Effect of nitrogen and acid deposition on soil respiration in a temperate forest in China

With the rapid development of the economy and society, synchronous increases in atmospheric nitrogen (N) and acid deposition might exert an important effect on the soil respiration of terrestrial ecosystems, simultaneously and interactively. To date, the interactive mechanisms of N and acid deposition on soil respiration (nutrient effect vs. acidification effect) remain unclear, because most studies only focused on simulating N deposition. Here, we conducted a field experiment in which simulated atmospheric N and acid deposition in a temperate forest of China, to explore their effects on soil respiration. Our results showed that N deposition reduced the cumulative release of CO2 by 7.47% during the growing season. Acid deposition and the interaction of N and acid deposition decreased soil respiration rate (RS) by 0.23% and 1.54%, respectively. Total phospholipid fatty acids (PLFAs) increased by 17.24% with N treatment. The interaction of N and acid deposition reduced total PLFAs by 6.14%. Unexpectedly, all experimental treatments reduced the temperature sensitivity (Q10) of soil respiration to some extent; thus, N and acid deposition might partially weaken the positive effect of warming on CO2 release from soils under global warming scenarios. The processes and ecological effects of N and acid deposition are simultaneous and inseparable in nature. Therefore, the effects of multi-factor interactions on soil respiration and their regional differences require further investigation.