Michaela Vítková1, Jan Čuda1, Jan Pergl1 and Petr Pyšek1,2
1Institute of Botany, Department of Invasion Ecology, The Czech Academy of Sciences, CZ-25243 Průhonice, Czech Republic
2Department of Ecology, Faculty of Science, Charles University, Viničná 7, CZ-12844, Czech Republic
The arctic-alpine tundra in the Krkonoše Mts (the Czech Republic) is an extremely fragile ecosystem highly sensitive to human disturbances and presence of alien species. Since the 16th century the area was used for extensive summer grazing, resulting in the development of agricultural settlements and increase of road networks. At the end of the 19th century, tourism started to play a major role and farming above the timberline gradually ceased. The main negative factors caused by tourism include eutrophication around chalets and other touristic facilities, as well as, trampling, soil erosion, and changes in soil chemistry along roads paved by foreign alkaline material (dolomite, melaphyre or their mixture. During 1996–2011 it was removed and replaced by indigenous siliceous material) followed by the introduction of alien plant species.
We investigated the effect of altered environmental conditions on the spread of alien species in this unique ecosystem. We used unpublished species inventories from the 1970s (by Jana Husáková) and revisited the same trails, about 80 km long (leading through the arctic-alpine tundra and sampled up to 2 m from the trailside) in 2005 and 2013-2014, and areas around five mountain chalets in 2014-2016. The soil changes were studied in detail on seven transects leading from natural vegetation, through the trail, trailside- and ecotone communities into the pristine arctic-alpine tundra in 1998 and 2018. We measured soil pH, moisture regime, organic matter and supply of 15 soil nutrients (NO3–-N, NH4+-N, P, K, S, Ca, Mg, Mn, Al, Fe, Cu, Zn, B, Pb, and Cd) using ion-exchange PRS® probes. Our study plots are included into LTER site “Arctic-alpine tundra”.
Preliminary results show that the soil properties substantially changed due to human impact. Much drier soils with low organic matter, but much higher pH and base saturation (mainly calcium and magnesium), created a new environment suitable for alien, synanthropic and low-altitude plant species spreading into unique plant communities of the tundra around trails and mountain chalets. We recorded 16 aliens in total, two archaeophytes and 14 neophytes, of which three are invasive in the Czech Republic. Two species, Heracleum mantegazzianum and Angelica archangelica, were recorded only in 1970s at the altitude of 1285 m a.s.l. The most invasive species is Rumex alpinus, which typically spreads from eutrophicated soils around chalets further along trails and watercourses into the pristine vegetation. We observed rapid vegetation changes during the past 40 years, the number of plant species increased from 196 to 270 in total. Native weak competitors (e.g. Nardus stricta, Calluna vulgaris) that are intolerant to trampling and high nutrient supply disappeared or reduced their covers and were replaced by tall-statured aliens and apophytes, which accounted for 69% of the altered trailside vegetation. Our results suggest that utilization of foreign alkaline material for stabilization of many trails in the 1970s had a greater impact on biotic and abiotic characteristics in the arctic-alpine tundra compared to landscape features or trail history, and this encouraged the spread of alien species even in such harsh climatic conditions.