Soil microbial respiration is a key process controlling the size of the soil organic C storage and C loss from terrestrial ecosystems to atmosphere. A small change in the rate of soil microbial respiration may have a large effect on the net C flux and climate dynamics because of the largest SOC stored in terrestrial soil systems. Therefore, understanding the response of soil microbial respiration and its temperature sensitivity (Q10) to atmospheric N deposition under global warming is important to improve the accuracy of predicting changes in global C cycles and its feedback to climate change.
In recent years, many works about microbial respiration and its Q10 have been done to investigate the effects of N deposition on soil microbial respiration and its Q10. However, most previous studies used single inorganic or organic N as N resource, which may not actually reflect the effects of atmospheric N deposition on soil microbial respiration and its Q10 because it indeed contains inorganic and organic N components.
Therefore, to advance the understanding of the responses of soil microbial respiration and its Q10 values to atmospheric N deposition, professor Wang Qingkui and his colleagues from the Institute of Applied Ecology of the Chinese Academy of Sciences conducted experiment with soils receiving long-term N addition to assess the effects of inorganic and organic N addition on soil microbial respiration and its Q10, and reveal their underlying mechanisms.
They had three important findings in this study. First, mixture of inorganic and organic N had the highest suppression on soil microbial respiration, following organic N and inorganic N. This suggested that suppression effect of atmospheric N deposition on soil microbial respiration was underestimated by previous studies based on single inorganic or organic N. Second, inorganic N addition significantly increased the averaged Q10 values, suggesting that inorganic N caused soil microbial respiration to be more sensitive response to climate warming than organic N. Third, soil microbial respiration was negatively controlled by NO3--N and microbial community composition, but Q10 was positively controlled by soil NH4+-N.
Their results highlighted the effects of inorganic and organic N addition on microbial respiration and its potential mechanisms, and implied the necessity of considering N type when predicting soil C cycling and dynamics in the increasing N deposition scenario.
These results were published as the title "Influences of N deposition on soil microbial respiration and its temperature sensitivity depend on N type in a temperate forest "Agricultural and Forest Meteorology".
The work was supported by the National key R & D projects in China, the National Natural Science Foundation of China, and the Strategic Priority Research Program of the Chinese Academy of Sciences.
Fig. 1 Cumulative respired C after 150-day incubation at 15 oC and 25 oC in a temperate forest. CT, IN, ON and MN represent control, inorganic N, organic N and their mixture treatments, respectively. The different letters above the bars represented significant differences among treatments at the same temperature (P < 0.05).
Fig. 2 The temporal variations of Q10 under different types of N deposition during 150 day incubation in a temperate forest. CT, IN, ON and MN represent control, inorganic N, organic N and their mixture treatments, respectively (Image by WANG Qingkui).
Fig. 3 Contributions of main controlling factors to explaining variations in soil cumulative respired C at 15 oC and 25 oC and its temperature sensitivity (Q10) based on redundancy analysis. NO3 and NH4 present nitrate and ammonium nitrogen; AP presents soil available P; C:N presents the ratio of soil organic C to total N; B:F denotes the ratio of bacterial PLFAs: fungal PLFAs; GP and GN denote gram-positive and –negative bacterial PLFAs, respectively. Cyc:mono, Sat:mono denote ratios of cyclopropyl to monoenoic fatty acids and total saturated to total monounsaturated fatty acids (Image by WANG Qingkui).
Email: yueqian@iae.ac.cn
Publication Name: WANG Qingkui et al.
