GeoLog

Biogeosciences

Imaggeo on Mondays: The ancient guard of Altai

Imaggeo on Mondays: The ancient guard of Altai

In the heart of Eurasia, an ancient stone statue overlooks the expanse of the Kurai Valley and the Altai Mountains in Russia. This relic was crafted more than a thousand years ago, sometime during the 6th or 7th century. A Turkish clan that inhabited the region, known as the First Turkic Khaganat, would often erect stones as monuments of funeral rituals.

Natalia Rudaya, who took this photograph, is a senior researcher at the Institute of Archeology and Ethnography of the Siberian Branch of the Russian Academy of Sciences. She and her research team were taking sediment cores from the bottom of Lake Teletskoye, the largest lake in the Altai Mountains, in southeastern West Siberia, close to the photograph’s location.

The lake samples give clues on how the local environment has shifted over the last couple thousand years, and how these changes might have influenced the human societies that inhabited the Altai Mountains. Investigating palaeoclimates and past vegetation shifts are also important for understanding how current climate change will affect Earth’s ecosystems.

By analysing sediment cores, Rudaya and her colleagues were able to reconstruct the region’s environmental and climatic history. Their results showed that in the beginning of the mid- to late- Holocene (roughly 4,250 years ago), the region exhibited a relatively cool and dry climate, and the land surface was dominated by Siberian pine and Siberian fir forests. However, starting around 3,900 years ago, plant populations faced significant deforestation for roughly three centuries. Then 3,600 years ago, dark coniferous mountain taiga began to extend across the territory; the sediment samples also show that this forest expansion coincided with slight increases in temperature and humidity. This climate persisted for roughly 2,000 years, then the mountainous environment faced cooler temperatures once again.

References

Rudaya, N. et al.: Quantitative reconstructions of mid- to late holocene climate and vegetation in the north-eastern altai mountains recorded in lake teletskoye, Global and Planetary Change., 141, 12-24, 2016

Huang, X. et al.: Holocene Vegetation and Climate Dynamics in the Altai Mountains and Surrounding Areas, Geophysical Research Letters, 45, 6628-6636, 2018.

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: 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/.

Imaggeo on Mondays: Namibia’s mysterious fairy circles

Imaggeo on Mondays: Namibia’s mysterious fairy circles

The grassy Namibian desert is pock-marked with millions of circular patches of bare earth just like these shown in the picture between linear dunes.

Viewed from a balloon, they make the ground look like a moonscape. Commonly known as fairy circles, the patches range from two to 12 metres across and appear in a 2000 kilometre strip that stretches from Angola to South Africa.

For many decades, the fairy circles extending uniformly over vast areas in the landscape, have puzzled laymen and scientists alike. They are subject to a lively debate and contrary hypotheses on their origin exist. Some researchers claim fairy circles were caused by termites, others propose they are the result of vegetation self-organization.

Description by Hezi Yizhaq, as it first appeared on imaggeo.egu.eu.

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: Arctic cottongrass in Svalbard

Imaggeo on Mondays: Arctic cottongrass in Svalbard

In the High Arctic, where vegetation is limited in height, cottongrass stands out as some of the tallest plant species around.

This photo shows a wispy white patch of Arctic cottongrass growing amongst other tundra vegetation in the Advent river floodplain of Adventdalen, a valley on the Norwegian archipelago island Svalbard.

Svalbard is of particular scientific interest as it is a relatively warm region for its high latitude. This is due to the North Atlantic Ocean, which transports heat from lower latitudes to Svalbard’s shores.

The photo was taken in September 2014, towards the end of the region’s growing season. In the background, you can see that the season’s first snow had already blanketed the valley’s neighboring mountain tops.

Cottongrass generally loves wet conditions and scientists sometimes even use this plant genus (Eriophorum) as an indicator of the ground’s fluctuating water level, especially in areas that begin to develop peat, an accumulation of more of less decomposed plant material in wet environments. The waters feeding this region’s wetland come from melted snow and ice travelling down the adjacent mountains and floodwater from the Advent river, which is primarily meltwater fed.

Arctic cottongrass also can exchange gases with their underground environment through their roots and even have been shown to alter the local carbon budget of regions where they grow. It is therefore a very important species to account for when studying permafrost carbon dynamics.

Gunnar Mallon, currently a teaching fellow at the University of Sheffield (UK), took this photo while on a fieldwork expedition together with Andy Hodson, a glaciology professor at the University Centre in Svalbard, for the LowPerm project.

The LowPerm project aimed to understand how nutrients are transported within permafrost landscapes in Norway and Russia and how that may affect the production of greenhouse gases, such as carbon dioxide (CO2) and methane (CH4). The study brought together scientists from the UK, Norway, Denmark and Russia and results from the extensive field and laboratory work are currently being analysed and made ready for publication.

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/.