J Integr Plant Biol. ›› 2004, Vol. 46 ›› Issue (3): 279-283.

• Research Articles • Previous Articles     Next Articles

Long-term Partitioning of Ammonium and Nitrate Among Different Components in an Alpine Meadow Ecosystem

XU Xing-Liang, OUYANG Hua, PEI Zhi-Yong, ZHOU Cai-Ping   


The fate of 15N-labeled ammonium and nitrate was determined in a Kobresia pygaea C. B. Clarke meadow after 11-13 months following 15N additions in order to understand the role of alpine meadows in retention of deposited nitrogen (N). It was shown that the fate of NO3--15N or NH4+-15N was distinctly different. In 11-13 months after 15N additions, total 15N recovery of NO3--15N was 92.83%, 92.64% and 79.96% while 15N recovery of NH4+-15N was 49.6%, 63.33% and 66.22%. Their different fates were obviously shown on partitioning of 15N among different components in alpine meadows. After 11-13 months following 15N additions, more NO3--15N was recovered in plants than in soil organic matter or in soil microorganisms. 15N retained in soil organic matter was also high and increased with time. 15N immobilized in soil microorganisms was close to that retained in soil organic matter within 11-12 months while it decreased significantly after 13 months. When NH4+-15N was added, more 15N was retained in soil organic matter than in plants or in soil microorganisms. 15N taken up by plants was constant while that immobilized in soil microorganisms altered greatly. Eleven to thirteen months after 15N additions, plants and soil microorganisms took up more NO3--15N than NH4+-15N while soil organic matter recovered more NH4+-15N than NO3--15N. It indicates that alpine meadows play different roles in retention of deposited NO3- and NH4+ after a long time.

Key words: NO3--15N, NH4+-15N, Kobresia pygaea meadow, soil organic matter, soil microorganisms, alpine plants

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