The Mississippi River Delta (MRD) is one of the largest wetlands in the world and is experiencing widespread dieback of its most prevalent plant species, Phragmites australis. The potential for revegetation of dieback sites was assessed by planting three genetically distinct lineages of P. australis at seven sites in the MRD that varied in water depth. These lineages include Delta, the most prevalent in the MRD, EU, a highly invasive lineage, and Gulf, a common lineage of the Gulf Coast and southern United States. Three additional wetland species were planted at a subset of these sites. Plantings were monitored for 32 months during which time, we surveyed plantings for survival, growth and infestation by a scale insect that has been implicated in P. australis dieback. Survivorship differed considerably among plant types and by 6 months, Delta, Gulf and California bulrush (Schoenoplectus californicus) had twice the survivorship of the other plant types. By the end of the study, Delta, Gulf and bulrush were the only plant types alive, with Delta persisting in more than twice as many sites and having > 6 times more area of coverage as Gulf and bulrush. For all P. australis lineages, water depth was negatively related to survivorship. Finally, although scale insects achieved twice the abundance on Delta than the other lineages, we found no evidence that scales were inhibiting the growth and survival of P. australis. Despite potential negative legacy effects of dieback, Delta can be used revegetate shallow-water sites within a year following dieback.

密西西比河三角洲 (MRD) 是世界上最大的湿地之一，其最常见的植物芦苇正在经历大范围的枯死。通过在 MRD 中水深不同的七个地点种植三种遗传上不同的澳洲 P. australis谱系，评估了顶枯地点重新植被的潜力。这些谱系包括 Delta（MRD 中最常见的谱系）、EU（高度侵入性谱系）和 Gulf（墨西哥湾沿岸和美国南部的常见谱系）。在这些地点的一部分还种植了另外三种湿地物种。我们对种植园进行了为期 32 个月的监测，在此期间，我们调查了种植园的存活率、生长情况以及介壳虫的侵染情况，该介壳虫与澳大利亚白头枯病有关。不同植物类型的存活率差异很大，六个月后，三角洲、海湾和加州芦苇 ( Schoenoplectus californicus ) 的存活率是其他植物类型的两倍。到研究结束时，三角洲、海湾和芦苇是唯一存活的植物类型，其中三角洲持续存在的地点是海湾和芦苇的两倍以上，覆盖面积是海湾和芦苇的六倍以上。对于所有australis谱系，水深与存活率呈负相关。最后，尽管介壳虫在三角洲上的丰度是其他谱系的两倍，但我们没有发现任何证据表明介壳虫会抑制澳大利亚拟南芥的生长和生存。尽管顶枯病可能产生负面影响，但 Delta 可以在顶枯病发生后一年内用于浅水区的植被恢复。