Abstract: With the shady and sunny northern slopes of Qilian Mountains along an altitude gradient from 2600 m to 3600 m as test objectives, this paper studied t he vertical distribution patterns of surface soil (0〖KG-*2〗-〖KG-*7〗20 cm) or ganic carbon (SOC) and total nitrogen (TN), and their relations to the altitude, landform, and vege tation. The results indicated that SOC and TN contents were significantly hi gher on shady than on sunny slope, and all increased with increasing altitude. The SOC and TN contents under different vegetation types were in the order of alpi ne bush >Picea crassifolia forest>alpine meadow>Sabina przewalskii fores t, and alpine bush >alpine meadow>P. crassifolia forest>S. przewalskii f orest, respectively. SOC had significant positive correlations with altitude , annual precipitation, soil moisture, and soil TN, and significant negative cor relations with soil pH and annual temperature. Soil C/N ratio along the gradient was within the range of 67〖KG-*2〗-〖KG-*7〗233, being favorable to the nu trient release dur ing organic matter decomposition. Among the factors affecting SOC, the annua l temperature, precipitation, and soil moisture content constituted the first pr incipal component, and soil C/N ratio constituted the second principal component . These two principal components accounted for 71% of the variance of SOC co ntent, suggesting that climate factors controlled the vertical distribution patt erns of SOC and TN along the altitude gradient.

Key words: Haplocladium microphyllum, water stress, osmo-regulation, antioxidant enzyme system.