Distributions of Medium Mineral Elements with Long-Term Grazing Exclusion in a Semi-Arid Grassland of Inner Mongolia

The variations of medium mineral elements in long-term grazing exclusion grassland have been few studied. Therefore, the contents, stocks, and proportions of calcium (Ca), magnesium (Mg), sulphur (S), and silicon (Si) in green plant-litter-root-soil continuum were evaluated by grazing exclusion for 18-, and 39-year (F18 and F39) and continue grazing (F0) in Mongolia grassland. Results showed that F18 and F39 decreased the stocks of Mg and Si in green plant and the stocks of Ca and Mg in 20–50 cm root (p < 0.05). F18 and F39 increased the stocks of S in 0–100 cm soil and the stocks of elements in litter (p < 0.05). Compared to F18, F39 increased the stocks of elements in 0–20 cm root, especially Si (p < 0.05), and a 30.3 % higher of Ca stock in green plant was observed (p < 0.05). The stock of Ca and Mg in 0–100 cm soil at F39 was 164.3 % and 72.6 % lower than that at F18, respectively (p < 0.05). F39 decreased the stocks of Mg, S, and Si in incomplete- and complete decomposed litter relative to F18. We concluded that four elements were shifted from root to other parts with long-term grazing exclusion. However, Ca, Mg, and Si were shifted from soil to plant with grazing exclusion for 39 years relative to 18 years, and Ca was shifted from root to litter, and Mg, S, and Si were shifted from litter to root or green plant.