Aquatic vegetation is a key component of large floodplain river ecosystems. In the Upper Mississippi River System (UMRS), there is a long-standing interest in restoring aquatic vegetation in areas where it has declined or disappeared. To better understand what constrains vegetation distribution in large river ecosystems and inform ongoing efforts to restore submersed aquatic vegetation (SAV), we delineated areas in ~1200 river km of the UMRS where the combined effects of water clarity, water level fluctuation, and bathymetry appeared suitable for establishment and persistence of SAV based on a 22-year dataset for total suspended solids (TSS), water surface elevation, and aquatic vegetation distribution. We found a large increase in suitable area downstream from a large natural riverine lake near the northern end of the UMRS (river km 1230) that functions as a sink for suspended material. Downstream from river km 895, there was much less suitable area due to decreased water clarity from tributary input of suspended material, changes in river geomorphology, and increased water level fluctuation. A hypothetical scenario of 75% reduction in TSS resulted in only minor increases in suitable area in the southern portion of the UMRS, indicating limitations by water level fluctuation and/or bathymetry (i.e., limited shallow area). These results improve our understanding of the structure and function of large river systems by illustrating how water clarity, fluctuations in water level, and river geomorphology interact to create complex spatial patterns in habitat suitability for aquatic species and may help to identify locations most and least likely to benefit from management and restoration efforts.

水生植被是泛滥河生态系统的重要组成部分。在上密西西比河水系（UMRS）中，恢复或减少已消失地区的水生植被一直是人们的长期兴趣。为了更好地了解是什么制约了大型河流生态系统中的植被分布，并为恢复水下淹没水生植物（SAV）所做的努力提供了信息，我们在UMRS约1200公里的河流中划定了区域，这些区域出现了水质清晰，水位涨落和测深的综合影响根据22年的总悬浮固体（TSS），水面高程和水生植被分布的数据集，适用于SAV的建立和持久性。我们发现，在靠近UMRS北端的大型天然河湖下游（河流1230公里），合适的区域大幅度增加，该湖起着悬浮物沉没的作用。在895公里公里的河流下游，由于悬浮物的支流输入导致水的清晰度降低，河流地貌的变化以及水位波动的增加，适合的区域减少了。假设的TSS降低75％的情况导致UMRS南部的合适面积仅略有增加，这表明受水位波动和/或测深法的限制（即，有限的浅层区域）。这些结果通过说明水的净度，水位的波动，