Table 1.

Results of statistical comparisons among groups for greenhouse gas.

Item	CO2		CH4		N2O
	QM	p-value	QM	p-value	QM	p-value
Rate of nitrogen input	24.03	<0.001	13.94	<0.001	28.21	<0.001
Climate	37.52	<0.001	28.52	<0.001	31.18	<0.001
Nitrogen compounds	9.81	<0.05	30.29	<0.001	38.09	<0.001
Types of wetlands	29.00	<0.001	24.35	<0.001	43.01	<0.001

Notes: All data were grouped into five nitrogen input rates (0–50, 50–100, 100–200, 200–300, >300 kg ha⁻¹·yr⁻¹), six climate types (alpine climate, temperate continental climate, temperate marine climate, monsoon climate of medium latitudes, subtropical monsoon climate, subtropical humid climate), four nitrogen compounds types (NH₄⁺, NO_3⁻, NH₄NO₃, organic nitrogen fertilizer) and five wetlands types (freshwater marsh, alpine wetland, estuary wetland, peatland, salt marsh). CO₂ is carbon dioxide, CH₄ is methane, and N₂O is nitrous oxide. Q_M: heterogeneity in group cumulative effect sizes.