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Abstract: The present and future spatiotemporal characteristics of reference evapotranspiration (ET0) are examined in this paper. ET0 during 1961–2009 are calculated by the Penman–Monteith method recommended by FAO (Food and Agriculture Organization) with historical weather data while ET0 during 2011–2099 are downscaled from HadCM3 (Hadley Centre Coupled Model, version 3) outputs under two emission scenarios (A2 and B2) by SDSM (Statistical DownScaling Model). The spatial distribution and temporal trend in ET0 are interpreted by Inverse Distance Weighted Interpolation and Mann–Kendall method, respectively. Results show that the annual mean ET0 is 1060.3mm, the lowest and highest values are found in the southwest and northwest region due to the spatial distribution of climatic factors, respectively. ET0 has increased significantly due to the downward trend in relative humidity and upward trend in temperature on the Loess Plateau during 1961–2009. HadCM3 projects a continuous increase in ET0 in the 21st century and the upward trend will be more pronounced after 2050. Averaged over the two emission scenarios for the whole area, the projected increase are 4%, 7% and 12% for the three periods 2011–2040, 2041–2070 and 2071–2099, respectively; the increase under A2 scenario are slightly greater than those under B2 scenario. An obvious gradient is detected for the projected increase in ET0 from northeast to southwest region in the 21st century. The increase in ET0 will possibly influence the water resource on the Loess in the 21st century and some countermeasures should be taken to reduce the adverse impacts. [Copyright &y& Elsevier]

Abstract: A simple transfer function method is used to spatially downscale extreme precipitation and temperature indices of six GCMs (CNRM-CM3, GFDL-CM2.1, INM-CM3.0, IPSL-CM4, MIROC3.2_M and NCAR-PCM) under three emission scenarios (A1B, A2, B1) from grid outputs to target station to project their potential spatiotemporal changes on the Loess Plateau of China during the 21st century. GCMs project that extreme climate events will keep the present change trend, i.e. longer heatwave duration and growing season length, less cold extremes, smaller annual extreme temperature range, more frequent and intense precipitation, and longer drought duration; and climate models suggest that the changes during the 21st century are a further amplification of those at present. Spatial variations exist in the changes of extreme indices, the greatest changes will occur in the southeast and northwest region for extreme precipitation indices while in the north and southeast region for extreme temperature events. The projected changes in extreme climate will possibly bring great impacts on the soil losses and agriculture on the Loess Plateau and countermeasures should be planned. [Copyright &y& Elsevier]

Abstract: There is a growing interest in using soil microbial parameters as indicators of soil quality changes after revegetation of disturbed soils. This study investigated the changes in different soil microbial parameters as well as physico-chemical parameters as affected by vegetation rehabilitation of soil in the Loess plateau of China subjected to natural succession after enclosure. The results showed that the soil nutrients tend to be concentrated in the soil surface layer, especially the soil organic C, total N and alkali extractable N with soil organic C being doubled (up to 20gkg−1) after 50 years of revegetation. Soil enzyme activities and microbial biomass C (Cmic) and N (Nmic) increased with rehabilitation time up to 23 years. After 23 years, soil Cmic and Nmic and enzyme activities remained stable. Enzyme activities increased rapidly during the early stage of revegetation, about 15–20 years after enclosure. Soil Cmic and Nmic also increased about 20% faster up to 23 years since enclosure in the 0–20-cm soil layer. Soil basal respiration (BR) in the 23 years site was higher than in other sites, indicating high microbial activity in this site. These findings demonstrated significant impacts of natural vegetation succession in overgrazed grassland on the properties of the surface soils, including the soil nutrients, organic matter, soil microbial biomass, respiration, and enzyme activities. [Copyright &y& Elsevier]

Summary: Land use and climate are two main factors directly influencing catchment hydrology, and separation of their effects is of great importance for land use planning and water resources management. Using the SWAT (Soil and Water Assessment Tools) model, we assessed the impacts of land use change and climate variability on surface hydrology (runoff, soil water and evapotranspiration) in an agricultural catchment on the Loess Plateau of China. Results indicated that SWAT proved to be a powerful tool to simulate the effect of environmental change on surface hydrology. The Nash–Sutcliffe model efficiency (Ens), Percent bias (PBIAS) and ratio of root mean square error to measured standard deviation (RSR) for annual flow was 0.87, 4.0%, 0.36 during calibration period and 0.87, 2.5%, 0.36 during validation periods, respectively. During 1981–2000, about 4.5% of the catchment area was changed mainly from shrubland and sparse woodland to medium and high grassland, and climate changed to warmer and drier. The integrated effects of the land use change and climate variability decreased runoff, soil water contents and evapotranspiration. Both land use change and climate variability decreased runoff by 9.6% and 95.8%, respectively, and decreased soil water contents by 18.8% and 77.1%. Land use change increased evapotranspiration by 8.0% while climate variability decreased it by 103.0%. The climate variability influenced the surface hydrology more significantly than the land use change in the Heihe catchment during 1981–2000; therefore, the influence of climate variability should be considered and assessed separately when quantifying the hydrological effect of vegetation restoration in the Loess Plateau. [Copyright &y& Elsevier]