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 alpinemeadows in retention of deposited...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 alpinemeadows in retention of deposited nitrogen (N). It was shown that the fate of NO3^--15N or NH4^+-15N wasdistinctly 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 wereobviously shown on partitioning of 15N among different components in alpine meadows. After 11-13 monthsfollowing 15N additions, more NO3^--15N was recovered in plants than in soil organic matter or in soilmicroorganisms. 15N retained in soil organic matter was also high and increased with time. 15N immobilizedin soil microorganisms was close to that retained in soil organic matter within 11-12 months while itdecreased significantly after 13 months. When NH4^+-15N was added, more 15N was retained in soil organicmatter than in plants or in soil microorganisms. 15N taken up by plants was constant while that immobilizedin soil microorganisms altered greatly. Eleven to thirteen months after 15N additions, plants and soil^--15microorganisms took up more NO3^--N than NH4^+-15N while soil organic matter recovered more NH4^+-15Nthan NO3^--15N. It indicates that alpine meadows play different roles in retention of deposited NO3- and NH4^+after a long time.展开更多
文摘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 alpinemeadows in retention of deposited nitrogen (N). It was shown that the fate of NO3^--15N or NH4^+-15N wasdistinctly 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 wereobviously shown on partitioning of 15N among different components in alpine meadows. After 11-13 monthsfollowing 15N additions, more NO3^--15N was recovered in plants than in soil organic matter or in soilmicroorganisms. 15N retained in soil organic matter was also high and increased with time. 15N immobilizedin soil microorganisms was close to that retained in soil organic matter within 11-12 months while itdecreased significantly after 13 months. When NH4^+-15N was added, more 15N was retained in soil organicmatter than in plants or in soil microorganisms. 15N taken up by plants was constant while that immobilizedin soil microorganisms altered greatly. Eleven to thirteen months after 15N additions, plants and soil^--15microorganisms took up more NO3^--N than NH4^+-15N while soil organic matter recovered more NH4^+-15Nthan NO3^--15N. It indicates that alpine meadows play different roles in retention of deposited NO3- and NH4^+after a long time.
