Abstract. Land use plays an important role in controlling spatial and temporal variations of soil moisture by influencing infiltration rates, runoff and evapotranspiration, which is important to crop growth and vegetation restoration in semiarid environments, such as Horqin sandy land in north China. However, few studies have been conducted comparing differences of dynamics of soil water conditions and the responses of soil to infiltration under different land use types in semiarid area. Five different land use types were selected to analyze soil moisture variations in relation to land use patterns during the growing season of 2 years. Results showed that soil moisture condition was affected by different land uses in semi-arid sandy soils. The higher soil moisture content among different land uses was exhibited by the grassland, followed by cropland, poplar land, inter-dunes and shrub land. The temporal variations of soil moisture in different land uses were not always consistent with the rainfall due to the dry sequence. Moreover, soil water at the surface, in the root zone and at the deep soil layer indicated statistical differences for different types of land cover. Meanwhile, temporal variations of soil moisture profile changed with precipitation. However, in the deep soil layer, there was a clear lag in response to precipitation. In addition, seasonal variations of profile soil moisture were classified into two types: increasing and waving types. And the stable soil water layer was at 80-120 cm. Furthermore, the infiltration depth exhibited a positive correlation with precipitation under all land uses. This study provided an insight into the implications for land and agricultural water management in this area.

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32Livestock grazing is a crucial cause of vegetation degradation and desertification in sandy lands. 33The sparse-elm grassland of Horqin Sandy Land, China has suffered severe degradation of 34 biodiversity and ecosystem services. Management to exclude grazing is often necessary for

Determination of the geographical distribution and life-form spectra of alien species with different invasive abilities are essential to understand the process of invasion and to develop measures to manage alien species. Based on six classifications of Chinese alien species, environmental and social data, species density, life-form spectrum of alien species, and the relationship between species density of alien species and climatic or social factors were determined. The species density of alien species *Manuscript (double-spaced and continuously LINE and PAGE numbered)-for final publication Click here to view linked References temperature were the most important factors for the non-invasive alien species. The invasive alien species had a high proportion of annual and biennial herbs and non-invasive alien had a high proportion of shrubs and trees. It is important to understand the geographical distribution and life-form spectra of various invasive alien species for alien species controls.

Currently the amount of data available on the effect of sand dune stabilization on species conservation in inter-dune lowland is very limited, especially for the sand dune systems in semi-arid regions. In this study, we determined whether the characteristics of above-ground vegetation, soil seed bank and their relationships with environmental factors changed with sand dune stabilization in the inter-dune lowlands in Horqin Sandy Land, China. Species composition, abundance and coverage of aboveground vegetation as well as soil seed bank composition and density were surveyed and their correlations with environmental factors (pH, organic matter content, total nitrogen and total phosphorus) were determined. The results showed that changes in the relationship between aboveground vegetation, soil seed bank and soil quality followed the changes in aboveground vegetation and soil seed banks. Aboveground vegetation species richness increased with sand dune stabilization, but soil seed bank species richness declined. The inter-dune lowland of active sand dunes could provide specific habitats for some endemic species and pioneer psammophyte species as indicated by data on aboveground vegetation and soil seed bank. Our results suggested that both active and stabilized sand dunes should be maintained since active sand dunes are essential for the survival of endemic or pioneer species and stabilized sand dunes are important for sustaining species richness.

Vegetation restoration as an effective sand fixation measure has made great achievements in China. However, soil water conditions deteriorate with the development and maturity of sand-fixing vegetation. In this study, we investigated the relationship between soil water content (SWC) and vegetation coverage (VC) at different portion (top, middle and bottom) on ten sand dunes during the growing season (April to October) in Horqin Sandy Land, northern China. We analyzed the temporal and spatial variation characteristics of SWC under different VC. The results indicate that VC and soil water storage were negatively correlated. The effect of vegetation on soil water storage on the sand dunes was greater in the dry season than the wet season. The VC and coefficient of coefficient of SWC were positively correlated at the 20 to 140 cm soil depth. As VC increased, the effect of drought stress increased at the 20 to 200 cm soil depths. The VC and SWC were negatively correlated at all the three portions of the sand dunes. According to soil water conditions and the concept of wilting humidity at different VC, we found that the suitable VC values were less than 0.46, 0.52, and 0.71 at the top, middle and bottom of the sand dunes, respectively.