Klebelsberg revisited: did primary succession of plants in glacier forelands a century ago differ from today?

Since the Little Ice Age maximum in mid-nineteenth century, glaciers of the Alps lost more than half of their respective area. The chance to observe primary succession in deglaciated areas has motivated researchers ever since with quite a number of studies on vegetation dynamics in glacier forelands dating back to the nineteenth and early twentieth century. Harsh site conditions make glacier forelands challenging environments for the colonization. Due to high mortality rates during establishment, plant colonization and vegetation dynamics in glacier forelands are commonly considered slow and delayed. Recent research, however, shows that primary succession of plants in glacier forelands is accelerated, most likely due to climate warming. This is demonstrated by a speedup of the colonization process itself as well as by changed colonization strategies of the plant species involved. Employing a virtually complete species list for 1911 provided by Raimund v. Klebelsberg and our data collected along a chronosequence roughly a century later, we compare the floristic composition and structural attributes of the plant species governing primary succession within the glacier foreland of Lenksteinferner (ferner is a Tyrolean toponym for glacier) (South Tyrol, Italy). We address questions of changes in the dynamics of colonization, the plant species involved and their respective biological traits. Our study confirms that present-day vegetation dynamics in the glacier foreland are accelerated, colonization occurs faster and more species are involved in early colonization than a century ago. However, the dominant early colonizers are essentially the same and there are no fundamental differences concerning the spectra of biological traits between the two sampling dates. Altered colonization strategies due to climate change could not be detected within the glacier foreland of the Lenksteinferner, probably due to a compensation of climate warming during the twentieth century by the shift of the glacier terminus to a higher elevation. As the difference in temperature between the two sampling areas matches the magnitude of warming between the two sampling dates, similar temperature conditions in front of the glacier terminus today and at Klebelsberg’s times can be assumed.