[Spatial differentiation and mechanism of carbon source/sink of forest swamps in riverside of Changbai Mountains, China].

To quantify the carbon source/sink function of riparian zone swamps and explore the feedback relationship with climate change, we measured the annual fluxes of soil greenhouse gas, soil carbon emission, net vegetation carbon sequestration and related environmental factors (temperature, water level, etc .) by static chamber-gas chromatography and relative growth equation methods in three kinds of forest swamps ( Alnus sibirica swamp, Betula platyphylla swamp, and Larix olgensis swamp) distributed along the water reduction gradient of lowland to highland in the stream riparian zone of Changbai Mountains. The results showed that the annual fluxes of CH ₄ (0.19-0.85 mg·m ^-2 ·h ^-1 ), CO ₂ (60.81-228.63 mg·m ^-2 ·h ^-1 ), and N ₂ O (-0.02-0.05 mg·m ^-2 ·h ^-1 ) showed spatial variations along the water gradient of lowland to highland, with a trend of first constant then decreasing, decreasing, and first absorption then emission, respectively. The spatial variations of annual fluxes of these greenhouse gases were controlled by water levels. The annual net carbon sequestration of vegetation (2.61-3.45 t C·hm ^-2 ·a ^-1 ) was constant along the water gradient, which was mainly promoted by nitrate nitrogen content. The carbon source/sink and global warming potential (GWP) undergo regular changes along water gradients. The A. sibirica swamp was a carbon sink (1.93 t C·hm ^-2 ·a ^-1 ), the B. platyphylla swamp was a weak carbon source (-0.18 t C·hm ^-2 ·a ^-1 ), and the L. olgensis swamp was a strong carbon source (-2.51 t C·hm ^-2 ·a ^-1 ). The spatial variation of carbon source/sink in forest swamps was jointly promoted by water level and nitrate nitrogen content. A. sibirica swamp exhibited a strong cooling effect with a strong negative feedback effect on climate change (-5.88 t CO ₂ ·hm ^-2 ·a ^-1 ). L. olgensis swamp exhibited a strong warming effect with a strong positive feedback effect (10.97 t CO ₂ ·hm ^-2 ·a ^-1 ). B. platyphylla swamp exhibited a weak warming effect, approximately neutral (2.95 t CO ₂ ·hm ^-2 ·a ^-1 ). The spatial variation of GWP in forest swamps was mainly inhibited by water level.