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Abstract: The nonparametric Mann–Kendall test was used to detect the trends of major hydroclimatic variables in the Tarim River Basin, the largest inland river basin in China for the period of 1960–2007. Results showed that both mean annual air temperature and precipitation experienced an increasing trend, while annual streamflow demonstrated a mixed trend of decreasing and increasing: The mountainous region upstream showed an increasing trend and the region downstream exhibited a decreasing trend. Impacts of the increased air temperature on streamflow have shown different characteristics depending on location and seasons: it has positive effect on the runoff at mountainous region due to snowmelt and glacier-melt in spring, but negative effect on the runoff at plain area due to the increase of actual evaporation in summer. In addition, human activity contributed to the declining of streamflow in the arid plain oases at downstream of the Tarim River Basin. The results obtained in this paper can be used as a reference for the planning and management of water resources to maintain the health of the river system. [Copyright &y& Elsevier]

Abstract: Vegetation restoration is one of the most common methods for combating desertification in northern China. The planting of shrubs on the southeast fringe of the Tengger Desert had significant effects on hydrological cycles, especially on the evaporation process. In this paper, a field experiment was conducted to investigate the effect of revegetation on evaporation process in a desert. The presence of shrubs reduced percolation from a lysimeter to zero. Caragana korshinskii Kom. showed greater evapotranspiration in the wetter of two study years, while Artemisia ordosica Krash. showed more evapotranspiration in the drier year. This was attributed to their different root distributions. The microlysimeter measurements showed that there was no significant difference in the evaporation rates between locations in the same quadrat, which means that the sparse vegetation had little effect on soil evaporation under the canopy, and thus modification of the microclimate was not a dominant factor in controlling soil evaporation in the revegetated desert area. The difference in soil evaporation between bare sand and the revegetated area was caused mainly by the formation of biological soil crusts. Simulated rainfall experiments showed that the crust had a retarding effect on evaporation under very low rainfall (⩽5mm), because its high proportion of finer particles slowed the evaporation rate, thus keeping the water in the soil surface longer. However, it allowed a higher evaporation rate under higher rainfall conditions. [Copyright &y& Elsevier]

Abstract: This paper describes the first results from a hydro-micrometeorological study designed to characterize the surface exchanges of water, and CO2, at a sky island forest site in the Santa Catalina Mountains. Data collected between June 2002 and December 2004 is used to describe the seasonal water/carbon dynamics of this ecosystem. During the severely dry pre-monsoon period (May–June) when vapor pressure deficit exceeded 2kPa, daytime relative humidity was below 20%, and soil moisture was less than 10%, the predominantly Douglas Fir/Pine forest severely reduced or curtailed its photosynthetic activity. At the onset of the monsoon season in July, the vegetation responded rapidly to the precipitation input, as soil moisture increased. The trees then remained relatively active throughout the fall and winter, particularly if there was adequate winter precipitation which promoted very high productivity into early spring. Given the relative importance of mountain island forest in this semi-arid landscape in terms of its contribution to area-average surface water and carbon exchange, the strong and somewhat unusual coupled seasonal cycles, this forest ecosystem likely has hitherto unrecognized implication for the seasonality of the regional-scale water and carbon cycle. [Copyright &y& Elsevier]