2003 · 15 citations · 0 references
Vegetation restoration is an effective measure to restore physical stability in severely degraded soil through organic matter deposition. However, the effective ness of different plants in restoring the structural stability of soil is not we ll understood. The objectives of the current study were (1) to measure soil aggr egate stability under different types of restorative vegetation and (2) to deter mine the relationship between soil organic matter and soil aggregate stability. Soil samples were derived from a long term experiment: (1) severely eroded bare land; (2) severely eroded land planted with Camphor trees (Cinnamomum camphor a), a common deciduous tree in China; (3) severely eroded land planted with L espedeza shrub (Lespedeza bicolor), a legume often grown for soil improvemen t; (4) one undisturbed soil with 30～40 year old Masson pine forest (Pinus mas soniana); and (5) a vegetable garden reclaimed since 1987 receiving 30 t/hm 2 of pig manure annually. The Le Bissonnais' method was applied to simul ate the breakdown mechanisms of slaking in fast wetting, differential swelling i n slow wetting, and mechanical breakdown by wet stirring. The aggregate stabilit y index, normalized mean weight diameter (NMWD), indicated that the fast wetting caused the most severe disruption to aggregates. The NMWD in the fast wetting t reatment ranked in the order of Masson pine vegetable garden Lespedeza Cam phor trees, eroded bareland. The NMWD order in the wet stirring treatment was ve getable garden, Masson pine eroded bareland Camphor trees Lespedeza. Howev er, there is no significant difference as affected by restorative vegetations in slow wetting. The organic carbon content in aggregates was significantly relate d to the NMWD in the fast wetting treatment (r=0 82 ** ) and wet stirri ng treatments (r=0 66 *). The larger slaked aggregate size had higher orga nic carbon content and C/N ratio after wetting treatment, indicating that young organic matter improved aggregate stability because C/N ratio was regarded as th e degree of decomposition of organic matter. The results suggest that restorativ e vegetation promotes soil structure formation and soil aggregate stability due to the deposition of soil organic matter.