Estimating Nitrous Oxide Emission From Chinese Forest And Grassland

Along with global warming, the long life greenhouse gases which contribute to global warming have drawn the attention from more and more people. As one of the most important greenhouse gases, nitrous oxide become familiar and important to general public not only attributesits high warming potential but alsoits immense damage to chemosphere.However, as nitrous oxide’s huge temporal and spatial variation, there is still big uncertainty and challenge for simulating regional nitrous oxide budget.We adopt the new process-based model TRIPLEX-GHG, using driving variables including meterological data, soil properties data, vegetation data, carbon dioxide concentration data, to simulate the nitrous oxide in Chinese typical forest and grassland and compared the results with mesured data.After finishing simulateing the site nitrous emission, we used calibrated model to simulate the temporal and spatial nitrous oxide emission from Chinese forest and grassland during 1960-2013. The results showed that the TRIPLEXE-GHG model performed well in simulating the forest nitrous oxide emission which index of agreement exceeded 0.8. However, it didn’t performed well when simulated the grassland’s emission especially for temporal variation.The index of agreement of Xilinhot and Haibei just reached at 0.57 and 0.64. Besides, we investigated the relationship between nitrous oxide emission and meterological data by using the regression method. From the regression results, it indicated that nitrous oxide emission had a positive relationship between temperature,precipitation and relative humidity while negative relationship with wind speed. Within certain range, increasing temperature and rainfall will increase the nitrification and denitrification which futherly promoted to discharge the nitrous oxide emission. Wind speed may pertubate the air flow which contributes to emission decrease. By scaling the results to national forest and grassland, we obtained the temporal and sptial nitrous oxide emission from 1960-2013. In general, the emission from forests and grasslands increase steadily, from 45.1Gg, 10.9Gg in 1960 to 78.3Gg, 19.2Gg in 2013 respectively. The emission from forests most came from northeast and sourthern China. And the emission rate increased with decreasing latitude. The distribution regions of grasslands’ emission were Inner Monglia grassland and Qinghai-Tibet pleateau and the emission rate of the latter was higher than the former. By contrast with other estimation for nitrous oxide emission,we can see our estimation was lower than others. However, our results may be reliable as the TRIPLEXE-GHG model can reflect the spatial variation of nitrous oxide in China.