Abstract
Impatiens parviflora is one of the most widely spread invasive species in central Europe, yet the factors affecting its spread are still subject to discussion. The aim of this study was to determine which factors affect the spread of I. parviflora.
This was achieved by observing the natural spread of the species on 15 permanent transects, in six different habitats, found within the Czech Republic from 2012 to 2016. The transects were divided into 321 plots, whilst data on environmental conditions, as well as of the spread of I. parviflora and its performance, were collected in each plot.
The results showed that individual stages of the I. parviflora life-cycle were affected by individual environmental conditions to different extents. The most important factor preventing seedling emergence and establishment was a high cover of herb layer.
It did not, however, affect survival of older plants. Thus, I. parviflora can grow in sites with dense cover of herb layer in case the cover formed after I. parviflora seedlings established.
Juvenile mortality was the highest in sites with low nutrient levels and low soil moisture. Canopy openness had a negative effect on I. parviflora performance.
Impatiens parviflora performed better in neutral soils, in comparison to acidic soils. Oak-hornbeam forests were the most suitable habitat for I. parviflora, followed by acidophilous oak and mixed coniferous forests.
However, I. parviflora was able to penetrate into even species-rich habitats, such as thermophilous oak forests, as well as steppe grasslands on rocks. This makes it a potential threat to biodiversity.
Only heathlands found on former pastures proved to be unsuitable for I. parviflora, as these remained uninvaded until the end of the study.