Mowing of Carex brevicuspis (Cyperaceae) improves food quality for herbivorous geese in Dongting Lake: the potential mechanisms

Tao Wu¹Le Xia²Baihan Pan^1*Yeai Zou^3,4*Feng Li^3,4Yonghong Xie^3,4Shengze Wang^3,4Zhuoya Li¹

• ¹College of Life Sciences, Hunan Normal University,.Changsha 410081, China, Changsha, Anhui Province, China
• ²Technology Innovation Center for Ecological Conservation and Restoration in Dongting Lake Basin, Ministry of Natural Resources；Hunnan Center Of Natural Resources Affairs，Changsha, 410007, China, Changsha, Anhui Province, China
• ³Key Laboratory of Agro-ecological Processes in Subtropical Regions, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China, Changsha, China
• ⁴National Field Scientific Observation and Research Station of Dongting Lake Wetland Ecosystem in Hunan Province, Changsha 410125, Hunan, China, Changsha, China

The operation of the Three Gorges Dam altered the hydrological regime of Dongting Lake, leading to earlier water level recession and premature lake bed exposure. The hydrological shift has accelerated the early development of Carex spp.-dominated meadows, resulting in phenological mismatches between Carex brevicuspis (the primary food source for herbivorous geese) and the arrival of herbivorous geese. This mismatch reduced suitable food resources for these geese during their wintering period. During the 2023/2024 wintering season, we studied the effects of mowing treatments on C. brevicuspis and the underlying mechanisms. Three treatments were applied: full mowing (FM; stubble height < 0.3 cm), stubble mowing (SM; stubble height 15 cm), and no mowing (CK). The results showed that mowing treatments significantly increased leaf moisture and nitrogen content, reduced crude fiber content, and thereby increased the food quality and food utilization rates by herbivorous geese. Additionally, mowing increased the food quality in C. brevicuspis by stimulating compensatory growth responses, which relies on resource of the belowground bud banks mechanisms. However, mowing treatments also significantly decreased plant height, density, aboveground biomass, and the biomass of belowground bud banks, which potentially impairing the long-term recovery and sustainability of plant. Therefore, while targeted mowing can effectively improve the food quality for herbivorous geese during wintering, careful consideration the management of mowing frequency and intensity are essential to maintain balance between wetland vegetation recovery and sustainable food supply for herbivorous geese.