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Forest litter layer plays an important role in controlling water and soil loss; however, few studies have examined how litter cover affects hydrological processes. In this research, the effects of forest litter cover on interception, runoff, infiltration and soil erosion were investigated using rainfall simulation on a loess hillslope in China. Field experimental plots (10 m × 1.5 m, 5°) with two litter species (needle-leaf species and broad-leaf species) and three litter masses (300, 500 and 800 g m−2) were exposed to two rainfall intensities (30 and 60 mm h−1) for 40 min. A modified Merriam interception model as well as a WEPP (Water Erosion Prediction Project) Hillslope model were subsequently employed to analyze the experimental data of litter interception as well as runoff generation and soil erosion, respectively. Results showed that litter interception storage capacity ranged from 0.55 to 2.10 mm; thus, 1.8–9.2% of total rainfall was intercepted by the litter layer. Interception storage increased with increasing litter mass and rainfall intensity, and broad-leaf litter could intercept more rainwater than needle-leaf litter. Litter cover reduced runoff rates from plots covered with needle-leaf and broad-leaf litter by 18.6% and 25.9%, respectively, compared to the bare plot. Although runoff rates were slightly lower in litter-covered plots than in the bare plot, soil loss was effectively controlled when litter mass levels reached a threshold value of 500 g m−2. Compared to that from the bare plot, the mean soil loss rate for litter-covered plots was lowered by 58.5%, 74.5% and 78.3% for litter masses of 300, 500 and 800 g m−2, respectively. These results indicate that the litter layer was more conducive to controlling soil loss than runoff generation. Furthermore, the determination coefficient and Nash-Sutcliffe efficiency coefficient of the modified Merriam model ranged between 0.838–0.998 and 0.912–0.998, respectively, indicating that this model could successfully simulate the litter interception process. The WEPP model predictions also agreed well with the measured runoff and soil loss rates, but may have under-estimated the measured data in low rainfall intensity events and over-estimated the measured data in high rainfall intensity events. The performance of the WEPP model could be obviously improved by reducing the effective hydraulic conductivity and soil erodibility. Overall, this study will enable the development of more accurate modeling approaches and lead to a better understanding of hydrological processes under litter cover conditions. • Litter cover played an important role in reducing water and soil losses. • Litter cover was more conducive to controlling soil loss than runoff generation. • Soil loss was effectively controlled when litter mass reached 500 g m−2. • The WEPP model could well predict runoff and soil loss under litter cover conditions. [ABSTRACT FROM AUTHOR]

• Hydrus-1D was used to simulate T and E of three grasslands in the Loess Plateau. • The effects of climate change on T were greater than that on E. • Precipitation was the most dominant climatic factor affecting T and E. • Constructed grasslands had higher water use efficiency than natural one. • Constructed grasslands led to worse soil water conditions than natural one. Investigating the effects of climate change on transpiration (T) and evaporation (E) in natural and constructed grasslands is of theoretical and practical significance for vegetation restoration and water resource management in the Loess Plateau, China. In this study, a two-year field experiment was conducted in one natural (Imperata cylindrica plot) and two constructed grasslands (Pennisetum giganteum and Medicago sativa plots) in the semi-arid Loess Plateau. Hydrus-1D models were then established and validated to simulate T and E processes under scenarios combining climate characteristics in both future periods and different hydrological years. The results showed that under all climate scenarios, T in the natural grassland, and P. giganteum and M. sativa plots ranged from 63.7–179.3, 126.8–245.5, and 96.9–243.1 mm, respectively, while E ranged from 90.6–131.9, 68.7–92.8, and 70.4–92.4 mm, respectively. Both T and E showed a decreasing trend in the future periods, exhibiting the highest values in wet years and the lowest values in dry years. The effects of climate change on T were greater than that on E in all three grasslands. Of the studied grasslands, T of M. sativa plot exhibited the strongest response, followed by that in the natural grassland and P. giganteum plot. However, E of the natural grassland responded to the strongest degree, followed by that of the P. giganteum and M. sativa plots. Precipitation during the growing-season was the most dominant climatic factor affecting T and E , and was positively linearly related with T and E (P < 0.01) in all three grasslands. The conversion thresholds of precipitation for T - E dominance were 435.8, 149.4, and 253.3 mm for the natural grassland, and P. giganteum and M. sativa plots, respectively. In constructed grasslands, more water was lost through T than through E ; hence, the T / ET ratios were high (>0.55). In contrast, T was high in the natural grassland only in conditions of sufficient precipitation; hence, the T / ET ratio was relatively lower (around 0.5). Precipitation distribution strongly affected the soil water supply, and the natural grassland was more efficient in maintaining soil water than the constructed grasslands. Our study not only improves our understanding of the hydrological processes and water budget under different grass restoration measures, but also provides valuable guidelines for the management of water resources and the restoration of ecological environment in the Loess Plateau. [ABSTRACT FROM AUTHOR]