| Mangroves are woody plants in the intertidal zone of tropical and subtropical coasts with significant social, economic and ecological benefits. Due to widely distributed, cold-resistant ability and high survival rate, country Kandelia obovata has been the important species in China’s southeast coastal mangrove ecosystem restoration project. In recent years, as the negative effects of Spartina alterniflora being more and more serious, while comes up with lots of methods for preventing and controlling as well. “ Spartina alterniflora bio- physical prevention and control techniques” is an efficient and environmental method to prevent and control S. alterniflora by using mangrove replacement combining with physical ways. In this study, we establish the "Quangang coastal wetlands S. alterniflora prevention and ecological restoration demonstration base" for our plot which based on the new method. In this study, by investigated and analyzed the population characteristics and leaf C, N, P content, we selected two ways: cutting then plowing, and K. obovata instead of S. alterniflora. Compared the physical and chemical properties, the density and biomass of macrobenthos between the soil and the S.alterniflora samples, follow-up analysis the population characteristics and leaf C, N, P content,we get the following conclusions:S.alterniflora seedlings appeared in early February, and started to breed in July and August,then began to become withered and yellow since October, and present a massive area lodging in January of the following year in Meizhou Bay. The density of S. alterniflora ranges from57-107 a square meter, the height ranges from 76.08 cm to 179.98 cm, and breadth ranges between 13.63cm-53.07 cm, dry weigh ranges between8.19g-27.29 g and water content ratio ranges between58.38%-69.43%. The Carbon content of S. alterniflora leaf ranges between302g/kg-370g/kg, the Nitrogen content ranges between 8.82g/kg-14.56g/kg and the Phosphorus content ranges between1.2g/kg-1.6g/kg; from which, C/N and N/P ratios of leaf are respectively20.8-42.02 and 7.35-8.93.In terms of time,except the leaf content of Carbon and the ratio of C/N, S. alterniflora’ s density, plant height, breadth, dry weight, moisture content, leaf content of Nitrogen and Phosphorus,and N/P ratios in summer appeared higher than in winter; In terms of space,indicators like the plant density, height, crown amplitude, fresh weight, dry weight, the content of Carbon, the content of Phosphorus and C/N ratios of S. alterniflora in high tide level during the summer is higher than or equal to the other tide; While indicators such as the plant height,crown amplitude, the content of Carbon and N/P ratios of S. alterniflora in low tide level during the winter is higher than the others.The effect of K. obovata managing S. alterniflora was Significantly better than the method of cutting, plowing and putting down. The effect of different seasons and different plant spacing on seedling height, breadth, fresh weight, and dry weight is significant. K. obovata seedlings in plant spacing of under 50 cm were significantly higher than that in other plant spacing, such as plant height, breadth, fresh weight, dry weight. The growth of plant height, breadth and crown width of K. obovata is the fastest from summer to autumn(July to October), with organic matter accumulation rate increasing quickly and gradually, which shows that K. obovata is in rapid growth stage. There were significant differences between different seasons(P<0.01).In spring the mean content of C reaches the highest value of 397g/kg, and the lowest in autumn is 339.82g/kg;however, the contents of Nitrogen and Phosphorus both show the highest in autumn, the lowest in spring. The leaf C:N ratio which is the highest in spring and the lowest in autumn is just in contrast to the leaf N:P ratio, from which it can be seen that there is a significant negative correlation between C:N and N:P.With mowing, tillage the S. alterniflora,simultaneously taking different densities K.obovata to replace and manange the S. alterniflora after two years,the results showed that it can bring about some effect on soil surface in the way of mowing,tillaging the S. alterniflora.The soil N contents and organic matter contents was increased,and the soil p H values was decreased,but it was not significant impact on P contents and salinity.The impact on soil subsurface was that the soil matter contents and p H values were incereaed, and the soil salinity, N content and P content were decreaed.Some effect on the soil surface was following by taking different densities K.obovata to replace and manange the S.alterniflora.The soil matter contents and N contents were significantly increaced,and the increases was propartional to the planting desity of K.obovata.When the desiy was rasied,the soil salinity was statistically improved,and the soil p H values was reduced which the higher the desity the lower the p H,but the soil P contents had not big diversfication.For the soil subsurface,the soil matter contents was increased,which was propartional to the desity.The soil p H values, N content and P content were decreased which the higher the desity the lower the p H. No effect on the soil N,P content and no law to be found on the soil salinity.The density of macrobenthos in the habitat of S. alterniflora and K.obovata are217ind/m~2-308ind/m~2 and 218.02ind/m~2-352.03ind/m~2 respectively, and the biomass in them are14g/m~2-28.19g/m~2 and 23.02g/m~2-44.58g/m~2. The density and biomass in the habitat of Spartina alterniflora decline from winter to summer, while in the habitat of K·obovata they rise. The density and biomass of polychaetes, crustaceans and other animals increase after planting K.obovata, but the density and biomass of molluscs reduce.By using mangrove instead method, we can effectively control the proliferation and growth of Spartina alterniflora. At the same time, Mangrove rehabilitation has an important significance in the local ecological environment construction.So we suggest to use this meathod in the recovery of the coastal wetland ecological engineering. |
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