Assessing the ecological value of dynamic mountain geomorphosites

Geoheritage is a component of geodiversity constituted by all the elements of geodiversity recognized by society for their particular values. The definition of these values, including the importance of geoheritage for biodiversity, plays a key role in the process of heritage recognition and geoconservation policymaking. In mountain environments, dynamic geomorphosites have a strong influence on plant diversity because the active geomorphological processes responsible for their formation act as renovators for habitats of pioneer species. In this paper, we propose criteria to assess the ecological value of dynamic mountain geomorphosites. We show that the interest of plant communities (species richness and presence of rare or protected species) and the influence of geomorphological processes on plant communities (disturbances, surface movement and soil) are fundamental criteria for assessing the ecological value in an exhaustive and objective way and that the question of the scale (local and national scales) is also a crucial parameter. We then illustrate this methodological proposal by evaluating the ecological value of three dynamic geomorphosites and a talus slope in the western Swiss Alps.

Multiscale Very-High Resolution Topographic Models in Alpine Ecology: Pros and Cons of Airborne LiDAR and Drone-Based Stereo-Photogrammetry Technologies

The vulnerability of alpine environments to climate change presses an urgent need to accurately model and understand these ecosystems. Popularity in use of digital elevation models (DEMs) to derive proxy environmental variables has increased over the past decade, particularly as DEMs are relatively cheaply acquired at very high resolutions (VHR; <1m spatial resolution). Here, we implement a multiscale framework and compare DEM-derived variables produced by Light Detection and Ranging (LiDAR) and stereo-photogrammetry (PHOTO) methods, with the aims of assessing their relevance and utility in species distribution modelling (SDM). Using a case study on the arctic-alpine plant Arabis alpina in two valleys in the western Swiss Alps, we show that both LiDAR and PHOTO technologies can be relevant for producing DEM-derived variables for use in SDMs. We demonstrate that PHOTO DEMs rivalled the accuracy of LiDAR, putting the current paradigm of LiDAR being the more accurate of the two methods into question. We obtained DEMs at spatial resolutions of 6.25cm-8m for PHOTO and 50cm-32m for LiDAR, where we determined that the optimal spatial resolutions of DEM-derived variables in SDM were between 1 and 32m, depending on the variable and site characteristics. We found that the reduced extent of PHOTO DEMs altered the calculations of all derived variables, which had particular consequences on their relevance at the site with heterogenous terrain. However, for the homogenous site, we found that SDMs based on PHOTO-derived variables generally had higher predictive powers than those derived from LiDAR at matching resolutions. From our results, we recommend carefully considering the required DEM extent to produce relevant derived variables. We also advocate implementing a multiscale framework to appropriately assess the ecological relevance of derived variables, where we caution against the use of VHR-DEMs finer than 50cm in such studies.

Linking glacier surface changes to subglacial conduit locations for a temperate Alpine glacier

<p>It is well understood that topography near the snout of an alpine glacier may evolve quickly due to differential melting depending on exposure to solar radiation and on debris cover thickness. However, the positioning and shape of subglacial conduits underneath shallow ice may also have an important influence on ice creep and thereby on the topography of this region. This relationship could potentially be used to determine locations of subglacial conduits via the detailed observation of glacier surface changes.</p><p>We monitored the ice-marginal zone of the Otemma Glacier in the south-western Swiss Alps with daily UAV surveys at high spatial resolution and with a network of ablation stakes over a period of three weeks. After subtraction of melt measured with ablation stakes, we produced maps of changes in ice surface topography that are due to processes other than melt. In two consecutive summers we conducted three-dimensional GPR surveys in the same area of interest. By looking at these spatially dense grids of GPR measurements, we are able to identify the locations and shape of sub-glacial conduits underneath the ice marginal glacier tongue, for ice thicknesses between 20 m and 50 m. Superposition of the GPR-derived channel maps with those showing the topographic changes suggest a correlation between ice surface changes and processes operating at the glacier bed.</p>

Alteration of Bumblebee Venom Composition toward Higher Elevation

Venomous animals use venom, a complex biofluid composed of unique mixtures of proteins and peptides, for either predation or defense. Bumblebees, which occur in various habitats due to their unique thermoregulatory properties, mainly use venom for defense. Herein, we conducted an exploratory analysis of the venom composition of a bumblebee species (Bombus pascuorum) along an elevation gradient in the western Swiss Alps using shot-gun proteomic approaches to assess whether their defense mechanism varies along the gradient. The gradient was characterized by high temperatures and low humidity at low elevations and low temperatures and high humidity at high elevations. Venom composition is changing along the elevation gradient, with proteomic variation in the abundances of pain-inducing and allergenic proteins. In particular, the abundance of phospholipase A2-like, the main component of bumblebee venom, gradually decreases toward higher elevation (lower temperature), suggesting venom alteration and thus a decrease in bumblebee defense towards harsher environments. Larger datasets may complement this study to validate the observed novel trends.