There's a world under the feet

The ground is not a solid block: mineral particles and organic matter share space with water, air and organisms. Rock, climate and living things all take part in soil formation.

Looking only at the surface leaves much life undiscovered. This explanation helps explore gardens and woods, but does not replace an analysis of Cabeceiras’s soils.

Life is not evenly distributed. FAO describes areas of intense activity near roots, where plant remains accumulate, and along the walls of earthworm tunnels. The immediate surroundings of a root have a name: the rhizosphere. Thinking about these small zones helps explain why two nearby pieces of soil can offer different conditions to organisms.

Some inhabitants are unlikely to be seen on a walk. Bacteria take part in transforming organic matter; some associate with roots and contribute to nitrogen fixation. Fungi also break down remains and can form relationships with plants. They do not all do the same job: soil brings together overlapping activities, from feeding to the transformation of materials.

A covering of leaves is more than a finishing layer on a woodland floor. It is material that can feed this community. In the interview published by the Gulbenkian, the researchers recommend retaining some leaf litter in green spaces and avoiding frequent deep disturbance of the soil. These are general conservation guidelines, not an assessment or prescription for every plot in the municipality.

Many earthworms eat plant remains or carry them through the tunnels they dig. A fallen leaf can therefore continue its journey beneath the surface.

By transforming organic matter and changing where they live, these animals act as ecosystem engineers. This is a general role, not an identification of species present in the municipality.

They do not all feed in the same place. FAO’s overview distinguishes worms that use debris near the surface from those feeding in deeper layers. Tunnels vary too: mainly vertical or horizontal, long-lasting or temporary shelters against unfavourable conditions.

Material passes through the digestive tract and returns to the soil as casts that bring together particles, organic matter and microorganisms. The work is therefore more than digging a tunnel: it involves transport and transformation. The tunnels support aeration, drainage and root penetration. Activity on the scale of a small animal can change the space available for water, air and other living things.

These differences explain why we should not imagine all earthworms as copies of one species. The story describes general roles and ways of life; it cannot count populations or measure a plot’s fertility just from the presence of one animal.

Some mites and springtails feed on fungi in the soil. This relationship connects small animals with leaf decomposition and nutrient cycling.

Springtails are microarthropods, only a few millimetres long. Many have a forked structure, the furcula, that lets them jump and escape predators. The description helps us imagine hidden soil life; it does not identify species present in Cabeceiras.

Scale helps tell this story. According to FAO, mites and springtails feeding on bacteria and fungi can affect microbial communities in a small area of soil. At the same time, larger animals change the structure in which that life develops. Climate, plants and soil properties complete the setting.

A food web beneath our feet is therefore not an isolated sequence of meals. What one organism eats and the spaces another transforms can influence each other. Following a fallen leaf to fungi and small animals is a way into that web, without assuming that all springtails have exactly the same diet.

A fungus does not need to swallow a leaf to use its nutrients. The mycelium releases enzymes outside itself; these break organic matter into simpler compounds, which the hyphae then absorb.

The network of threads also grows and branches. Connections between hyphae allow nutrients to travel to other parts of the mycelium. Something that seems motionless may therefore be exploring new spaces and redistributing resources without a mushroom appearing on the surface.

Growth also follows the distribution of food. The Australian National Botanic Gardens describe more branching and slower advance in nutrient-rich areas; where nutrients are scarce, hyphae may lengthen faster and branch less. The network does not always need the same density.

Some fungi form cords of hyphae called rhizomorphs. These can help cross gaps between food sources, such as two separate pieces of wood. On reaching fresh wood, the hyphae may branch and occupy it. This explains growth strategies, not a confirmed description of any thread found on a walk.

A fallen leaf can become food for decomposer fungi. They absorb nutrients from dead organic matter and help recycle it. The material matters: some fungi are associated with leaves, wood or humus. Decomposition describes a feeding relationship; the shape of a cap alone does not explain that way of life.

Protecting this underground life also involves how soil is treated. In the Gulbenkian Garden interview, Susana Gonçalves explains that excessive soil disturbance and compaction can damage mycelial networks. This is general conservation guidance, not an assessment of any particular piece of land in the municipality.

Names offer clues to the growing surface too: foliicolous fungi grow on fallen leaves, lignicolous fungi on wood and humicolous fungi in decaying plant remains. These words describe where they live, not species names. In the same landscape, different materials offer different food possibilities; leaving a leaf or branch in place also preserves part of that context.

In mycorrhizas, a plant and a fungus form a partnership. The plant supplies organic compounds; the mycelium associated with the roots helps obtain water and nutrients.

Oaks, chestnuts and pines can take part in these relationships. A nearby tree gives an observation context, but does not reveal a mushroom’s identity on its own.

Researcher Susana Gonçalves also distinguishes ectomycorrhizas: in these associations, the fungus surrounds the root tips. This example shows that there are different kinds of relationships between plants and fungi, beyond the visible appearance of mushrooms.

The partnership extends the area from which the plant can obtain resources: its roots connect with the fungal network. But the participants are not always the same. Some fungi can associate with several plants, while others have very specific partners. Knowing the trees in a place therefore helps us understand the environment without replacing identification of the fungus.

Water flowing over the surface can carry soil and nutrients into waterways. The municipal environmental report of February 2025 connects this process with erosion and incorrect use of fertilisers rich in phosphorus and nitrogen. Excessive nutrient enrichment can encourage eutrophication, changing the aquatic environment.

The document also distinguishes groundwater: it notes that excessive use of nitrogen fertilisers can contribute to nitrate accumulation and increased salinity. What happens on the land therefore matters both to the water we see flowing and to water underground.

These are potential pressures described in an environmental assessment. They do not identify a discharge in a particular field or let us assess a river by appearance. To understand the system, connect land, surface runoff and aquifers while keeping general possibilities separate from measurements at a site.

Studying a river involves knowing which organisms live in it and how abundant they are. The Portuguese Environment Agency includes benthic invertebrates among the elements used in biological assessment, alongside other groups such as fish and plants.

Assessment also considers chemical, physical-chemical and hydromorphological aspects. Observations, sampling and analysis need to be combined: clear water or a single animal is not enough to classify a river. This explanation does not assign a current status to Cabeceiras’s watercourses.