**3. Soil carbon sequestration in riparian buffers**

Riparian buffer installation is an important land management option to support soil carbon sequestration. In Ontario, Canada, Vijayakumar et al. [17] compared carbon stocks of riparian buffers and associated agriculture fields. Soil organic carbon concentrations of mature riparian buffers averaged 193 Mg C ha−1, whereas the associated agricultural fields exhibited soil organic carbon concentrations of 88 Mg C ha−1. Riparian buffers having deciduous vegetation had greater soil organic carbon concentrations than riparian buffers with coniferous vegetation.

In Quebec, Canada, Fortier et al. [18] compared riparian buffers having (i) hybrid poplar (*Populus deltoides* and *Populus nigra*), (ii) natural woodlands, and (iii) herbaceous species. Considering the soil organic carbon concentrations to a depth of 0.6 meters, the hybrid poplar riparian buffer carbon concentrations ranged from 9 to 27 t C ha−1, (ii) natural woodlands ranged from 8.8 to 74 t C ha−1, and (iii) the herbaceous species ranged from 0.6 to 1.3 t C ha−1. In the natural woodlots the fine root mass correlated with the soil organic carbon. In southern Ontario, Canada, Ofosu et al. [19] recorded that a 103-year-old coniferous stand exhibited 358 Mg C ha−1 and a 94-yearold deciduous stand exhibited 311 Mg C ha−1. Rehabilitated buffers accumulated carbon at a rate of 4.7 Mg C ha−1 yr.−1, whereas as a natural forest accumulated carbon at a rate of 3.1 Mg C ha−1 yr.−1. Dybata et al. [20] performed a meta-analysis of carbon sequestration in riparian forests. Their data analysis demonstrated the potential for rapid initial carbon sequestration, with carbon stocks ultimately ranging from 68 to 158 Mg C ha−1.

Across the lower reaches of the Yellow River in China, Hou et al. [21] studied changes in the carbon stocks across reclaimed soil chronosequences. In the upper 20 cm soil, soil organic carbon accumulated at an average rate of 2.7 Mg C ha−1 yr.−1, whereas the average soil inorganic carbon accumulation rate was 5.5 Mg C ha−1 yr.−1. In California, Matzek et al. [22] observed revegetation projects across 42 streambank sites. Soil organic carbon accumulation averaged 0.87 Mg C ha−1 yr.−1 for floodplains and 1.17 Mg C ha−1 yr.−1 for more elevated landforms. Soil carbon persistence was supported by increased C:N ratio and smaller fulvic acid contents.
