|其他摘要||Salinization of soil is one of the main contravariants that restricts the agriculture production. Soil salinization threats over 32% of the arable land in Xinjiang, and the second soil salinization becomes more and more serious. The type of salinized soil is various, which are mainly composed by NaCl, Na2SO4 and NaHCO3. Neutral salts (NaCl and Na2SO4) influence plant growth and development through osmotic stress and ion toxic. Alkaline stress caused by alkaline salts (NaHCO3 and Na2CO3) damage to plant much lager than salt stress. The effects of salt-alkali mix stress on the growth of halophytes were studied, and it’s of great significance for improving saline soil by planting halophytes. Improving heavy saline soil by planting halophytes is a long process and the soil salt content gradually decreases in this process. The salt accumulation of halophytes will change with the soil salt content change. In this paper, two parts are mainly focused on. In the first study，the effect of salt-alkali mix stress on the growth of two typical halophytes(S. salsa and S. europaea ) were studied based on pot soil experiment. In the second study, the changes of salt accumulation of S. salsa in different planting years were studied based on field experiment. The main results were shown as follows:
(1) Because S. salsa and S. europaea are salt-dilution halophytes so they have high salt tolerance. S. Salsa was capable of surviving in all levels of salinity in most of salt treatments, and the highest soil salt content was 5.5%.In D group of salt S. Salsa also was survived in all levels of salinity expect 5.5%.
(2) With the increasing of soil salt content, the dry matter yield of S. salsa and S. Europaea presented earlier increase and later decrease trend in all types of salt. Low soil salt content treatments increased dry matter yield of S. salsa and S. Europaea. The soil salt content that two halophytes had the highest dry matter yield were different in different types of salt. In treatments of four groups, the max of dry matter yield of S. Salsa were appeared on 0.5%, 1.5%, 1.5% and 1.5% of soil salt, respectively, and S. europaea were appeared on 1.5%, 1.5%, 0.5% and 0.5% of soil salt. The dry matter yield of two halophytes were decreasing significantly in high soil salt content treatments, and S. europaea's rating decreased significantly more than S. Salsa's rating. The salt of content of two halophytes were gradually increased with the increase of salinity. In different types of salt treatments, the salt accumulation of two halophytes increase at first and then descend with the increase of salinity. Under low salinity, the salt accumulation of S. salsa showed Cl-＞SO42-—Cl-＞Cl-—SO42-＞SO42-, under moderate and high salinity, the salt accumulation of S. salsa showed SO42-—Cl-＞Cl-—SO42-＞SO42-＞Cl-. Under low salinity, the salt accumulation of S. europaea showed Cl-—SO42-＞SO42-＞Cl-＞SO42-—Cl-, under moderate and high salinity the salt accumulation of S. europaea showed smiley with S. Salsa. The results of two-factor variance analysis showed that the dry matter yield, plant height, branch number, chlorophyll content, salt content and salt accumulation were affected remarkably by the soil salinity, treatment group and their interactive effect. Among them, the soil salinity is the leading factor, but the content of chlorophyll were much influence by treatment group.
(3)There were obvious difference on plant height, stem diameter, fresh weight unit area, dry weight unit area, and succulent degree on different planting years of S. Salsa, and the plant height, stem diameter, fresh weight unit area and dry weight unit area were increased with increasing years of planting, but succulent degree changed in the opposite trend. The shoot salt content and main ions content showed an decreased trend year by year from planting to the 3th year on all the growth stages, and the shoot salt content and main ions of seeding stage was obvious higher than adult stage and flowering and seed filled stage. The salt accumulation was controlled by shoot biomass and salt content on late stage. There were significant differences among different planting years, and that illustrated S. Salsa had steady accumulation of salt in improving Saline-alkali land under the condition of artificial cultivation.
(4)After planting S. Salsa on the heavy saline-alkali soil, the the soil salt and ions distribution in soil profile was significantly affected by planting years, the upper layers (0～40cm) of soil salinity decreased gradually with the increase of planting years, while the under layer(40～120cm) of soil salinity was increased first then decreased. Na+ and Cl- were easy to be leached and uptake by the plant, and the contents of which decreased considerably between different planting years. The decreasing rates of the two ions in upper layer soil were all above 49% after three planting years. Since it's hard for Ca2+ and SO42- to move with water, the speed of two ions' leaching were slow. HCO3- and Mg2+ contents in soil influenced by hydrated radius and the speed of two ions' leaching in second and third plantings higher than first year. The percentage of Cl- in salt content of upper layers decreased the percentage of Ca2+ increased, the SAR value and the soil salinity decreased significantly after three planting years.|