All Things Moss Come to an End
Presenting the scientific theses in July, and submitting my printed thesis and receiving my degree in November.
After two challenging years, I am happy to share that I recently completed my Master’s in Applied & Environmental Geosciences at Eberhard Karls Universität in Tübingen, Germany. As some of you may know, I previously studied Environmental Biology at Clarion University (now PennWest Clarion); pivoting deeper into the geosciences for my graduate studies was challenging, but rewarding, as I now have an even more holistic understanding of our environment. I took a variety of classes that expanded my knowledge in the environmental sciences including environmental chemistry, human health and environmental risk assessment, geosphere-biosphere interactions, environmental physics, sustainable biotechnology, and many others. To conclude the master’s program, all students must complete a thesis as a culmination of their studies. Naturally, I wanted to combine my love of science and writing by completing a literature review for my thesis. I would love to briefly share the topic of my thesis with you all to celebrate this milestone.
Moss is one of the world’s most ubiquitous life forms, ranging from deserts to boreal and arctic regions. Compared to bare soil, moss-covered soils have higher carbon storage, more nutrients, and greater microbial activity. The presence of moss also affects the water content of the soil. Despite their significant contributions to soil health, mosses are often overlooked in ecosystem assessments, and moss research has been heavily focused on peatlands over the last several decades. Biological soil crusts (biocrusts), on the other hand, is an emerging area of research that has gained traction particularly within the last 10 years.
Biocrusts are akin to the skin of the soil surface, forming a distinguishable layer within the top few centimeters of soil. Biocrusts are a combination of soil microbes (bacteria, archaea, protists, microarthropods, fungi, algae, cyanobacteria), lichens, and bryophytes (moss, liverworts). Varying morphologically depending on the diversity and number of organisms, biocrusts develop in successional stages. Following a disturbance, such as animal trampling, wildfires, or the physical removal of vegetation and topsoil, biocrusts immediately begin to colonize the soil, stabilizing the soil surface and developing in successional stages. Early successional stage biocrusts are typically cyanobacteria-dominant and would be called cyanobacteria biocrusts; an intermediate successional stage occurs where there is a great variety of biocrust types; late successional stage biocrusts are usually lichen and/or moss dominant and would be called lichen biocrusts or moss biocrusts. Of the approximately 11,000 moss species, only about 250 species have been found incorporated in biocrusts.
Moss biocrusts are typically the last successional stage before vascular plants begin to appear. Vascular plants include conifers and angiosperms (flowering plants) that have specialized tissues to conduct water. Mosses are unique because they do not have these specialized tissues, and they instead rely solely on the environment for moisture. Amazingly, mosses can fully dry out for long periods of time and then rehydrate upon the availability of water without incurring physical damage. This is a phenomenon known as poikilohydry, and this makes mosses resilient to hot and dry conditions that are otherwise inhospitable to vascular plants.
So, why are moss biocrusts significant? Moss biocrusts, in particular, modify soil characteristics to create a hospitable environment for vascular plants to grow. Moss tissues are made of complex chemical structures that are hard for soil microbes to decompose; this allows its tissues to accumulate in the soil, enhancing soil organic carbon. Moss biocrusts also stimulate soil microbial activity and increase soil aggregation which is the process of soil particles binding together, increasing its resistance to erosion. Soil aggregates also create a better soil structure, allowing the flow of oxygen, water, and nutrients through soil pores. Although small and inconspicuous, mosses also perform a significant amount of photosynthesis! Overall, moss biocrusts improve the fertility and stability of the soil, which encourages vascular plants to grow.
Soil moisture is also very important for plant growth, but the relationship between moss biocrusts and soil moisture is more complex and varies across ecosystems. Due to their poikilohydric nature, mosses act almost like a sponge, absorbing and holding water in the top 10 centimeters of soil. The textured mossy surface can also help to capture water and reduce runoff. However, this can also mean that mosses intercept precipitation, retain the water in a thick mossy layer, and prevent the percolation of water deeper into the soil. So, sometimes mosses retain water, increase soil moisture, and prevent water runoff and erosion; in other cases, mosses retain too much water and eventually become oversaturated, which leads to runoff, erosion, and decreased soil moisture.
Regardless, it is clear that moss biocrusts play an essential role by acting as ecosystem engineers. Moss biocrusts inhabit the interspaces between sparsely distributed vascular plants in dry, hot desert ecosystems; moss biocrusts are also the first-responders following soil disturbances in our forests. Through their establishment, moss crusts altogether protect, alter, and enhance soil properties, increasing soil organic carbon storage, enhancing soil microbial activity and biodiversity, and improving the soil structure. Despite their diminutive size, mosses and moss biocrusts, specifically, fulfill a necessary niche across global ecosystems.
If you would like to read more about moss biocrusts, please feel free to contact me, and I would be more than happy to share my thesis with you. You can learn more about how moss biocrusts are negatively affected by climate change (such as through increased warming and altered rainfall events) and land disturbances (including karst desertification, wind erosion, mining activity, animal trampling, invasive species, and wildfires) and how moss biocrusts combat these disturbances. You can also learn about a promising area of research for soil remediation that involves using moss propagules to inoculate the bare soil surface. Moss biocrusts are truly fascinating, and there is still so much more to learn and research to be done!
Places around Tübingen:
(1) A view from the Neckarbrücke of the colorful houses lining the Neckar River (Image by Rachel Dressler),
(2) The Tübingen Rathaus (townhall) in the city center,
(3) The Schloß Hohentübingen clock,
(4) The entrance to Schloß Hohentübingen,
(5-6) Tübingen rooftops from Schloß Hohentübingen,
(7-8) Tübingen Glyptothek statues,
(9-10) Places around Tübingen,
(11) A view of the Neckar River from Schloß Hohentübingen,
(12) A statue of the Wildpferd (wild horse) near the Geo- und Umweltforschungszentrum (Geo- and Environmental Center) where I studied (Images by Faith Forry).
Written by Faith Forry — December 3, 2024
