Temperature Sensitivity of N2O and N2 Emissions from Ten Forest Soils
Abstract
Temperature sensitivity (Q10) of soil N2O and N2 emissions from terrestrial ecosystems and its controlling factors are essential for predicting the effects of global warming on nitrogen(N) cycle. Although the warming-induced effects on soil N cycle is considered to be positive in general, our understanding of how N2O and N2 emissions respond to climate change is rather limited. To quantify the Q10 of N2O and N2 emissions in forest soils and to identify their major driving factors, we performed an incubation experiment using 15N tracer (Na15NO3) with soil samples from ten forest sites with a large geographic distribution and a wide range of climate conditions. The sites stretched from temperate to tropical zones, with mean annual temperature (MAT) ranging from 3 to 21.5oC and mean annual precipitation (MAP) ranging from 300 to 2449 mm. The soil pH varied between 3.57 to 6.27. The samples were incubated for 12 or 24 hours under anaerobic condition at temperature from 5 to 35oC with an interval of 5oC, respectively. Soil temperature strongly affected the production of N2O and N2; N2O and N2 production rates showed a positive exponential relation with incubate time and temperature for all forest soils. Our results showed that the Q10 values ranged from 1.31 to 2.98 for N2O emission and 1.69 to 3.83 for N2 emission, indicating a generally positive feedback of N2O and N2 production to warming. Higher Q10 values for N2 than N2O implies that N2 emission is more sensitive to temperature increase. The N2O/(N2O+N2) decreased with increasing temperature in seven of ten forest soils, suggesting that warming accelerates N2 emission. Strong spatial variation in Q10 were also observed, with tropical forest soils exhibiting high Q10 values and relatively low Q10 in temperate forest soils. This variation is likely attributed to the inherent differences in N biogeochemical cycling behavior between the microbial communities among sites. Despite soil temperature primarily controls the N2O and N2 emissions, we will further explore the effects of other factors such as pH and C/N, and perform additional experiments to elucidate the role of other factors on Q10. In addition, we will partition N2O and N2 emissions to different microbial processes (e.g., denitrification, co-denitrification and anammox) and examine the temperature sensitivity of those different microbial processes, on the basis of the 15N isotope pairing technique. Key words: Temperature sensitivity, N2O, N2, Forest soil, Nitrogen cycle, Global warming
- Publication:
-
EGU General Assembly Conference Abstracts
- Pub Date:
- April 2019
- Bibcode:
- 2019EGUGA..2114227Y