Conradin A. Burga

One century of vegetation change on Isla Persa, a nunatak in the Bernina massif in the Swiss Alps

Abstract Question: How did the vascular plant species composition of a nunatak in the alpine vegetation belt change over a time span of 100 years? Location: A 5.6-ha nunatak, Isla Persa in the Swiss Alps, that remained ice-free during the last maximum glacier advance in the 1850s and is today partly covered with climactic alpine grassland and dwarf heath shrubs. Methods: Floristic inventories in 1906, 1927, 1972, 1995, 2003 and 2004 and a comparative analysis of the species composition over the period 1906–2004. Results: 31 species that were not recorded in the first inventory were found in the following surveys. However, among them only six were common by 2004. Generally, the new species prefer warmer conditions than those previously present and most newcomers are associated with montane or sub-alpine grasslands and woodlands. In particular, the observed increase of Vaccinium myrtillus and the arrival of shrub and tree species further substantiate a trend towards vegetation composition of the lower altitudinal belt. Ferns represented 26% of the newcomers, probably due to the high dispersal ability of their lightweight spores. The observed species enrichment was globally small compared to previously inventoried summits. Conclusion: Floristic change strongly suggests warmer climatic conditions as the main factor contributing to species compositional change. The relative stability of species richness may be explained by several factors: the isolation of the nunatak and the difficulties for plants to reach the site, the colder local climate, a limited available species pool and interactions of established alpine plants with newly immigrating taxa. Supplementary data collected at a similar altitude would be necessary to better understand the influence of climate change on alpine grasslands. Nomenclature: Aeschimann et al. (2004).

Vegetation development on the glacier forefield Morteratsch (Switzerland)

Abstract. Within the glacier forefield Morteratsch (1900–2100 m a.s.l.)near Pontresina, OberEngadin, Switzerland), the dominant plant species and communities of areas, deglaciated between 1857 and 1997, have been investigated. This study takes three species groups into consideration: (1) pioneer species; (2) subalpine forest and dwarf-shrub/heath species; and (3) grassland species. On the basis of species cover-abundance values and age data on the deglaciated areas, time-related dynamics of selected plant species and the establishment of the Epilobietum fleischeri, Oxyrietum digynae and Larici-Pinetum cembrae were estimated. First, invaders of the Epilobietum fleischeri appeared after ca.7yr (obtaining higher cover-abundance values after ca. 27 yr). This community persists on the whole glacier forefield. The first plants of the Oxyrietum digynae appear after ca. 12 yr (though earlier on some sites); this community disappears after ca. 27 yr. The establishment of the Larici-Pinetum cembrae took place after ca. 77 yr, while the climax stage was reached after ca. 97 yr since deglaciation.

Vegetation on Alpine rock glacier surfaces: a contribution to abundance and dynamics on extreme plant habitats

In the area of Piz Corvatsch (Upper Engadin, Grisons, Switzerland), the actual vegetation on active and inactive rock glacier surfaces has been mapped. The floristic composition (vascular plants and lichens) of the different rock glacier surfaces has be en mapped and compared with photogrammetrical measurements of surface movements of the active rock glaciers. In general, the active rock glacier surfaces show a very low cover of vascular plants. Most of them are located at the edge and at the front of the rock glacier where fine-grained soil material occurs in small pockets. Lichenometry has been used as an additional method on Murtel rock glacier and on the protalus rampart. Measurements of Rhizocarpon geographicumthalli revealed increasing sizes from the root zone of the rock glacier to its front. On the Murtel rock glacier, Rhizocarpon geographicumthalli with a diameter > 4cm occur on surfaces with ages between 5000 and 6000 years B.P. The statistical analysis (MULVA-5) of the dense vegetation cover of the inactive and relict rock glaciers revealed four plant sociological groups, which are composed of species reflecting well consolidated sites : alpine grassland, subalpine dwarf shrubs and small patches with single small trees of Swiss stone pine ( Pinus cembra) and larch (Larix decidua).

Vegetation history of Abies alba Mill. (silver fir) in Switzerland – pollen analytical and genetic surveys related to aspects of vegetation history of Picea abies (L.) H. Karsten (Norway spruce)

Abstract. This contribution deals with some new aspects of the relationship between the vegetation history of Abies alba Mill. (silver fir) and genetic studies of this tree species in Switzerland. The results of the present study confirm the pollen analytical hypothesis that A. alba re-immigrated into Switzerland mainly from glacial refugia located in northern and central Italy. In particular, some distinct immigration routes of silver fir into the Ticino Alps, Valais, the Bernese Oberland (northwestern Alps), and Graubünden (eastern Alps) could be confirmed by genetic studies. Furthermore, the occurrence of other area-specific alleles indicates an additional influence from eastern European refugia on the Swiss gene pool. Moreover, genetic studies on Picea abies (L.) H. Karsten (Norway spruce) confirmed the general immigration routes from the eastern to the western Alps and from Savoie to the Jura Mountains. The combination of tree pollen and macrofossil analyses of Quaternary sediments with genetic studies of the same tree species represents a considerable research potential and is a new approach of floristic and genetic research.

