The restoration potential of fynbos riparian seed banks following alien clearing

Riparian areas contribute significantly to the spread of many invasive alien tree species which alter the ecosystem by bringing about significant water loss and changing the natural flow regimes of the system. For this reason, many alien clearing initiatives initially focus on riparian areas but limited resources allows for little restoration to these areas after clearing. The aim of this project was to assess the composition and viability of riparian seed banks before and after invasion to be used by conservation managers and land-owners in assessing post-disturbance restoration requirements. The focus was on riparian seed bank composition in four river systems in the south-western part of the Western Cape province (the Berg, Eerste, Molenaars and Wit Rivers). Equal number of plots were selected in both relatively un-invaded (<25% IAP cover) and invaded (>75% IAP cover) sections of the rivers. The seedlings that emerged from the soil samples were compared in terms of diversity, species richness, similarity and assembly groupings. Findings show that invasion alters the assembly patterns within riparian seed banks. Species richness, diversity and similarity of species showed no clear pattern and was suggested to be site specific. It is suggested that after intesive alien infestation, restoration will only be successfull if a seed source is restored by re-planting certain key riparian tree species that are not present in the seed bank and follow-up treatements continue. To evaluate the restoration potential of riparian seed banks after invasion

河岸带（riparian areas）在诸多外来入侵乔木物种的扩散过程中发挥着重要作用，此类入侵物种会通过造成显著水分流失、改变系统自然水文情势而破坏生态系统。正因如此，诸多外来物种清除项目最初均以河岸带为核心实施区域，但受限于资源匮乏，清除完成后可用于该区域生态修复的投入寥寥无几。
本项目旨在评估入侵前后河岸带种子库（riparian seed bank）的组成与活性，以期为保护管理者与土地所有者评估扰动后修复需求提供参考。研究聚焦于南非西开普省西南部四条河流系统——伯格河（Berg River）、厄尔斯特河（Eerste River）、莫伦阿尔斯河（Molenaars River）与威特河（Wit River）的河岸带种子库组成。在各河流的相对未入侵（入侵外来植物（Invasive Alien Plant, IAP）盖度<25%）与入侵（IAP盖度>75%）区段，各选取等量样地。对土壤样品萌发的幼苗，从物种多样性、物种丰富度、群落相似性与群落组装模式等维度开展对比分析。
研究结果表明，入侵作用会改变河岸带种子库内的群落组装模式。物种丰富度、多样性与群落相似性未呈现明确规律，且被认为具有生境特异性。研究提出，在遭受严重外来物种入侵后，唯有通过补植种子库中缺失的关键河岸带乔木物种以恢复种子源，并持续开展后续管护措施，修复工作方能取得成功。本研究旨在评估入侵后河岸带种子库的修复潜力。