Heavily intensified grazing reduces root production in an Inner Mongolia temperate steppe

The temperate steppe in Inner Mongolia is China's largest steppe. Heavily intensified grazing has been widely used in an Inner Mongolia grasslands. However, the effects of the grazing on fine root demography have been little studied in grassland ecosystems. In this study, we conducted in situ field measurements for root production, mortality, and standing crop in Inner Mongolia steppe under both ungrazed and heavily intensified grazed conditions using the improved rhizotron techniques. Our results showed that root production and mortality in the steppe displayed seasonal dynamic patterns, whereas no clear seasonal dynamic patterns for the standing crop were detected. Long-term heavily intensified grazing did not alter seasonal dynamic patterns of root production, mortality and standing crop. Root production, mortality and standing crop distributed in different soil layers responded to livestock grazing differently. The grazing increased root production, mortality and standing crop in 0-10 cm soil layer, while it reduced root production, mortality and standing crop in 10-20 and 20-30 cm soil layers, with an overall reduction in the three variables across 0-30 cm soil layer. The grazing-induced reduction in root production, mortality and standing crop was mainly accounted for by reductions in aboveground biomass and soil water contents. These results indicate that long-term heavily intensified grazing can lead to the loss of soil organic matters and nutrients in the steppe. Thus, appropriate measures have to be taken for an effective management of the livestock grazing in Inner Mongolia steppe.