The ecological water diversion project in the Heihe River Basin is the first successful case in China in which the ecological systems in a river basin have been rescued. This project serves as a valuable example for the management of ecosystems in other inland river basins. This paper reviews the integrated studies of the water–ecosystem–economy relationship in the Heihe River Basin and concludes that sustainable development in inland river basins requires the basin to be considered as a whole, with the relationships between the upstream, midstream and downstream areas of the basin coordinated appropriately. Successful development in these basins will be reflected in an improved output per cubic meter of water and the implementation of integrated river basin management practices.

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Nitrous oxide (N 2 O) emissions can be significantly affected by the amounts and forms of nitrogen (N) available in soils, but the effect is highly dependent on local climate and soil conditions in specific ecosystem. To improve our understanding of the response of N 2 O emissions to different N sources of fertilizer in a typical semiarid temperate steppe in Inner Mongolia, a 2-year field experiment was conducted to investigate the effects of high, medium and low N fertilizer levels (HN: 200 kg Nha ) respectively and N fertilizer forms (CAN: calcium ammonium nitrate, AS: ammonium sulphate and NS: sodium nitrate) on N 2 O emissions using static closed chamber method. Our data showed that peak N 2 O fluxes induced by N treatments were concentrated in short periods (2 to 3 weeks) after fertilization in summer and in soil thawing periods in early spring; there were similarly low N 2 O fluxes from all treatments in the remaining seasons of the year. The three N levels increased annual N 2 O emissions significantly (P<0.05) in the order of MN > HN > LN compared with the CK (control) treatment in year 1; in year 2, the elevation of annual N 2 O emissions was significant (P < 0.05) by HN and MN treatments but was insignificant by LN treatments (P>0.05). The three N forms also had strong effects on N 2 O emissions. Significantly (P<0.05) higher annual N 2 O emissions were observed in the soils of CAN and AS fertilizer treatments than in the soils of NS fertilizer treatments in both measured years, but the difference between CAN and AS was not significant (P>0.05). Annual N 2 O emission factors (EF) ranged from 0.060 to 0.298% for different N fertilizer treatments in the two observed years, with an overall EF value of 0.125%. The EF values were by far less than the mean default EF proposed by the Intergovernmental Panel on Climate Change (IPCC).

Nitrogen addition to soil can play a vital role in influencing the losses of soil carbon by respiration in N-deficient terrestrial ecosystems. The aim of this study was to clarify the effects of different levels of nitrogen fertilization (HN, 200 kg N ha -1 year -1 ; MN, 100 kg N ha -1 year -1 ; LN, 50 kg N ha -1 year -1 ) on soil respiration compared with non-fertilization (CK, 0 kg N ha -1 year -1 ), from July 2007 to September 2008, in temperate grassland in Inner Mongolia, China. Results showed that N fertilization did not change the seasonal patterns of soil respiration, which were mainly controlled by soil heat-water conditions. However, N fertilization could change the relationships between soil respiration and soil temperature, and water regimes. Soil respiration dependence on soil moisture was increased by N fertilization, and the soil temperature sensitivity was similar in the treatments of HN, LN, and CK treatments (Q 10 varied within 1.70-1.74) but was slightly reduced in MN treatment (Q 10 = 1.63). N fertilization increased soil CO 2 emission in the order MN [ HN [ LN compared with the CK treatment. The positive effects reached a significant level for HN and MN (P \ 0.05) and reached a marginally significant level for LN (P = 0.059 \ 0.1) based on the cumulative soil respiration during the 2007 growing season after fertilization (July-September 2007). Furthermore, the differences between the three fertilization treatments and CK reached the very significant level of 0.01 on the basis of the data during the first entire year after fertilization (July 2007-June 2008. The annual total soil respiration was 53, 57, and 24% higher than in the CK plots (465 g m -2 year -1 ). However, the positive effects did not reach the significant level for any treatment in the 2008 growing season after the second year fertilization (July-September 2008, P [ 0.05). The pairwise differences between the three N-level treatments were not significant in either year (P [ 0.05).