Stoichiometric ratios support plant adaption to grazing moderated by soil nutrients and root enzymes.

BACKGROUND

Vegetation succession is one of the major driving processes of grassland degradation. Stoichiometry significantly contributes to vegetation dynamics. However, a knowledge gap exists in how soil nutrients and root enzymes influence the stoichiometric ratio to affect vegetation dynamics.

METHODS

To address these questions, we selected a dominant species ( (Trin.) Tzvel.) and a degraded-dominant species ( Willd.) under different management regimes (enclosure and grazing) on the Inner Mongolia steppe. We measured (i) plant nutrient concentrations, (ii) root enzymes and (iii) soil nutrients to investigate how the selected plant species responded to grazing.

RESULTS

The results show that: (i) N and P concentrations and the C:N:P ratio in different organs are significantly affected by grazing, and there is variation in the plant species' response. Grazing significantly increased N and P in the leaves and stems of and the stems and roots of . (ii) Grazing significantly increased the activities of glutamine synthase but decreased the activities of acid phosphatase in . The nitrate reductase and acid phosphatase activities significantly increased in under grazing conditions. (iii) Grazing decreased the total nitrogen, total phosphorus, and available nitrogen, but increased the available phosphorus in the soil.

CONCLUSION

We conclude that is better adapted to grazing than possibly because of its relatively increased stem and root growth, which enhance population expansion following grazing. Conversely, showed increased leaf and stem growth, but suffered nutrient and biomass loss as a result of excessive foraging by livestock, which severely affected its ability to colonize. Root enzymes coupled with soil nutrients can regulate plant nutrients and stoichiometric ratios as an adaptive response to grazing. Thus, we demonstrated that stoichiometric ratios allow species to better withstand grazing disturbances. This study provides a new understanding of the mechanisms involved in grazing-resistance within a plant-soil system.