The effects of neutral salt and alkali on the ion distribution were investigated in two alfalfa (Medicago sativa L.) cultivars, including Zhongmu 1, a high salt-tolerant cultivar, and Algonquin, a low salt-tolerant cultivar. The alkali stress expressed more serious growth inhibition than the neutral salt stress at the same Na+ concentration. Compared with Algonquin, Zhongmu 1 did not exhibit a higher alkali tolerance under the Na₂CO₃-NaHCO₃ treatment with the low Na+ concentration (50 mmol L^–1). The alkali increased the accumulation of Na⁺, Ca²⁺, and Mg²⁺ in the root and changed the Ca²⁺ and Mg²⁺ balance in the entire alfalfa plant. The salt and alkali stresses decreased the K+ and Fe³⁺ contents of the roots and leaves, the root Mn²⁺ content, and the shoot Zn²⁺ content, but they increased the Fe³⁺ accumulation of the shoots, the shoot and leaf Cu²⁺ contents, and the leaf Zn²⁺ content in both alfalfa cultivars. Based on the results obtained under the conditions of this experiment, we found that the salt and alkali stresses reduced the plant growth in both alfalfa cultivars, while the alkali caused a stronger stress than the neutral salt in alfalfa. Thus, we conclude that under hydroponic conditions, the deleterious effects of the alkali on plants are due to the distribution change of some trophic ion balance in the roots, shoots, and leaves of the plants by causing of Na+, CO₃^2–, and/or HCO₃^– stresses.

    Studying the changes in nutrient use strategies induced by grazing can provide insight into the process of grassland degradation and is important for improving grassland quality and enhancing ecosystem function. Dominant species in meadow steppe can optimize their use of limiting resources; however, the regulation of nutrient use strategies across grazing gradients is not fully understood. Therefore, in this study, we report an in situ study in which the impact of grazing rates on nutrient use strategies of Leymus chinensis, the dominant plant species in eastern Eurasian temperate steppes, was investigated. We conducted a large randomized controlled experiment (conducted continuously for five years in grassland plots in a natural pasture in Hailar, eastern Mongolia Plateau, China) to assess the effects of grazing rate treatments (0.00, 0.23, 0.34, 0.46, 0.69, and 0.92 adult cattle unit (AU) ha^–1) on L. chinensis along a grazing gradient and employed a random sampling approach to compare the accumulation, allocation, and stoichiometry of C, N, and P in leaves and stems. Our findings demonstrated the follows: (i) The height of L. chinensis decreased with an increase in the grazing gradient, and the concentrations of C, N, and P significantly increased; (ii) the accumulation of C, N, and P per individual was negatively correlated with the concentration of aboveground tissues, suggesting that there was a tradeoff in L. chinensis between nutrient accumulation and concentration at the individual scale; (iii) the leaf-to-stem ratio of C, N, and P accumulation increased with grazing intensity, indicating a tradeoff in nutrient allocation and plant size at the individual plant level; and (iv) grazing rates were negatively correlated with the ratios of C:N and C:P in the stem; however, these ratios in leaves significantly increased with grazing intensity. Our findings suggest that L. chinensis in meadow steppe adapts to grazing disturbance through tradeoffs between plant size and nutrient use strategies. Moreover, our results imply that grazing produces a compensatory effect on nutrient use efficiency between the stems and leaves of L. chinensis.

Spatial and structural characteristics of plant communities in the steppe ecosystems of the Baikal region, Russian Federation have been researched in connection with climate change and grazing. The present study, based on a total of 15 typical steppe sampling plots, investigated above-ground biomass (AGB), below-ground biomass (BGB), total biomass (TB) and root:shoot ratios (R:S) and their relationships with climatic factors and grazing. All biomass components varied widely depending on the climatic parameters and the degree of grazing affected transformation. A strong negative correlation between mean annual temperature (MAT) and total plant biomass was revealed for all study area. Mean annual precipitation (MAP) significantly affected communities productivity increasing only in the south of the region. Due to the large and mountainous territory, the influence of latitude and elevation (mountain) factors on the components of the biomass were studied. Although all studied plant steppe communities were transformed by uncontrolled grazing, their productivity is significantly reduced only at plots with maximum digression. Vegetation shift is an indicator of climate change, as well as providing a diagnostic tool to build predictive models. Based on the complex index of effective precipitation, it was revealed that at the end of last century in the steppes of the Baikal region the structural and production processes will be affected by an arid climate trend.