Plant community responses to biocontrol of invasive plants are understudied, despite the strong influence of the composition of replacement vegetation on ecosystem functions and services. We studied the vegetation response to a folivore beetle (Diorhabda genus, Coleoptera) that has been introduced along southwestern US river valleys to control the invasion of non-native shrubs in the genus Tamarix (Tamaricaceae). We collected detailed plant compositional and environmental data during four different surveys over 7 years (2010–2017), including two surveys prior to when substantial beetle-induced dieback occurred in summer 2012, along the lower Virgin River, Nevada. The study river was of special interest because it is one of only a few largely unregulated rivers in the region, and a large flood of 40-year return period occurred between the first and second surveys, allowing us to study the combined effects of fluvial processes, which typically drive riparian plant community assembly, and biocontrol. Vegetation trajectories differed as a function of the dominant geomorphological process. Tamarix cover declined an average of 75% and was replaced by the native shrub Pluchea sericea as the new dominant species in the floodplain, especially where sediment deposition predominated. Following deposition, and especially erosion, opportunistic native herbs, Tamarix seedlings, and noxious weeds colonized the understory layer but did not increase in cover over time. Stands of the native shrub Salix exigua, a desirable replacement species following Tamarix control, only increased slightly and remained subordinate in the floodplain. Overall, our results showed that, by successfully controlling the target non-native plant, a biocontrol agent can substantially modify the replacement plant communities in a riparian system, but that fluvial processes also strongly influence the resulting communities.

尽管替代植被的组成对生态系统功能和服务有很大影响，但对植物群落对入侵植物生物控制的反应仍未得到充分研究。我们研究了植被响应食叶动物甲虫（Diorhabda已经沿着美国西南部河谷引进来控制非本地灌木的入侵属属鞘翅目），柽柳（T科）。我们在7年（2010-2017年）的四次不同调查中收集了详细的植物成分和环境数据，包括两次调查之前，这是在2012年夏季，内华达州下维京河沿岸发生大量的甲虫诱发的死亡。研究河流特别受关注，因为它是该地区仅有的几条不受监管的河流之一，并且第一次和第二次勘测之间发生了长达40年的重现期洪灾，这使我们能够研究河流过程的综合影响，通常会推动河岸植物群落的组装和生物防治。植被的轨迹因主要的地貌过程而异。mari柳的覆盖率平均下降了75％，取而代之的是天然灌木Pluchea sericea作为洪泛区中新的优势物种，尤其是在沉积物沉积为主的地区。在沉积，尤其是侵蚀之后，机会性的本地草药，Ta柳幼苗和有害杂草定居在林下层，但覆盖率并未随时间增加。本地灌木柳柳（Salix exigua）的林分，在塔马里克斯（Tamarix）控制之后是理想的替代树种，仅略有增加，并在洪泛区保持从属地位。总体而言，我们的结果表明，通过成功地控制目标非本土植物，生物防治剂可以在河岸系统中实质性地改变替代植物群落，但是河流过程也强烈地影响着最终的群落。