Natalie S. Haussmann

FINE SCALE VARIABILITY IN SOIL FROST DYNAMICS SURROUNDING CUSHIONS OF THE DOMINANT VASCULAR PLANT SPECIES (AZORELLA SELAGO) ON SUB‐ANTARCTIC MARION ISLAND

Abstract. Through changing soil thermal regimes, soil moisture and affecting weathering and erosion processes plants can have an important effect on the physical properties and structure of soils. Such physical soil changes can in turn lead to biological facilitation, such as vegetation‐banked terrace formation or differential seedling establishment. We studied the fine scale variability in soil temperature and moisture parameters, specifically focusing on frost cycle characteristics around cushions of the dominant, vascular plant species, Azorella selago, on sub‐Antarctic Marion Island. The frost season was characterised by numerous low intensity and very shallow frost cycles. Soils on eastern cushion sides were found to have lower mean and maximum temperatures in winterthan soils on western cushion sides. In addition, lower variability in temperature was found on eastern cushion sides in winterthan on western cushion sides, probably as a result of higher wind speeds on western cushion sides and/or eastern, lee‐side snow accumulation. Despite the mild frost climate, extensive frost heave occurred in the study area, indicating that needle ice forms at temperatures above −2°C. Our results demonstrate the effectiveness of frost pull as a heave mechanism under shallow frost conditions. The results highlight the importance of Azorella cushions in modifying site microclimates and of understanding the consequences of these modifications, such as potentially providing microhabitats. Such potential microhabitats are particularly important in light of current climate change trends on the island, as continued warming and drying will undoubtedly increase the need for thermal and moisture refugia.

Referencing practices in physical geography How well do we cite what we write

Accurate citation practices are important, from both an ethical and a scientific point of view. Using an easily reproducible, previously published method, we assess citation accuracy in 120 articles published in the first half of 2011 and listed under ‘Physical Geography’ in Thomson Reuters’ ISI Web of Knowledge Science Citation Index. Our results indicate that at least 19% of citations in physical geography do not provide clear support for the statements they are meant to support. These results are in line with previously published findings for ‘field-orientated’ sciences. We propose that both authors and editors help remedy this problem, by employing more rigorous writing and editing practices.

Spatial Association of Lemming Burrows with Landforms in the Swedish Subarctic Mountains: Implications for Periglacial Feature Stability

Abstract Burrowing mammals often have considerable geomorphological impacts, and their tunneling activities may decrease the stability of landforms. We document the spatial distribution of Norwegian lemming burrows in a subarctic alpine meadow to determine the preferred locations for burrow entrances and to examine the potential for burrowing to decrease the stability of periglacial landforms at the site. Burrow entrances were disproportionately common into the base and sides of landforms (>68% of burrows), probably reflecting the lower energetic cost of moving soil horizontally, rather than vertically, out of burrows. Most burrow entrances (>60%) were also located under large rocks, which probably improve burrow stability by providing a firm ceiling to the entrance. Field observations show that these burrows are relatively stable, as only 3% were associated with any signs of increased erosion or landform instability. Therefore, in contrast to some previous studies, and despite burrowing being concentrated on landforms, we suggest that these rodents have little direct impact on landform integrity at this site.

Soil movement by burrowing mammals : a review comparing excavation size and rate to body mass of excavators

Mammal burrowing plays an important role in soil translocation and habitat creation in many environments. As a consequence, many burrowing mammals have at some point been studied in an ecosystem engineering context. From a geomorphological point of view, one of the focus areas of burrowing mammal research is on the amount of soil that is excavated and the rate at which this happens. As such, reviews exist on the volumes and rates of sediment removal by burrowing mammals in specific environments or for specific groups of species. Here, a standardised comparison of mammal burrowing across a broad range of burrowing mammal species and environments is provided, focussing on both burrow volume and excavation rate. Through an ISI Web of Science-based literature search, articles presenting estimates of burrow volumes and/or excavation rate were identified. Relationships between species body size and burrow volume/excavation rate were explored and the influence of sociality and method of burrow volume estimation were assessed. The results show that, although larger species construct larger burrows, it is the smaller species that remove more sediment per unit time at larger, site-level spatial scales. Burrow volume estimates are, however, independent of species sociality (solitary versus group-living) and method of burrow volume estimation (excavation-based versus mound-based). These results not only confirm previously established relationships between species body size and burrow volume, but, more importantly, they also add to this, by exploring larger scale impacts of burrowing mammals along a body size gradient.