Seasonal variability of N₂O emissions and CH₄ uptake by tropical rainforest soils of Queensland, Australia

Abstract

[1] Over 1 year we followed the seasonal variations of N 2 O and CH 4 fluxes at a tropical rain forest site in Australia. In addition, meteorological parameters, litter fall and decomposition, plant species composition, and concentrations of NH 4 + /NO 3 À in the soil and N 2 O and CH 4 in the soil atmosphere were measured. N 2 O emissions showed a pronounced seasonal pattern with highest rates in the wet season (108.6 mg N m , and, thus, approximately 7 times lower than a previous estimate for the year 2000. The marked differences in N 2 O emissions between different years indicate that the interannual variability of N 2 O emissions from rain forest soils cannot be neglected. With regard to CH 4 the soil functioned throughout the entire year as a significant sink. Rates of CH 4 uptake during the dry period (35-68 mg CH 4 m À2 h À1 ) were higher as compared to the wet period (4-45 mg CH 4 m À2 h À1 ). A close linear correlation between soil moisture and magnitude of CH 4 uptake was found. The calculated annual CH 4 uptake (N = 6090) is 3.2 kg CH 4 ha À1 yr À1. This implies that tropical rain forest soils function as significant sinks for atmospheric CH 4 on a global scale.

Spatial variations of nitrogen trace gas emissions from tropical mountain forests in Nyungwe, Rwanda

“…Keller and Reiners, 1994;Verchot et al, 1999) and in tropical regions of Australia (e.g. Kiese et al, 2003;Butterbach-Bahl et al, 2004). The only datasets of N 2 O emissions from tropical rain forest soils of Africa was reported by Serca et al (1994) and Werner et al (2007b), who worked in the Mayombe forest in the DR Congo and the Kakamega forest in Kenya, respectively.…”

“…Davidson et al, 2000). Besides agricultural soils, tropical forest soils are considered as important sources for atmospheric N 2 O (Bouwman et al, 1993;Matson et al, 1990;Mosier et al, 1998;Breuer et al, 2000;Butterbach-Bahl et al, 2004;Kiese et al, 2003;Werner et al, 2006). Similarly, NO from tropical forest soils represents a significant source within the global atmospheric budget (Butterbach-Bahl et al, 2004;Gut et al, 2002).…”

Atmospheric methane uptake by tropical montane forest soils and the contribution of organic layers

“…Most tropical lowland rainforest soils are sinks for atmospheric CH 4 (Kiese et al 2003(Kiese et al , 2008Werner et al 2006). Uptake of atmospheric CH 4 in aerobic tropical forest soils is estimated to account for about 28% of the global annual soil consumption (6.2 Tg year -1 ) (Dutaur and Verchot 2007).…”

Spatio-temporal variability in N<sub>2</sub>O emissions from a tea-planted soil in subtropical central China

“…Accurate estimates of the amount and characteristics of N 2 O emissions are important prerequisites for reducing N 2 O emissions from agro-ecosystems (Akiyama et al, 15 2013;Ambuset al, 1994;Han et al, 2013;Kiese et al, 2003;Konda et al, 2008Konda et al, , 2010Lin and Han, 2009;Mosier et al, 1996Mosier et al, , 1998Turner et al, 2008). However, N 2 O is microbially mediated; it is produced via microbial processes of nitrification under aerobic conditions and denitrification under anaerobic conditions (Firestone and Davidson, 1989;Hayatsu, 1993;Mathieu et al, 2006;Venterea and Rolston, 2000; both the inherent complexities of N 2 O emissions and our own epistemic defects (Li et al, 2013).…”

“…Moreover, the mini chambers captured the temporal variations in the N 2 O fluxes, whereas the large chambers reflected a trend that was stationary in time. One rea-10 son was that the one week interval between gas sampling instances unintentionally avoided the N 2 O emission peak, which can strongly influence the accuracy of regional N 2 O emissions estimates (Akiyama et al, 2013;Ambus and Christensen et al, 1994;Kiese et al, 2003;Mosier et al, 1996Mosier et al, , 1998. Thus, a suitable temporal interval for gas sampling should be determined based on an analysis of the spatio-temporal structure …”