Grassland responses to grazing: effects of grazing intensity and management system in an Inner Mongolian steppe ecosystem

Abstract

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.

Effect of Grazing Exclusion on Vegetation Characteristics and Soil Organic Carbon of Leymus chinensis Grassland in Northern China

“…Among these, overgrazing is regarded as a dominant factor in causing grassland degradation [4]. Previous studies have shown that degraded grassland induced by overgrazing is characterized by reductions in vegetation coverage, biodiversity, and biomass [5,6]. Moreover, heavy grazing has resulted in soil vulnerability to water and nutrient loss while also decreasing the plant available water [7].…”

Mehlich 3 extractant used for the evaluation of wheat-available phosphorus and zinc in calcareous soils

“…The potential reason was that the continuous removal of standing biomass by livestock and the corresponding decrease in above-and belowground biomass (Schönbach et al 2011). Meanwhile, the UG and LG had more grasses and less forbs (P < 0.01) compared to MG and HG (Table 2), maybe the reason of the dominated species (grasses species of Stipa bungeana and S. grandis, etc.)…”

Effects of mowing regimes and climate variability on hay production of Leymus chinensis (Trin.) Tzvelev grassland in northern China

“…Although the cost of haymaking (128 yuan ha -1 ) is less than the value of the hay made (340 yuan ha -1 ), it is obviously more justified to leave the grassland for grazing and so save the unnecessary cost of the mowing operation. Wan et al (2011) and Schönbach et al (2011) tested a mixed land-management system in the study region in which grasslands were alternatively grazed and mowed from year to year, and suggested it was a better system than the traditional continuous grazing system. Our results support the mixed grasslandmanagement system but suggest that a more adaptive mowing strategy should be used as the basis of forage production, that is, to mow the grassland in highproduction years and graze in low-production years.…”