Light mowing supports fine-root production in a temperate saline-alkaline grassland soil

The dynamic changes and differential responses of roots - an important research hotspot in belowground ecology-are one of the most fascinating yet elusive focuses in terrestrial ecology. We conducted a two-year field experiment in a temperate saline-alkaline grassland soil of northern China to generalize the effects of mowing intensity on root production, mortality, standing crop, turnover, and lifespan. Four mowing intensities were established, including no mowing, light mowing, moderate mowing, and heavy mowing. Fine root dynamics were monitored in situ using the root-window method at 15-day intervals from May 2018 to October 2019, and measurements were performed in the 0-10 cm and 10-20 cm soil. Root production and mortality showed clear seasonal patterns, both peaking in the late growing season, with root production reaching its maximum in August and mortality peaking in September. These seasonal dynamics were mainly associated with variations in growing-season precipitation and were not markedly altered by mowing intensity. However, root production and turnover rate were affected by mowing treatment and soil depth. In the 0-10 cm depth, light mowing produced the highest cumulative root production and root turnover rate, which increased by 20% and 18% compared with the no mowing, respectively. In contrast, the mowing effect was weaker in the 10-20 cm soil depth. Structural equation modeling indicated that mowing influenced root production through both direct and indirect pathways, with soil water content, soil temperature, and the fraction of belowground net primary production playing key roles. Overall, light mowing had a positive effect on fine root production and accelerated root turnover without disrupting seasonal root dynamics, indicating its potential to optimize belowground carbon allocation and sustain root-mediated soil carbon inputs in saline-alkali grasslands. These findings provide new evidence for identifying sustainable mowing thresholds in fragile grassland ecosystems.