Seed bank dynamics of Impatiens
Persistent soil seed banks have been highlighted as a mechanism which can contribute to invasive alien plants being able to persist in invaded locations. Soil seed banks can maintain genetic diversity within the population which can improve the ability of a species to respond to novel site conditions. When management measures (including eradication) are carried out, the length of time a seed bank can persist is an important factor to consider. The seed bank dynamics of Impatiens species (Balsaminaceae) is poorly understood. Much of the current information is based on indirect observations. To address this, a five-year seed burial experiment was conducted using seed of two non-native Impatiens, I. glandulifera (EPPO List of Invasive Alien Plants) and I. parviflora, and a native, I. noli-tangere. Seeds were collected from four sites which differed in environmental conditions (temperature, precipitation and soil nutrients) in 2008. Following storage at room temperature, seeds of each species were divided into small batches (50 seeds), placed in polyamide bags and buried at a depth of 5 cm in November of the same year at each of the four sites. The seeds were exhumed in the following years in late March and late May (2009-2012) and in late March in 2013. Following removal from the soil, seeds were separated into seeds which had germinated, seeds which had decayed, and seeds that remained viable. Both invasive species had a high seed germination rate in the first year while < 50 % of seeds of the native Impatiens germinated in the first year. All seeds of I. parviflora germinated in the first year indicating the species has a transient seed bank. Survival of I. glandulifera seeds differed between sites, where seeds decomposed at two sites and some germinated in one site after two years and another site after four years. The germination of I. glandulifera was slightly limited by low nitrogen but this effect was not found for I. parviflora seeds.
Sources
Skálová H, Moravcová L, Čuda J, Pyšek P (2019) Seed-bank dynamics of native and invasive Impatiens species during a five-year field experiment under various environmental conditions. NeoBiota 50, 75-95.