Invasive species are considered to be one of the major threats to biodiversity, but in fact the impact of an invasion is often difficult to assess because of its dependency on several contexts. Impatiens glandulifera is an excellent model species to study context dependencies. For although I. glandulifera heavily invaded several habitats in Central Europe its impact on native plant communities is ambiguous. We hypothesize that growth of I. glandulifera and its impact on plant communities depends on micro-site conditions leading to that ambiguous results.
Material and Methods
We evaluated micro-niche characteristics of I. glandulifera stands considering abiotic factors as well as plant species composition at five riverside sites in the region of Bayreuth that were invaded by I. glandulifera. Investigated habitats ranged from mesotrophic grasslands and tall herbaceous vegetation to elder woods. In 114 systematically arranged plots we gathered the plant species’ identity and cover as well as soil moisture and light conditions.
I. glandulifera occurred on the hole range from rather dry to flooded patches and from closed to open sites. Its cover only slightly depended on soil moisture and light conditions and was highest at intermediate soil moisture and light. Pooling all plots there was no obvious correlation between the resident herbaceous plant community composition and I. glandulifera cover. In addition the species number did not depend on I. glandulifera cover.
Broad tolerance of I. glandulifera to soil moisture and light conditions enables the invasion of many habitats. However the impact of I. glandulifera on plant community composition seems to be rather low, or it is only obvious under certain conditions. Therefore future perspective of our study is to identify micro-site conditions that might affect the interaction of I. glandulifera with plant communities.