The impact of invasive species is often difficult to assess due to species × ecosystem interactions. Impatiens glandulifera heavily invaded several habitat types in Central Europe but its impact on native plant communities is rated ambiguously. One reason could be that the impact differs between habitat types or even between environmentally heterogeneous patches (micro-habitats) within one habitat type. In the present study a vegetation survey was performed within heterogeneous riverside habitats in Germany investigating the impact of I. glandulifera on native vegetation in dependence of environmental conditions. The vegetation was recorded in summer and spring because of seasonal species turnover and thus potentially different impact of the invasive plant. We found that the cover of I. glandulifera depended on environmental conditions resulting in a patchy occurrence. I. glandulifera did not have any impact on plant alpha-diversity but reduced the cover of the native vegetation, especially of the dominant species. This effect depended on micro-habitat and season. The native vegetation was most affected in bright micro-habitats, especially those with a high soil moisture. Not distinguishing between micro-habitats, plant species composition was not affected in summer but in spring. However, environmental conditions had a higher impact on the native vegetation than I. glandulifera. We conclude that within riparian habitats the threat of I. glandulifera to the native vegetation can be rated low since native species were reduced in cover but not excluded from the communities. This might be due to patchy occurrence and year-to-year changes in cover of I. glandulifera. The context-dependency in terms of micro-habitat and season requires specific risk assessments which is also an opportunity for nature conservation to develop management plans specific to the different habitats. Particular attention should be given to habitats that are bright and very wet since the effect of I. glandulifera was strongest in these habitats.

中文翻译：

---

入侵凤仙花对本地植被的微生境和季节依赖性影响

由于物种×生态系统的相互作用，入侵物种的影响通常很难评估。凤仙花（Impatiens glandulifera）严重入侵了中​​欧的几种生境类型，但其对本土植物群落的影响却被模棱两可。一个原因可能是，影响在生境类型之间甚至在一种生境类型内的环境异质斑块（微生境）之间都不同。在本研究中，在德国的异质河边栖息地内进行了植被调查，调查了兰头鸢尾草对环境条件的影响对本地植被的影响。由于季节性物种更新，因此在夏季和春季记录了植被，因此入侵植物的影响可能不同。我们发现我的封面。腺体依赖于环境条件而导致斑块状发生。I. glandulifera对植物的α多样性没有任何影响，但是减少了本地植被的覆盖率，尤其是优势种的覆盖率。此效果取决于微栖息地和季节。原生植被在明亮的微生境中受影响最大，尤其是那些土壤湿度高的生境。不区分微生境，植物种类的组成在夏季并没有在春季受到影响。但是，环境条件对本地植被的影响要比普通兰（I. glandulifera）大。我们得出的结论是，在河岸生境中，I。glandulifera对本地植被的威胁可被评定为低，因为本地物种的覆盖率有所降低，但并未从社区中排除。这可能是由于斑点状I. glandulifera的发生不规则和逐年变化。在微观栖息地和季节方面的上下文相关性要求进行特定的风险评估，这也是自然保护制定针对不同栖息地的管理计划的机会。应特别注意明亮且非常潮湿的栖息地，因为在这些栖息地中，I。glandulifera的影响最强。