TheM inera liza tion of So il Nitrogen and ItsMotiva ting Factors to the DragonSpruce Forest and AlpineMeadows of the Qilian Mounta ins The Applica tion of the D istr ibuted Eco-hydrolog ica lModel TOPOGin a Mounta inous Sma llWa tershed of Tempera te Zone:A Ca se Study in the Sma llWa tershed of Pa ilugou in Qilian Mounta ins Responses of foliar δ13C in Sabina przewalskii and Picea crassifolia to altitude and its mechanism in the Qilian Mountains, China