Effects Of Grazing On Underground Biomass And Individual Plant Root Traits Of A Typical Grassland Community

The underground parts of plants are one of the important component part of ecosystem, the research of which is a critical area in the current ecological studies. Underground productivity and root functional trait variation of the grassland ecosystem are important indicators for degrading succession of grassland. In-depth analysis of the responses of these indicators to grazing is helpful to scientific stage partition of grassland degrading succession, providing basic data for appropriate protection and use of grassland. With a typical grassland in Xilingol, Inner Mongolia as the study subject, this work measures and analyzes the spatial-temporal pattern of underground biomass, plant reproduction, and plant nutritional traits under different grazing intensity, grazing styles, and degrading/recovering succession stages using soil core-drilling method and root system spectroscopy. The main results are summarized as follows.1. Compared to the communities without grazing, the plant community with moderate grazing intensity significant increase of total underground biomass. However, heavy grazing intensity tends to cause decline of underground biomass and shallow distribution of roots. Different grazing styles also have impacts on the underground biomass of community. That is, under the same grazing intensity, the impacts of cow-sheep mixed grazing on underground biomass are greater than that of pure cow grazing or pure sheep grazing.2. Compared to communities without grazing, a plant community with moderate grazing shows a remarkable increase of the fine-root quantities of Stipa grandis and Anemarrhena asphodeloides, as well as the quantities of Leymus chinense and Cleistogenes squarrosa. Heavy grazing intensity leads to decrease of section spacing for rhizomatous plant. Under the same grazing intensity, all grazing styles affect the fine-root quantities of plants, but the extent of response is different among species.3. Heavy grazing intensity significantly reduces the root diameter of all plants while moderate grazing intensity increased the root diameter of Stipa grandis. The specific root length of Stipa grandis remarkably decreases under heavy grazing intensity, whereas Leymus chinense, and Cleistogenes squarrosa, show no significant change. Under the same grazing intensity, different grazing styles have almost the same effects on the specific root lengths of plants. Heavy grazing intensity leads to a great increase in the specific surface area of Stipa grandis, Anemarrhena asphodeloides, Artemisia frigida, and Cleistogenes squarrosa. Under the same grazing intensity, no significant differences are observed from the effects of different grazing styles on the specific root length and specific surface area of plants.This provide a foundamental basis for the grazing management of typical grassland in the research of underground biomass and plant functional traits of roots.