河西走廊荒漠盐碱地人工柽柳林土壤水盐分布

土壤盐碱化是一个全球性问题,植树造林是一种主要的改良措施.为了研究荒漠盐碱地10年人工柽柳林土壤水盐空间分布及生态改良效果,对2、4、6和8m行间距柽柳灌下和行间的土壤水盐进行分析,并构建结构方程模型量化土壤水盐对植被的影响程度.结果表明:林地浅层土壤(0~40 cm)可溶性盐明显低于林外(CK),灌下土壤含水率高于行间.且6m行间距柽柳的高度和冠幅及其灌下草本植物的盖度和生物量均大于其他行间距柽柳,阳离子在柽柳周围的富集程度为Na^+>K^+>Ca^2+>Mg2+,阴离子的富集程度为Cl^->HCO3^->SO4^2-.土壤盐分含量最高的是MgSO4,其次是CaCl2、NaCl和MgCl2,KHCO3含量最少.土壤水盐中影响植被生长的最大因素是土壤水分,其次是盐分,最小为pH,权重大小分别是50.6%、29.5%和19.9%.

Distribution of soil moisture and salt of Tamarix ramosissima plantation in desert saline-alkali land of Hexi Corridor Region,China

Soil salinization is a global problem. Afforestation is a major improvement practice for desert saline-alkali land. To examine ecological improvement effects and spatial distribution of soil moisture and salinity in Tamarix ramosissima plantation with the age of 10 years in desert saline-alkali land, soil moisture and salt content between rows and under shrubs with row distance of 2, 4, 6, and 8 m were measured. The structural equation model was used to quantify the effects of soil water and salt changes on plant growth. The results indicated that soluble salt in shallow soil (0-40 cm) of T. ramosissima plantation was significantly lower than that outside the plantation, but soil moisture under shrubs was higher than that between rows. Among different row distances, the maximum values of height and canopy size of T. ramosissima and coverage and biomass of vegetation under the shrubs were found in row distance of 6 m. The enrichment degree of soil cations around taproot was in order of Na⁺>K⁺>Ca²⁺>Mg²⁺ and anions were enriched with Cl^->HCO₃^->SO₄^2-. There were five kinds of salts in soil, with MgSO₄ being the most abundant, followed by CaCl₂, NaCl and MgCl₂, and the lowest being KHCO₃. Soil moisture had the strongest effects on vegetation, followed by soil salinity, and the lowest was soil pH, with values of 50.6%,29.5% and 19.9%, respectively.