GeoLog

Biogeosciences

Imaggeo on Mondays: An expedition to better understand Antarctic soils

Imaggeo on Mondays: An expedition to better understand Antarctic soils

A dramatic evening sky puts the frame to a photo taken during the Brazilian Antarctic expedition to James Ross Island in 2016. Brazilian palaeontologists and soil scientists together with German soil scientists spent over 40 days on the island to search for fossils and sample soils at various locations of the northern part of the island.

The island was named after Sir James Clark Ross who led the British expedition in 1842, which first charted locations at the eastern part of the island. James Ross Island is part of Graham Land, the northern portion of the Antarctic Peninsula, separated from South America by the stormy Drake sea passage.

Map of the Antarctic Peninsula featuring the James Ross Archipelago (Credit: The Scientific Committee on Antarctic Research, Antarctic Digital Database Map Viewer)

This photo was taken in the northern Ulu Peninsula, which is the northernmost part of the relatively large James Ross Island and the largest ice-free area in the Antarctic Peninsula region. The island’s characteristic appearance is formed by Late Neogene volcanic rocks (3-7 million years old) over fossil rich Late Cretaceous sandstones (66-120 million years old).

In the photo we are looking from a higher marine terrace at the Santa Martha Cove, the ‘home’ to the 2016 Brazilian Antarctic expedition, towards the steep cliffs of Lachman Crags, a characteristic mesa formed by Late Neogene lava flows. The Lachman Crags mesa, the Spanish word for tablelands, dominates the landscape of the northern part of the Ulu Peninsula. Above the cliffs visible in the photo, a glacier covered plateau stretches to the Northwest.

The marine terrace on which the tent is standing is comprised of a flat area that has been ice-free for approximately 6000 years and thus makes for a great model system to study soil development after glacial retreat. The ground is composed of a mixture of volcanic rocks and Cretaceous sandstones rich in all sorts of fossils, from fossilised wood to shark teeth, ammonites and reptile bones.

The strong winds that can start in Antarctica from one moment to the other and the very low precipitation led to the characteristic desert pavement, with stones sorted in a flat arrangement on top of the fine textured, deeply weathered permafrost soils. Although these soils host a surprisingly high number of microorganisms, most terrestrial life is restricted to wetter areas surrounding fresh water lakes and melt water streams. Thus lakes and snow meltwater-fed areas make for higher primary production of algae and mosses, fostering biodiversity and soil development by organic matter input.

As there are no larger bird rookeries on James Ross Island the only way sea-derived nutrients reach the Ulu Peninsula is by a rather grim feature:  dead seal carcasses that lie distributed across the lowlands (< 150 m asl) of the Ulu Peninsula. Carcasses fertilise the soils in their direct vicinity while slowly decomposing over decades, thus feeding small patches of lichens and mosses within the barren cold arid desert. The region is thus an illustration of the harsh Antarctic environment where even Weddell seals, animals that are well adapted for the living in dense pack ice during the polar night, die when losing track on land on the way to the water.

By Carsten Müller, Technical University of Munich Chair of Soil Science, Germany

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

Imaggeo on Mondays: Patterns in the peatland

Imaggeo on Mondays: Patterns in the peatland

This magnificent pattern is the result of hundreds and hundreds of years of evolution. In this structured minerotrophic peatland in Northern Quebec (Canada), which can also be called a string fen or aapa mire, the green peat ridges (or strings) alternate with water-filled hollows (or flarks). Often flarks are replaced by ponds, which vary in number and size. This pattern of strings and flarks (or ponds) runs perpendicular to the flow of ground water.

Many theories exist to explain the dynamics of this pattern; however, we still do not know the mechanism responsible. Almost all of the present theories suggest that the movement of water could be a major driver of the landscape’s features. The permafrost and frost action, the gradual down-slope slipping, and expansion of peat, the merging of hollows, and fire outbreaks are also considered to be potential factors. Further research is going on to deeply understand the complex relation between abiotic and biotic factors influencing how the string fens take shape.

