Warming impacts on carbon, nitrogen and phosphorus distribution in soil water-stable aggregates

A five-year (2010-2015) field experiment was conducted to investigate warming impacts on organic carbon (OC), total nitrogen (TN) and total phosphorus (TP) contents and their ratios in bulk soil and soil water-stable aggregates in an alpine meadow of the Tibetan Plateau. Compared with unwarmed control, warming had no significant effects on OC, TN and TP contents and their ratios in bulk soil. The contents of OC, TN and TP associated with macroag-gregates and microaggregates decreased, whereas those associated with silt + clay fractions significantly increased. The C:N and C:P ratios in macro-and microaggregates and silt + clay fractions decreased, with significant differences for C:P ratio in microaggregates and C:N and C:P ratios in silt + clay fractions. The results indicated that C, N and P were protected chemically in silt-and clay-size fractions under warming, which offset the loss of C, N and P protected physically by macro-and microaggregates. Both physically and chemically protected C decomposition proceeded relatively more rapidly or accumulated relatively more slowly than did N and P. Our results suggest that C, N and P distributions within soil aggregate size fractions influence their net changes in bulk soil under future climate change scenarios.