ENCYCLOPEDIA OF SOIL SCIENCE, VOLS I-III, 3RD EDITION, ss.553-557, 2017 (SCI-Expanded)
The soil component of the agro system consists of plant roots, microflora, fauna, organic matter, and the abiotic geochemical matrix. Soil can be a sink for atmospheric carbon dioxide and mitigate the "greenhouse effect." Soil is a complex living and fragile system that must be protected and managed for its long-term stability and productivity. Soil degradation has been defined as the loss of a soil's capacity to produce crops and also as the antithesis of soil resilience and quality, which describe biological degradation as the decline in soil organic matter and biomass carbon, a decrease in diversity and activity of soil flora and fauna, or the indiscriminate use of chemicals and pollutants. The increasing loss of species in the past few decades has been a consequence of habitat destruction and direct exploitation of plant populations. As a result, most plant species that are unique to a defined geographic location (called) have disappeared simultaneously with most rhizosphere organisms, such as mycorrhizal fungi and Rhizobium bacteria, causing the decline in soil biological diversity. Mycorrhizal fungi are the largest existing symbiotic plant communities in plant roots, which are an essential part of healthy plant growth, survival, and soil biological quality, particularly in desertified landscapes, because of their essential role in sustaining the vegetation cover. In natural soils, beneficial rhizosphere microorganisms such as mycorrhizae are abundant and readily available to plants for their health and soil quality. Desertified and mismanaged ecosystems are very fragile and subject to progressive disturbance of the vegetation cover and rapid degradation of soils.