Grazing overrides precipitation reduction to regulate growth of a dominant species in a typical steppe

Abstract

Overgrazing and drought are critical drivers of grassland degradation, yet their combined impacts on plant growth and succession, especially the dominant species, are still poorly understood, making it difficult to develop the sustainable pasture management. We conducted a three-year field experiment (2019–2021) on China’s Loess Plateau to assess the intricate impacts of grazing management (NG – no grazing, CG – cassation of grazing, and HG – grazing with high intensity) and precipitation reduction (R0 – no precipitation reduction, R30 – 30 % precipitation reduction, and R60 – 60 % precipitation reduction) on the growth and reproduction of Artemisia capillaris, a dominant species in the semi-arid grassland ecosystem. Our results show that HG significantly decreased plant height, crown width, reproductive branches, and aboveground biomass. CG only facilitated partial recovery of these traits, suggesting a prolonging grazing cassation is essential for ecosystem restoration after a long period of overgrazing. A. capillaris exhibited a preference for asexual reproduction, with potential trade-offs between sexual and asexual modes in response to varying environmental conditions. Precipitation reduction primarily affected vertical growth, with cumulative effects observed after three years (i.e., in 2021). Compared to precipitation reduction, grazing imposed a more substantial negative impact on aboveground biomass, indicating the need for optimum grazing strategies in grassland management. The findings underscore the importance of considering dominant species and highlight the long-term consequences of overgrazing that must be incorporated into sustainable grassland management practices in semi-arid regions. The study delivers insights into pasture management science, and addresses that grazing cessation may be an appropriate method of grassland management, mitigating the negative effects of prolonged overgrazing and precipitation reduction on the growth and reproduction of dominant species in semi-arid regions.