the effect of proportion of concentrate in the diet was not uniform. The curvilinear relationship between fecal CP concentration (observed range, 100 to 300 g/kg of OM) and diet OM digestibility (observed range = 57 to 80%) may be used to estimate diet OM digestibility, particularly for field trials, as it requires no feed samples and does not physically restrict the animal.