Optimization of Plants Community of Riparian Buffer Zones

Different vegetations native and common to Shanghai were selected to form plant communities different in sod∶shrub∶arbor ratio for an experiment laid out in a riparian buffer zone experiment base,Dongfeng Port,Qingpu District,Shanghai,to determine their effects on control of non-point source pollution and soil erosion.Results indicate that buffer strips of sod were the strongest in ability to intercept pollutants from runoff,a 12 m-long buffer strip of Cynodon dactylon arrested around 70% of the suspended solid(SS),and over 20% the TN and TP in the runoff;buffer strips of the combination of sod and arbor trees not only showed high effect in removing SS,N and P from runoffs,but also effectively controlled runoff-triggered soil erosion on barren land surface.Sod roots helped improve resistance of the surface/upperlayer soil(0-20 cm) to erosion.The average shearing strength of the buffer strip of Cynodon dactylon was the highest,reaching as high as 98.28 kPa;the combination of shrubs and arbors was much better in improving resistance of the soil in deep layers(20-25 cm) to erosion.The average shearing strength of the buffer strips of Salix integra and Ligustrum lucidum was 103.10 and 122.08 kPa,respectively,while that of the buffer strip of Cynodon dactylon was 77.88 kPa only.It could,therefore,be concluded that reasonable plant combination can improve the function of riparian buffer zones in controlling non-point source pollution and soil erosion.