EcoLab (Laboratoire Ecologie Fonctionnelle et Environnement), CNRS, INPT, UPS, Université de Toulouse, 118 Route de Narbonne Bâtiment 4R1, 31062, Toulouse Cedex 9, France.
Department of Biological Sciences, University of Denver, F. W. Olin Hall, 2190 E Iliff Avenue, Denver, Colorado, 80208, USA.
Ecol Appl. 2017 Sep;27(6):1789-1804. doi: 10.1002/eap.1566. Epub 2017 Jul 7.
Most studies assessing vegetation response following control of invasive Tamarix trees along southwestern U.S. rivers have been small in scale (e.g., river reach), or at a regional scale but with poor spatial-temporal replication, and most have not included testing the effects of a now widely used biological control. We monitored plant composition following Tamarix control along hydrologic, soil, and climatic gradients in 244 treated and 172 reference sites across six U.S. states. This represents the largest comprehensive assessment to date on the vegetation response to the four most common Tamarix control treatments. Biocontrol by a defoliating beetle (treatment 1) reduced the abundance of Tamarix less than active removal by mechanically using hand and chain-saws (2), heavy machinery (3) or burning (4). Tamarix abundance also decreased with lower temperatures, higher precipitation, and follow-up treatments for Tamarix resprouting. Native cover generally increased over time in active Tamarix removal sites, however, the increases observed were small and was not consistently increased by active revegetation. Overall, native cover was correlated to permanent stream flow, lower grazing pressure, lower soil salinity and temperatures, and higher precipitation. Species diversity also increased where Tamarix was removed. However, Tamarix treatments, especially those generating the highest disturbance (burning and heavy machinery), also often promoted secondary invasions of exotic forbs. The abundance of hydrophytic species was much lower in treated than in reference sites, suggesting that management of southwestern U.S. rivers has focused too much on weed control, overlooking restoration of fluvial processes that provide habitat for hydrophytic and floodplain vegetation. These results can help inform future management of Tamarix-infested rivers to restore hydrogeomorphic processes, increase native biodiversity and reduce abundance of noxious species.
大多数评估美国西南部河流沿线入侵柽柳林控制后植被响应的研究规模较小（例如，河流流域），或者在区域范围内，但时空再现性较差，而且大多数研究都没有测试现在广泛使用的生物控制的效果。我们在六个美国州的 244 个处理和 172 个对照点，沿着水文、土壤和气候梯度监测柽柳林控制后的植物组成。这是迄今为止对四种最常见的柽柳控制处理的植被响应进行的最大规模综合评估。一种食叶甲虫的生物防治（处理 1）对柽柳的丰度减少作用小于机械地使用手锯和链锯（2）、重型机械（3）或焚烧（4）进行的主动清除。柽柳的丰度也随温度降低、降水增加和柽柳重新发芽的后续处理而降低。在主动清除柽柳的地点，原生植被通常会随着时间的推移而增加，然而，观察到的增加很小，并且主动植被恢复并没有持续增加。总体而言，原生植被与永久性溪流流量、较低的放牧压力、较低的土壤盐分和温度以及较高的降水有关。柽柳被清除的地方物种多样性也增加了。然而，柽柳处理，尤其是那些产生最高干扰的处理（焚烧和重型机械），也常常促进外来草本植物的二次入侵。在处理过的地点，水生植物的丰度明显低于对照地点，这表明美国西南部河流的管理过于注重杂草控制，而忽略了恢复为水生植物和洪泛区植被提供栖息地的河流地貌过程。这些结果可以帮助为未来受柽柳入侵的河流管理提供信息，以恢复水文地貌过程，增加本地生物多样性，并减少有害物种的丰度。
