Rocks and Rain Fix Nitrogen in Post-Glacial Sites

A new study in Plant and Soil found that the input of nitrogen from the atmosphere, via a process of rain funneling through rocks, created levels of nitrogen that are adequate to support plant growth in post-glacial alpine soil, challenging the common view that the element is the primary limiting factor in deglaciated areas.

In fact, the researchers found that phosphorous, due to the low-weathering rates and high nitrogen deposition of the region, is the element in soil which limits post-glacial plant life colonization. The team was lead by Hans Göransson of the University of Natural Resources and Life Sciences, Vienna.

The finding challenges the widely-held view that the only plants capable of colonizing post-glacial environments are species that are able to fix nitrogen from the atmosphere. Instead, as this work shows, natural processes enable other plants to become colonizers in the European Alps.

Nitrogen-fixing plants on a post-glacial site in Glacier Bay, Alaska. (Photo:Elizabeth/Flickr)
Nitrogen-fixing plants on a post-glacial site in Glacier Bay, Alaska. (Photo: Elizabeth/Flickr)

This research may have implications for future ecosystem plant colonization and biodiversity, a topic of interest to scientists as glaciers retreat and expose new soils in many regions of the world.

The team, focusing on Damma Glacier in Switzerland, found that the expected nitrogen-fixing plants were usually absent in the early stages of these post-glacial sites, contradicting what previous research has suggested. The study’s findings differ from the research done in recently deglaciated areas in Glacier Bay in Alaska and on the Franz Josef glacier in New Zealand, which show an abundance of nitrogen-fixing plants in post-glacial sites.

Most plants are unable to process atmospheric nitrogen directly and can only absorb it once it undergoes a transformation within the soil. (Nitrogen is essential for plant growth.) Some plants, however, undergo a process called nitrogen fixation which converts atmospheric nitrogen into a form useful for them. Bacteria in the plant’s roots help, as they are able to convert the nitrogen into a usable form.

Because of this capacity, nitrogen-fixing plants are generally thought of as the colonizing species in post-glacial sites, since these rocky areas are typically so low in soil nitrogen that plants that cannot fix nitrogen would not be able to grow. Once the nitrogen-fixing plants begin to die and the nutrients from them return to the soil, a more diverse second generation of plants can grow.

Damma Glacier in Switzerland. (Photo:Paebi/Wikimedia Commons)
Damma Glacier in Switzerland. (Photo: Paebi/Wikimedia Commons)

The team set out to explore how plants in the region were colonizing even when nitrogen-fixing plants were not present. They found that nitrogen from the atmosphere was deposited into the soil by newly exposed rocks, which acted as funnels when it rained. This process provided sufficient amounts of nitrogen for plant growth, and thus allowed non-nitrogen fixing plants to grow in these areas.

The researchers divided the Damma post-glacial area into a total of 21 sites across three time periods related to the age of the soil since the glacier retreated: pioneer (fewer than 16 years since deglaciation), intermediate (57-80 years), and late-stage (108-137 years). The Damma glacier has had a long and well-tracked retreat, making the separation of time periods easy.

The team used ion exchange resin bags at each site that measure the amount of nitrogen in the soil. They also took the above-soil measurements by collecting the biomass growing at the sites and analyzing the nitrogen levels.

They found that nitrogen levels were high in the pioneer stage, followed by low levels in the intermediate, and high levels again in the late stage.

As the nitrogen channels through rocks and into the soil, it creates an overabundance of nitrogen at first, since there is little or noplant life to use the element. This process eventually creates hotspots of plant growth, but as soil and organic matter increases, the rocks become covered. Once the rocks are covered, the atmospheric nitrogen can no longer be deposited into the soil. This, along with the increased presence of plants using the soil nitrogen, leads to a decrease in nitrogen availability within the soil in the intermediate stage.

High levels of nitrogen return in the late-stage sites once the vegetation has matured and therefore requires less of the element for growth. With more plant cover, nitrogen increases as plants die and the nutrients are returned to the soil through decomposition.  

