Accumulation of glomalin-related soil protein benefits soil carbon sequestration with tropical coastal forest restoration

Tropical coastal areas endure severe soil erosion due to heavy rainfall, especially after deforestation. Glomalin-related soil protein (GRSP), the product of arbuscular mycorrhizal fungi (AMF), improves soil structure and soil organic carbon (SOC) sequestration with vegetation restoration. Therefore, the contribution of GRSP to soil property improvement in a tropical coastal area was performed in four different restoration practices: a barren land (BL, unrestored control), a Eucalyptus exserta planted forest (EF), a mixed broadleaved forest (MF), and a secondary natural forest (SF). Results showed that vegetation restoration practices increased easily-extractable GRSP (EE-GRSP) and total GRSP (T-GRSP) by 3.9–12.3 and 1.9–4.6 times, respectively, compared with BL. The proportions of EE-GRSP/SOC and T-GRSP/SOC were 1.6–2.0% and 6.5–15.8%. The concentrations of GRSP, SOC and the GRSP/SOC ratio were similar or greater under MF than under SF. 13C NMR analysis showed that the relatively easily degradable O-alkyl-C of SOC was significantly higher under MF than under EF and SF, while the recalcitrant aromatic-C or alkyl-C were highest under SF or EF, respectively. A significantly positive relationship was found between the GRSP/SOC ratio and aromatic-C, and between GRSP and soil aggregate stability. Our study indicates that GRSP contributes a large proportion of SOC, and benefits SOC sequestration through increasing soil aggregate stability and recalcitrant SOC. Among these artificial or natural growing forest restorations, the mixed forest restoration practice with native tree species provides a promisingly preferable restoration strategy in heavily eroded land restoration from the aspect of soil aggregation and SOC sequestration.

热带沿海地区由于降雨量大，尤其是在森林砍伐之后，遭受严重的土壤侵蚀。球囊霉素相关土壤蛋白（GRSP）是丛枝菌根真菌（AMF）的产物，随着植被恢复，它能改善土壤结构并促进土壤有机碳（SOC）的固定。因此，在热带沿海地区的四种不同恢复措施中研究了GRSP对土壤性质改善的贡献：荒地（BL，未恢复的对照）、窿缘桉人工林（EF）、阔叶混交林（MF）和次生天然林（SF）。结果表明，与荒地相比，植被恢复措施使易提取球囊霉素相关土壤蛋白（EE - GRSP）和总球囊霉素相关土壤蛋白（T - GRSP）分别增加了3.9 - 12.3倍和1.9 - 4.6倍。EE - GRSP/SOC和T - GRSP/SOC的比例分别为1.6 - 2.0%和6.5 - 15.8%。阔叶混交林下GRSP、SOC的浓度以及GRSP/SOC的比值与次生天然林相似或更高。13C核磁共振分析表明，阔叶混交林下SOC中相对较易降解的O - 烷基 - C显著高于窿缘桉人工林和次生天然林，而次生天然林或窿缘桉人工林下难降解的芳香族 - C或烷基 - C分别最高。GRSP/SOC比值与芳香族 - C之间以及GRSP与土壤团聚体稳定性之间存在显著的正相关关系。我们的研究表明，GRSP在SOC中占很大比例，并通过提高土壤团聚体稳定性和难降解SOC来促进SOC的固定。在这些人工或自然生长的森林恢复措施中，从土壤团聚和SOC固定的角度来看，采用本地树种的混交林恢复措施为严重侵蚀土地的恢复提供了一种有前景的、更优的恢复策略。