Regulatory Effects of Mowing on Biomass Allocation and Compensation Growth Mechanisms in <i>Elymus</i> Species

Mowing is a crucial grassland management practice; however, its effects on biomass allocation and compensatory mechanisms across different growth stages remain insufficiently understood. This study investigated five <i>Elymus</i> forage species (<i>Elymus nutans</i> ‘Aba’, <i>Elymus sibiricus</i> ‘Qingmu No.1’, <i>Elymus submuticus</i> ’Tongde’, <i>Elymus breviaristatus</i> ‘Tongde’, and <i>Elymus sibiricus</i> ‘Tongde’). Four mowing intensities (control, light, moderate, and heavy) were applied at three phenological stages (jointing, booting, and flowering). Biomass allocation patterns among plant components (roots, stems, leaves, and spikes) were assessed, and allometric growth relationships were analyzed. Structural equation modeling (SEM) was used to evaluate the contributions of mowing timing and organ biomass to overall compensatory ability. The results showed that mowing significantly altered biomass allocation patterns, characterized by an increase in root-biomass proportion, a decrease in stem and spike proportions, and species- and stage-specific changes in leaf proportion. The allometric growth relationships between plant organs varied across growth stages and were significantly influenced by mowing intensity, affecting organ growth coordination. SEM analysis revealed that mowing timing and root biomass were the primary drivers of total biomass compensation, with root biomass playing a particularly critical role under moderate to heavy mowing. Mowing exerts complex regulatory effects on biomass allocation and compensatory growth in <i>Elymus</i> species, with impacts varying by intensity, growth stage, and species. To enhance overcompensatory growth, moderate mowing at the jointing stage is recommended, while heavy mowing during the flowering stage should be avoided. Furthermore, maintaining root health is crucial for improving compensatory growth capacity. These findings provide valuable insights for the sustainable management of <i>Elymus</i> grasslands.