Studies On Introducing Salt-tolerant Wood Plants Into The Yellow River Delta

Yellow River Delta, one of the three largest river estuary deltas in China, has high potentials of land development and utilization, but the widely distributed saline soils here in the coastal area at Bohai-Sea severely obstruct the development of agriculture. The fairly high salt contents, mainly chlorates, of the saline soils, ranging from 0.4%-3% in the surface layer, worsen the soil structure and lower the soil fertility. Considering the soil properties and other conditions in Yellow River Delta we have introduced purposely 10 tree species into the area and investigated their propagation methods, salt-tolerance, effect of salt-reduction and soil-improvement, ecological adaptability, and application values. The results confirm a successful introduction for 9 tree species that adapt the conditions in Yellow River Delta. Only one species, Hibiscus hamabo, which can not survive winter outdoors in this area, is an exception. This study has contributed to enriching the foresting and gardening resources and offered more scientific information for improving the forest quality and ecologically controlling the saline lands. The main contents and results of this study are presented as following:1. The propagation methods of various tree species were investigated. All 10 species could get relatively high propagation rate through corresponding methods respectively.2. The salt-tolerances of various tree species were determined through experiments of pot culture with salt-watering and of saline soil pools in the field. Atriplex canescens., Nitraria tangutorum, and Hibiscus hamabo can tolerate salt content to 1.2% in their growing period. Ammopiptanthus mongolicus and Lycium barbarum to 0.8%, Lonicera maackii to 0.6%, Lonicera japonica, Sambucus buergeriana, tetraploid Robinia pseudoaccacia., and Melia azedarach to 0.4%. Based on foresting trials in the field a linear recursive equation for each species was constructed. The salt-tolerance and limits of each species in periods of transplanting, recovering and growing were calculated in return with the statistical models. The salt-tolerances of various species in the field can be arranged in a sequence as: Nitraria tangutorum(0.81%)> Atriplex canescens(0.79%)> Lycium barbarum(0.61%)> Ammopiptanthus mongolicus(0.57%)> Lonicera maackii(0.26%)=Melia azedarach(0.26%)>...