| Planting the suitable tree species is the important principle of afforestation smoothly. There are a lot of factors which restrict the afforestation in saline areas:salinity is heavy, the pH value of soil is high, and fertility is low, drought and flood disaster, etc. Therefore, choosing the suitable plants is very important. In this paper, based on the previous water cultivation and pot experiment, taking the saline-alkali soil of Tianjin coastal as the experimental field, selected30kinds of poplar which have high salt tolerant as the test material, field contrast experiments were done. Through determinating the growth indexes of the experimental poplar, comprehensive evaluated the growth performance to elect more excellent salt-tolerant populus, this provides a strong theoretical support for selection and popularization the high salt-tolerant populus. The main conclusions are as follows:(1) The field contrast test in Tianjin port, selected30kinds of salt-tolerant populus as tested materials, salinity of experimental field were3.43‰and3.91‰separately. Through determined the survival rates, height growth, the diameter growth and the breast diameter et al, using membership function to value growth performance of selected species, the result of preliminary evaluation:JY-14, JY-16, JY-17, JY-36, JY-26, JY-33and JY-31have better comprehensive performance; synthesis performance of JY-13, JY-7, JY-51, JY-24, JY-9, JY-44, JY-23, JY-2and JY-30is medium; other varieties has lower or unstable comprehensive ability.(2) Field contrast complementary test. Selected9kinds of salt-tolerant populus as tested materials, improved the soil in tree holes, investigated the survival rate and indicators of growth, and evaluated the comprehensive performance by membership function. The order of integrated performance by the optimal to bad was that:JY-24, JY-26, JY-33, JY-10, JY-30, JY-14, JY-7, JY-44, and JY-52, ranking in the front, performance the better.(3) Seedling propagation for the outstanding performance of10kinds of salt-tolerant populus. The effect of the growth was investigated. Through determinating the indexes, such as growth of tree height and DBH, the ranking of propagation effect were:JY-26, JY-24, JY-33, JY-14, JY-7, JY-13, JY-36, JY-10, JY-2, and JY-44. Average growth of tree height is up to2.50m, the maximum can be as high as4.02m, average DBH is up to2.24cm. It is useful to provide a large number of pure qualities of seedlings. At the same time, plastic film can keep warm, and remove plastic to reduce transpiration in time, these can improve the survival rate of seedlings significantly.(4) The basic investigation of greening populus in Tianjin port. Based on the soil index and poplars growth situation of the selected17locations, the conclusions are drawn as follows:①nder the condition of replace with out-soil in greening, the growth performance of poplar is well, soil salinization reduces, and soil fertility enhance, the overall change trend is good obviously, this increased the long-term stability and adaptability of poplar in the coastal areas.②The performance of Populus tomentosa and P.×euramericana Guinier (mainly107) are outstanding, annual growth average increment of tree height is more than1.1m, DBH>1.2cm; the crown of P.alba var.pyramidalis Bge. is small, growth quantity is low, benefit is poor.③There is close relationship between poplar’s growth and conditions of site. The annual growth of Populus tomentosa and soil organic matter had a significant positive correlation; the annual growth of Populus tomentosa and the total salt content in soil had a significant negative correlation; technical measures such as increasing soil fertility and reducing the salt content in the soil are can promote their growth, and improve the afforestation effect.(5) The field contrast experiment and field contrast complementary tests are the important stage in screening salt-tolerant poplars, the two results are persuasive, and that has great function and significance in selecting suitable salt-tolerant poplars for Tianjin coastal area. Comprehensive two test results:JY-10, JY-24, JY-14, JY-16, JY-17, JY-36, JY-26, JY-33and JY-31have the better comprehensive performance; the synthesis performance of JY-13, JY-7, JY-51, JY-22, JY-9, JY-44, JY-23, JY-2and JY-30is medium; JY-52, JY-3, JY-42, JY-40, JY-41, JY-46and JY-1have a low adaptation. The growth performances of several others were instability, and should continue to observe. At the same time, methods such as local soil improvement method and cover plastic in greening can improve the survival rate of afforestation in Tianjin coastal area. |
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