Soil organic carbon stocks did not change after 130 years of afforestation on a former Swiss Alpine pasture

Soil organic matter (SOM) plays an important role in the global carbon cycle, especially in alpine ecosystems. However, ongoing forest expansion in high-elevation systems potentially alters SOM storage through changes in organic matter (OM) inputs and microclimate. In this study, we investigated the effects of an Picea abies L. afforestation chrono-sequence (0 to 130 years) of a former subalpine pasture in Switzerland on soil organic carbon (SOC) stocks and SOM dynamics. We found that SOC stocks remained constant throughout the chrono-sequence, with comparable SOC stocks in the mineral soils after afforestation and previous pasture (SOC forest40 = 11.6 ± 1.1 kg m−2, SOC forest130 = 11.0 ± 0.3 kg m−2 and SOC pasture = 11.5 ± 0.5 kg m−2). However, including the additional carbon of the organic horizons in the forest, reaching up to 1.7 kg m−2 in the 55-year old forest, resulted in an increase in the overall SOC stocks following afforestation. We found that the soil C:N ratio in the mineral soil increased in the topsoil (0–5 cm) with increasing forest stand age, from 11.9 ± 1.3 in the pasture to 14.3 ± 1.8 in the 130-year old forest. In turn, we observed a decrease in the soil C:N ratio with increasing depth in all forest stand ages. This suggests that litter-derived organic matter (C:N from 35.1 ± 1.9 to 42.4 ± 10.8) is likely to be incorporated and translocated from the organic horizon to the mineral topsoil (0–10 cm) of the profiles. Due to the high root C:N ratio (pasture 63.5 ± 2.8 and forests between 54.7 ± 3.9 and 61.2 ± 2.9), particulate root-derived organic matter seems to have a rather small effect on forest soil C:N ratios, as well as on SOC accumulation in the mineral soil. These results suggest that, although afforestation does not change the SOC stock in the mineral soil, there is an apparent alteration in the SOM dynamics through changes in the litter composition caused by the vegetation shift. We conclude that, at our study site, spruce afforestation on a former subalpine pasture does not change the total SOC stock and that, consequently, there is no additional SOC sequestration on a decadal to centennial scale

Schweizer LandwirtInnen in ungleichen agrarischen Wertschöpfungsketten : eine Analyse über die Möglichkeiten zur Reduktion von Pflanzenschutzmitteln

Pflanzenschutzmittel werden hauptsächlich in der Landwirtschaft, aber auch im Siedlungsraum und in weiteren Bereichen eingesetzt, um Ertrags- oder Qualitätseinbussen duch Schadorganismen zu verhindern. Der heutige Einsatz dieser Mittel belastet sowohl Mensch als auch Umwelt und insbesondere die Biodiversität beträchtlich. Im Jahr 2016 gelang es in der Schweiz, einen nationalen Aktionsplan zu Pflanzenschutzmitteln einzuführen und klare Ziele zur Verringerung der pestizidbedingten Risiken aufzuzeigen. Obschon seit dann zahlreiche Gesetze und Verordnungen die Zulassung von sowie den Umgang mit Pflanzenschutzmitteln regeln, werden nach wie vor Überschreitungen von Grenzwerten in der Umwelt festgestellt. In dieser Masterarbeit liegt der Fokus auf den Schweizer LandwirtInnen, da schlussendlich sie es sind, die die ausschlaggebenden Entscheidungen im Pflanzenschutz in ihrem Betrieb treffen. Die Arbeit hat einen explorativen Charakter und gibt dank Interviews Einblick in die verschiedenen Sichtweisen zu Pflanzenschutzmitteln. Das Ziel ist es, verschiedene Aspekte der agrarwirtschaftlichen Wertschöpfungskette und mögliche Wege zur Reduktion von Pflanzenschutzmitteln aufzuzeigen. Der Beitrag soll zudem das Bewusstsein für die Herausforderungen und Spannungsfelder in diesem Themenbeeich schärfen. Mithilfe der Convention Theory werden die Interviews eingeordnet. Als Orientierung dienen dabe die Welten von Boltanski und Thévenot aus ihrem Werk >. Möglichkeiten für eine Reduktion der Pflanzenschutzmitteln in der Schweizer Landwirtschaft werden hauptsächlich in einem sich ändernden Konsumverhalten sowie in der Digitalisierung der Landwirtschaft gesehen. Die Rolle der KonsumentInnen wird als nachhaltigkeitsrelevant erachtet, weil sie mit ihrem Nachfrageverhalten Einfluss nehmen können, wie Lebensmittel produziert und vermarktet werden. Die Digitalisierung ermöglicht wiederum, auf den Betrieben die Produktion zu optimieren und sowohl Kosten als auch negative Auswirkungen auf Mensch und Umwelt zu reduzieren

Formation and decay of peat bogs in the vegetable belt of Switzerland

The rapidly collapsing glacial systems of the Alps produced a large number of melt-water lakes and mires after the Last Glacial Maximum (LGM) in the Late Glacial period. The Rhone-Aare-glacier system gave rise to large moorlands and lakes in the region of the Three Lakes Region of Western Switzerland. When moorlands are formed, they are efficient sinks of atmospheric carbon, but when transformed to agricultural land they are significant C sources. In addition, mires can be used as archives for reconstructing landscape evolution. We explored in more detail the dynamics of the landscape of the Three Lakes Region with a particular focus on the formation and degradation of mires. The Bernese part of the Three Lakes Region developed to become—after the optimisation of the water-levels of the Swiss Jura—the vegetable belt of Switzerland. The situation for agriculture, however, has now become critical due to an overexploitation of the peatland. Until c. 13 ka BP the entire region was hydrologically connected. An additional lake existed at the western end of the plain receiving sediments from the Aare river. Around 13 ka BP, this lake was isolated from the Aare river and completely silted up until c. 10 ka BP when a mire started to form. In the valley floor (‘Grosses Moos’), the meandering Aare and the varying level of the nearby lake of Neuchâtel caused a spatio-temporally patchy formation of mires (start of formation: 10–3 ka BP). Strong morphodynamics having high erosion and sedimentation rates and a high variability of the chemical composition of the deposited material prevailed during the early Holocene until c. 7.5 ka BP. The situation remained relatively quiet between 5 and 2 ka BP. However, during the last 2000 years the hydrodynamic and geomorphic activities have increased again. The optimisation of the Swiss Jura water-levels during the nineteenth and twentieth centuries enabled the transformation of moorland into arable land. As a consequence, the moorland strongly degraded. Mean annual C-losses in agricultural land are c. 4.9 t ha$^{−1}$ and c. 2.4 t ha$^{−1}$ in forests. Because forests limit, but not stop, the degradation of mires, agroforestry might be tested and propagated in future as alternative land-use systems for such sensitive areas