The rainfall in loess hilly and gully area is concentrated, and mostly comes in the form of rainstorms. The runoff on the slope caused by rainstorms is the main cause of serious soil and water loss in the loess hilly area, and the grassland vegetation has a good inhibitory effect on the runoff on the slope. Therefore, it is of great significance to reveal the role of grassland vegetation in the process of runoff generation, and the mechanisms for controlling soil erosion in this area. In this study, typical grassland slopes in hilly and gully regions of the loess plateau were taken as research objects. Through artificial rainfall in the field, the response rules of the slope rainfall-runoff process to different grass coverage were explored. The results show that: (1) With the increase in rainfall intensity, the inhibitory effect of grassland vegetation on slope runoff decreased, which was mainly reflected in the gradual decrease in runoff rate and runoff coefficient, and the time required to reach stability gradually shortened. (2) Under 60 mm/h rainfall intensity, the sensitivity of runoff coefficient to 31.5% of grass cover change is the lowest, and the cost performance of grass cover with 55% coverage is the highest. (3) Grass coverage inhibited slope runoff by changing the hydraulic characteristics of the slope, but this effect was only obvious in low rainfall intensity and early rainfall. Rainfall in the loess hilly area is characterized by intense rain. The regulating effect of grass cover on slope runoff is not particularly significant under high intensity rainfall. If only considering the regulation of grassland vegetation on slopes, more than 60% grassland coverage is more efficient in inhibiting slope runoff under medium and low intensity rainfall.

Understory vegetation is one of the most important links for improving forest biodiversity, and its restoration is conducive to sustainable forest development, energy flow, and nutrient cycling. However, little is known about the developmental dynamics and main driving factors of the long-time series coverage, biomass, diversity, and species composition of plantation understory vegetation. In a case study of three typical plantations, with a natural secondary forest as reference in the Loess Plateau of China, we collected understory vegetation from a Robinia pseudoacacia Linn. deciduous broad-leaved plantation, Pinus tabulaeformis Carr. evergreen coniferous plantation, and mixed plantation with an age span of 10 to 50 years. (1) The understory plantation coverage and biomass results of stands with different ages showed the R. pseudoacacia plantation to be significantly higher than the P. tabulaeformis plantation, and the species diversity of the P. tabulaeformis plantation changed the most with the stand age. However, the growth resource imbalance, and drastic changes in the stands’ environment caused by excessive intraspecific competition in the early stage of the P. tabulaeformis plantation vegetation restoration, are the main reasons that make the species diversity of undergrowth vegetation of P. tabulaeformis plantation lower than that of other stand types. (2) The understory species composition of the plantations revealed their degree of community stability. Compared to the R. pseudoacacia plantation and P. tabulaeformis plantation, the mixed plantation had higher stability, and its species composition closely resembled a natural secondary forest. The community stability of the P. tabulaeformis plantation was the lowest because it had the lowest coverage, biomass, and species diversity of understory vegetation. However, the understory species composition of the three plantation types converged, which was due to atypical species contribution. (3) The dynamic changes of canopy and soil nutrients were the main driving factors affecting the R. pseudoacacia plantation understory vegetation species composition. Stand density and elevation limited the understory vegetation communities of P. tabulaeformis plantation restoration. Soil bulk density is the key factor affecting understory vegetation in mixed plantations, and this effect weakens with the stand age. In future studies, the focus should be on the converged action and further development trend of atypical species, choosing an appropriate recovery strategy (active or passive), and providing more possibilities for the intensive management of vegetation under different plantations.

