Fate of pioneering vegetation patches in a dynamic meandering river

Fluvial biomorphodynamics in actively meandering rivers entail interactions between hydromorphodynamics and pioneering tree species that have eco-engineering effects. Here we study spatiotemporal patterns of vegetation patches smaller than 150 m² in a 4 km reach of the river Allier in France in order to unravel causes for tree persistence and mortality and identify spatial trends across the river valley. To this end we analysed aerial photographs by object-based image analysis over a period of 56 years and tracked individual patches through time. Furthermore the cover and surface age of the study reach were classified. The large-scale shifts of channels, bars and vegetation are consistent with the meandering process and chute cutoffs. However, the spatiotemporal patterns of the vegetation patches are surprising in that they are ubiquitous and have ages up to decades on the highly dynamic meander belt, but hardly expand into larger vegetation patches. Patches disappear exponentially as a function of their age, and faster so in the last decades. Causes are amalgamation into the riparian forest flanking the meander belt and mortality likely due to desiccation or erosion. Patches have a higher probability of survival when further away from the active channel and closer to high vegetation patches and valley boundary. The window of opportunity of vegetation settlement widens towards the valley boundaries and in floodplain lows of former channels and chutes. These results imply a gradual cross-valley gradient of riparian vegetation settling, survival and succession. © 2019 The Authors. Earth Surface Processes and Landforms Published by John Wiley & Sons Ltd.     

Estimated calving interval for the New Zealand southern right whale (Eubalaena australis)

Southern right whales (Eubalaena australis) were widespread in New Zealand waters before commercial whaling in the nineteenth century caused drastic declines in their abundance and distribution. Following the cessation of whaling, the population has been recovering and is now slowly recolonising its former range. Estimates of population demographics, including reproductive output, are essential for predicting the trajectory of this population. We gathered photo-identification data on female southern right whales during annual field trips to the Auckland Islands, the principal calving area in New Zealand waters. Forty-five calving intervals were observed between 2006 and 2013 (mean interval?=?3.31 years, 95% CI?=?3.06–3.57). Incorporating the effects of possible missed calving events produced a plausible range of mean calving intervals from 3.17 to 3.31 years. Our results suggest that the calving interval of New Zealand southern right whales is similar to that found in populations elsewhere.     

Glacier balance trends in the Kongsfjorden area, western Spitsbergen, Svalbard, in relation to the climate

For the last thirty years, the mean net balance of two glaciers, Austre Brøggerbreen and Midre Lovénbreen, has been -0.43 and -0.34 m of water equivalent (w.e.). respectively. The mean net balance of Kongsvegen, a tidewater glacier that has been measured since 1987, is 0.11 m w.e. The negative balances of the two first glaciers are driven by the increase in atmospheric temperature which occurred at the end of the Little Ice Age at the beginning of the century. The positive balance of Kongsvegen is due to its higher elevation and larger accumulation area. There is no significant trend in the net balances and no increase of the melting has been detected during the last thirty years.
A correlation coefficient of R = 0.83 has been obtained between the net balance of Lovénbreen and the winter precipitation, together with the summer temperature recorded at the neighbouring station of Ny-Ålesund since 1969. With 14 years of data, the correlation coefficient between the net balance and climatic parameters does not increase consistently by introducing any radiation component, but the coefficient correlation between the summer balance of Austre Brøggerbreen and summer temperature increases from 0.68 to 0.77 when introducing global and long-wave radiation for July and August. Weather conditions and the frequency of their changes influence the balance between global and long-wave radiation and changes in albedo values.     

