[Environmental significance of wet deposition composition in the central Qilian Mountains, China].

A total of 90 precipitation samples were collected from individual precipitation events at the Qilian Alpine Ecology & Hydrology Research Station (Hulugou Station, 30 degrees 47'N, 90 degrees 58'E; 3 260 m a. s. l) located in the central Qilian Mountains from August 2012 to November 2013. All samples were analyzed for major cations (Na, K+, Ca2+ and Mg2+), anions (Cl- , NO3- and SO4(2-)) and conductivity. Precipitation EC values ranged from 2.26 to 482 µS x cm(-1) with an average value of 41.9 µS x cm(-1). The precipitation was of SO4(2-) -Mg(2+) -Ca2+ type, which contributed > 70% to the total ionic concentration. The same as the precipitation alkalinity, precipitation events occurred around summer showed lower concentrations, while it had higher concentrations in winter and spring with little precipitation and larger wind speed. Enrichment factor (EF), correlation and factor analysis indicated that regional crustal aerosols and species from central Asian and northwestern China arid regions brought by the westerly circulation were the major sources for these ions, some dust from human pollution were the secondary sources, and the contribution of sea salt was the least due to the long distance transport. These characteristics could be also confirmed by the correlation between ionic concentrations and metrological data in the study region. It is also interesting that the precipitation chemistry was different under the different atmospheric circulation: the monsoon precipitation, the interaction precipitation events ( influenced both by monsoon and westerly) and the westerly precipitation.

[Measurement and estimation of grassland evapotranspiration in a mountainous region at the upper reach of Heihe River basin, China].

Evapotranspiration (ET) is an important component of water cycle, but its measurement in high altitude mountainous region is quite difficult, inducing the insufficient understanding on the actual ET in high altitude mountainous region and the effects of ET on this region' s water cycle. In this paper, two small type weighing mini-lysimeters were applied to measure the daily ET in a piece of grassland in a high altitude mountainous region of the Heihe River basin from July 1st, 2009 to June 30th, 2010. Based on the measured data, the methods of FAO-56 Penman-Monteith (F-P-M), Priestley-Taylor (P-T), and Hargreaves-Samani (H-S) were employed to estimate the ET to analyze the applicability of the three methods for the mountainous region, and the pan coefficient at the measurement spots was discussed. During the measurement period, the total annual ET at the measurement spots was 439.9 mm, accounting for 96.5% of the precipitation in the same period, and the ET showed an obvious seasonal distribution, being 389. 3 mm in May-October, accounting for 88. 5% of the annual value. All the three methods could be well applied to estimate the summer ET but not the winter ET, and their applicability followed the sequence of P-T > F-P-M > H-S. At the measurement spots, the daily pan coefficient in summer was 0.7-0. 8, while that in winter was quite variable.

[Characteristics of stemflow for typical alpine shrubs in Qilian Mountain].

Taking the typical alpine shrubs Potentilla fruticosa, Salix cupularis, Hippophae rhamnoides, and Caragana jubata in Qilian Mountain as test objects, a field investigation from June 1 to October 31, 2010 was conducted on the variation characteristics of the shrub stemflow, and analyzed the affecting effects of rainfall intensity and canopy structure morphology. The stemflow generated when the rainfall in early period was 2.1 mm, with an average of 3.4%, 3.2%, 8.0%, and 4.2% of the gross rainfall for P. fruticosa, S. cupularis, H. rhamnoides, and C. jubata, respectively. There was a significant positive linear correlation between the stemflow and rainfall intensity. With increasing rainfall, the stemflow percentage showed a trend of increase-decrease-increase. Stemflow played an important role in supplying water to the shrub rhizosphere, and the average funneling ratio was 59, 30, 110, and 49 for P. fruticosa, S. cupularis, H. rhamnoides, and C. jubata, respectively. The stemflow percentage had a significant exponential relationship with the maximum rain intensity in 10 minutes (I10). When the I10 was more than 6.0 mm x h(-1), the stemflow of H. rhamnoides and C. jubata showed a persistently increasing trend, while that of P. fruticosa and S. cupularis tended to be stable. Canopy structure morphology had complicated effects on the stemflow. In the same rainfall intensities, the height and crown projection area of the shrubs were the important factors affecting the generation of stemflow.