Acacia implexa in South Africa: an emerging invader and potential candidate

Invasive alien plant species have major impacts on biodiversity and ecosystem functioning in most<br> parts of the world. Early detection and rapid response is a crucial part of management programmes.<br> Eradication of invasive species at the early stage of invasion is a very cost-effective intervention, but<br> not all species can be eradicated. This paper reports on a study of Acacia implexa, the screw-pod<br> wattle from Australia, an emerging invader, to determine whether it is a suitable candidate for<br> eradication in South Africa.<br> The species was introduced to South Africa in around 1986. Its current range comprises three<br> populations: in Stellenbosch, Tokai and Wolseley. The populations sizes ranges between 100 and<br> 200ha, with the Tokai population covering the largest area but comprising the fewest plants. The<br> density of the plants ranges from very high to very low, with Stellenbosch (Papegaaiberg) having the<br> highest density. The plants reproduce vegetatively (through suckering and resprouting) and sexually<br> (via seeds). A very high occurrence of suckering was present and few seedlings were observed.<br> Spread is mainly along rivers. Current treatments by area managers are unsuccessful for controlling<br> the species.<br> I consider that eradication of this species is feasible. The eradication plan should place strong<br> emphasis on the effective use of herbicides, communication and cooperation between different<br> managerial organizations, and prioritization of treatment efforts.外来入侵植物物种对全球多数区域的生物多样性与生态系统功能具有显著负面影响。早期监测与快速响应是入侵物种管理项目的核心组成部分。在入侵初期开展入侵物种根除工作是极具成本效益的干预措施，但并非所有入侵物种均可被根除。 本文针对源自澳大利亚的新兴入侵物种——螺旋荚金合欢（Acacia implexa，俗称screw-pod wattle）展开研究，以评估其在南非开展根除工作的适宜性。 该物种于1986年左右被引入南非，目前仅存三个种群，分别分布于斯泰伦博斯（Stellenbosch）、托凯（Tokai）与沃尔瑟利（Wolseley）。各种群的分布面积介于100至200公顷之间，其中托凯种群的分布面积最大，但植株数量最少。植株种群密度跨度极大，从极高到极低不等，其中斯泰伦博斯的帕派山（Papegaaiberg）种群密度最高。该物种兼具营养繁殖（通过萌蘖与萌芽更新）与有性繁殖（通过种子）两种繁殖方式。其萌蘖现象极为普遍，但野外仅观测到少量实生幼苗。该物种主要沿河流进行扩散，当前区域管理者采用的防治手段均无法有效控制其种群扩张。 笔者认为，该物种在南非的根除工作具备可行性。根除方案应重点强化三方面举措：高效合理施用除草剂、加强不同管理机构间的沟通协作，以及对防治工作进行优先级排序。