Аннотация:For many generations, black soils have been prized for their rich organic matter content and the great natural fertility that results from this stored organic material. The inherent natural high fertility of black soils has led to the use of approximately one third of natural ecosystems (grasslands and forests) for crop production. Although only approximately 17 percent of global cropland occurs on black soils, in 2010, 66 percent of sunflower seeds, 51 percent of small millet, 42 percent of sugar beet, 30 percent of wheat and 26 percent of potatoes were harvested globally from black soils. The importance of crop production from black soils has been highlighted by the disruption of the global food supply caused by the current conflict in the heart of black soils.The looming crisis of human-induced climate change has focused attention on the critical importance of the carbon locked up in the organic matter of black soils. Black soils occupy 725 million hectares of the land surface and constitute 5.6 percent of global soils but contain 8.2 percent of the world’s soil organic carbon (SOC) stocks: approximately 56 billion tonnes of carbon (Pg of C). Recently, the ability of soils to remove carbon from the atmosphere and lock it up in soil organic matter (called carbon sequestration) has been proposed as an important solution to mitigate humaninduced climate change. The Global Soil Organic Carbon Sequestration Potential (GSOCseq) map showed that black soils can provide 10 percent of the total SOC sequestration potential of global soils.The need to consistently identify and promote black soils led to the establishment of the International Network of Black Soils (INBS) by FAO’s Global Soil Partnership in 2017. Work by the INBS has led to a consistent definition of black soils and the first ever Global Black Soil Distribution map (GBSmap). This work was critical to identify the regions where black soils are found and to assess both the threats to these soils and the successful management approaches to counter these threats.Major areas of black soils are found in Eurasia (Russian Federation (327 million ha), Kazakhstan (108 million ha), and Ukraine (34 million ha)), Asia (China (50 million ha), Mongolia (39 million ha)), North America (United States of America (31 million ha), Canada (13 million ha)), and Latin America (Argentina (40 million ha), Colombia (25 million ha), Mexico (12 million ha)). In many of these regions the black soils are associated with the great midlatitude grasslands: the Pampas of Argentina, the Great plains of North America, the northeast black soil region of China, and the Forest-Steppe and Steppe regions, of the Ukraine and the Russian Federation. In all of these regions undisturbed black soils were the home for a complex assemblage of burrowing soil fauna and their actions mixed the organic matter from the grasses into upper part of the mineral soil, creating a thick, black, topsoil layer. Throughout these regions the grasslands have been extensively converted to cropland, but approximately 37 percent of black soils remain under grass cover. The INBS’s GBSmap shows that an important area of black soils also occurs in forested environments. These black soils have their greatest extent in the Russian Federation and Canada and in total, approximately 29 percent of black soils are under forest cover.Smaller areas of black soils have formed in volcanic ash deposits in countries such as Japan, in wetlands where water retards the decomposition of added organic material and in high alpine areas where the cold temperatures also slow decomposition and allow the buildup of soil organic matter. There are also significant areas where humans have formed black soils through the addition of organic matter over decades or centuries of use. Perhaps the best known of these are the Terra Preta do Índio in the Amazon basin, which have been formed by the addition of charcoal and other organic materials by indigenous groups over centuries of use. In Europe, plaggen soils have formed primarily by continued additions of manure and straw to soils. Both Terra Preta do Índio and plaggen soils demonstrate the ability of humans to fundamentally alter soils through our management practices.The greatest threat to black soils is the loss of organic matter through both conversion of natural landscapes to agriculture and by continuing mismanagement of cultivated black soils. Studies in many black soil regions have documented losses of 20 to 50 percent of the original soil organic matter when grassland or forested black soils are converted to agriculture. These initial losses occur when stable aggregates in the soil are broken apart by soil tillage, exposing protected soil organic matter to decomposition by microbes in the soil. The carbon dioxide that is released to the atmosphere during decomposition has been a significant contributor to the atmospheric carbon pool through time.Continuing losses of soil organic matter on cultivated black soils occur due to the physical transport of soil particles (including organic matter) by erosion. Water erosion affects all soils, but wind erosion is a particular issue in black soils of former grasslands – the drier climates these soils are found in are naturally susceptible to high rates of wind erosion. The black soil areas of North America were particularly devastated by wind erosion during the 1930s, dust storms caused several adverse effects such as respiratory diseases causing the death of people and animals, farmlands becoming unusable, and hunger and poverty spreading across several states of North America. Continuing losses of soil organic matter through erosion have been shown to more than offset any gains in soil organic matter through carbon sequestration and hence erosion control on these soils is essential. In addition, nutrient imbalance and physical–structural deterioration should be considered as major threats to black soils. In some regions soil salinization, pollution and soil sealing due to urban advancement also occurs.Fortunately black soils have proven to be well suited to the adoption of reduced and no-till cultivation systems (also called conservation tillage). These systems minimize or eliminate disruption of the soil surface by tillage implements and leave a cover of crop residue on the soil surface. This cover reduces water losses to the atmosphere and protects the soil from wind and water erosion as well as any erosion associated with the tillage. Adoption of reduced and no-till systems has been especially high in Argentinian Pampas and in the Great plains of North America.This report highlights throughout the importance of two main goals: the preservation of the natural vegetation cover on black soils under grassland, forest and wetland vegetation and the adoption of sustainable soil management approaches on cropped black soils. The preservation of natural cover protects the rich organic matter levels from decomposition and release of large amounts of CO2 into the atmosphere; the adoption of sustainable management approaches such as reduced tillage and no-till allows soil organic matter levels to stabilize and (ideally) to increase. While adoption of improved management occurs at the individual farm level, protection of natural landscapes often requires the development of monitoring systems for the status of and changes to the condition of black soils, and governance at sub-national and national levels. Currently only China has a national law in place to protect, conserve and encourage sustainable management of black soils.With this report, the International Network of Black Soils has documented the extent and importance of black soils to agricultural production and seeks to address the global threat of rising atmospheric carbon levels and the climate warming that result from this. It is hoped that the many examples of beneficial soil management and governance it contains can serve as an inspiration for the adoption of improved management approaches throughout the black soil zones of the world.