Monitoring of Eastern and Southern Swiss Alpine Timberline Ecotones

Firstly, general features of the upper limit of the Swiss Alpine forest and tree limits have been discussed. There are so far numerous investigations and definitions of these different boundaries. The timberline ecotone is here defined as the altitudinal interval between the forest limit and the tree species or lethal limit. The most important question is which are the crucial parameters affecting the upper forest and tree limit. Furthermore, there is the difficulty of distinction of natural and anthropozoogenic factors influencing the present timberline ecotone. Finally, physico-geographical and geological parameters which form the definitive “fades” of the timberline ecotone have to be taken into account.

Vegetation Monitoring on a Small-Scale Restoration Site in the Alpine Belt: Pilatus Kulm, Switzerland

The vegetation restoration of a site (ca. 300 square metres) on Pilatus Kulm (2060 metres a. s. l., Obwalden, Switzerland) located in the alpine belt was observed between 1990 and 1998. Severe damage to the vegetation cover had occurred during construction of a sewer pipeline from Pilatus Kulm down to the valley and establishment of military installations. In a first stage, plant recolonization was induced by planting different seedlings of herbs. In a second stage, seeds of alpine grass species were used to achieve a denser pioneer vegetation cover. A vegetation study made at different plots of the investigation area revealed that over 80% of the transplants survived the four-year period (1990–1994). On the whole, the plant cover increased to up to 40% on the slope and up to 80% on tilted borders within the four-year period. The species diversity increased faster in the random area due to natural immigration. With the introduction of seedlings in 1994, along with favourable circumstances, the establishment of the vegetation has been accelerated, resulting in an area which is now covered by dense herbaceous vegetation. In 1998, the control plots showed a plant cover of 60% on the slope and up to 95% on tilted borders. During the eight-year monitoring period, considerable fluctuations of species could be observed.

Schlussbetrachtungen und Zusammenfassungen

Man kann sich fragen, ob die in dieser Arbeit gesammelten Hinweise auf die tardi- und postglazialen Gletscheroszillationen in den sudratischen Alpen im Rahmen bisheriger Studien stehen (vgl. Vorbemerkungen) oder ob daruber hinaus auch neue Erkenntnisse uber das Verhalten des spateiszeitlichen Eisstromnetzes gewonnen werden konnten. Bis zu einem gewissen Grade kann letztere Frage bejaht werden, denn dank dem grosseren Untersuchungsgebiet zeichnet sich ein fur die Sudalpen allgemein gultiges Schema im Verhalten der einzelnen Eisstrome ab: Im alteren Tardiglazial, d.h. im Poschiavo-, Pozzulasc- bzw. Zernez-, Livigno- bzw. Bormio-, Premadio/ Isolaccia-Stadium bestanden noch weitgehend intakte Eisstromnetze der Haupt- und Seitentaler, wobei noch fast alle hochwurmeiszeitlichen Eistransfluenzen aktiv waren (Bernina- pass, Forcola di Livigno, La Stretta, Passo d’Eira, Foscagno- pass, Trelinapass, Valle di Fraele; Verva-, Dosde- und Viola- pass). Im jungeren Tardiglazial, d.h. seit der Zeit des Daun- Stadiums, welches sicher alter als das Allerod- und wohl auch alter als das Bolling-Interstadial ist, also um 13 000 bis 14 000 BP, beginnen die Eisstromnetze im La Rosa- bzw. Tre- palle- bzw. A. Campo-Stadium sich in einzelne grossere Karoder Seitengletscher aufzulosen. Alle diese weitgehend selbstandig gewordenen Gletscher stiessen aber nochmals kraftig oft bis zur Seitentalmundung vor. Erst gegen Ende des Spat- glazials, also etwa zur Zeit der Jungeren Dryas im Egesen- Stadium, waren alle Eisstromnetze vollstandig zu kleinen bis mittleren Kargletschern aufgelost, die im Cavaglia- bzw. Fos- cagno- bzw. Dosde I-Stadium letztmals kraftig vorstiessen. In den meisten Fallen erreichten damals die Gletscher letztmals uber neuzeitliche Grossenordnungen hinausreichende Ausdehnungen.

Übersicht zu den bisherigen geomorphologischen und pollenanalytischen Arbeiten

In den folgenden beiden Ubersichten sind in chronologischer Weise (nach dem Jahrgang der Veroffentlichung) die das Untersuchungsgebiet (vgl. Kap. 1.1.) betreffenden geomorphologischen und pollenanalytischen Publikationen aufgefuhrt. Bei der Liste zur Geomorphologie handelt es sich nicht um bibliographische Vollstandigkeit, jedoch durften alle Veroffentlichungen erfasst sein, die fur die vorliegende Arbeit von Belang sind.

Das Puschlaver Haupttal (Poschiavino-Palü-Campo-System)

Im Kap. 4.1.1 sind die geographischen, geomorphologischen und geologischen Verhaltnisse des Puschlav kurz dargelegt, worauf an dieser Stelle nochmals hingewiesen sei.

Übrige Puschlaver Seitentäler

Die Puschlaver Seitentaler, welche teilweise eine ausgepragte Stufenmundung aufweisen und oft durch eine spater entstandene Schlucht steil zum Haupttal verlaufen, weisen an ihrer Mundung Gletscherstande auf, die eindeutig Vorstosse uber die alte Talgletscherlinie darstellen. Dieses Kriterium erwahnte schon R. STaub (1938) in seiner Arbeit zur Frage einer Schlussvereisung im Berninagebiet als klaren Beweis fur den Vorstosscharakter dieser Gletscherstande (vgl. Kap. 6.1).