Abbreviations GLMM = generalized linear mixed modelling or generalized linear mixed models; DEM = Dynamic equilibrium model; IDH = Intermediate disturbance hypothesis. AbstractQuestions: What are the interactive effects of succession time, disturbance and productivity on the fine-scale species richness of beach vegetation? How do these effects differ between functional groups that are known to represent different adaptive strategies?Location: Boreal beach and dune systems (ca. 60°-65°N) of the Baltic Sea coast in Finland, characterized by steep environmental gradients, post-glacial land uplift and resulting primary succession.Methods: The analysis was based on an extensive and systematic survey of vascular plant, bryophyte and lichen species and environmental factors. Total species richness and the species richness of seven functional groups were modelled as functions of succession time, disturbance, productivity and their statistical interactions. The effects of the local environmental variability were taken into account by applying generalized linear mixed models (GLMM).Results: All three environmental factors and their statistical interactions, including the three-way interaction, were highly significant in explaining total species richness. The effect of disturbance on total species richness changed from negative to positive along succession time and productivity gradients. The response of beach specialist richness to succession time and disturbance was unimodal, while the responses of the generalist functional groups were monotonic. Beach specialist richness showed a strong positive response to productivity, whereas the richness of the generalist groups was not related to changes in productivity. Conclusions:The patterns of species richness on uplifting beaches are determined by the interplay of primary succession, disturbance and productivity. When both succession time and productivity increase, competitive exclusion starts to limit total species richness. In these circumstances, disturbance favours diversity by creating gaps in the vegetation. A combination of long succession time, low disturbance and low productivity result in maximum species richness. The richness of functional groups, particularly the opportunistic and disturbance-tolerant beach specialist group and the competitive but disturbance-sensitive groups, reach their peak in divergent environmental conditions. Consequently, the complex richness patterns observed on uplifting beaches are created not only by strongly interacting environmental drivers but also by differences in species' adaptive strategies.

No abstract

No abstract

Arctic deltas, such as the Mackenzie Delta, are expected to face major climate change and increased human influence in the near future. Deltas are characterised by highly dynamic fluvial processes, and changing climate will cause considerable evolution of the riverine environment.The changes are difficult to predict with existing knowledge and data. This study quantified channel planform change of the Mackenzie Delta , analysing its temporal and spatial patterns. We addressed the main obstacle of research on large remote areas, the lack of data, by developing a unique work flow that utilised Landsat satellite imagery, hydrological time series, remote sensing-based change analysis, and automatic vectorisation of channels. Our results indicate that the Mackenzie Delta experienced constant evolution but at a highly varying rate over the 30 years. The study demonstrates that the magnitude and duration of flood peaks and the presence of spring ice breakup floods determine the rate of Arctic delta planform change.Changing winter conditions and spring flood magnitudes may therefore affect the stability of Arctic deltas. However, no clear trends towards decreased recurrence or magnitude of spring floods or increased instability of the delta plain have yet been observed in the Mackenzie Delta.The delta plain was most dynamic at the beginning and at the end of the examined period, corresponding to intense flooding, whereas the rates of change were subtle during the low-flood period 1994-2007. The largest changes have occurred along the wide Middle Channel and in the outermost delta. Relative to their size, however, smaller meandering channels have been highly dynamic. Hotspots of change in the delta plain are located in anastomosing and braiding channel segments and, at the local scale, in point bars and cut-banks along meandering channels. Our study describes how Landsat satellite data can be utilised for advancing fluvial geomorphological research in remote areas. However, cloudiness in the delta restricts production of dense time series with simultaneous coverage of the whole area and requires manual preprocessing.

Grain size properties and the variation of organic matter in coastal beach and dune environments are assumed to be controlled by the intensity of aeolian processes, time and the sediment source. However, assumptions are based on relatively limited empirical studies. In this study, we examined which environmental variables are the main predictors of multiple topsoil properties. To achieve this, we analysed an extensive dataset systematically collected across all beach zones and a large geographical area at the Finnish Baltic Sea coast characterized by post‐glacial land uplift. We included a comprehensive set of predictors in the analysis and applied boosted regression trees, a modern modelling technique particularly suited for analysis without prior assumptions of the data model. The results suggest that mean grain size and sorting are mainly determined by northing and fetch. Northing, disturbance and fetch predicted the variation of soil organic matter while litter cover was strongly related to disturbance. Based on the analyses, we were able to identify the main drivers of multiple topsoil properties on land uplift beaches. Parent material is suggested to determine sediment textural properties, which largely masks the effects of transient processes. Mean grain size and sorting are highly interdependent: grains become finer and sorting improves with increasing shore exposure. The intensity of momentary geomorphic processes controls the accumulation of litter whereas the slower accumulation of organic matter in the soil is influenced also by the static exposure setting. Skewness and kurtosis of the grain size distribution are mainly influenced by unmeasured processes, potentially relating to the geomorphological origin of the sediment. Copyright © 2014 John Wiley & Sons, Ltd.