Schematic from the study showing the build up of soil and plant matter on top of the rocks. This eventually stops the funneling process found in early stages. (Figure:by Kristel Perreijn)
Schematic from the study showing the build up of soil and plant matter on top of the rocks. This eventually stops the funneling process found in early stages. (Figure:Kristel Perreijn)

The team also looked at phosphorous, another important element for plant growth, and found little difference in its levels in the soil, regardless of the time since deglaciation. Since nitrogen levels changed with time, the ratio of phosphorus to nitrogen also varied. The researchers found that phosphorus stabilized at a low level. When the nitrogen levels were high, in the pioneer and late stages, phosphorus was the limiting element. This relationship flipped in the intermediate stage when nitrogen availability was low. Thus, as the nitrogen availability changes, so too does the element that is limiting plant growth.

The researchers concluded that colonizing plants found in the bedrock typical to the Alps are more likely to be limited by phosphorous due to the high levels of nitrogen deposition and the low weathering rates needed to release phosphorus from minerals. This gives an advantage to plants that can use the phosphorus from mineral sources, thus affecting the composition of the plant life in those areas throughout the different stages of deglaciation.

“In succession, the next set of species coming in is dependent on [those] already present. Thus a change in primary succession may lead to dramatic change in the plant community later on,” Göransson, the lead author, told GlacierHub in an email interview.

 

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The Challenge of Sediment Management

Moinak Hydro Power Plant.
Moinak Hydro Power Plant, on the Sharyn River in Kazakhstan. (Photo: Wikipedia Commons)

A new research study entitled “Ecosystem impacts of Alpine water intakes for hydropower: the challenge of sediment management” explores the effects of different hydropower capture techniques on human and ecosystem water needs. Rivers fed by glacial melt and snowmelt in Alpine regions serve as a critical resource for hydroelectric power production. However, the management systems used in hydroelectric systems heavily impact both river and sediment flow. This disruption, in turn, heavily, and often negatively, impacts downstream communities and ecosystems, which face consequences of habitat change, degradation, and temperature increases. The authors note that few policy solutions are currently available to reduce and manage these impacts, and call for fresh ideas to address them.

The cover image of the Wiley' January/February 2016 issue.
Researchers taking measurements at a stream gauge (Photo: Jim Constanz)

The study, published in the latest January/February issue of Wiley Interdisciplinary Reviews: Water, reviews the three main types of water management techniques used in hydropower systems. Dams impound water behind barrages in a valley, while abstraction removes water from a ground source. Once abstracted, water is moved laterally (shifted nearby) or downstream (to a lower part of a river) in order to reach the hydroelectric plant.

The article systematically examines how these different methods impact water and sediment flow of the river. Though previous work has studied the impact of different types of water management techniques on river flow, this study is the first of its kind to closely investigate the impact of water abstraction and transfer systems on sediment displacement, which, the study argues, “can significantly influence habitat, which in turn impacts ecosystems.”

The disruption and transfer of sediments have important impacts on human and natural ecosystems because they interfere with what the researchers call the “the natural sediment ‘conveyor belt’” — the process of sediment transfer that is usually determined by natural processes such as erosion, abrasion, sorting, and deposition. Though rivers primarily transport water, they are also vital vessels of sediment transfer. Fine sediment particles enter the river as the water erodes the banks, or tiny fragments break off from rocks in the water. The river carries these particles downstream, allowing the larger ones to drop out—or be deposited—in places where currents slow down.

Disruption of water and sediment flow puts Alpine ecosystems, whose flow regimes are a “key driver” of their physical habitat, at risk. Alpine habitats face risk of physical habitat change, degradation, temperature increases, and major changes to riparian vegetation. Previously inundated rivers may become dry. Such rapid changes in stream flow may leave Alpine fish not able to adapt quickly enough to sustain these alterations. Water abstraction may also “induce lower or higher nutrient levels, depending on the geology; increase electrical conductivity depending on the solute-richness; and/or increase pH.”

