Impacts Of Two Kinds Of Salt-tolerant Plants Cropping On Coastal Saline Ecosystem

Abstract:Coastal saline land has always been a hot zone for introduction and screening of salt-tolerant plants and the research of soil improvement, Recently with energy problems became increasingly serious, and with the pressure of climate change,many carbon sequestration projects were undertaken, bioenergy industry was also on the rise.As a marginal land, bioenergy industry based on cropping of salt-tolerant oil plants was also trying to develop on coastal saline land and hoping to get both ecological and economic benefits.However,the coastal saline land is a fragile ecosystem, the distribution of vegetation is dependent on soil salinity, salt-water dynamic is strongly affected by climate conditions and human disturbances, poor resilience stability. Whether the development of bioenergy on coastal saline land could act as carbon sink and its effects on coastal ecosystems need to be seriously investagated. This study was based on a two years'observation of seven experimental plots, including four salt-tolerant plants cropping plots and three natural vegetation plots, spatial and temporal dynamics of soil properties of different cropping patterns and vegetation types were analyzed, The productivity of salt-tolerance plants and natural vegetation were compared, a comprehensive analysis of the potential impact of salt-tolerant plants cropping as bioenergy on economic and ecological development had been done,the result showed that:[a] There were some negative effects on coastal saline land at the beginning of salt-tolerant plants transplanting,as the average electrical conductivity of topsoil increased, the fluctuation of salt-water dynamic aggravated;while on the lands with salt-tolerent plants continuous cropping,the average electrical conductivity of topsoil was lower than the area with natural vegetation.and the amplitude of fluctuation was smaller, soil environment was stable.[b] Soil fertility of coastal saline land was on a low level,there were some improvements on nitrogen, phosphorus and organic matter content in the soil of salt-tolerent plants cropping area, but partly due to fertilization during the process of cropping.[c] The number of soil microbes had a significant positive relationship with vegetation condition,while it was not quite correlated with salt-tolerent cropping. But under the condition of cropping, the number of microorganisms on castor cultivation lands was significantly higher than Kosteletzkya virginica cropping lands.[d] The total amount of carbon content on the lands with salt-tolerent plants continuous cropping was more than natural vegetation and showed a carbon sink effect,but was lower at the beginning of cropping compared with Phragmites-Imperata grass land.Overall, there were intensely human disturbances at the beginning of salt-tolerent cropping.resulting in an instable soil environment,which caused a performance of regressive succession of soil and vegetation.But when the cultivation was success, and the growth of salt-tolerent plants was stable, the cropping of salt-tolerent plants finally showed a positive role in remediation of coastal saline ecosystem,and had a contribution to the improvement of carbon sequestration of this ecosystem.