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Carbon and Nitrogen Dynamics in Soil Aggregates under Long‐Term Nitrogen and Water Addition in a Temperate Steppe
Author(s) -
Wang Ruzhen,
Dungait Jennifer A.J.,
Creamer Courtney A.,
Cai Jiangping,
Li Bo,
Xu Zhuwen,
Zhang Yuge,
Ma Yini,
Jiang Yong
Publication year - 2015
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2014.09.0351
Subject(s) - steppe , nitrogen , soil water , environmental chemistry , soil carbon , chemistry , temperate climate , soil organic matter , grassland , environmental science , ecosystem , terrestrial ecosystem , organic matter , agronomy , soil science , ecology , biology , organic chemistry
Anthropogenic‐driven changes in N and water availability are two of the most important factors determining soil C and N turnover in temperate grassland ecosystems. To gain insight into changes in soil aggregation and C and N dynamics in response to N and water addition, we collected soil samples from a field study conducted for 9 yr in a semiarid steppe grassland in Inner Mongolia, China. Three aggregate size classes (microaggregates, <250 μm; small macroaggregates, 250–2000 μm; macroaggregates, >2000 μm) were isolated and analyzed for their mass proportions, soil organic C (SOC), total N (TN), total extractable inorganic N (TIN), and stable isotope ratio of 13 C relative to 12 C (δ 13 C) and stable isotope ratio of 15 N relative to 14 N (δ 15 N) values. Water addition on average increased large macroaggregates by 33% and decreased microaggregates by 42%. Nitrogen and water addition interacted significantly and increased TIN concentration but had no impact on SOC or TN. Soil organic C was negatively correlated with δ 13 C values of large and small macroaggregates under ambient precipitation and within all soil aggregates under water addition. Significant positive correlations between TIN and δ 15 N values were detected for large macroaggregates and microaggregates under ambient precipitation. Our results suggest that water addition accelerated plant residue incorporation into soil organic matter (SOM) (indicated by depleted 13 C values) while N addition potentially increased gaseous N losses (suggested by 15 N enrichment without changing soil C and N concentrations). Water, but not N, improved soil structure in this semiarid grassland. Our study provides new insights for using natural abundance 13 C and 15 N to better understand the sensitivity of SOM within different soil particles to coupled N–water changes under global change scenarios.