Chilime Hydropower Dam
The Chilime Hydropower Dam in Nepal. Image credit: Wikipedia (Photo:Wikipedia Commons)

In order to guarantee both human and ecosystem water needs and minimally disrupt natural sediment transfer processes, hydroelectric systems and water management systems must replicate as close to a natural flow regime as possible. However, attempts to mimic variables of water magnitude, frequency, duration, timing, and rate of charge of each river are unlikely to be met due to simple “constraints of hydroelectric production,” the researchers note. Natural river and sediment flows fluctuate seasonally, making them difficult to mimic because hydropower systems are designed to operate with steady, slow flows. These flows, in turn, rarely provide enough speed to carry larger particles, but also never slow enough to allow smaller particles to settle.

The researchers offer several suggestions to reduce the impacts of sediment transfer on downstream ecological and human communities. They seem some promise in sediment management processes, such as reducing sediment flushing during flows, creating artificial sediment sinks, and finding ways to permanently accumulate remaining sediment into floodplain systems. Such management processes, the researchers noted, are “rarely considered in legislation designed to create more environmentally sustainable river flows.” As such, their suggestions create important policy implications for alpine and glacial river communities near hydropower facilities.

Reinforsen power plant, norway
The Reinforsen power plant in Mo i Rana, Norway. (Photo: Flickr/Statkraft)

However, researchers noted that it is still difficult to determine best practice procedures for sedimentation management which could improve river ecology. They comment that “[t]his is a particular problem for water intake systems where there are almost no experiments, and hence scientific bases, that might be used to define the kinds of instream flow needs necessary.”

Though hydropower poses promise for clean, alternative energy, the study introduces underlying environmental tensions between clean energy solutions and the negative impacts of such alternative energy sources on surrounding communities and ecosystems. In this way, it alerts policy-makers and the public at large to challenges in bringing about a successful transition to low-carbon energy systems. economies and societies.

 

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Glacier Retreat Threatens Insect with Extinction

As glaciers retreat, a species of glacier-dependent stonefly faces extinction.

In 2010, the Center for Biological Diversity petitioned for Zapada glacier, a western glacier stonefly only found in alpine streams of Glacier National Park, Montana, to be listed as endangered species under the U.S. Endangered Species Act. This species – one of more than 3500 species of stonefly –  is highly restricted to cold, glacial meltwater with limited dispersal ability.

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Zapada glacier adult female from the Grinnell Glacier Basin in Glacier National Park (approximate length is 12 mm) (Source: Giersch et al./Freshwater Science).

Now, in an effort to save this endangered stonefly, the Center for Biological Diversity filed a lawsuit against the U.S. Fish and Wildlife Service to address the urgency of protecting this stonefly. The insect could potentially be taken to other clean cold streams outside its established range, perhaps further north or at higher elevation where it might survive – but time is running out.

Species evolve to survive in specific temperature ranges; however, when the environmental conditions have exceeded the range, species are unable to adapt to new conditions immediately. Climate change has put many species in danger, but this is the first time that an insect species has been threatened with extinction by glacier retreat.

“Protection can’t come soon enough for this stonefly,” said Tierra Curry, a senior scientist at the Center for Biological Diversity. “Glacier National Park will have no glaciers in 15 years if we don’t take action to curb climate change.”

Stoneflies are a particularly ancient order of insects that spend most of their lives in water. They are considered the most sensitive indicators of water quality in streams as they require fresh, clean water and don’t tolerate pollution. The insects have a one to two-year life cycle starting in the nymph stage in fresh meltwater. They usually emerge from the water in late spring when the stream is uncovered by melting snow. Z. glacier has a narrow temperature preference around 3.3 degrees Celsius. It is this narrow temperature preference that makes this insect especially susceptible to climate change.

Between 1960 to 2012, the average summer temperature in Glacier National Park has risen by approximately 1 degree Celsius. Additionally, since 1850, 125 of the 150 glaciers in Glacier National Park have melted away while the remaining 25 are predicted to disappear by 2030. The loss of glaciers as well as restricted suitable environmental conditions and limited dispersal ability of the stonefly threaten the species’ ability to survive.

Many Glacier in GNP (Source: Esther Lee/Flickr).
Glaciers in Glacier National Park (Source: Esther Lee/Flickr).

