Grazing Affects the Ecological Stoichiometry of the Plant–Soil–Microbe System on the Hulunber Steppe, China

• Main Authors: Juan Cao, Ruirui Yan, Xiaoyong Chen, Xu Wang, Qiang Yu, Yunlong Zhang, Chen Ning, Lulu Hou, Yongjuan Zhang, Xiaoping Xin
• Format: Article
• Language: English
• Published: MDPI AG 2019-09-01
• Series: Sustainability
• Subjects: aboveground; belowground; microbial biomass; nutrient ratios; N-limitation; rhizosphere; temperate meadow steppe
• Online Access: https://www.mdpi.com/2071-1050/11/19/5226

Grazing affects nutrient cycling processes in grasslands, but little is known by researchers about effects on the nutrient stoichiometry of plant−soil−microbe systems. In this study, the influence of grazing intensity (0, 0.23, 0.34, 0.46, 0.69, and 0.92 AU ha^−1) on carbon (C), nitrogen (N) and phosphorus (P) and their stoichiometric ratios in plants, soil, and microbes was investigated in a Hulunber meadow steppe, Northeastern China. The C:N and C:P ratios of shoots decreased with grazing increased. Leaf N:P ratios <10 suggested that the plant communities under grazing were N-limited. Heavy grazing intensities increased the C:N and C:P ratios of microbial biomass, but grazing intensity had no significant effects on the stoichiometry of soil nutrients. The coupling relationship of C:N ratio in plant−soil−microbial systems was tightly significant compared to C:P ratio and N:P ratio according to the correlation results. The finding suggested grazing exacerbated the competition between plants and microorganisms for N and P nutrition by the stoichiometric changes (%) in each grazing level relative to the no grazing treatment. Therefore, for the sustainability of grasslands in Inner Mongolia, N inputs need to be increased and high grazing intensities reduced in meadow steppe ecosystems, and the grazing load should be controlled within G0.46.