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标题：Continental soil drivers of ammonium and nitrate in Australia
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作者：Lee, Juhwan ; Garland, Gina M. ; Viscarra Rossel, Raphael A. 等
期刊名称：SOIL
印刷版ISSN：2199-3971
出版年度：2018
卷号：4
期号：3
页码：213-224
DOI：10.5194/soil-4-213-2018
出版社：Copernicus GmbH
摘要：Soil N is an essential element for plant growth, but its mineral forms are subject to loss from the environment by leaching and gaseous emissions. Despite its importance for the soil-plant system, factors controlling soil mineral N contents over large spatial scales are not well understood. We used NH 4 + and NO 3 - contents (0–30 cm depth) from 469 sites across Australia and determined soil controls on their regional variation. Soil mineral N varied regionally but depended on the different land uses. In the agricultural region of Australia, NH 4 + tended to be similar (median 4.0 vs. 3.5 mg N kg −1 ) and NO 3 - was significantly enriched (3.0 vs. 1.0 mg N kg −1 ), compared to the non-agricultural region. The importance of soil controls on mineral N in the agricultural region, identified by the model trees algorithm Cubist, showed that NH 4 + was affected by total N, cation exchange capacity (CEC) and pH. In the non-agricultural region, NH 4 + was affected not only by CEC and pH, but also by organic C and total P. In each of the regions, NO 3 - was primarily affected by CEC, with more complex biophysical controls. In both regions, correlations between mineral N and soil C : N : P stoichiometry suggest that more NH 4 + was found in P-depleted soil relative to total C and total N. However, our results showed that only in the non-agricultural region was NO 3 - sensitive to the state of C and its interaction with N and P. The models helped to explain 36 %–68 % of regional variation in mineral N. Although soil controls on high N contents were highly uncertain, we found that region-specific interactions of soil properties control mineral N contents. It is therefore essential to understand how they alter soil mechanisms and N cycling at large scales.