Grazing impact on forage quality and macronutrient content of rangelands in Qilian Mountains, NW China

Abstract

An important indicator of the rangeland health, associated with land degradation, is the ability of semi-natural rangelands to provide forage of sufficient quality for livestock production. In Qilian Mountains (Gansu Province, NW China) biomass production and forage quality are dependent on the seasonality of precipitation and temperature; most of the precipitation falls during summer season, when sheep, goats and yaks graze mountain rangelands. To sustain the rangelands and to improve the management strategies, the assessment of the forage quality should be implemented. The purpose of this research was to study the response of biomass, forage quality and macronutrient content different levels of grazing intensity in Qilian rangelands. We sampled aboveground biomass in the growing seasons in 2012 and 2013 within spring/autumn or summer grazing regimes in two altitudinal zones below and above 3000 m a.s.l. (montane-subalpine and subalpine-alpine respectively). In order to estimate forage quality, biomass was sampled in 1 m × 1 m plots, assigned to the center of 10 ×10 m sites, from which we collected different indicator parameters of rangeland health. Mineral and fiber content of forage biomass was estimated under different levels of grazing intensity with regard to the growing period. It was found that an increase in grazing intensity led to a decrease in dry matter weight. No linearity was observed in the relationship between nutritive value and grazing intensity. The highest fiber content (59.20 %) was found in plots mostly disturbed by grazing. The highest protein (16.30 %) and the lowest fiber (51.30 %) contents were associated with slightly grazing intensity. Concentrations of the mineral elements, such as Zn, P, K and S varied significantly and showed maximum values under low grazing intensity.