Abstract: Brackish groundwater is an important irrigation resource in Xinjiang. In this study， ten representative forage species were exposed to simulated brackish water containing eight salt types at five salinity levels （0， 2， 4， 6 and 8 g·L^-1）. We systematically evaluated each species’ morphological， physiological-biochemical， and functional trait responses， then applied correlation analysis combined with an entropy-weight regression model to determine salt-tolerance thresholds. Under moderate to high salinity， Sophora alopecuroides and Psathyrostachys juncea showed significant increases in root length， whereas Medicago sativa and Astragalus adsurgens prioritized aboveground biomass allocation. As salinity rose， most species experienced declines in maximum quantum yield of PSII （Fv/Fm） and increases in malondialdehyde （MDA）， indicating inhibited photosynthetic efficiency and intensified membrane lipid peroxidation； notably，Astragalus adsurgens exhibited the greatest increase in peroxidase （POD） activity， while Bromus inermis displayed the largest rises in superoxide dismutase （SOD） and catalase （CAT） activities. Functional trait analysis revealed that Psathyrostachys juncea and Agropyron cristatum adapted by enhancing root absorption capacity， whereas Medicago sativa and Sophora alopecuroides optimized shoot-root balance by reducing their shoot-to-root length ratios. Regression modeling yielded salt-tolerance thresholds of 7.00， 7.50， 7.75， 8.67， and 10.80 g·L^-1 for Psathyrostachys juncea， Astragalus adsurgens， Agropyron cristatum， Bromus inermis， and Sophora alopecuroides， respectively. These five species are thus recommended as preferred cultivars for brackish-water-irrigated pastures in Xinjiang， while the remaining species are less suitable under high-salinity conditions.

Key words: Slightly saline water, Mineralization, Physiological and biochemical properties, Functional traits, Tolerance thresholds

摘要： 微咸水是新疆重要的灌溉水资源，本研究选取紫花苜蓿等10种新疆具有代表性的牧草，配置含有8种盐类的混合盐来模拟新疆的微咸水，设置0，2，4，6，8 g·L^-1五个矿化度梯度，系统考察植株在生物学特性、生理生化特性及功能性状方面的响应，并结合相关性分析与熵值法构建加权回归模型。结果显示，在生物学特性方面，中高矿化度下苦豆子和新麦草的根长显著提高，紫花苜蓿与沙打旺优先分配地上生物量；生理生化特性方面，随矿化度升高，多数牧草Fv/Fm下降、MDA含量升高，表明牧草在高矿化度下均光合效率受抑且膜脂过氧化加剧，其中沙打旺POD活性和无芒雀麦SOD、CAT活性上升最为显著；功能性状分析表明，新麦草、扁穗冰草等通过提高根系吸收能力适应盐胁迫，而紫花苜蓿、苦豆子则通过降低“株高/根长”来优化地上与地下部分的资源分配。回归模型计算得出新麦草、沙打旺、扁穗冰草、无芒雀麦和苦豆子的耐盐阈值分别为7.00，7.50，7.75，8.67和10.80 g·L^-1，上述牧草耐盐性较强，可作为新疆微咸水灌溉下人工草地的优选品种，其余品种耐盐性较弱，不宜在高矿化度条件下推广。

关键词: 微咸水, 矿化度, 生理生化特性, 功能性状, 耐受阈值