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Soil environment

Soils in natural ecosystems

Soil and its microorganisms and plants are vital for each other’s composition. Acidic, sandy soil can only support hardy species or species with traits that make them able to absorb the limited nutrients in these ecosystems. These species may include plants like sundew, which gets its nutrients by catching insects, or heather, which gets its nutrients by growing with (symbiosis) fungi in the soil, which enables the heather to use the soil’s organic nitrogen. This enables dwarf shrubs like crowberry and common heather (in dry soils) and bell heather (in moist soils) to dominate the plant community and, thus, be the species that create the ecosystem (ecosystem creators). In areas richer in nutrients, more species are able to survive. In such areas, species are able to outperform by growing so large that they shade out the other species. These species include meadowsweet and mercury, but can also include forest trees such as ash and elm. Plants may use chemical warfare in all types of soil, and these consist of plants secreting chemical compounds into the soil that make it difficult for other species to germinate and grow or that the plants contain chemical compounds, such as polyphenols, that make them unpalatable to animals and, in turn, contribute to slowing down the rate of degradation and in this way forming a moor layer. The fact that the species are competing for exclusive rights to the nutrients in the soil affects the soil’s appearance, composition and chemical properties, including its buffer system.

The Department of Bioscience conducts research on the interactions between ecosystems and soil. E.g. we are studying how adding nutrients will exceed the ecosystem’s critical load and, consequently, affect the biodiversity in nutrient poor ecosystems by creating a basis for species that require more nutrients, e.g. purple moor grass, fireweed and trees. Species that outperform the natural heather-dominated community and change the soil, so that the moor layer created by the heather species is degraded and the heather loses its dominance of the nutrient cycle: dce2.au.dk/pub/SR69.pdf.

Studies may also include how a species, such as thyme, secretes chemical compounds in order to dominate the plant community and change the nutrient cycle to exclude other species.

Nature conservation is used to protect non-forest ecosystems from overgrowing. Conservation consists of keeping vegetation low and open to light, using methods such as mowing, burning and grazing. However, no one knows how conservation in the long term may cause imbalances in the nutrient cycle by removing rare nutrients that are only slowly replaced by decomposing minerals and deposition from the air.