Background
Grassland ecosystems are an important component of the global carbon cycle, playing a critical role in soil carbon sequestration, water conservation, and biodiversity maintenance. However, arid and semi-arid grasslands are highly sensitive to fluctuations in rainfall and grazing disturbances. Short-term, intense rainfall can rapidly alter soil moisture, thereby influencing plant growth, microbial activity, and ecosystem carbon exchange; meanwhile, grazing intensity further modulates this response by adjusting vegetation structure and soil water-holding capacity. Although previous studies have examined the impacts of either grazing or rainfall on grassland carbon cycling, the short-term dynamic mechanisms through which these two factors synergistically regulate soil moisture, plant communities, and carbon exchange remain poorly understood and require further investigation.
Addressing this research gap, Professor Dong Zhi’s team from Shandong Agricultural University took the typical desert steppe of Xilamuren in Inner Mongolia as their study site. Combining different grazing intensity treatments with five typical rainfall events during the 2024 growing season, they systematically observed the short-term responses of soil moisture, plant communities, and ecosystem carbon exchange. The related findings have been published in Agriculture, Ecosystems and Environment, providing data support for the management of moderate grazing in grasslands.
Key findings
(1)Grazing intensity significantly alters the soil moisture response to rainfall; moderate grazing enhances the sensitivity of the topsoil to moisture and helps maintain soil moisture stability, whereas heavy grazing diminishes the response of deeper soil layers to moisture and their water retention capacity.
Figure 1. Response of soil water content and soil temperature to rainfall stimulation. (a), (b), and (c) represent the responses of soil water content in the 0–10 cm, 10–20 cm, and 20–40 cm soil layers, respectively, to rainfall pulses. (d) shows the response of soil temperature in the 0–10 cm layer to changes in soil water content. (e) illustrates the variation in soil water content under different grazing intensities following rainfall. (f) depicts the effect of grazing intensity on the coefficient of variation of soil water content.
(2) Rainfall pulses significantly enhance carbon exchange processes in desert grasslands, while moderate grazing helps maintain more stable carbon uptake capacity and carbon sink function.
Figure 2. NEE, ER, and GEP are influenced by grazing intensity and rainfall patterns. (a), (b), and (c) show the responses of NEE, ER, and GEP to rainfall pulses under different grazing intensities. (d), (e), and (f) illustrate the responses of NEE, ER, and GEP to short-term rainfall events and their subsequent effects under varying grazing intensities. (g) presents the average changes in NEE, ER, and GEP during rainfall events at different grazing intensities.
(3) Heavy grazing weakens the coupling between plant carbon uptake and soil carbon release, leading to a decline in the stability of the carbon cycle process.
Figure 3. Correlation among ecosystem carbon exchange, N₂O and CH₄ concentrations, and soil CO₂ emissions under the influence of rainfall.
(4) Although heavy grazing can temporarily increase species richness, this effect primarily relies on an increase in short-lived plant species. Ultimately, it will lead to a simplification of community structure and weaken long-term ecological stability.
Table 1. Diversity Index Analysis
Figure 4. Response of functional group importance values to rainfall duration and grazing intensity ((a) CK, (b) LG, (c) MG, (d) HG)
Figure 5. The response of species richness to rainfall duration and grazing intensity
(5) Grazing and rainfall, by regulating soil temperature, moisture conditions, and soil CO₂ emissions, jointly influence carbon exchange and overall functional stability in grassland ecosystems.
Figure 6. Structural equation modeling analysis of the interactions among soil temperature, biodiversity, soil water content, soil CO₂ emissions, ecosystem carbon flux, CH₄, and N₂O under the influence of precipitation and grazing intensity.
Experimental method
The study took the typical desert steppe of Xilamuren in Inner Mongolia as its research area and set up four treatment groups:
Grazing prohibition control (CK);
Light grazing (LG): 1.5 sheep/hm²·month;
Moderate grazing (MG): 3.0 sheep/hm²·month
Heavy grazing (HG): 4.5 sheep/hm²·month;
During the growing season from July to August 2024, five effective rainfall events were selected, and continuous observations were conducted according to the sequence: “pre-rain—rainfall pulse period—post-rainfall effect period.”
Main indicators: soil moisture, soil moisture storage, soil temperature, soil fluxes of CO₂, CH₄, and N₂O, species composition, density, height, and canopy cover, etc.;
Data Analysis: We employed repeated-measures ANOVA, linear regression, and structural equation modeling to comprehensively assess the mechanisms by which grazing intensity, rainfall events, and their interaction influence soil moisture, plant communities, and ecosystem carbon exchange.
During the experiment, the PS-9000 Portable Soil CO₂ Flux System, developed and manufactured byBeijing LICA United Technology Ltd., was used to determine the soil CO₂ flux. Before the measurements, researchers calibrated the instrument using standard CO₂ gas of known concentration and pre-inserted a PVC ring-shaped base into the soil to a depth of approximately 8 cm to define the measurement area. During sampling, after removing the aboveground vegetation within the ring, the SC-12 soil respiration chamber was placed onto the PVC ring and connected to the PS-9000 for measurement. The instrument simultaneously recorded soil temperature, and the measurement periods were from 8:00 a.m. to 12:00 p.m. and from 2:00 p.m. to 5:00 p.m.
Conclusion
Studies have shown that the response of desert grasslands to rainfall depends not only on the amount of precipitation but is also significantly influenced by grazing intensity. Moderate grazing helps maintain the stability of soil moisture, plant communities, and carbon sink functions, whereas heavy grazing may reduce ecosystem resilience and the stability of the carbon cycle. In the future, by integrating long-term observations with multi-scale carbon flux monitoring, we can further elucidate the mechanisms underlying carbon-water coupling under different rainfall and grazing conditions, providing a scientific basis for grassland ecological restoration, grazing management, and carbon sink enhancement.
Journal of Publication: Agriculture, Ecosystems and Environment [Impact Factor: 7.7]
Research Institutions: Shandong Agricultural University, Collaborative Innovation Center for Water and Soil & Forest-Grassland Ecological Protection in the Yellow River Basin of Shandong Province’s Universities, and others.
Study location: Xilamuren Grassland, Inner Mongolia
Equipment used: PS-9000 Portable Soil CO₂ Flux System
DOI: https://doi.org/10.1016/j.agee.2026.110625