The dynamic changes in vegetation significantly impact the sustainability, safety, and stability of ecosystems in the source region of the Yellow River. However, the spatiotemporal patterns and driving factors of these changes remain unclear. The MODIS NDVI dataset (1998–2018), together with climatic records from meteorological stations and socio-economic statistics, was collected to investigate the spatiotemporal characteristics of vegetation coverage in the study area. For the analysis, we employed linear trend analysis to assess long-term changes, Pearson correlation analysis to examine the relationships between vegetation dynamics and climatic as well as anthropogenic factors, and t-tests to evaluate the statistical significance of the results. The results indicated the following: (1) From 1998 to 2018, vegetation in the source region of the Yellow River generally exhibited an increasing trend, with 92.7% of the area showed improvement, while only 7.3% experienced degradation. The greatest vegetation increase occurred in areas with elevations of 3250–3750 m, whereas vegetation decline was mainly concentrated in regions with elevations of 5250–6250 m. (2) Seasonal differences in vegetation trends were observed, with significant increases in spring, summer, and winter, and a non-significant decrease in autumn. Vegetation degradation in summer and autumn remains a concern, primarily in southeastern and lower-elevation areas, affecting 25% and 27% of the total area, respectively. The maximum annual average NDVI was 0.70, occurring in 2018, while the minimum value was 0.59, observed in 2003. (3) Strong correlations were observed between vegetation dynamics and climatic variables, with temperature and precipitation showing significant positive correlations with vegetation (r = 0.66 and 0.60, respectively; p < 0.01, t-test), suggesting that increases in temperature and precipitation serve as primary drivers for vegetation improvement. (4) Anthropogenic factors, particularly overgrazing and rapid population growth (both human and livestock), were identified as major contributors to the degradation of low-altitude alpine grasslands during summer and autumn periods, with notable impacts observed in counties with higher livestock density and population growth, indicating that for each unit increase in population trend, the NDVI trend decreases by an average of 0.0001. The findings of this research are expected to inform the design and implementation of targeted ecological conservation and restoration strategies in the source region of the Yellow River, such as optimizing land-use planning, guiding reforestation and grassland management efforts, and establishing region-specific policies to mitigate the impacts of climate change and human activities on vegetation ecosystems.

Conflicts between humans and land use in the process of using water and conflicts between humans and water resources in the process of using land have led to an imbalance between natural ecosystems and socio-economic systems. It is difficult to understand the impact of the processes of water production and consumption on land patches and their ecological effects. A grid-type, basin-distributed hydrological model was established in this study, which was based on land-use units and coupled with groundwater modules to simulate the water production and consumption processes in different units. By combining land use and net primary productivity, the runoff coefficient and the water use efficiency (NPP/ET) of different land units were used as indicators to characterize the interaction between water and land resources. The results showed that the average runoff coefficients of cultivated land, forest land and grassland were 0.7, 0.5 and 0.9, respectively. Moreover, the average runoff coefficients of hills, plains and basins were 0.7, 0.7 and 0.8, respectively. The NPP produced by the average unit, evapotranspiration, in cultivated land, forest land and grassland was 7 (gC/(m²•a))/mm, 0.7 (gC/(m²•a))/mm and 0.2 (gC/(m²•a))/mm, respectively. These results provide quantitative scientific and technological support in favor of the comprehensive ecological management of river basins.

Vegetation restoration is widely used to combat soil erosion on the Chinese Loess Plateau, where intense rainfall and steep slopes make this region one of the most eroded areas in the world. However, the effectiveness of strip grass cover (Vc) in reducing erosion under varying rainfall and topographic conditions remains insufficiently quantified. In this research, based on indoor simulated rainfall experiments in a soil tank, we investigated the erosion characteristics of slopes under six Vc levels (0%, 20%, 30%, 40%, 50%, and 60%), three rainfall intensities (RI) (1.33, 1.67, and 2.0 mm·min⁻¹), and four slope gradients (SG) (10°, 15°, 20°, and 25°), and quantified the effects of Vc on slope erosion processes. Runoff and sediment reduction effects by Vc ranged from 3.5% to 62.6% and from 15.2% to 99.1%, respectively. An exponential decay in erosion rate was observed with increasing Vc, whereas runoff velocity initially decreased and then increased as the Vc increased. By integrating RI, SG, and Vc, the average runoff rate and erosion rate models accurately simulate erosion processes on Vc slopes. These findings provide laboratory-based evidence that Vc substantially reduces slope erosion, and support the development of empirical models for predicting runoff and erosion under the tested conditions.