a b s t r a c t a r t i c l e i n f oImplementation of the Grain-for-Green project has resulted in significantly increased vegetative cover on the Loess Plateau of China during the past few decades. The plant communities influence soil moisture recharge and usage processes, particularly the input process, which is directly related to transformation of the limited precipitation into available soil water in the semi-arid Loess Plateau. A study to measure soil moisture dynamics of typical land cover types associated with precipitation events was conducted in a re-vegetated catchment area. Smart probes were inserted at 6 different depths below the ground surface under grass (Andropogon), subshrub (Artemisia scoparia), shrub (Spiraea pubescens), tree (Robinia pseudoacacia), and crop (Zea mays) vegetation to record volumetric soil moisture at 10-minute intervals for a period of 60 days during the growing season in 2011. The advance of the wetting front and total accumulated infiltrated water were measured. The rainfall events were sporadic with widely different intensities, and the soil moisture was replenished mainly by 3-4 heavy precipitation events during July and August. The mean soil moisture content profiles of the 5 vegetation types can be ordered as crop > grass > subshrub> tree> shrub and this relationship displayed time stability. The different land cover types clearly influenced the water infiltration and water input amounts in the re-vegetated area. The subshrub site showed the highest total infiltration amount (164 mm) with precipitation (227 mm) during the study period. The grass site had an infiltration amount of 156 mm. The tree site had a total precipitation of 154 mm and an infiltration amount of 97 mm. The infiltration amount was 136 mm for the shrub site and was the lowest (83 mm) for the crop site. Natural grasses displayed a rapid infiltration rate and the wetting front was able to reach a greater depth.

a b s t r a c t a r t i c l e i n f oSoil erosion is a critical environmental problem of the Loess Plateau, China. As an important project for soil and water conservation in the semi-arid environment, the Grain-for-Green extensively transformed a wide range of farmland into vegetated land after the 1980s. Yet, the effects of vegetation restoration on soil erosion reduction are not well understood. In this study, we monitored runoff and sediment yield at sites restored with six typical restoration vegetation types including shrubs (Armeniaca sibirica, Spiraea pubescens and Artemisia coparia), grasses (Andropogon), and shrub-grass-compounds (Andropogon and A. coparia) in the Loess Plateau. We employed structural equation modelling (SEM) to systematically analyze the relative effects of precipitation and vegetation on soil erosion. The results showed that the runoff and sediment yield at the grasslands were significantly higher than other cover types. The shrub cover had the strongest soil conservation capacity of all restoration vegetation. SEM results showed varying impacts of precipitation (i.e., total amount and erosive rainfall intensity) on runoff and soil erosion under different vegetation types owing to differences in canopy structure and surface litter layer. Our study quantitatively revealed the interactive effects of precipitation and vegetation on runoff and sediment, which may be beneficial to conserving available water and soil resources in the semiarid environment.

Abstract. We studied the impacts of re-vegetation on soil moisture dynamics and evapotranspiration (ET) of five land cover types in the Loess Plateau in northern China. Soil moisture and temperature variations under grass (Andropogon), subshrub (Artemisia scoparia), shrub (Spiraea pubescens), plantation forest (Robinia pseudoacacia), and crop (Zea mays) vegetation were continuously monitored during the growing season of 2011. There were more than 10 soil moisture pulses during the period of data collection. Surface soil moisture of all of the land cover types showed an increasing trend in the rainy season. Soil moisture under the corn crop was consistently higher than the other surfaces. Grass and subshrubs showed an intermediate moisture level. Grass had slightly higher readings than those of subshrub most of the time. Shrubs and plantation forests were characterized by lower soil moisture readings, with the shrub levels consistently being slightly higher than those of the forests. Despite the greater post-rainfall loss of moisture under subshrub and grass vegetation than forests and shrubs, subshrub and grass sites exhibit a higher soil moisture content due to their greater soil retention capacity in the dry period. The daily ET trends of the forests and shrub sites were similar and were more stable than those of the other types. Soils under subshrubs acquired and retained soil moisture resources more efficiently than the other cover types, with a competitive advantage in the long term, representing an adaptive vegetation type in the study watershed. The interactions between vegetation and soil moisture dynamics contribute to structure and function of the ecosystems studied.