Does global warming favour the occurrence of extreme floods in European Alps? First evidences from a NW Alps proglacial lake sediment record

Flood hazard is expected to increase in the context of global warming. However, long time-series of climate and gauge data at high-elevation are too sparse to assess reliably the rate of recurrence of such events in mountain areas. Here paleolimnological techniques were used to assess the evolution of frequency and magnitude of flash flood events in the North-western European Alps since the Little Ice Age (LIA). The aim was to document a possible effect of the post-19(th) century global warming on torrential floods frequency and magnitude. Altogether 56 flood deposits were detected from grain size and geochemical measurements performed on gravity cores taken in the proglacial Lake Blanc (2170 m a.s.l., Belledonne Massif, NW French Alps). The age model relies on radiometric dating (Cs-137 and Am-241), historic lead contamination and the correlation of major flood- and earthquake-triggered deposits, with recognized occurrences in historical written archives. The resulting flood calendar spans the last ca 270 years (AD 1740-AD 2007). The magnitude of flood events was inferred from the accumulated sediment mass per flood event and compared with reconstructed or homogenized datasets of precipitation, temperature and glacier variations. Whereas the decennial flood frequency seems to be independent of seasonal precipitation, a relationship with summer temperature fluctuations can be observed at decadal timescales. Most of the extreme flood events took place since the beginning of the 20(th) century with the strongest occurring in 2005. Our record thus suggests climate warming is favouring the occurrence of high magnitude torrential flood events in high-altitude catchments

Non-Native, Non-Naturalised Plants Suffer Less Herbivory Than Native Plants Across European Botanical Gardens

Aim The enemy release hypothesis states that the invasion success of non-native species is partly due to their escape from natural enemies, e.g., herbivores. Large-scale studies of herbivory using multiple species across multiple sites are needed to test the generality of herbivory release in non-native plants. Location Europe. Methods We carried out leaf-herbivory surveys from 2007 to 2021 in 15 botanical gardens ranging in latitude from 47°N (Switzerland) to 63°N (Norway) to investigate how herbivory levels differed between (i) native and non-native species, and (ii) native and non-naturalised or naturalised species. Results Overall, we found that herbivory levels were lower on non-native than native species. In addition, we found that non-naturalised plants suffered less herbivory than natives and that naturalised plants showed similar levels of herbivory to native plants. Main Conclusions We find broad support for lower herbivory of non-native plant species compared to natives. However, the stronger reduction in herbivory for non-naturalised plants suggests that herbivore release may be transient and less pronounced for naturalised non-native species that have become abundant and integrated into resident communities. This has implications for the management of naturalised non-native plants, which are performing well in their non-native ranges despite suffering comparable herbivory levels to native species

Non‐Native, Non‐Naturalised Plants Suffer Less Herbivory Than Native Plants Across European Botanical Gardens

Aim: The enemy release hypothesis states that the invasion success of non‐native species is partly due to their escape from natural enemies, e.g., herbivores. Large‐scale studies of herbivory using multiple species across multiple sites are needed to test the generality of herbivory release in non‐native plants. Location: Europe. Methods: We carried out leaf‐herbivory surveys from 2007 to 2021 in 15 botanical gardens ranging in latitude from 47°N (Switzerland) to 63°N (Norway) to investigate how herbivory levels differed between (i) native and non‐native species, and (ii) native and non‐naturalised or naturalised species. Results: Overall, we found that herbivory levels were lower on non‐native than native species. In addition, we found that non‐naturalised plants suffered less herbivory than natives and that naturalised plants showed similar levels of herbivory to native plants. Main Conclusions: We find broad support for lower herbivory of non‐native plant species compared to natives. However, the stronger reduction in herbivory for non‐naturalised plants suggests that herbivore release may be transient and less pronounced for naturalised non‐native species that have become abundant and integrated into resident communities. This has implications for the management of naturalised non‐native plants, which are performing well in their non‐native ranges despite suffering comparable herbivory levels to native species

Local Extinction in the Bird Assemblage in the Greater Beijing Area from 1877 to 2006

Recent growth in industrialization and the modernization of agricultural activities, combined with human population growth, has greatly modified China’s natural environment, particularly in the vicinity of large cities. We compared avifauna checklists made between 1877 and 1938 with current checklists to determine the extent of local bird extinctions during the last century in the greater Beijing area. Our study shows that of the 411 bird species recorded from 1877–1938, 45 (10.9%) were no longer recorded from 2004–2006. Birds recorded as ‘rare’ in 1938 were more likely to have disappeared in subsequent years. Migrant status also influenced the probability of local bird extinction with winter migrants being the most affected class. Moreover, larger birds were more likely to have disappeared than smaller ones, potentially explained by differential ecological requirements and anthropogenic exploitation. Although our habitat descriptions and diet classification were not predictors of local bird extinction, the ecological processes driving local bird extinction are discussed in the light of historical changes that have impacted this region since the end of the 1930 s. Our results are of importance to the broader conservation of bird wildlife

Effects of land-use change on deposition and composition of organic matter in Frickenhauser See, northern Bavaria, Germany

Characterization of bulk organic matter (OM) from lacustrine sediments of Frickenhauser See (northern Bavaria, Germany) reveals considerable variation during the last two millennia. Atomic C/N ratios and total organic carbon (TOC) content are positively correlated with arboreal pollen percentages which are used as an indicator of land-use intensity. Despite possible alterations of OM during early diagenesis, differences between three major lithological units are large enough to be interpreted as human impact on the sedimentation of OM in the lake. Sediments deposited prior to deforestation in the catchment area (unit C) are characterized by mean C/N ratios of 14.5, indicating a mixed composition of organic matter derived from lacustrine and terrestrial sources (forest litter). During a period of intensive soil erosion (ca. 1000 AD until 1870 AD; unit B), low C/N ratios of around 7.7 suggest that the relative proportion of forest litter decreased in favour of the lacustrine component and soil OM. Terrestrial plant detritus is only transported into the lake through numerous turbidite events. Deforestation and agriculture also coincide with a decreasing TOC content from an average value of 10.7% to 1.5%. This decrease is explained through a dilution effect due to the high input of minerogenic matter. Stable carbon isotopes indicate eutrophication of the lake due to the mobilization of nutrients through soil erosion. Starting around 1870 AD, organic-rich sapropelic sediments are deposited (unit A). A decline of turbidite events and increased wind shelter from trees due to reduced land-use intensity led to meromictic conditions. Consequently, negative excursions in the delta13C isotope record at the onset of unit A probably reflect methanogenesis under permanently anoxic conditions