Few studies have investigated the impacts of climate change on alpine species distributions. To compensate for this knowledge gap, J. Joseph Giersch from US Geological Survey and other researchers looked at the current status and distribution of Z. glacier. Their results were published in Freshwater Science.

Giersch et al. sampled 6 alpine streams, where Z. glacier was historically known to live, to examine the relationship between species occurrence and environmental variations of temperature and glacial extent. In order to identify the current geographic distribution and distinguish Z. glacier from the other 6 Zapada species in Glacier National Park, the researchers used morphological characteristics, the outward appearance of adults and the DNA of nymphs.

Giersch et al. identified 28 suitable alpine locations in Glacier National Park as potential habitats for Z. glacier. From this study, Z. glacier was only found in 1 of the 6 historically occupied streams – the outlet of Upper Grinnell Lake. The results suggest increased temperature and glacier retreat have already caused local extinction of Z. glacier from several historical locations.

Upper Grinnell Lake in Glacier National Park, where Zapada glacier can be found (Source: GlacierNPS/Flickr).
Upper Grinnell Lake in Glacier National Park, where Zapada glacier can be found (Source: GlacierNPS/Flickr).

The stonefly was also detected in 2 new high-elevation locations in Glacier National Park. Therefore, only 3 out of the 28 potential habitats have Z. glacier. The results indicate that the historical distribution of this stonefly in Glacier National Park was already restricted and its distribution will be further reduced in the future due to increased stream temperatures and habitat loss.

“The plight of the glacier stonefly is a wakeup call that unless the United States takes major action to reduce our greenhouse gas emissions, this special insect and more than one-third of all plants and animals on Earth could go extinct by 2050,” said Curry.

For more stories on invertebrates near glaciers, read here and here.

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Photo Friday: Alpine Photography by Fi Bunn

Fiona Bunn, a landscape photographer and alpinist, has been traveling to the Alps for over 25 years. Her alpine photography work has been frequently shared on social media, including The Alpine Club as well as Zermatt Tourism. Her work was recently included in an exhibition for a second time at The Brick Lane Gallery in the Shoreditch district of London’s East End. The exhibition featured the relationship between photographers and alpinists. Fi finds the worldwide alpine community to be supportive, with a desire to appreciate and express their interest in art. She  wrote “my aim is that my work highlights this vibrant, friendly, international community, who celebrate a shared interest for alpine exploration which literally crosses borders.” In addition, Fi is also concerned about climate change and glacial retreat. In her travels she has seen a large reduction in the size of glaciers firsthand. In an email she told GlacierHub,”I hope that my photos of these amazing mountains and glaciers perhaps help focus attention on how environmentally essential they are.

For more alpine photographs by Fi, please check out her website.

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Photo Friday highlights photo essays and collections from areas with glaciers. If you have photos you’d like to share, let us know in the comments, by Twitter @glacierhub or email us at glacierhub@gmail.com

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Where Can Alpine Plants Hide from Global Warming?

Androsace alpine living on rock glaciers as well as moraine ridges and deglaciated forelands (Source: Apollonio Tottoli/Flickr).

Environmental conditions, including climate, strongly influence the distribution of plant species. As temperatures continue to rise around the world, many people are concerned about the possible shifts in distribution of plant species, since plants are immobile, and many of them have a limited ability to disperse. These restrictions to changes in their distribution are particularly severe for plants that are adapted to cold conditions, such as those found in high mountain regions.

Studies by Valenti Rull and others have shown that during interglacial periods in the geological past, alpine plants were able to disperse to microrefugia, small-scale sites which allowed species to persist when most of their ranges became unsuitable for them. Thus, in the current era of warming, such sites, with locally favorable climate, could once again prove to be important for the survival of cold-adapted alpine species. A newly published study by Rodolfo Gentili of the Department of Environmental Sciences at the University of Milan and several co-authors in Ecological Complexity establishes a fresh approach to the study  of microrefugia. The authors examined the geomorphological and ecological features of microrefugia during earlier interglacial stages and used these features to identify potential microrefugia areas for alpine plants in and near glaciers, in both the present and the near future.