Pollen analysis of faeces as a method of demonstrating seasonal variations in the diet of Svalbard reindeer (Rangifer tarandus platyrhynchus)

Analysis of the pollen and spore content of 40 fresh samples of faeces collected from Svalbard reindeer during 1994/5 and 1996 shows variations among and within seasons, with distinct species/pollen types dominating each season. Winter samples were characterized by high amounts of Salix and moss spores , while spring samples contained decreasing amounts of the plants grazed in winter and increasing values of species grazed in summer, such as Oxyria digyna and Pedicualaris spp. Summer samples had a large quantity of pollen and a great number of pollen types. Autumn samples indicated that grasses are the most important forage species in this period. The seasonally varying proportions of pollen types are related to such factors as plant phenology, abudance, palatability and nutritional quality, as well as the prefereence of reindeers for grazing in low, wet areas in the summer but on higher, wind-blown ridges during the winter. The results mostly confrim other studies of Svalbard reindeer diet and grazing behaviour. The advantages and limitations of the pollen analysis method for such investigations are discussed.     

Discharge regime and the effect of drying on macroinvertebrate communities in a temporary karst stream in East Westphalia (Germany)

The special hydrological situation of temporary streams has a great influence on the abiotic processes and other habitat conditions for organisms. To monitor possible impacts of stream drying on the composition of lotic communities, streamflow measurements and collections of the macrozoobenthos were conducted in a temporary and an adjacent upstream permanent section of the karst stream Sauer (East Westphalia, Germany) in 1996. The Sauer has a summer-dry temporary flow regime. The seasonal dry phase can last from spring to early autumn, so the duration of the dry phase varies from one to several months, increasing with distance downstream from the upstream permanent section. The number of invertebrate taxa and individuals decreases with increasing duration of the dry phase. The permanent section is characterized by taxa typical of montane and submontane streams, whereas the fauna of the temporary section is quite different, composed of representatives of various zonal areas. Limnephilid caddisflies are particularly characteristic of this section. Life cycle strategies and specific adaptations with respect to habitat drying are discussed for several species. It can be concluded that the temporary discharge regime of the karst stream Sauer has a clear effect on the invertebrate communities. They mainly consist of species which can be seen as characteristic faunal elements of temporary streams.     

Production, preservation and prediction of source-rock facies in deltaic settings

This article hypothesizes that production and preservation of source-rock type facies in deltaic systems, both landward and seaward of a coastline, is mutually exclusive, time-successive and related to the dynamics of relative sea level. Sedimentologic research in the Holocene Mississippi and Rhône delta complexes suggests that rheotrophic peats and associated organic-rich beds preferably accumulate in the accommodation space created behind landward stepping shorelines in a transgressive systems tract (TST). Such a setting also allows for a sufficient supply of recharging fresh nutrient-rich groundwater into the peat forming mires [Kosters, E.C., Suter, J.R., 1993. Facies relationships and systems tracts in the late Holocene Mississippi Delta Plain. Journal of Sedimentary Petrology 63 (4) 727–733.]. Independently carried-out quantitative paleoecological studies in the same delta systems (and in addition in the Orinoco and Po deltas) suggest that in a progradational setting (highstand systems tract/HST), seasonally discharged nutrient- and sediment-laden river waters on the shelf may give rise to anoxia or dysoxia. Subsequent overfertilization of the shelf leads to accumulation of organic-rich mud belts on the shelf [VanderZwaan, G.J., Jorissen, F.J., 1991. Biofacial patterns in river-induced anoxia. In: Tyson, R.V., Pearson, T.H. (Eds.), Modern and Ancient Continental Shelf Anoxia. Geological Society of London, Special Publication no. 58, pp. 65–82.]. Thus, production and preservation of source-rock type facies landward of a shoreline (as peats and related sediments) is preferred in a TST, when accommodation space and nutrient supply are landward of the shoreline. Vice versa, production and preservation of such facies seaward of a shoreline (as organic-rich shelf muds) occurs preferentially in a highstand systems tract. In that situation, accommodation space is on the shelf, where river-fed nutrients are supplied as well. This hypothesis suggests further potential for application of sequence stratigraphic concepts for improved understanding of the occurrence of source-rock type facies.     

