CH4 and N2O emissions from smallholder agricultural systems on tropical peatlands in SE Asia

Antonio Jonay Jovani-Sancho,Gusti Anshari,Patrick O'Reilly,Sofie Sjögertsten,Caroline Upton,Adi Jaya,Jamaludin Jamaludin,Stephanie Evers,Yosep Redin,Jing Ye Gan,Xin Yi Chong,Paul Wilson,Christopher N Gibbins,Christopher D Evans,Neil Crout,Susan Page

doi:10.5194/egusphere-egu22-9928

Abstract

&lt;p&gt;Few studies have measured GHG emissions from smallholder agricultural systems in tropical peatlands, or non-CO&lt;sub&gt;2&lt;/sub&gt; emissions from human-influenced tropical peatlands more generally. &amp;#160;The aim of this study was to quantify CH&lt;sub&gt;4&lt;/sub&gt; and N&lt;sub&gt;2&lt;/sub&gt;O fluxes from agricultural landscapes on tropical peatlands in SE Asia and assess their environmental controls. The study was carried out in four peatland areas in Malaysia and Indonesia. At each site CH&lt;sub&gt;4&lt;/sub&gt; and N&lt;sub&gt;2&lt;/sub&gt;O fluxes and environmental parameters was measured in four land use types, short rotation agricultural crops, oil palm plantation, tree plantation, and adjacent secondary/degraded forest. &amp;#160;annual CH&lt;sub&gt;4&lt;/sub&gt; emissions were 1.8 &amp;#177; 1.2, 2.1 &amp;#177; 0.8, 2.3 &amp;#177; 0.4, 6.1 &amp;#177; 1.2 and 105.6 &amp;#177; 18.1 kg CH&lt;sub&gt;4&lt;/sub&gt; ha&lt;sup&gt;-1&lt;/sup&gt; year&lt;sup&gt;-1&lt;/sup&gt; at the degraded forest, tree plantation, oil palm, cropland and intact forest land use classes, respectively, while annual N&lt;sub&gt;2&lt;/sub&gt;O emissions were 0.6 &amp;#177; 0.3, 3.3 &amp;#177; 0.9, 12.5 &amp;#177; 3.0, 18.0 &amp;#177; 7.3 and 32.7 &amp;#177; 5.8 kg N&lt;sub&gt;2&lt;/sub&gt;O ha&lt;sup&gt;-1&lt;/sup&gt; year&lt;sup&gt;-1&lt;/sup&gt; at the intact forest, tree plantation, degraded forest, oil palm and cropland land use classes, respectively. CH&lt;sub&gt;4&lt;/sub&gt; emissions were strongly determined by WTD following an exponential relationship with production of CH&lt;sub&gt;4&lt;/sub&gt; starting when annual WTD was above &amp;#8211;25 cm. By contrast, N&lt;sub&gt;2&lt;/sub&gt;O emissions were strongly correlated with TDN, following a log-normal relationship. The optimum TDN concentration for N&lt;sub&gt;2&lt;/sub&gt;O production was 10 mg N L&lt;sup&gt;-1&lt;/sup&gt; and beyond this threshold, the availability of mineral N was no longer limiting the N&lt;sub&gt;2&lt;/sub&gt;O production, with other environmental variables such as WTD, soil water content, and temperature becoming more important. The new emission factors for CH&lt;sub&gt;4&lt;/sub&gt; and N&lt;sub&gt;2&lt;/sub&gt;O presented here should be included in country level GHG inventories to improve their accuracy. The strong impact of substrate supply on N&lt;sub&gt;2&lt;/sub&gt;O emissions shows that fertilisation practices strongly impact net emissions suggesting that policies that result in reduced fertilisation rates can directly cut emissions.&lt;/p&gt;

Full Text