Changes in species composition in alpine snowbeds with climate change inferred from small-scale spatial patterns

Alpine snowbeds are characterised by a very short growing season. However, the length of the snow-free period is increasingly prolonged due to climate change, so that snowbeds become susceptible to invasions from neighbouring alpine meadow communities. We hypothesised that spatial distribution of species generated by plant interactions may indicate whether snowbed species will coexist with or will be out-competed by invading alpine species – spatial aggregation or segregation will point to coexistence or competitive exclusion, respectively. We tested this hypothesis in snowbeds of the Swiss Alps using the variance ratio statistics. We focused on the relationships between dominant snowbed species, subordinate snowbed species, and potentially invading alpine grassland species. Subordinate snowbed species were generally spatially aggregated with each other, but were segregated from alpine grassland species. Competition between alpine grassland and subordinate snowbed species may have caused this segregation. Segregation between these species groups increased with earlier snowmelt, suggesting an increasing importance of competition with climate change. Further, a dominant snowbed species (Alchemilla pentaphyllea) was spatially aggregated with subordinate snowbed species, while two other dominants (Gnaphalium supinum and Salix herbacea) showed aggregated patterns with alpine grassland species. These dominant species are known to show distinct microhabitat preferences suggesting the existence of hidden microhabitats with different susceptibility to invaders. These results allow us to suggest that alpine snowbed areas are likely to be reduced as a consequence of climate change and that invading species from nearby alpine grasslands could outcompete subordinate snowbed species. On the other hand, microhabitats dominated by Gnaphalium or Salix seem to be particularly prone to invasions by non-snowbed species.

Von implizitem Know-how zu expliziten Thesen Inter- und transdisziplinärer Wissensaustausch

Um komplexe gesellschaftliche Probleme lösen zu können, sollte relevantes Wissen aus allen Bereichen genutzt werden. Welche Methoden eignen sich, um den Austausch von Wissen zwischen verschiedenen Akteursgruppen aus unterschiedlichen Wissenssystemen zu ermöglichen? Die AG Wissensaustausch der SAGUF (Schweizerische Akademische Gesellschaft für Umweltforschung und Ökologie) begibt sich auf die Suche nach Erfolgsfaktoren für den Wissensaustausch.

Erosion Damage Mapping: Assessing Current Soil Erosion Damage in Switzerland

Within the scope of a comprehensive assessment of the degree of soil erosion in Switzerland, common methods have been used in the past including test plot measurements, artificial rainfall simulation, and erosion modelling. In addition, mapping guidelines for all visible erosion features have been developed since the 1970s and are being successfully applied in many research and soil conservation projects. Erosion damage has been continuously mapped over a period of 9 years in a test region in the central Bernese plateau. In 2005, two additional study areas were added. The present paper assesses the data gathered and provides a comparison of the three study areas within a period of one year (from October 2005 to October 2006), focusing on the on-site impacts of soil erosion. During this period, about 11 erosive rainfall events occurred. Average soil loss rates mapped at each study site amounted to 0.7 t ha-1, 1.2 t ha-1 and 2.3 t ha-1, respectively. About one fourth of the total arable land showed visible erosion damage. Maximum soil losses of about 70 t ha-1 occurred on individual farm plots. Average soil erosion patterns are widely used to underline the severity of an erosion problem (e.g. impacts on water bodies). But since severe rainfall events, wheel tracks, headlands, and other “singularities” often cause high erosion rates, analysis of extreme erosion patterns such as maximum values led to a more differentiated understanding and appropriate conclusions for planning and design of soil protection measures. The study contains an assessment of soil erosion in Switzerland, emphasizing questions about extent, frequency and severity. At the same time, the effects of different types of land management are investigated in the field, aiming at the development of meaningful impact indicators of (un-)sustainable agriculture/soil erosion risk as well as the validation of erosion models. The results illustrate that conservation agriculture including no-till, strip tillage and in-mulch seeding plays an essential role in reducing soil loss as compared to conventional tillage.

Verbreitung der Direktsaat in der Schweiz

Direktsaat ist eine wirksame Erosionsschutzmassnahme, die diverse ökologische und ökonomische Vorteile aufweist. Sie gewann in der Schweiz in den letzten Jahren zunehmend an Bedeutung: Seit Mitte der 1980er hat die direkt gesäte Fläche von wenigen Hektaren auf rund 12'000 ha im Jahre 2006 zugenommen. Gemessen am gesamten Ackerland ist diese Fläche aber nach wie vor gering (3 %). Regional kann die Direktsaat jedoch beachtliche Anteile aufweisen. Die in diesem Artikel vorgestellten Karten geben einen nationalen Überblick über die räumliche Verbreitung der direkt gesäten Fläche im Jahr 2006. Als Datengrundlage diente eine im Winter 2006 / 07 durchgeführte Befragung von Landwirten und Lohnunternehmern. Die Karten zeigen sehr heterogene Muster, machen aber auch verschiedene Schwerpunktregionen sichtbar. Die Interpretation dieser Muster veranschaulicht, dass die Verbreitung der Direktsaat an eine Vielzahl von Faktoren gebunden ist und nicht nur anhand naturräumlicher Gegebenheiten erklärt werden kann. Kantonale Förderprogramme spielen dabei eine ebenso wichtige Rolle wie das persönliche Engagement der beteiligten Experten und Lohnunternehmer, bestehende landwirtschaftliche Netzwerke sowie die Lebenswelten der Landwirte.