Mosses are among the oldest land plants. They are found all over the world, from lush tropical rainforests to the driest deserts and even the windswept hills of Antarctica.
They are everywhere; grows in cracks along roads and paths, on tree trunks, on rocks and buildings, and especially on the ground.
Yet despite this ubiquity, we have a relatively poor understanding of how important they are, particularly the types of mosses that thrive on soil.
New global research on ground mosses, published today in Nature Geoscience, shows they play a crucial role in sustaining life on our planet. Without ground mosses, the earth’s ability to produce healthy soils, provide habitat for microbes, and fight pathogens would be severely limited.
A global survey of ground mosses
The results of the new study suggest we may have underestimated the importance of ground mosses.
Using data from 123 sites on all continents, including Antarctica, we show that soil under mosses has more nitrogen, phosphorus and magnesium and greater activity of soil enzymes than bare surfaces without plants.
In fact, mosses affect all major soil functions, increasing carbon sequestration, nutrient cycling, and organic matter breakdown. These processes are critical to sustaining life on Earth.
Our modeling revealed that ground mosses cover a huge area of the planet, about 9 million square kilometers – the size of China. And that’s not counting mosses from boreal forests, which weren’t included in the study.
The strength of the effect of mosses on the soil depends on their growing conditions. They have the strongest effect in natural environments with low productivity, such as B. Deserts. They are also more important on sandy and saline soils and where rainfall varies greatly.
Not unexpectedly, mosses have the greatest impact on soils where vascular plants—those that contain specialized tissues to channel water and minerals—are sparse.
An intimate connection
Mosses lack the piping that allows vascular plants to grow tall and draw water underground. As a result, they remain relatively short and develop an intimate connection with the top layers of soil.
Mosses are extremely absorbent and can attract dust particles from the air. Some of these particles are incorporated into the underlying soil. It is therefore not surprising that they have such a powerful effect on soils.
Our modeling shows that mosses globally store 6.4 gigatons more carbon than soils without vegetation.
Losing just 15% of global ground moss cover would equate to global carbon emissions from all land use changes over a year such as deforestation and overgrazing.
Not all mosses are the same
We have also found that some mosses are more effective than others at promoting healthy soil. Long-lived mosses have tended to be associated with more carbon and better control of soil pathogens.
The ability of mosses to provide ecosystem services and support a diverse microbial, fungal, and invertebrate community was strongest in sites with high coverage of mat- and turf-forming mosses, such as sphagnumwhich are widespread in boreal forests.
Soil is a huge reservoir of soil pathogens, but soil under mosses had lower levels of plant pathogens. Mosses can help reduce pathogen loads in soils. This ability possibly arose when mosses evolved as land plants.
A special group in the desert
A special type of moss thrives in deserts. They either live hard (perennial mosses) or die young (annual mosses).
Mosses from the Pottiaceae family are uniquely adapted to life in arid and inhospitable conditions. Many have specialized structures that allow them to survive when water is scarce. These include boat-shaped leaves with long hairy tips that help channel water to the center of the plant. Some mosses twine around their trunk to reduce the area exposed to the sun and conserve moisture.
In addition, desert mosses protect the soil from erosion, affect the flow of water through the upper layers, and even change the chances of plant seedlings surviving.
Other mosses have special moisture-absorbing cells (papillae) that swell and provide them with moisture storage when they are dry.
Our global study showed that mat and turf-forming mosses such as sphagnum had the strongest positive impacts on microbial, fungal and invertebrate diversity, as well as critical services such as nutrient supply. Predictably, longer-lived mosses supported more soil carbon and had better control over plant pathogens than short-lived mosses.
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Protect the mosses
Overall, our work shows that mosses influence important soil processes and function in the same way as vascular plants. Their impact may not be as strong, but their total coverage means mosses are potentially just as significant when summed across the globe.
But mosses are increasingly threatened worldwide; Disruptions from ranching, over-harvesting, deforestation, and even climate change are the biggest threats.
We need greater recognition of the services that ground mosses provide to all life on this planet. This means better education about their positive benefits, identifying and mitigating the top threats they face, and incorporating them into routine surveillance programs.
Ground mosses are ubiquitous, but their future is far from assured. They are likely to play an increasingly important role as vascular plants decline under predicted hotter, drier, and more variable global climates.
David John Eldridge, Professor of Dryland Ecology, UNSW Sydney and Manuel Delgado-Baquerizo, Ecosystem Ecologist, Spanish National Research Council, Consejo Superior de Investigaciones Científicas (CSIC)
This article has been republished by The Conversation under a Creative Commons license. Read the original article.
also read | Let’s protect nature, but not only for the benefit of the people
