Restoration patterns and influencing factors for the vegetation structure and carbon storage in mangroves converted from abandoned ponds

Abstract

Afforestation of mangroves in abandoned ponds is considered an effective approach for global mangrove restoration. Although several studies have assessed recovery outcomes of reforested mangroves, the studies about the synergistic recovery of mangrove vegetation and ecosystem carbon stocks in abandoned ponds are still limited. The present study compared the vegetation structure and carbon stocks of pond-to-mangrove sites with different restored methods in Dongzhaigang Bay, Hainan Province, China. We found that the vegetation structure (tree density and Shannon diversity) had no significant differences between afforestation sites and natural mangroves. The total ecosystem carbon stocks of all the sample sites ranged from 64.07 to 224.91 (mean ± SD: 114.82 ± 49.30) Mg C ha⁻¹, while there were no significant variations between restoration sites in 2014 (p > 0.05). In addition, 85.44 % of the total carbon stocks were stored in the soil among the study sites. The soil physicochemical properties such as soil pH, total organic carbon, total nitrogen had effects on tree height, diameter at breast height and carbon stocks composition. Meanwhile, in-situ soil redox potentials, Shannon diversity, tree height, density and diameter at breast height affected carbon stock. Moreover, the soil physicochemical properties, absolute elevation and vegetation structural variables could explain 76.83 % of the carbon stock variance. This study demonstrated that artificial planting had no superiority in vegetation restoration and carbon sequestration over natural regeneration. Under appropriate environmental conditions, natural regeneration is an economically effective way to restore mangroves from abandoned ponds to realize the co-benefits of biodiversity and carbon storage restoration.