蒸发条件下潜水埋深对土壤-柽柳水盐分布的影响

盐水矿化度下模拟设置4个潜水埋深(0.9、1.2、1.5、1.8 m),分析不同土层的土壤相对含水量(RWC)、含盐量(S_C)和土壤溶液绝对浓度(C_S)等水盐参数,及柽柳叶片和新生枝条的含水量及Na~+含量,探讨盐水矿化度下土壤-柽柳水盐参数对潜水埋深的响应规律。结果表明:各土层RWC与潜水埋深呈负相关,0.9 m潜水埋深下各土层的RWC均最高,且各土层RWC随土层深度的增加呈先降低后增加的趋势,其它潜水埋深下各土层RWC均逐渐增加,1.2 m是地下水所能上升且保持柽柳柱体土壤表层湿润的最高高度。各土层S_C和C_S与潜水埋深呈抛物线型,均表现为先增加后降低,潜水埋深1.2 m时,各土层S_C均最高。随土层深度的增加,各潜水埋深下S_C先降低后增加,而C_S呈现减少趋势;潜水埋深越高,土层间C_S变化幅度越激烈。潜水埋深对柽柳叶片和新生枝条的含水量无显著影响(P0.05),而随潜水埋深的增加,柽柳叶片Na~+含量逐渐增加,新生枝条Na~+含量则先增加后降低。从整个柽柳土柱看,随潜水埋深的增加,整个土壤剖面的RWC均值逐渐降低,而S_C和C_S均值先增加后降低,潜水埋深1.2 m是盐分变化的分界点,建议栽植柽柳的潜水埋深大于1.2 m。

Effect of groundwater depth on the distribution of water and salinity in the soil-Tamarix chinensis system under evaporation conditions

In order to investigate the response of water and salt distribution in the Tamarix-soil system to groundwater depth under saline conditions, a soil column experiment was carried out with Tamarix chinensis planted under four treatments with different groundwater depths (0.9 m, 1.2 m, 1.5 m, and 1.8 m). The soil relative water content (RWC), soil salt content (S_C), and absolute concentration of soil solution (C_S) were determined in different profiles of water content and Na⁺ content of the leaves and new branches of T. chinensis. The RWC in each soil profile was negatively correlated with the groundwater depth, and the maximum values for each soil layer were observed in groundwater depth treatment that was 0.9 m deep. With the increase in soil depth, the RWC in this treatment increased initially and then decreased, while it constantly increased at other groundwater depths. The results showed that the 1.2 m groundwater depth treatment was the greatest depth to which water could reach and keep the soil surface moist in the soil column planted with T. chinensis. With the increase in groundwater depth, S_C and C_S of each soil profile increased initially and then decreased, displaying a parabola pattern, The maximum content at each soil layer was observed in the 1.2 m groundwater depth treatment. With the increase in soil depth, S_C in all groundwater depth treatments decreased initially and then increased, while C_S decreased gradually. The change range of C_S between soil layers increased with the increase of groundwater depth. Significant differences were not observed (P>0.05) between the water content in either the leaves or new branches of Tamarix at different groundwater depths, while the content of Na⁺ in the leaves increased gradually and that in the new branches decreased after an initial increase. For the whole Tamarix-soil column, the mean of RWC decreased gradually with the increase in groundwater depth, whereas the mean of S_C or C_S increased initially followed by a decrease. The groundwater depth of 1.2 m is the demarcation point of salinity change, suggesting that the groundwater depth for Tamarix should be more than 1.2 m.