Whether referring to humans, plants, or animals, we all live within interconnected communities where giving and receiving resources are essential for the collective flourishing of all. This concept is easily transferable to any ecosystem: just as humans have unique roles in society (‘Luckily, we are all different in our way’), so too do plants and animals contribute differently to the Earth’s nutrient cycle. To understand the bigger picture, the following lines will delve into the importance of soil organisms, both microorganisms (archaea, fungi, bacteria, and protists) and soil fauna (nematodes, mesofauna, and macrofauna), and their roles in maintaining ecosystem health.
What is nature’s nutrient cycle?
Often referred to as the ‘biogeochemical cycle,’ nature’s nutrient cycle is the ongoing process through which essential elements and compounds circulate within Earth’s ecosystems. These cycles involve the transfer of nutrients between the living (biotic) components, such as plants, animals, and microorganisms, and the non-living (abiotic) components, including soil, water, and the atmosphere.
Key nutrient cycles include:
- The nitrogen cycle encompasses various processes, including nitrogen fixation, nitrification, assimilation, ammonification, and denitrification. It transforms atmospheric nitrogen into forms usable by plants and returns it to the atmosphere;
- The carbon cycle encompasses processes like photosynthesis, respiration, decomposition, and combustion. It regulates the flow of carbon among the atmosphere, biosphere, oceans, and geosphere;
- The phosphorus cycle refers to the movement of phosphorus through rocks, soil, water, and living organisms. Unlike other cycles, it doesn’t have a gaseous phase and mainly involves weathering of rocks, absorption by organisms, and sedimentation;
- The sulfur cycle involves the movement of sulfur through the atmosphere, lithosphere, and biosphere via volcanic activity, weathering, microbial activity, and atmospheric deposition.
These cycles are fundamental in maintaining nutrient balance, supporting plant growth, animal health, and ecological stability. Disruptions to these cycles, such as pollution or excessive use of fertilizers, can lead to environmental issues, including eutrophication, climate change, and biodiversity loss.
How do microorganisms benefit soil function?
Microorganisms are vital to soil health, playing a central role in the Earth’s nutrient cycles. They decompose organic matter, releasing essential nutrients necessary for plant growth, and transform nutrients into bioavailable forms. Their activity improves soil structure, enhances aeration, and increases water retention, all of which support healthy ecosystems.
Archaea, Fungi, and Bacteria
The roles of Archaea, Fungi, and Bacteria are fundamental to soil nutrient dynamics, forming the backbone of Earth’s nutrient cycle and supporting life.
- Archaea such as Nitrososphaera viennensis and Nitrosocosmicus exaquare are ammonia-oxidizing archaea that facilitate nitrification, converting ammonia into nitrite, a key step in nitrogen cycling. They also help mitigate greenhouse gases by controlling nitrogen oxide emissions;
- Bacteria, through species like Bacillus subtilis, promote plant growth through antibiotic production and soil health enhancement, while Pseudomonas fluorescens acts as a biocontrol agent, suppressing soil-borne pathogens and supporting root health;
- Symbiotic fungi such as Glomus intraradices (also known as ‘Rhizophagus irregularis’) form mycorrhizal associations with plant roots, increasing phosphorus uptake. Trichoderma virens stimulates plant resistance and promotes root development.
Mesofauna
Mesofauna, the small yet mighty contributors to soil health, also play an essential role in maintaining the balance of nutrient cycles within ecosystems. Their presence indicates a healthy soil environment and supports the overall nutrient cycle, which is vital for sustaining plant life and, ultimately, life on Earth.
- Among the organisms can be found Collembola, commonly known as’ springtails’ – these are vital for decomposing organic matter and enhancing soil fertility;
- Notable species such as Isotoma viridis and Sminthurinus elegans actively participate in breaking down plant residues and facilitating nutrient mineralization.
Macrofauna
Macrofauna species are larger soil creatures that are indispensable for sustaining the nutrient cycle, as they play a crucial role in maintaining the health and productivity of soil ecosystems. Let’s see what species significantly contribute to this process:
- Lumbricidae (Lumbricus terrestris) act as’ natural soil engineers’ by burrowing and creating channels that improve soil aeration and water infiltration. They consume organic matter and excrete nutrient-rich casts, enhancing soil fertility. Also, Lumbricidae facilitate the breakdown of organic material, releasing essential nutrients for plant uptake;
- Arachnida (Pseudoscorpiones) prey on soil-dwelling pests and other small invertebrates, helping regulate soil microbial communities. They contribute to the decomposition process indirectly by influencing the populations of other decomposers.
The role of nematodes
Nematodes, the microscopic worms, regulate pest populations and decompose organic matter, thus supporting plant health and growth. A mixture of different nematode species can enhance soil health by exploiting their diverse feeding and predatory behaviors:
- Bunonema species feed on bacteria, aiding nutrient cycling;
- Clarkus and Mylonchulus sigmaturus are predatory nematodes that control pest populations;
- Steinernema species are entomopathogenic, targeting insect pests and reducing their impact.
Protists
Protists enhance nutrient accessibility and maintain soil health as well, contributing to the overall balance of ecosystems. Their activities help sustain soil fertility and promote healthy plant growth.
- Euglypha decomposes organic matter, releasing vital nutrients such as nitrogen and phosphorus, and thereby improving soil structure.
Understanding the complex relationships between soil organisms and ecosystem services is essential as global pressures threaten ecological balance. Maintaining healthy ecosystems ensures the sustainability of habitats while also supporting vital functions such as nutrient cycling, climate regulation, and food production.
By deepening our understanding of these complex interactions, we can develop more effective strategies to protect and restore ecosystems, fostering harmonious coexistence with nature in our daily activities, whether in agriculture or other land uses.
‘Before we roll up our sleeves to develop innovative indicators, it is essential first to recognize and understand the diverse microorganisms already thriving in our soils.These tiny yet mighty organisms form the foundation of healthy ecosystems and provide numerous benefits. Being aware of their functions and roles enables us to harness their potential better and promote sustainable land management across Europe‘ – BIOserivcES consortium.