“…For example, studies showed that nitrogen deposition stimulated N 2 O emission Zhang et al, 2014], which partially canceled out the stimulating impact on CO 2 uptake [Niu et al, 2010;Niu et al, 2009;Volk et al, 2011]; few other studies found that nitrogen addition stimulated CH 4 flux in semiarid grasslands [Chen et al, 2013;Li et al, 2012;Louro et al, 2013;Šimek et al, 2014;Stiehl-Braun et al, 2011;Zhang et al, 2014]; manipulative experiments found that increased precipitation enhanced ecosystem CO 2 uptake through its stimulating effect on gross primary production [Chimner et al, 2010;Nagy et al, 2007;Yan et al, 2011]. For CH 4 uptake, the impact of water addition could be inhibition [Blankinship et al, 2010b;Liu and Greaver, 2009], neutral [Liu and Greaver, 2009;Mariko et al, 2007], or stimulating [Blankinship et al, 2010a;Xu et al, 2015]; while for N 2 O emission, the impact of water addition could be stimulating [Horváth et al, 2010;Zhang and Han, 2008] or neutral [Liu and Greaver, 2009;Unteregelsbacher et al, 2013] in semiarid grassla nds.…”