Biogeosciences News

After a Glacier Retreats, Plants Thrive Thanks to Phosphorus

Grasses, small flowers, and mosses colonize glacial till in the Peruvian Andes when researchers apply a phosphorus fertilizer, an ecological surprise with implications for carbon sequestration.

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High in the Peruvian Andes, Puca glacier is receding and exposing lifeless, rock-covered land in its wake, like other glaciers around the world. Researchers have now shown that a single dose of phosphorus fertilizer kick-starts plant growth on these barren stretches of land.

This finding comes as a surprise because nitrogen, rather than phosphorus, has long been pegged as the limiting nutrient in developing ecosystems. As glacial retreat yields new landscapes, the exposed slopes are potentially prone to mudslides. Spurring plant growth will help to stabilize these slopes and sequester the atmospheric carbon that is contributing to climate change, the research team suggests.

This study shows that “phosphorus on its own increases plant and microbial abundance by a couple orders of magnitude,” said Duncan Menge, an ecologist at Columbia University in New York City who was not involved in the research.

A Martian Landscape

In 2010, Steve Schmidt, a microbial ecologist at the University of Colorado Boulder, and his colleagues traveled to Puca glacier in southern Peru. They were there to study whether plant and microbial life might be coaxed into existence in the harsh, high-altitude environment. Schmidt and his team focused on the area exposed by the receding Puca glacier, which has been retreating by about 30 meters per year. Some of the rocks revealed by the glacier were tinged red, evoking landscapes on another planet. “It looked like Mars,” said Schmidt.

Schmidt and his colleagues sprayed solutions containing nitrogen and phosphorus onto square meter plots. These common ingredients in fertilizers are “the two most essential elements for life besides carbon,” said Schmidt. Would a single pulse of nutrients be sufficient to kick-start life, the researchers wondered, in a frigid, arid environment 5,000 meters above sea level?

An Explosion of Plant Life

Over the next 6 years, Schmidt and his team returned to Puca glacier five times to carefully analyze the plots for signs of microbial life and plant life like grasses, small flowers, and mosses. By 2013, they started seeing differences between the plots that had received phosphorus and those that hadn’t. “It was really obvious that the plants were just taking off” in the phosphorus-infused plots, said Schmidt. “That was totally unexpected.”

Plant and microbial life was likely starved for phosphorus because the element was still locked up in rocks, Schmidt and his colleagues hypothesized. In more temperate environments, bacteria and weathering events like acid rain leach phosphorus from rocks. But high in the Andes, rainfall is scarce. Nitrogen, on the other hand, was already present in the soil—cyanobacteria were functioning as “nitrogen fixers,” capturing nitrogen from the atmosphere and converting it into forms that plants could use.

Three years later, the researchers counted hundreds of plant stems in the eight plots fertilized with only phosphorus or both phosphorus and nitrogen. The four plots fertilized with only nitrogen contained about a fifth as many stems, and the four plots that had received only water had almost no stems. Complementary analyses, including remote chlorophyll sensing and measurements of plant coverage, revealed similar results. The researchers reported their results last month in Science Advances.

Thriving Plants Protect the Land and Air

Demonstrating that plant life can thrive in the harsh environment around Puca glacier is more than just a proof of concept, the team maintains. If you can get these lands to be productive, they sequester more of the atmospheric carbon that is leading to climate change, said Schmidt. Plants also stabilize slopes against mudslides, a perennial problem in steep alpine environments.

These results reveal that life can thrive in seemingly inhospitable places, Schmidt suggests. This work “expands the boundaries of life.”

—Katherine Kornei (email: [email protected]; @katherinekornei), Freelance Science Journalist

Citation: Kornei, K. (2018), After a glacier retreats, plants thrive thanks to phosphorus, Eos, 99, https://doi.org/10.1029/2018EO100579. Published on 06 June 2018.
Text © 2018. The authors. CC BY-NC-ND 3.0
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