Alpine debris-covered glaciers as a habitat for plant life

Abstract

Debris-covered glaciers represent a significant, increasing fraction of glaciers and can host plant life on their surface. The goal of this work was to evaluate the suitability of supraglacial debris as a habitat for plant life and to discuss its ecological and biogeographic role. The research was carried out on the Miage Glacier (Mont Blanc massif, Western Alps, Italy). Vegetation cover was sampled using a regular sampling grid, recording plant species and number of individuals in 71 plots. Detailed glaciological parameters (surface temperature, debris thickness, glacier surface velocity) were recorded or derived from published data. Relationships between vegetation and environmental variables were assessed through Generalized Linear Models, Principal Components Analysis and Canonical Correspondence Analysis. The glacier surface hosted a high biodiversity, with 40 vascular plant species, including trees and shrubs. Plant cover was arranged along an altitude/glacier velocity gradient, whilst debris thickness as low as 10 cm could sustain plant growth on moving ice. Glacier velocity was the main physical factor affecting vegetation cover, probably through its influence on debris stability. The observed species assemblage is comparable with those of subalpine glacier forelands, but with the addition of high-altitude species. Debris-covered glaciers can provide a relatively favourable habitat for plant life wherever the glacier surface is sufficiently stable, acting as a refugium of high-altitude taxa below their altitudinal limits. Glaciers may behave as a dispersal vector for alpine plant species, which could have been important both during glacial periods and during warm stages of the Holocene.

The response of vegetation dynamics of the different alpine grassland types to temperature and precipitation on the Tibetan Plateau

“…6a-c). Some reports also hold that the positively correlated relationship between NDVI and surface heat source is more remarkable in the western than the eastern Tibetan Plateau (Caccianiga et al 2011). However, Xu et al (2008) suggested that the annual mean vegetation cover trends were significantly out of phase with the increase in air temperature.…”

Bacterial community structure on two alpine debris-covered glaciers and biogeography of Polaromonas phylotypes

“…Annual surface velocity of both glaciers was measured by the differential global positioning system method (Diolaiuti et al, 2005;Caccianiga et al, 2011). Surface elevation was extracted from 2003 Digital Elevation Models.…”

“…As a result, the glacier surface is covered by a continuous debris layer, whose thickness generally increases toward the glacier terminus. The long transport on the glacier surface allows debris weathering and alteration, and its colonization not only by microorganisms but also by animals (for example, arthropods) and plants (Pelfini et al, 2007(Pelfini et al, , 2012Caccianiga et al, 2011;Gobbi et al, 2011). Ecological communities therefore exist on the surface of DCGs, and may be structured according to a chronosequence, with communities increasing in complexity towards the glacier terminus (Gobbi et al, 2011).…”

Nematodes and rotifers on two Alpine debris-covered glaciers

“…The thick debris cover of DCGs reduces ice ablation (Nakawo & Rana 1999), but the debris surface can be heated by solar radiation to temperatures that can exceed +30°C (Brock et al 2010). During the long transport on the glacier surface, the debris is weathered and altered, and can be colonized by microorganisms (Franzetti et al 2013), plants (if the glacier elevation is lower than the treeline; Pelfini et al 2007Pelfini et al , 2012Caccianiga et al 2011) and animals (Gobbi et al 2011). It is important to note that not only pioneer organisms can live on the surface of DCGs.…”

“…It is important to note that not only pioneer organisms can live on the surface of DCGs. For example, trees up to 2 m high grow on the surface of the Miage Glacier (Caccianiga et al 2011), and herbaceous plants can colonize DCG surfaces above the tree line, suggesting that organisms typical of soil fauna can live in the debris of DCGs.…”