Vegetation in string fens differs between strings and flarks. Strings are dominated by sedges like Carex exilis, Trichophorum cespitosum, Eriophorum angustifolium, and dwarf birches (Betula glandulosa). On the other hand, flarks or ponds are dominated by Menyanthes trifoliata (also known as bogbean), depending on the level of the water within the ground. The peat moss Sphagnum subfulvum is found on strings while a different species of moss Sphagnum majus can be found on floating mats, at the margin of ponds.

This type of peatland is abundant in the boreal regions of the world, and its predominance can be explained by cooler weather conditions, that limit Sphagnum growth and foster greater surface water flow, especially when the snow melts in the spring.

I encountered this beauty on a field trip during summer of 2016 when I was looking for fens burned by natural wildfires. Unfortunately (or not) this one did not burn, even though all the forests at the margin of the peatland burned pretty heavily. Indeed, the ground of the burned forests was covered by Polytrichum strictum, a pioneer moss known to colonize burned forests or peatland soils (look for the apple green vegetation in the bottom of the photograph).

By Mélina Guêné-Nanchen, Laval University, Québec, Canada

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

Geosciences Column: Using volcanoes to study carbon emissions’ long-term environmental effect

Geosciences Column: Using volcanoes to study carbon emissions’ long-term environmental effect

In a world where carbon dioxide levels are rapidly rising, how do you study the long-term effect of carbon emissions?

To answer this question, some scientists have turned to Mammoth Mountain, a volcano in California that’s been releasing carbon dioxide for years. Recently, a team of researchers found that this volcanic ecosystem could give clues to how plants respond to elevated levels of carbon dioxide over long periods of time. The scientists suggest that studying carbon-emitting volcanoes could give us a deeper understanding on how climate change will influence terrestrial ecosystems through the decades. The results of their study were published last month in EGU’s open access journal Biogeosciences.

Carbon emissions reached a record high in 2018, as fossil-fuel use contributed roughly 37.1 billion tonnes of carbon dioxide to the atmosphere. Emissions are expected to increase globally if left unabated, and ecologists have been trying to better understand how this trend will impact plant ecology. One popular technique, which involves exposing environments to increased levels of carbon dioxide, has been used since the 1990s to study climate change’s impact.

The method, also known as the Free-Air Carbon dioxide Enrichment (FACE) experiment, has offered valuable insight into this matter, but can only give a short-term perspective. As a result, it’s been more challenging for scientists to study the long-term impact that emissions have on plant communities and ecosystems, according to the new study.

FACE facilities, such as the Nevada Desert FACE Facility, creates 21st century atmospheric conditions in an otherwise natural environment. Credit: National Nuclear Security Administration / Nevada Site Office via Wikimedia Commons

Carbon-emitting volcanoes, on the other hand, are often well-studied systems and have been known to emit carbon dioxide for decades to even centuries. For example, experts have been collecting data on gas emissions from Mammoth Mountain, a lava dome complex in eastern California, for almost twenty years. The volcano releases carbon dioxide at high concentrations through faults and fissures on the mountainside, subsequently leaving its forest environment exposed to the emissions. In short, the volcanic ecosystem essentially acts like a natural FACE experiment site.

“This is where long-term localized emissions from volcanic [carbon dioxide] can play a game-changing role in how to assess the long-term [carbon dioxide] effect on ecosystems,” wrote the authors in their published study. Research with longer study periods would also allow scientists to assess climate change’s effect on long-term ecosystem dynamics, including plant acclimation and species dominance shifts.

Through this exploratory study, the researchers involved sought to better understand whether the long-term ecological response to carbon-emitting volcanoes is actually representative to the ecological impact of increased atmospheric carbon dioxide.

Remotely sensed imagery acquired over Mammoth Mountain, showing (a) maps of soil CO2 flux simulated based on accumulation chamber measurements, shown overlaid on aerial RGB image, (b) above-ground biomass (c) evapotranspiration, and (d) normalized difference vegetation index (NDVI). Credit: K. Cawse-Nicholson et al.

To do so, the scientists analysed characteristics of the forest ecosystem situated on the Mammoth Mountain volcano. With the help of airborne remote-sensing tools, the team measured several ecological variables, including the forest’s canopy greenness, height and nitrogen concentrations, evapotranspiration, and biomass. Additionally they examined the carbon dioxide fluxes within actively degassing areas on Mammoth Mountain.

