Interactions between lakes and the atmosphere at high altitudes are still poorly understood due to difficulty in accessibility of direct measurements. This is particularly true for the Qinghai‐Tibet Plateau (QTP), where approximately 50% of the lakes in China are located. Continuous direct measurements of the water flux and surface energy budget were made over the largest high‐altitude saline lake in China, Qinghai Lake on the northeastern QTP, using the eddy covariance method from 11 May 2013 to 10 May 2015. Results indicated that annual evaporation of Qinghai Lake was 832.5 mm for 2013/2014 and 823.6 mm for 2014/2015, respectively. The surface energy budget and evaporation showed a strong seasonal pattern, with peaks in the latent and sensible heat flux observed in autumn and early winter. There was a 2–3 month delay between the maximum net radiation and maximum latent and sensible heat fluxes. Intraseasonal and seasonal variations in latent and sensible heat flux were strongly affected by different air masses. Westerly cold and dry air masses increased evaporation while southeast moist air mass suppressed evaporation, suggesting that the lakes might serve as an “air conditioner” to modify the temporal heat and water flux in the QTP.

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Natural vegetation restoration and tree plantation are the two most important measures for ecosystem restoration on the Loess Plateau of China. However, few studies have compared the effects of the two contrasting measures on soil organic and inorganic carbon (SOC and SIC) sequestration or have further used SOC and SIC isotopes to analyze the inherent sequestration mechanism. This study examined a pair of neighboring small watersheds with similar topographical and geological backgrounds. Since 1954, natural vegetation restoration has been conducted in one of these watersheds, and tree plantation has been conducted in the other. The two watersheds have now formed completely different landscapes (naturally restored grassland and artificial forestland). Differences in soil bulk density, SOC and SIC content and storage, and SOC and SIC δ(13)C values were investigated in the two ecosystems in the upper 1m of the soil. We found that SOC storage was higher in the grassland than in the forestland, with a difference of 14.90 Mg ha(-1). The vertical changes in the δ(13)CSOC value demonstrated that the two ecosystems have different mechanisms of soil surface organic carbon accumulation. The SIC storage in the grassland was lower than that in the forestland, with a difference of 38.99 Mg ha(-1). The δ(13)CSIC values indicated that the grassland generates more secondary carbonate than the forestland and that SIC was most likely transported to the rivers from the grassland as dissolved inorganic carbon (DIC). The biogeochemical characteristics of the grassland were favorable for the formation of bicarbonate. Thus, more DIC derived from the dissolution of root and microbial respired CO2 into soil water could have been transported to the rivers through flood runoff. It is necessary to study further the transportation of DIC from the grassland because this process can produce a large potential carbon sink.

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Understanding the variation regularity of lake level and the potential driver factors can provide insights into lake conservation and management. In this study, inter-and inner-annual variations of lake level in Qinghai Lake during the period 1961-2012 were analyzed to determine whether climatic factor or runoff factor were responsible for the variations. The results showed that lake level decreased significantly during the period 1961-2004 at a rate of À7.6 cm/yr, while increasing significantly during the period 2004-2012 at a rate of 14 cm/yr, and all were significant at a p value of <0.01. Lake level was most sensitive to climate and river runoff. Precipitation and river runoff had directly positive effects on lake level, but inverse evaporation and wind speed played a significantly negative role on lake level. The relative contributions of influencing factors in the Southeast Asian monsoon (SEAM) and the westerly circulation periods on annual lake level variations were approximately 49.8% and 27.8%, respectively. The relative contributions of temperature, precipitation, evaporation, and wind speed on lake level variation were approximately 13.8%, 36.3%, 27.1%, and 18.4%, respectively. In general, the annual lake level was primarily influenced by precipitation and evaporation of the SEAM period.

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