荒漠盐生植物根际土壤盐分和养分特征

Soil salt and nutrient concentration in the rhizosphere of desert halophytes

中国西北地区是我国干旱、盐碱化土壤分布面积较广、土壤积盐较重的地区,这里发育着丰富的盐生植物。目前对于干旱荒漠区盐生植物根际特征的研究相对较少,而不同盐生植物的根际特征对于研究盐生植物适应盐渍环境的机制有着重要意义。本研究利采用盆栽根袋法对7种不同类型的荒漠盐生植物的根际盐分和养分特征进行了初步探索。结果表明:盐分在盐生植物根际发生富集,稀盐盐生植物和泌盐盐生植物根际土壤中总盐和8种主要盐分离子的含量都有所增加,而在拒盐盐生植物根际中增加不显著,其中Cl-和Na+的富集程度相对其它6种离子的富集程度要高。稀盐盐生植物和泌盐盐生植物根际土中的SO42-/Cl-比土体有显著的降低,表明在稀盐盐生植物和泌盐盐生植物根际土壤中Cl-的富集程度比SO42-高,拒盐盐生植物根际土盐分SO42-/Cl-比略有提高。7种盐生植物根际土中的Na+/K+,Na+/Ca2+,Na+/Mg2+比均较土体有显著的增加,芦苇根际土中的增加最小。在所有研究植物中,根际土壤中全N含量比土体的含量高,但全P和全K含量却比土体的含量低;根际土壤中有效态养分的变化则与全态相反,根际土壤中的有效N含量比土体中的都显著降低,除芦苇外,其他六种盐生植物根际土壤中有效P和有效K的含量都高于土体,但有效P的富集不及有效K富集的程度高。在研究的七种植物中,钠猪毛菜根际土壤的有效N亏缺量最高,有效P和速效K富集也最少。7种植物,尤其是稀盐盐生植物和泌盐盐生植物的地上部分的主要盐离子含量比地下部分高,如Cl-、Na+、Ca2+和K+,在根际富集程度最高的Cl-和Na+,在植株的地上部分也增加的最多。

North-West China is an arid region where the saline soil is widely distributed, and therefore is rich in halophyte plants. Very little is known on the rhizospheric soil of the halophytes in this arid desert region, as few research works had been done. We conducted a rhizobag experiment on desert solonchak soil to investigate the salt and nutrient content of the rhizospheric soil of the desert halophytes, and to compare them with the bulk soil. The results revealed that soil salts were accumulated in the rhizosphere of desert halophytes, with total salt and the concentrations of major ions increased for both succulent halophytes and salt secrete halophytes, but this increase was insignificant for salt-resisting halophytes. Accumulation of Cl^- and Na^＋ is the most significant among the 8 major ions. The SO4^2-/ Cl^- ratio of rhizosphere decreased remarkably in succulent halophytes and salt secrete halophyte, as comparing to bulk soil, and this indicated that accumulation of Cl-was more significant than SO4^2-. The Na^＋/ K^＋ ,Na^＋/ Ca^2＋ ,Na^＋/ Mg^2＋ ratio in the rhizosphere were higher than bulk soil to all seven halophytes. Total N increased significantly in the rhizosphere, but total P and total K decreased. However, the available N, P and K in the rhizosphere behaved in an opposite way： with available N decreased but available P and available K increased in the rhizosphere except for Phragmites communis Trin. Deficit of available N is the most significant, and accumulation of available P and available K were the least for Salsola nitraria Pall. among all seven halophytes. The ionic contents of the above ground part of the plants were higher than the underground part in all seven halophytes, especially for Cl^-, Na^＋ , Ca^2＋ and K^＋. Accumulation of Cl^- and Na^＋ in the aboveground part of the plant were the most significant among 8 major ions, which coincided with the ionic accumulation in the rhizosphere, especially for succulent halophytes and salt secrete halophyte.