Rating the Degradation of Natural Hay Pastures in Northern China

Natural hay pastures in semi-arid pastoral areas produce the highest yields of hay in northern China. However, long-term continuous hay harvesting with no rest interval has resulted in severe degradation across widespread areas of these natural hay pastures. In addition, no clear data exist on the spatial distribution or degree of degradation occurring in natural hay pastures primarily because a nationally unified and normative evaluation standard is lacking. In view of the above problems, we employed an analytic hierarchy process to carry out screening and accuracy validation of evaluation indicators for natural hay pastures in north China grasslands (temperate meadow steppes, temperate steppes, mountain meadows, and lowland meadows). Our study identified seven easily measured indicators that reflect the state of natural hay pastures (average height, aboveground biomass, coverage, proportion of medium grasses, litter biomass, proportion of degradation-indicative plants, and proportion of bare spots and saline-alkali spots). A five-level scoring method was employed to delineate the threshold range for these indicators, The results of this study show that this method effectively solved the technical bottleneck for graded evaluation of degradation in natural hay pastures. This provides a theoretical basis for the scientific assessment of natural hay pasture degradation as well as important technical support for sustainable use of natural hay pastures and livestock production.