Post-flooding disturbance recovery promotes carbon capture in riparian zones

Vegetation, water, and carbon dioxide have complex interactions on carbon mitigation in vegetation–water ecosystems. As one of the major global change drivers of carbon sequestration, flooding disturbance is a fundamental but poorly discussed topic to date. The aquatic and associated riparian systems are highly dynamic vegetation–water carbon capture systems driven by fluvial processes such as flooding. However, their global carbon offset potential is largely unknown. This study examines daily inline-formulaCO₂ perturbations under flooding disturbance in the river (fluvial area) and associated riparian areas with 2 year in situ observations along the Lijiang. We find that, though the submerged riparian area behaved as a carbon source during the flooding season (inline-formulaCO₂ flux: 2.790 inline-formula $M3inlinescrollmathmlunit\mathrm{normal\; g}{\mathrm{normal\; m}}^{-\mathrm{normal\; 2}}{\mathrm{normal\; d}}^{-\mathrm{normal\; 1}}$ 47pt15ptsvg-formulamathimg87d3355337ab5aa113f75741ca9d5949 bg-20-1357-2023-ie00001.svg47pt15ptbg-20-1357-2023-ie00001.png ), the riparian area and the fluvial area as a whole transformed from a carbon source in pre-flooding season (1.833 inline-formula $M4inlinescrollmathmlunit\mathrm{normal\; g}{\mathrm{normal\; m}}^{-\mathrm{normal\; 2}}{\mathrm{normal\; d}}^{-\mathrm{normal\; 1}}$ 47pt15ptsvg-formulamathimg3e89477f7519a516b0295bd8cc3fbab7 bg-20-1357-2023-ie00002.svg47pt15ptbg-20-1357-2023-ie00002.png ) to a carbon sink after recovery in post-flooding season (inline-formula−0.592 inline-formula $M6inlinescrollmathmlunit\mathrm{normal\; g}{\mathrm{normal\; m}}^{-\mathrm{normal\; 2}}{\mathrm{normal\; d}}^{-\mathrm{normal\; 1}}$ 47pt15ptsvg-formulamathimg49531a2214f5f53e1e3bd328ce90b8a0 bg-20-1357-2023-ie00003.svg47pt15ptbg-20-1357-2023-ie00003.png ). The fluvial area sequestered carbon (inline-formula−0.619 inline-formula $M8inlinescrollmathmlunit\mathrm{normal\; g}{\mathrm{normal\; m}}^{-\mathrm{normal\; 2}}{\mathrm{normal\; d}}^{-\mathrm{normal\; 1}}$ 47pt15ptsvg-formulamathimg413a4704a6a1039135a0d6851c9343f3 bg-20-1357-2023-ie00004.svg47pt15ptbg-20-1357-2023-ie00004.png ) in post-flooding season instead of releasing carbon as in pre-flooding season (2.485 inline-formula $M9inlinescrollmathmlunit\mathrm{normal\; g}{\mathrm{normal\; m}}^{-\mathrm{normal\; 2}}{\mathrm{normal\; d}}^{-\mathrm{normal\; 1}}$ 47pt15ptsvg-formulamathimg756a597cf5f59d3f750d4da41d50dcbd bg-20-1357-2023-ie00005.svg47pt15ptbg-20-1357-2023-ie00005.png ). Also, the carbon sequestration capacity of the riparian area was enhanced in post-flooding season (pre-flooding season: inline-formula−0.156 inline-formula $M11inlinescrollmathmlunit\mathrm{normal\; g}{\mathrm{normal\; m}}^{-\mathrm{normal\; 2}}{\mathrm{normal\; d}}^{-\mathrm{normal\; 1}}$ 47pt15ptsvg-formulamathimg9ff2f512053c4d0a7c6f6d864a8e0fcc bg-20-1357-2023-ie00006.svg47pt15ptbg-20-1357-2023-ie00006.png , post-flooding season: inline-formula−0.500 inline-formula $M13inlinescrollmathmlunit\mathrm{normal\; g}{\mathrm{normal\; m}}^{-\mathrm{normal\; 2}}{\mathrm{normal\; d}}^{-\mathrm{normal\; 1}}$ 47pt15ptsvg-formulamathimgcb43a188c95fe696e3461dcd2324554f bg-20-1357-2023-ie00007.svg47pt15ptbg-20-1357-2023-ie00007.png ). We suggest that post-disturbance recovery of riparian vegetation played a vital role in this transformation, due to its stronger carbon uptake capacity after recovery from the flooding disturbances. The findings shed light on the quantitative modelling of the riparian carbon cycle under flooding disturbance and underlined the importance of the proper restoration of riparian systems to achieve global carbon offset.