A global inventory of N₂O emissions from tropical rainforest soils using a detailed biogeochemical model

Abstract

[1] Beside agricultural soils, tropical rainforest soils are the main source of atmospheric N 2 O. Current estimates of the global N 2 O source strength of tropical rainforest soils are still based on rather simplistic upscaling approaches and do have a large range of uncertainty. In this study, the biogeochemical ForestDNDC-tropica model was recalibrated and intensively tested on the site scale prior to inventory calculations. For this, the model was coupled to a newly developed global GIS database holding relevant information on model initialization and driving parameters in 0.25°Â 0.25°resolution. On average, the mean annual N 2 O emission source strength of rainforests ecosystems worldwide for the 10-year-period 1991-2000 was calculated to be 1.2 kg N 2 O-N ha À1 yr À1. Using a total rainforest area of 10.9 Â 10 6 km 2 , this amounts to a total source strength of 1.34 Tg N yr À1 . The result of an initialization parameter uncertainty assessment using Latin Hypercube sampling revealed that the global source strength of N 2 O emissions from tropical rainforests may range from 0.88 to 2.37 Tg N yr À1. Our calculations also show that N 2 O emissions do vary substantially on spatial and temporal scales. Regional differences were mainly caused by differences in soil properties, whereas the pronounced seasonal and interannual variability was driven by climate variability. Our work shows that detailed biogeochemical models are a valuable tool for assessing biosphere-atmosphere exchange even on a global scale. However, further progress and a narrowing of the uncertainty range do crucially depend on the availability of more detailed field measurements for model testing and an improvement of the quality of spatial data sets on soil and vegetation properties.Citation: Werner, C., K. Butterbach-Bahl, E. Haas, T. Hickler, and R. Kiese (2007), A global inventory of N 2 O emissions from tropical rainforest soils using a detailed biogeochemical model, Global Biogeochem. Cycles, 21, GB3010,

A new approach to identify the sensitivity and importance of physical parameters combination within numerical models using the Lund–Potsdam–Jena (LPJ) model as an example

“…A detailed description and evaluation of the model can be found in Sitch et al (2003). The LPJ model has been widely employed to discuss the variation in terrestrial ecosystems and the carbon cycle (Werner et al 2007;Hickler et al 2008). and its simulation of PFTs has been shown to be in agreement with the observations in China.…”

Seasonal variability in methane and nitrous oxide fluxes from tropical peatlands in the western Amazon basin

“…Interestingly, differences in N 2 O fluxes were not associated with the nutrient status of the peatland; i.e., more nutrientrich ecosystems, such as forested vegetation and mixed palm swamp, did not show higher N 2 O fluxes than their nutrientpoor counterparts, such as forested (short pole) vegetation and M. flexuosa palm swamp. This may imply that N availability, one of the principal drivers of nitrification, denitrification, and N 2 O production (Groffman et al, 2009;Werner et al, 2007), may not be greater in nutrient-rich versus nutrientpoor ecosystems in this part of the western Amazon. Alternatively, it is possible that even though N availability and N fluxes may differ between nutrient-rich and nutrient-poor systems, N 2 O yield may also vary such that net N 2 O emissions are not significantly different among study sites .…”

Nitrous oxide emissions 1999 to 2009 from a global atmospheric inversion

“…On the other hand, it is known from in situ flux measurements that terrestrial biosphere fluxes of N 2 O are strongly determined by climatological factors such as soil temperature, moisture and precipitation (Bouwman et al, 2002;Skiba and Smith, 2000;Smith et al, 1998). A number of land ecosystem models now include the nitrogen cycle and simulate N 2 O fluxes (Potter et al, 1996;, but owing to the non-linear response of N 2 O production to soil and climate parameters, as well as to nitrogen substrate availability, the modelled fluxes are associated with large uncertainties (Werner et al, 2007). Some ecosystem models predict a significant N 2 O soil-flux-climate link.…”