In 2016, our team acquired approx. 1000 specimens of Groenlandia densa from Germany and Austria (Osterholz-Scharmbeck, Oberau, Bregenz, Feldkirch, Mining). In the period from autumn 2016 to spring 2018, the plant was multiplied by a team of specialists from the Adam Mickiewicz University in Poznań. The first placement of Groenlandia densa in the field – due to its rapid growth – was carried out in 2017 (at the turn of July and August and the end of October), while the main placement took place in June and July 2018.
The sites have been regularly monitored since 2017 – monitoring cards were established for 13 sites. The monitoring of the Groenlandia densa population state also includes assessing the status of its habitat.
The observed sites are located in Natura 2000 areas PLH 320022 “Dolina Radwi, Chocieli and Chotli” and PLH 320003 “Dolina Grabowaj”, in the area of Forest Districts: Manowo, Polanów and Bobolice. The results obtained so far have allowed to assess the potential of individual sites in terms of predicted development of a plant and pointed out some key threats to its sustainability in the future…
The data – at the end of 2019 – summarized in the Table below, indicate differences in comparison to the status of 2018. At some sites, the population of Groenlandia densa disappeared, which was mainly caused by a drastic change in water relations, weakening of groundwater supply (prolonged drought and reduced rainfall in 2019), lowering the water level in rivers and streams and, as a result, the spread of competitive vegetation overgrowing dry and silted riverbeds (Leśników Park near Osetno)
Another factor that significantly threatened the placed Groenlandia densa specimens was feeding of animals, facilitated in 2019 by the reduced water level in watercourses. In many cases, the game completely or partially ate well-grown shoots of Groenlandia densa and foraging lasted virtually all year, despite the availability of other food. Some cases of game feeding in watercourse beds, mainly due to persistent drought, were observed at the following sites: Chociel in Bobolice1 area, Węglanowy Watercourse, Błotnica in Wielin area and Zgniła Struga 6.
On the other hand, at several other sites, the increase of the area inhabited by Groenlandia densa was noted, as well as its spontaneous fragmentation and colonization of new places (Road to Rosnowo – Zegrze Pomorskie, Chociel in the area of Bobolice 2, Headwaters valley of the Biegała river, a tributary of the Białka (Zielenica), Kurowo 1). Therefore, in 2020 it is expected to examine the sections of watercourses below the placement sites (up to 500 m) in order to check whether the fragmenting shoots have not moved down the watercourses and settled new locations. Further monitoring of the effects of Groenlandia densa placement is also expected in 2020, with particular emphasis on natural regeneration and reconstruction of the shoots, and limiting, as far as possible, game access to the placement sites, e.g. by coating with declining trees on the banks of watercourses, in order to reduce losses in reintroduced species’ patches.
|No. site||Site’s name||2018||2019||Current patch area of Groenlandia densa 30.09.2019|
|1||Site on a watercourse near Wieleń reserve (4)||U1||U1||0,5 m2|
|2||Błotnica near Wielin||U1||U2||0 m2 / disappearance of the population|
|3||Road to Rosnowo – Zegrze Pomorskie||U1||FV||9 m2 / spontaneous spread|
|4||Chociel near Bobolice 1||U1||U2||0 m2 / disappearance of the population|
|5||Chociel near Bobolice 2||U1||FV||0,5 m2 / spontaneous spread|
|6||Site on a watercourse near Wieleń reserve (2)||U1||U1||0,5 m2/ no changes|
|7||Headwaters valley of a watercourse of the Biegała river, a tributary of the Białka (Zielenica)||FV||FV||6 m2 / spontaneous spread|
|8||Kurowo 1||U1||FV||1 m2 / spontaneous spread|
|9||Kurowo 2||U1||U1||0,2 m2 / no changes|
|10||Węglanowy Watercourse||U1||U1||0,5 m2 / no changes|
|11||Leśników Park near Osetno||U1||U2||0 m2 / disappearance of the population|
|12||Zgniła Struga 6||FV||U1||0,5 m2 / reducement of the inhabited area|
|13||Drężnianka near Lubowa||U1||U1||0,3 m2 / no changes|
The total area of Groenlandia densa patches on the monitored sites is about 19 m2.
Photos Condition of Groenlandia densa at different sites.