Leucanthemopsis alpine living on mountain summits (Source: Apollonio Tottoli)
Leucanthemopsis alpine living on mountain summits (Source: Apollonio Tottoli/Flickr).

In general, there are three recognized strategies which alpine plants can adapt to survive under a warming climate. They can migrate to higher elevation, remain at local microrefugia or evolve through genetic differentiation to adapt to new climate. However, there had been no overview to date of how plants in the Alps and other high mountains of Europe could respond to future warming. Gentili and his co-authors conducted  a thorough literature review, focusing in particular on geomorphological processes and landforms associated with plant communities in alpine environment. (They found only one study which addressed the genetic evolution of an alpine plant.)

The authors developed a typology of alpine landforms and characterized each one according to its “vegetation features, climatic controls, microclimate features of active landforms and microrefugium functions.” They recognized eight landform types, which differ in terms of the processes that generate them. These landforms are mountain summits, debris-covered glaciers, moraine ridges and deglaciated forelands, nivation niches or snow patches,rock glaciers, alpine composite debris cones (debris slopes and scree), alpine corridors (composite channels, including avalanche channels and tracks), and ice caves.

Saxifraga oppositifolia living on alpine corridors (Source: Alastair Rae/Flickr).
Saxifraga oppositifolia living on alpine corridors (Source: Alastair Rae/Flickr).

Taken individually, all of these eight landforms have been documented in the published literature as serving currently as microrefugia, except for the debris-covered glaciers, which nonetheless are promising as future microrefugia because of their relatively cool temperatures which result from the presence of sub-surface ice. The other landforms all have been shown to function as microrefugia. They offer a number of advantages, including suitable sites for colonization (moraine ridges and deglaciated forelands), cooler temperatures (debris-covered glaciers, rock glaciers, nivation niches or snow patches, ice caves), a vertical range that facilitates dispersal (alpine corridors) and a large variety of niches (alpine composite debris cones). Taken together, these landforms provide a very wide range of habitats, increasing the likelihood that any given alpine species could have a favorable spot to which it could disperse. These relations are indicated in the figure from the paper, shown below, which demonstrates that the geomorphological heterogeneity—the diversity of habitats within and across landforms—promotes the survival of species.

The relation of geomorphological diversity to species survival (Source: Gentili et al./Ecological Complexity).
The relation of geomorphological diversity to species survival (Source: Gentili et al./Ecological Complexity).

The researchers note that these glacial and pre-glacial landforms are potential microrefugia for alpine plants under warming conditions. They recognize that human intervention—purposive translocation of plants—may assist in the survival of species. In addition, they point out that the plant species themselves may adapt genetically to changing environmental conditions. They conclude by suggesting that researchers could profitably direct their attention to evolutionary processes within this geomorphologically complex and climatically dynamic environment, seeing whether species, pressed by climate change, can adapt, or even evolve into new species.

Saxigrada bryoides living on debris-covered glaciers (Source: /Flickr).
Saxigrada bryoides living on debris-covered glaciers (Source: Benoit Deniaud/Flickr).
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Roundup: Nepal Symposium, Microrefugia, Climate Change

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Symposium on Glaciology in High-Mountain Asia (1 – 6 March, 2015)

“The high mountains of Asia are estimated to contain one of the greatest concentrations of glacier ice outside the polar regions, and are the headwaters of rivers which support agriculture and livelihoods of over one billion people. Changes in snow, ice, and permafrost due to climatic changes will impact water resources, ecosystems and hydroelectric power generation, and will aggravate natural hazards. To understand these impacts, the symposium will provide a forum to discuss advances in measurements, modeling, and interpretation of glaciological and cryospheric changes in high mountain Asia.”

Read more about this International Symposium in Kathmandu, Nepal.

 

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Potential Warm-Stage Microrefugia for Alpine Plants

“In Alpine regions, geomorphologic niches that constantly maintain cold-air pooling and temperature inversions are the main candidates for microrefugia. Within such microrefugia, microhabitat diversity modulates the responses of plants to disturbances caused by geomorphologic processes and supports their aptitude for surviving under extreme conditions on unstable surfaces in isolated patches. Currently, European marginal mountain chains may be considered as examples of macrorefugia where relict boreo-alpine species persist within peculiar geomorphological niches that act as microrefugia.”