They used all this data to model the structure, composition, and function of the volcano’s forest, as well as model how the ecosystem changes when exposed to increased carbon emissions. Their results revealed that the carbon dioxide fluxes from Mammoth Mountain’s soil were correlated to many of the ecological variables analysed. Additionally, the researchers discovered that parts of the observed environmental impact of the volcano’s emissions were consistent with outcomes from past FACE experiments.  

Given the results, the study suggests that these kind of volcanic systems could work as natural test environments for long-term climate research. “This methodology can be applied to any site that is exposed to elevated [carbon dioxide],” the researchers wrote. Given that some plant communities have been exposed to volcanic emissions for hundreds of years, this method could help paint a more comprehensive picture of our future environment as Earth’s climate changes.

By Olivia Trani, EGU Communications Officer

References

Cawse-Nicholson, K., Fisher, J. B., Famiglietti, C. A., Braverman, A., Schwandner, F. M., Lewicki, J. L., Townsend, P. A., Schimel, D. S., Pavlick, R., Bormann, K. J., Ferraz, A., Kang, E. L., Ma, P., Bogue, R. R., Youmans, T., and Pieri, D. C.: Ecosystem responses to elevated CO2 using airborne remote sensing at Mammoth Mountain, California, Biogeosciences, 15, 7403-7418, https://doi.org/10.5194/bg-15-7403-2018, 2018.

Imaggeo on Mondays: Bristlecone pines, some of Earth’s oldest living life forms

Imaggeo on Mondays: Bristlecone pines, some of Earth’s oldest living life forms

About 5,000 years ago, the ancient city Troy was founded, Stonehenge was under construction, and in the rugged Sierra Nevada mountain range, groves of bristlecone pine seedlings began to take root. Many of these pines are still alive today, making them the world’s oldest known living non-clonal life forms. Raphael Knevels, a PhD student from the Friedrich-Schiller-University’s Department of Geography in Jena, Germany explains why these particular species live so long.

On a field trip in the western United States, my colleagues and I traveled to various interesting spots in the beautiful and scenic diverse California. One of the most unforgettable places we visited during our trip was the Inyo National Forest in the eastern Sierra Nevada mountain range. Here, we could experience the oldest known individual living life forms on Earth: the bristlecone pines.

Scientific interest in the bristlecone pine started around 1953 with Edmund Schulman, a dendrochronologist from the University of Arizona who studied tree-rings to better understand the impact of past climate change. Schulman and his scientific team discovered many ancient trees, some older than 4,000 years. But why do bristlecone pines persist so long?

Bristlecone pines are located in the upper-mountain ranges of the Great Basin of the western United States in altitudes of 2,700 to 3,700 m. The environment is relatively arid with an annual rainfall of around 315 mm. They grow typically on limestone outcroppings that provide sparse ground cover and scarce litter, making the trees relatively safe from wildfires. Especially at high-elevation sites, the population is isolated, stands are open and productivity is low. Scientists believe that past fires in the region have been infrequent, usually small, and of low-severity, with an expected likelihood of an outbreak occurring once in 300 years. Moreover, their retention of needles for 20 to 30 years provide a kind of stable photosynthetic capacity that can carry a tree over several years of stress. Some species have even shown drought-sensitivity records in their growth-ring sequences of almost 1700 years.

With the ongoing global warming, the effects that our changing climate will have on the bristlecone pine are assumed to be severe; increasing temperatures can lead to a higher pine mortality rate and can introduce invasive weeds and lower elevation conifers. This can in turn change the composition of organic material on the soil surface, and as a result, make the region more prone to wildfire.

Generally, the ecosystem of the bristlecone pine is still not fully understood, and the tree’s longevity remains a mystery. More research must be done to better understand the pine’s relationship with its environment and create appropriate adaption strategies to manage this species within a human-introduced changing climate. On that the trees continues to be the longest-lived life forms on Earth.

By Raphael Knevels, Friedrich-Schiller-University Jena (Germany)

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.