European Atlas of Soil Biodiversity

Abstract

Biodiversity has different meanings depending on the situation and the target audience. For example, the Oxford English Dictionary defines biodiversity as being ¿The variety of plant and animal life in the world or in a particular habitat¿. While this is definition is clearly sufficient for non-specialists, it doesn¿t do justice to the level of biodiversity found in the soil which is teaming with other groups such as fungi, bacteria and archea. Soil is such as diverse system when considered biologically (as well as physically or chemically) it is necessary to include all taxonomic groups. Therefore, throughout this atlas, when referring to ¿soil biodiversity¿ it will be in reference to the variety of all living organisms found within the soil system. ¿Soil biota¿ is term with a similar meaning to soil biodiversity, but is more specific and refers to the complete community within a given soil system. For example, it is possible to say that the soil biota in a grassland soil is generally more diverse than that in an arable system, or that grassland soils generally have higher levels of soil biodiversity than the soil in arable systems. The meaning is the same in both instances. The soil system is extremely complex and varies greatly spatially and over time. Soil itself consists of a ¿mineral¿ portion containing mainly silica and a mixture of trace metals, an ¿organic matter¿ portion containing a large variety of different organic compounds, and vast array of different organisms as well as water in all but the direst soils. Soil can exist at a variety of textures; meaning they have different proportions of sand, silt and clay. It can contain areas of relative dryness, down to micropores which are almost always water filled apart from in times of extreme drought. The level of organic matter content varies both with depth (generally decreasing with depth), and spatially. This high level of heterogeneity means that soil contains an extremely large number of ecological niches which have given rise to a staggering array of biodiversity. Using a taxonomic approach to measure biodiversity, it is often said that more than half the world¿s estimated 10 million species of plant, animal and insects live in the tropical rainforests. However, when this approach is applied to the soil, the level of diversity is often in the range of hundreds of thousands to possibly millions of species living in just 1 handful of soil!