Melting glaciers in the Himalayas have exposed land underneath, allowing new forms of life to migrate to deglaciated landscapes. Recently, these glacial changes have led to the discovery of the world’s highest altitude vascular plants, made possible by the early colonization of microbes in the space left by retreating glacier ice, according to a recent report in the journal Microbial Ecology.
It was during a 2012 expedition that researchers first recorded six plants at an unprecedented altitude in India, 6,150 meters above sea level. The plants were growing in a small patch of undeveloped soil. The glaciers in the region had rapidly receded since the 1990s due to a spike in temperatures in the region. As a sparsely populated, cold desert with limited rainfall, the northwestern Himalayas present arid and highly stressful conditions to plants. Still, the six plants seemed to be in stable condition, according to the researcher’s report.
Based on the monitored temperature and snow cover, there were only a few weeks per year that these plants could use for growth. The researchers emphasize that these are vascular plants, with tissues that contain vessels that conduct water and dissolved nutrients.
But how does plant life first reach these deglaciated landscapes once the glaciers have receded? By definition, subnival zones are places where plants and microorganisms can grow and refers to the altitudinal zone between the nival zone of permanent snow (nival) and the alpine zone, the highest area of extensive vegetation, characterized by low shrubs, grasses, and cushion plants. Microorganisms such as bacteria and some types of fungi colonize subnival zones within a few years of glacial recession, making way for plants and other life forms.
Bacteria and fungi typically arrive first to the deglaciated landscape because they disperse more easily and are more stress-tolerant. They disperse spores that travel in the wind to reach remote places high in mountainous regions. Because the glaciers have receded from the section of the Himalayas visited by the researchers, an opportunity arrives for microorganisms to live in the soil that was once buried underneath the ice and snow.
There are several biological processes by which these microorganisms help develop the soil and allow plants to grow. For one, many bacteria can carry out photosynthesis, using sunlight to synthesize food from carbon dioxide and water. Some bacteria and fungi can also carry out nitrogen fixation, which is the process of converting nitrogen in the atmosphere to ammonia, more readily absorbed by plants. The nitrogen, in turn, can be used by other organisms. These biological processes help cultivate the soil in deglaciated landscapes by depositing nutrients, which ultimately allow plants to grow. Plant seeds and spores, also dispersed by the wind, make their way to high elevation areas. But once there, the plants rely on microorganisms to supply minerals and fix nitrogen.
Rooey Angel, a coauthor of the report on the high altitude plants, talked to GlacierHub about his team’s findings. “Indeed, microbial colonisation of glacial forefield is crucial for starting soil development processes, release of minerals from soil particles, accumulation of organic carbon and nitrogen fixation,” he said. “However, with respect to nitrogen, it is important to remember that there’s a large effect of atmospheric nitrogen deposition on the forefield ecosystem, which makes nitrogen fixation less crucial.”
Once plants arrive up the mountain, they further enrich the soil in deglaciated landscapes with organic matter and nutrients through a process of rhizodeposition (in which roots release organic compounds into the environment) and by weathering the bedrock. The soil surrounding the plant and containing its roots, known as the rhizosphere, is high in microbial activity. The plants use microorganisms to supply minerals and fix nitrogen, making it impossible for plants to precede microorganisms in colonization. Lack of nitrogen is one of the only biological reasons plants cannot arrive first in newly deglaciated soils.
The specimens located by the researchers included five perennial herbs and one perennial grass, ranging in color and structure. All of the plants were found at high altitudes formerly covered in glaciers, often at elevations from 5,000 to 6,000 meters above sea level. Of the four plants where age could be determined, three were less than 10 years old and one, Ladakiella klimesii, was approximately 15 years old.
The L. klimesii, also known as Alyssum klimesii, is a plant in the mustard family and a close relative of sweet alyssum, a plant commonly grown in gardens for its hardiness and drought tolerance as well as for its profuse white blooms and rich fragrance. The specimen of L. klimesii resembles a tiny gray bush and is 1-3 cm tall and 2-10 cm in diameter. The species is endemic to the Tibetan Plateau and grows in subnival zones. In Ladakh these plants are found in 5,350 to 6,150 meters, with optimum altitudes at 5,800 meters. The researchers emphasize that this new specimen provides evidence of the recent upward migration of plants and rapid changes affecting the western Himalayan slopes.
In addition, the researchers discovered that the roots of the plants harbored several hundred types of microbes; these are termed OTUs or operational taxonomic units, and correspond to species. Other harsh climates like the patches of soil in coastal and interior Antarctic environments have similar OTUs, which demonstrates the remarkable resilience of these microbes.
Thanks to microorganisms cultivating land that had once been covered by glacier ice, researchers have discovered the highest-ever elevation plants, a surprising side effect of climate change. This new record offers testimony both to the profound effects of climate change on ecosystems and to the vigor of the diverse organisms on our planet.