地下水矿化度对柽柳根系生长及构型的影响

为探明柽柳根系形态、构型指标对地下水矿化度变化的响应规律，以3年生柽柳幼苗为研究对象，在1.8 m地下水水位条件下，模拟设置黄河三角洲淡水（0 g/L）、微咸水（3 g/L）、咸水（8 g/L）和盐水（20 g/L）4个矿化度，测定分析柽柳根系直径、根长、生物量、根冠比、拓扑指数、连接长度等生长和构型指标。结果表明：地下水矿化度对土壤含水量影响不显著，但对土壤含盐量、土壤溶液绝对浓度具有显著影响，进而对柽柳幼苗根系生长及构型产生影响。随地下水矿化度的升高，柽柳根径、根长、侧根数、主根及侧根生物量均呈现先升高后降低的趋势，在微咸水矿化度下达到最大值。在淡水、微咸水矿化度下，柽柳根系拓扑指数接近0.5，根系分支趋向于叉状分支模式；在咸水、盐水矿化度下，柽柳根系拓扑指数较大接近1.0，趋向于鱼尾形分支模式。不同地下水矿化度下柽柳根系总长度显著大于根系内部连接长度，外部连接长度大于内部连接长度，柽柳根系均呈现向外扩张的生长策略。不同地下水矿化度处理下柽柳根系形态及构型特征既有差异性又有相似性，表现出不同的水盐适应特征。适当提高地下水矿化度至微咸水可促进柽柳根系的生长，而高于咸水矿化度则会对柽柳根系的生长产生抑制作用。

The Influence of Groundwater Salinity on the Growth and Architecture of Tamarix chinensis Root System

To explore the response patterns of the root morphology and architecture indexes of Tamarix chinensis to changes in groundwater salinity. Taking three-year-old T. chinensis seedlings as the research object. Under the condition of 1.8 m groundwater level, 4 salinity levels of fresh water (0 g/L), brackish water (3 g/L), saline water (8 g/L), and salt water (20 g/L) were created. To measure the root growth and architecture indexes, such as root diameter, root length, root biomass, root-shoot ratio, topological index, and link length. The results showed that the groundwater salinity has no significant effect on the soil water content, but has a significant effect on the soil salt content and the absolute soil solution content, thus affecting the growth and architecture of root system of T. chinensis. With the increase of groundwater salinity, T. chinensis root diameter, root length, lateral root number, main root, and lateral root biomass all show a trend of first increasing and then decreasing, reaching the maximum under brackish water salinity. In the fresh water and brackish water treatments, the TI of the T. chinensis roots was close to 0.5, and the root architecture was close to a dichotomous branching pattern. In the saline water and saltwater treatments, the TI of the T. chinensis roots was large and close to 1.0, and the root architecture was close to a herringbone branching pattern. Under different groundwater salinities, the total root length was significantly greater than the internal link length, the external link length was greater than the internal link length, and the root system showed an outward expansion strategy. There were differences and similarities in the morphology and architecture characteristics of the root system of T. chinensis, exhibiting different adaptation characteristics to different soil water and salt conditions. Appropriately, increasing the groundwater salinity to brackish water can promote the root growth of T. chinensis, while higher salinity than brackish water will inhibit the root growth.