Read more about this article.

 

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Mountains and Climate Change

“Large mountain ranges often act as climatic barriers, with humid climates on their windward side and semi-deserts on their lee side. Due to their altitudinal extent, many mountain regions intersect important environmental boundaries such as timber lines, snow lines or the occurrence of glaciers or permafrost. Climatically induced changes in these boundaries could possibly trigger feedback processes affecting the local climate. For instance, a rising snow line and thawing permafrost could increase the risk of natural hazards as well as accelerate warming trends due to lower reflectance. Changes in these boundaries can have sharp consequences for ecosystems and can influence natural hazards, economic potential and land use.”

Read more about this article.

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Life Blooms in Tiny Cities at the Surface of Glaciers

Cryoconite holes (Source:  Joseph Dsilva)
Cryoconite holes (Source: Joseph Dsilva)

You might think glaciers would be hostile to life. But small water-filled holes at the surfaces of glaciers called cryoconite holes contain diverse collections of organisms. Like individual cities in a continent of ice, each hole contains its own distinct population of creatures.

Some scientists believe glaciers should be considered a separate biome given the unique ecosystems that thrive there.

Krzysztof Zawierucha  (Source:  Dwarf)
Krzysztof Zawierucha
(Source: Dwarf)

While the bacteria that live in cryoconite holes have been studied extensively, little is known about the invertebrates that feed on them and on algae found in the holes—only 26 papers have been published on these invertebrates in the past 100 years. Polar biologist Krzysztof Zawierucha from the University of Poznan in Poland and other researchers recently attempted to catalog these invertebrates in a review paper published in the Journal of Zoology.

Cryoconite holes, are created by cryoconite—windblown dust containing rock particles and soot—which darkens the surfaces of glaciers and accelerates melting. Cryoconite holes can form long-lasting habitats given that they are relatively unaffected by rapid environmental changes. These holes can be covered over by ice, or open to the elements.  For a brief explanation of what cryoconite is and how cryoconite holes are created, watch this video:

Only 25 species of cryophilic invertebrates have so far been catalogued and studied, few of them endemic to cryoconite holes. These include insects and two phyla of worms (the ringed worms also known as annelids, and roundworms also known as nematodes), as well as the microscopic rotifers, and the less well known waterbears, whose technical name is  tardigrades.

tardigrades
tardigrades

The species makeup of the cryoconite holes differs slightly in the Arctic, Antarctic, Patagonian, Alpine and Himalayan glaciers where they have been studied. Some of these hole-dwelling invertebrates have geographically restricted ranges, existing only on glaciers in the Alps or Himalayas. The authors suspect there are many more species living in these remote ice holes waiting to be discovered.

The invertebrates are varied in coloration; some are black, others white, and still others are colorless; Zawierucha and his coauthors cite other studies indicating that the coloration may have adaptive value in these environments where ultraviolet radiation is strong. They have different mechanisms for surviving the very low temperatures and the threat of desiccation: some produce very hardy eggs, while others can enter a state of anabiosis—a sort of suspended animation—until conditions improve.

A glacier copepod (scale bar in um), a Plecoptera (scale bar in mm), and tardigrade Pilatobius recamieri (scale bar in um) Source:  Zawierucha et al., 2014.
A glacier copepod (scale bar in um), a Plecoptera (scale bar in mm), and tardigrade Pilatobius recamieri (scale bar in um) Source: Zawierucha et al., 2014.

Cryophilic ecosystems are threatened due to the melting of glaciers caused by climate change and pollution. But cryophilic animals may accelerate the melting of glaciers themselves, particularly those that are black in coloration. Because so little research has been conducted on them, it is possible that some species of cryophilic invertebrate will become extinct before it is catalogued by scientists. If you happen to stumble upon a cryoconite hole on a glacier, treat it with respect. It likely contains an entire world of busy organisms.

For a story on plant spores that live on glacier surfaces, look here.

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