| Based on salt-resistant Poplar planting experiment in the field in Tianjin coastal area,growth indexes of different testing tree species was observed continuously, comparing theeffects of the growth of the planted Poplar varieties in different environmental conditions. Atthe same time, the changes of chlorophyll content were measured in order to explore thegrowth rule and the suitable ecological conditions of Poplar in Tianjin coastal saline-alkaliland area and select some suitable salt-tolerant fast-growing Poplar varieties for Tianjincoastal area growing. Finally, soil environmental change was evaluated after plangting, andsoil improvement effect was analysised. Thus the theory basis of Poplar salt-tolerant forpopularization and application was provided for Tianjin coastal area. The conclusions were asfollows:(1)In the salt content of0.35%and0.39%respectively, the survival rate of JY-17, JY-24,JY-26, JY-27, JY-31, JY-36and JY-42can reach100%. On the salt content of0.35%plot, thegrowth of the trees was obviously superior to the salt content of0.39%plot due to the lightersalinity degree. Analysis of variance showed that the growth status of Poplar varieties wasobviously different. The average tree height changed between4.17~7.01m. Changes in theaverage diameter at breast height were3.16~5.98cm. The variation range of average crownwas0.72~2.40m. From the analysis of average annual growth rate index, tree height growthof20species was more than1.0m/year, and DBH growth of13varieties was more than1.5cm/year. On the salt content of0.39%plot, changes in the average tree height were3.39~6.00m, average diameter at breast height changed between2.71~6.52cm, and thevariation range of average crown was0.92~2.96m. From the point of average annual growthrate index, tree height growth of16species was more than1.0m/year, and DBH growth of11varieties was more than1.5cm/year.(2)There were significant differences in the the survival rate, tree height, DBH andcrown growth performance of different Poplar varieties in the environmental conditionswhich the soil salt content were0.35%and0.39%respectively. That indicated that ecologicaladaptability of the varieties was different. Method of membership grade function was used inthe screening of salt-tolerance Poplar varieties. On the basis of comprehensive consideration,six prominent varieties were chosen which should be popularization and application prioritilyin Tianjin coastal area, respectively was: JY-27, JY-44, JY-24, JY-18, JY-26and JY-36.(3)The changes of chlorophyll content in Cathay Poplar Group JY-44, Section AigeirosJY-26, JY-21, JY-17and JY-18, Section Leuce JY-42were selected to measure from July toOctober. The trend of chlorophyll content changes showed a downward after rising first withthe changes of seasons. Chlorophyll average levels of six varieties in salt content0.39%plotwere higher than that of0.35%salinity plot. The different factions of chlorophyll content in Poplar from low to high were: Cathay Poplar Group＜Section Aigeiros＜Section Leuce.(4)The changes of soil environment after afforetation in three years showed that forestplanting can make the soil pH value fall slightly. Salt content was obviously decreased. Thecontent of organic matter was improved. The content of K+, Na+and Cl-, SO42-was decreased.The content of CO32-increased and the content of Ca2+and Mg2+had no obvious change.(5)Planting in local experimental zone was carried out in order to achieve the result offield experiment and make the experiment good reproducibility. After three years, theperformance ranking of tree species was fertilizer JY-33, sand and fertilizer JY-33, sand JY-33, JY-33under the same breed in different content of experiment conditions. Under thecondition of the same content, the performances of JY-24, JY-26, JY-33, JY-52, and JY-10were good and were in accordance with the field testing, which verify the higher degree ofthese species. |
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