Citizens' perceptions of justice in international climate policy: an empirical analysis

Relying on a recent survey of more than 3400 participants from China, Germany, and the US, this article empirically analyses citizens' perceptions of key guiding principles for sharing mitigation costs across countries, justification of climate policy and trust in climate policy. Our findings suggest that the ranking of the main principles for burden-sharing is identical in China, Germany, and the US: accountability followed by capability, egalitarianism, and sovereignty. Thus, on a general level, citizens across these countries seem to have a common (normative) understanding of fairness. We therefore find no evidence that citizens' (stated) fairness preferences are detrimental to future burden-sharing agreements. In all three countries a majority of citizens considers international climate policy to be justified, but citizens' perceptions differ across specific items and countries. Finally, a substantial portion of citizens in all countries exhibit a lack of trust in international climate agreements.

Policy relevance

Disagreement over the distribution of mitigation costs across countries is blocking current negotiations about a new international climate change agreement to be adopted in 2015. At the heart of this disagreement are different perceptions of distributive justice among those involved in climate policy making. Our findings show that there is no difference in the ranking of fairness principles across citizens in China, Germany, and the US, suggesting that the common ground for crafting a future agreement is larger than expected. In particular, the accountability principle should weigh heavily when deciding on the burden-sharing. In addition, our findings suggest that in order to gain support among citizens, international climate policy may need to take measures to improve trust.     

The role of forcing and internal dynamics in explaining the “Medieval Climate Anomaly”

Proxy reconstructions suggest that peak global temperature during the past warm interval known as the Medieval Climate Anomaly (MCA, roughly 950–1250 AD) has been exceeded only during the most recent decades. To better understand the origin of this warm period, we use model simulations constrained by data assimilation establishing the spatial pattern of temperature changes that is most consistent with forcing estimates, model physics and the empirical information contained in paleoclimate proxy records. These numerical experiments demonstrate that the reconstructed spatial temperature pattern of the MCA can be explained by a simple thermodynamical response of the climate system to relatively weak changes in radiative forcing combined with a modification of the atmospheric circulation, displaying some similarities with the positive phase of the so-called Arctic Oscillation, and with northward shifts in the position of the Gulf Stream and Kuroshio currents. The mechanisms underlying the MCA are thus quite different from anthropogenic mechanisms responsible for modern global warming.     

Multiple drivers of Holocene lake level changes at a lowland lake in northeastern Germany

Many German lakes experienced significant water level declines in recent decades that are not fully understood due to the short observation period. At a typical northeastern German groundwater‐fed lake with a complex basin morphology, an acoustic sub‐bottom profile was analysed together with a transect of five sediment cores, which were correlated using multiple proxies (sediment facies, μ‐XRF, macrofossils, subfossil Cladocera). Shifts in the boundary between sand and mud deposition were controlled by lake level changes, and hence, allowed the quantification of an absolute lake level amplitude of ~8 m for the Holocene. This clearly exceeded observed modern fluctuations of 1.3 m (AD 1973–2010). Past lake level changes were traced continuously using the calcium‐record. During high lake levels, massive organic muds were deposited in the deepest lake basin, whereas lower lake levels isolated the sub‐basins and allowed carbonate deposition. During the beginning of the Holocene (>9700 cal. a BP), lake levels were high, probably due to final melting of permafrost and dead‐ice remains. The establishment of water‐use intensive Pinus forests caused generally low (3–4 m below modern) but fluctuating lake levels (9700–6400 cal. a BP). Afterwards, the lake showed an increasing trend and reached a short‐term highstand at c. 5000 cal. a BP (4 m above modern). At the transition towards a cooler and wetter late Holocene, forests dominated by Quercus and Fagus and initial human impact probably contributed more positively to groundwater recharge. Lake levels remained high between 3800 and 800 cal. a BP, but the lake system was not sensitive enough to record short‐term fluctuations during this period. Lake level changes were recorded again when humans profoundly affected the drainage system, land cover and lake trophy. Hence, local Holocene water level changes reflect feedbacks between catchment and vegetation characteristics and human impact superimposed by climate change at multiple temporal scales.