Predicted effects of simulated ambient warming and moisture on forage nutrient quality and community composition in Mongolian an arid grassland

Sustainable forage and livestock production in grazed grasslands are threatened by global climatic change. In this study, we examined how forage quality at the species and community levels in Mongolian drylands might be affected by warming and additional moisture. Four different treatments, a control, open-top chambers (OTCs) only, OTCs with heaters, and OTCs with additional watering, were set up in the field, and air and soil temperature and soil moisture were monitored. A vegetation survey was conducted and plants were harvested during summer, 1 and 2 years after experimental treatments were established. The harvested plant samples were separated into a dominant species (Stipa) or 'other species', and analysed to determine acid detergent fibre (ADF) and in vitro dry-matter digestibility (IVDMD). ADF was measured with the detergent method and the digestibility with the pepsin-cellulase assay. Overall, the warming treatments alone (OTC and OTC with heater) increased ADF 10% and 5% more than did the control at the species and community levels respectively, and decreased digestibility 12% and 11% below the control at the community level. Changes in plant nutritional value may have occurred as a result of changes in plant structure for some or all the plant species monitored, and an indirect effect of the shift in botanical species composition owing to warming. Unlike moist grassland, grass nutrition in arid grasslands was sensitive to treatments associated with the predicted effects of global warming as the results of changes in plant nutrition. It is therefore highly possible that Mongolian livestock production will be negatively affected as a result of ongoing global warming.