地下水位对黄河三角洲柽柳根系生长的影响

Abstract

为揭示黄河三角洲柽柳根系生长特征对地下水位的响应规律，明确柽柳生长适宜的地下水位，在咸水矿化度（6 g/L）下，模拟设置0、0.3、0.6、0.9、1.2、1.5、1.8 m共7个地下水位。测定分析栽植柽柳土柱的水盐参数与根系生长指标。结果表明：在咸水矿化度下，地下水位可显著影响土壤水盐变化，从而影响柽柳根系的生长。随地下水位的降低，土壤含水量、含盐量和土壤溶液绝对浓度显著降低。在高水位（≤0.6 m）下，柽柳根系生长受水盐胁迫影响显著，柽柳根长、根径、侧根数、总生物量、侧根生物量、根系连接长度均较低，拓扑结构呈叉状分支；中水位（0.9 m）时，土壤水盐条件适宜，柽柳侧根数、根径、二级侧根和毛细根生物量达到最大值，拓扑结构由叉状分支向鱼尾形分支过渡；低水位（≥1.2 m）下，土壤水盐含量低，柽柳根系总生物量、主根生物量、一级侧根生物量和根系平均连接长度在1.2 m水位达到最大值后降低，拓扑结构呈鱼尾形分支。柽柳根系生长与地下水位密切相关，柽柳通过改变根系生长和调整构型来适应不同土壤水盐和地下水位条件。高水位（≤0.6 m）下柽柳以降低根系生长深度，增加分叉，调配各组织器官的生物量来适应水盐胁迫；中水位0.9 m下土壤水盐条件最适宜柽柳生长；低水位（≥1.2 m）下柽柳主要受土壤干旱胁迫而使根系向下生长，增加根系连接长度，以此扩大资源获取效率。柽柳根系生长及根系构型对咸水矿化度下不同地下水位表现出较强的适应性和可塑性。;The depth of groundwater can affect the root growth of plants. However, we know little about how groundwater depth influences the root growth characteristics and root architecture of Tamarix chinensis in the Yellow River Delta. To reveal the response law of the root growth characteristics of T.chinensis in the Yellow River Delta concerning groundwater depth and determine a suitable groundwater depth of T.chinensis, we conducted a greenhouse experiment to test the response of root growth characteristics of T. chinensis to the groundwater depth. We grew T. chinensis under seven groundwater depths (0, 0.3, 0.6, 0.9, 1.2, 1.5 and 1.8 m) with a saline water of 6 g/L. The results showed that in saltwater, the groundwater depth had significant effect on the growth of the T. chinensis root system by changing the soil water and salinity contents. When the groundwater depth was less than 0.6 m, the root length, root diameters, lateral root number, total biomass, lateral root biomass and root link length of T.chinensis were significantly decreased. The topological structure was dichotomous. While, the number of lateral roots, root diameters, the number of secondary lateral roots and fine root biomass of T. chinensis were the greatest at 0.9 m depth of groundwater. The topological structure transitioned from dichotomous to herringbone-like. The total root biomass, taproot biomass, first-order lateral root biomass and average length of links of T.chinensis decreased once the groundwater depth over 1.2 m, and the topological structure was herringbone-like. Thus, the root growth of T. chinensis is closely related to groundwater depth. T.chinensis root growth changed, and the configuration was adjusted to adapt to different soil water and salt and groundwater depth. At a shallow groundwater depth (≤ 0.6 m), the root growth of T.chinensis was suppressed but branching increased, and the biomass of various tissues and organs was altered to adapt to water and salt stress. The most suitable groundwater depth for the growth of T.chinensis was at 0.9 m. When the groundwater depth was more than1.2 m, the roots of T.chinensis grew downward mainly due to soil drought stress, which increased the length of root, thus improved the efficiency of resource acquisition. We conclude that the T.chinensis can adapt to groundwater depth by altering root growth and morphology. Therefore, the adaptability of T.chinensis root system to different groundwater levels is of great significance to the study of vegetation restoration and ecological restoration of coastal saline-alkali wetlands under different groundwater conditions in the Yellow River Delta.