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Climate and ecosystem 15 N natural abundance along a transect of Inner Mongolian grasslands: Contrasting regional patterns and global patterns
Author(s) -
Cheng Weixin,
Chen Quansheng,
Xu Yuqing,
Han Xingguo,
Li Linghao
Publication year - 2009
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2008gb003315
Subject(s) - transect , abundance (ecology) , ecosystem , environmental science , terrestrial ecosystem , ecology , grassland , physical geography , geography , biology
Nitrogen isotopes provide integrated information about nitrogen cycling in terrestrial ecosystems. This study explores the regional patterns of ecosystem 15 N abundance along a 1200 km transect in Inner Mongolian grasslands and their relationships with climate. Results indicate that climatic variables control approximately 50% of the variation in ecosystem 15 N abundance along the transect. Ecosystem 15 N abundance decreases as both mean annual precipitation (MAP) and mean annual temperature (MAT) increase. Regional patterns obtained from our study differ from reported global patterns. Ecosystem 15 N abundance is negatively correlated with MAT along the eastern part of the transect, while a positive correlation between MAT and ecosystem 15 N is apparent at the global scale. MAP exerts stronger controls on ecosystem 15 N abundance along the western part of the transect than what is shown in a global regression model. Ecosystem 15 N abundance in the western part of the transect is substantially higher (ca. 3‰) than the values projected by a global model. The Δ 15 N soil‐plant (‰) (difference in δ 15 N values between plant and soil) values in Inner Mongolian grasslands are not significantly correlated with either MAP or MAT; but Δ 15 N soil‐plant values are positively correlated with MAT and negatively correlated with MAP at the global scale. These conflicting trends strongly indicate that climatic controls on ecosystem 15 N abundance are scale‐dependent. Regional N deposition gradients, grazing‐induced ammonia volatilization, and variation in plant‐soil types are among the possible causes of these inconsistencies.