Soil biodiversity
According to the Australian Department of the Environment and Water Resources, biodiversity is "the variety of life: the different plants, animals and micro-organisms, their genes and the ecosystems of which they are a part.
Conversely, biological activity is a primary factor in soil's physical and chemical formation.
[2] Soil provides a vital habitat, primarily for microbes (including bacteria and fungi), but also for microfauna (such as protozoa and nematodes), mesofauna (such as microarthropods and enchytraeids), and macrofauna (such as earthworms, termites, and millipedes).
[2] The primary role of soil biota is to recycle organic matter that is derived from the "above-ground plant-based food web".
[4] A "subtle synchrony" is how Baskin (1997) describes the relationship between the soil and the diversity of life above and below the ground.
[6] The height of the plants has also seen a marked restriction when grown in acidic soils, as seen in American and Russian wheat populations.
[8] Particularly concerning is the evidence showing that this acidification is directly linked to the decline in endangered species of plants, a trend recognized since 1950.
[10] Extremely low pH soils may suffer from structural decline as a result of reduced microorganisms and organic matter; this brings a susceptibility to erosion under high rainfall events, drought, and agricultural disturbance.
[6] Selectively breeding the stronger plants is a way for humans to guard against increasing soil acidity.
[6] Further success in combatting soil acidity has been seen in soybean and maize populations suffering from aluminum toxicity.
It is now uncontested that microbial exudates dominate the aggregation of soil particles and the protection of carbon from further degradation.
[17] For example, cultivation causes the mechanical mixing of the soil, compacting and sheering of aggregates and filling of pore spaces—organic matter is also exposed to a greater rate of decay and oxidation.
Continued crop cultivation eventually results in significant changes within the soil, such as its nutrient status, pH balance, organic matter content, and physical characteristics.
In high levels, sodium ions break apart clay platelets and cause swelling and dispersion in soil.
If changing the soil, one must add calcium to displace the excess exchangeable sodium that causes the disaggregation that blocks water flow.
Soil erosion occurs naturally, but human activities can greatly increase its severity.
[31][34] For example, attempts at afforestation in the northern Loess Plateau, China, have led to nutrient deprivation of organic materials such as carbon, nitrogen, and phosphorus.
The excessive availability of chloride in soil can trigger physiological disorders in plants and microorganisms by decreasing cells' osmotic potential and stimulating the production of reactive oxygen species.
The interconnection spans vast spatial and temporal scales; the major degradation issues of salinity and soil erosion, for instance, can have anywhere from local to regional effects – it may take decades for the consequences of management actions affecting soil to be realised in terms of biodiversity impact.
Examples of such approaches as applied to an agricultural setting include the application of lime (calcium carbonate) to reduce acidity so as to increase soil health and production and the transition from conventional farming practices that employ cultivation to limited or no-till systems, which has had a positive impact on improving soil structure.
[41] Soils encompass a huge diversity of organisms, which makes biodiversity difficult to measure.
