Effects of mowing disturbance and competition on spatial expansion of the clonal plant Leymus chinensis into saline-alkali soil patches

Abstract

Mowing disturbance and interspecific competition could affect the expansion of clonal plant under homogeneous conditions. However, with the current degradation of patchy grasslands, how these factors affect the expansion of clonal plant–Leymus chinensis, a dominant perennial grass in meadow steppe, into saline-alkali patches with different stress levels is largely unknown. To test this, we conducted an experiment in which L. chinensis was grown in a pot with half healthy and half saline-alkali soils and the healthy part was treated with mowing and interspecific competition (with Hierochloe glabra). Results showed that mowing or competition treatment alone significantly promoted the expansion of L. chinensis in healthy patches into saline-alkali patches under a moderate saline-alkali stress (i.e., higher rhizome length was found), while this effect was not significant in the combined mowing and competition treatment. On the contrary, all of the mowing and competition treatments decreased the expansion of L. chinensis into the saline-alkali patches (i.e. lower rhizome length) under a severe saline-alkali stress. Also, results showed that mowing or competition alone reduced aboveground biomass of ramets in healthy patches, but increased their above- and below-ground biomass in saline-alkali patches under a moderate stress, indicating that mowing and competition promoted L. chinensis to allocate more biomass to improve expansion abilities. Moreover, compensatory growth was induced by mowing treatment from a physiological perspective (e.g., with an increase in photosynthesis rate). L. chinensis employed different adaptive strategies in response to mowing and competition during the process of expansion. We conclude that mowing and competition can significantly affect the expansion of L. chinensis into saline-alkali patches, and the effects strongly depend on the stress level of saline-alkali patches. Overall, our results imply that in slightly degraded patchy grasslands, moderate grazing or mowing utilization may accelerate their restoration, and that L. chinensis communities with more diverse species mixtures could have larger potential to restore the degraded patches.