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Biological invasions are a threat to ecosystems across all biogeographical realms. Riparian habitats are considered to be particularly prone to invasion by alien plant species and, because riparian vegetation plays a key role in both aquatic and terrestrial ecosystems, research in this field has increased. Most studies have focused on the biology and autecology of invasive species and biogeographical aspects of their spread. However, given that hydrogeomorphological processes greatly influence the structure of riparian plant communities, and that these communities in turn affect hydrology and fluvial geomorphology, scant attention has been paid to the interactions between invasions and these physical processes....
Species-level conservation activities tend to be focused on those species that are highly threatened with global or regional extinction in the near future. This is broadly logical, if one of the principal goals is to retain as great a proportion of the composition of original species assemblages as possible, within the severe constraints of available conservation resources. In the main, those species which have a high likelihood of rapidly becoming regionally or globally extinct also have small total population sizes and/or restricted geographic ranges within the appropriate region or worldwide (Gaston, 1994; 2003). That is, the importance of each individual organism to the persistence of the species is on average...
Because of the difficulties involved with separating natural fluctuations in climatic variables from possible directional changes related to human activities (e.g., heightened atmospheric CO2 concentrations related to fossil fuel consumption), some researchers have focused on developing alternative indicators to detect hypothesized climate changes. It has, for example, been suggested that the locations of ecotones, transitions between adjacent ecosystems or biomes, should be monitored. It is assumed that changes in climate, especially increases in atmospheric temperature, will result in shifts in the location (altitude or latitude) of ecotones as plants respond to the newly imposed climatic conditions. In this article,...
Studies of feedback between ecological pattern and process can benefit from the analysis of visually striking patterns, as they may reveal underlying processes and clarify the relative role of exogenous versus endogenous factors in driving vegetation change. Roughly linear forest patches are common in subalpine environments, including `hedges', `ribbon forest', and `Shimagare' or `wave regenerated forests' (waves). The influence of wind is common among these patterns, but the role of positive feedback, the most important component of self-organization in biological systems, varies. Hedges are orientated parallel to prevailing winds in several mid-latitude mountain ranges worldwide. Desiccation and ice-particle abrasion...
Understanding climate change and its potential impact on species, populations and communities is one of the most pressing questions of twenty-first-century conservation planning. Palaeobiogeographers working on Cenozoic fossil records and other lines of evidence are producing important insights into the dynamic nature of climate and the equally dynamic response of species, populations and communities. Climatic variations ranging in length from multimillennia to decades run throughout the palaeo-records of the Quaternary and earlier Cenozoic and have been shown to have had impacts ranging from changes in the genetic structure and morphology of individual species, population sizes and distributions, community composition...
Understanding the timing of mountain building and desert formation events in western North America is crucial to understanding the evolutionary history of the diverse arid-adapted biota that is found there. While many different, often conflicting descriptions exist regarding geobiotic change in western North America, little work has been done to synthesize these various viewpoints. In this paper we present several case studies that illustrate the differences in the various explanations, based on geological and paleobiological data, detailing mountain uplift and desertification in western North America. The majority of the descriptions detailing mountain building in this area fall into two major periods of uplift,...
Macroecology is a big-picture, statistical approach to the study of ecology. By focusing on broadly occurring patterns and processes operating at large spatial and temporal scales and ignoring localized and fine-scaled details, macroecology aims to uncover general mechanisms operating at organism, population and ecosystem levels of organization. Although such an approach is evident in writings dating from the mid- to late 1800s, not until 1989 was the domain of macroecology clearly articulated. Since then there has been an exponential growth in publications employing a macroecological perspective. Here we (1) briefly review the history of macroecology, with emphasis on cultural, scientific and technological innovations...
Terrestrial snow cover is of significance to global geophysical systems because of its influence on both climatological and hydrological processes. Snow cover acts as a layer which modifies energy exchange between the surface and atmosphere, and as the frozen storage term in the water balance, affecting runoff and streamflow. This review addresses two challenges with regard to snow cover: how to monitor this variable adequately over time, and how to couple trends and variability in snow cover to atmospheric circulation. Developments in remote-sensing technology have provided a range of satellite-derived data products which complement in situ snow measurement procedures. Variability in data spatial resolution and...