Ash and fire, char, and biochar in the environment

Abstract

Fire is an extreme event leading to rapid and dramatic losses of carbon (C), nutrients, and ballast elements from ecosystems and leaving ash and char on the soil surface. This affects soil processes, properties, and functions. Similar effects can be induced by applying biochar—the product of artificial pyrolysis of plant materials and organic wastes. The nutrients in ashes remaining after a fire or in biochar after pyrolysis will be leached within a few years, and only the highly condensed material will remain in the soil over centuries and millennia. This Special Issue (SI) is devoted to ash, fire, char, and biochar in the environment, with a special focus on soil processes and properties. We begin by comprehensively summarizing the positive and negative effects of fire, ash, char, and biochar on the physical, chemical, and biological properties of soils. We then review the 15 papers contributing to this SI. The first group of studies focuses on reconstructing fires during the Holocene and then linking them to human activities and land use. These studies clearly concluded that the fire frequency strongly increased with human invasion and occupation, and that charcoal properties are useful in reconstructing anthropogenic activities. The second group of studies is mainly devoted to changes in physical, chemical, and biological soil properties as well as to interactions between soil functions depending on fire, ash, and char properties. The final group describes the effects of biochar on soil properties and functions such as nutrient availability, C sequestration, microbial diversity and community structure, and heavy metal fixation. The overall conclusion is that fire and the remaining ash and char as well as the application of biochar have short‐ and long‐term consequences for soil. Despite the dramatic effects of fire on vegetation, these factors have many positive effects on soil properties and functions, whereby the influences extend from local, landscape, and regional scales to the global scale.

Post-fire recovery of soil organic carbon, soil total nitrogen, soil nutrients, and soil erodibility in rotational shifting cultivation in Northern Thailand

“…The ashes were produced under different heating temperatures, which changed their color. Black ash is produced at low temperatures (<300 °C) and is the product of incomplete combustion of the litter (Úbeda et al, 2009;Kuzyakov et al, 2018), which contains a high proportion of carbon (Khanna et al, 1994). The reddish color is due to the oxidation of iron minerals at low temperatures (Markl et al, 2006).…”

Potential of Biochar to Alternate Soil Properties and Crop Yields 3 and 4 Years after the Application

“…As it is known, these soils are characterized by high fertility [6,7]. According to Kuzyakov et al [8] Glinka was the first to recognize the importance of pyrogenic C in the year 1914: "There was almost no soil profile, in which charcoal particles did not occur in the upper horizon." In contrast to many other topics in soil science, the importance of ash and fire, char and biochar for processes in soils was recognized only two to three decades ago.…”

“…Biochar related to the Terra Preta de Índio phenomenon and many environmental benefits reported in various studies has become a hot topic for many scientific teams [5,[9][10][11][12]. The soils throughout the world contain specific amounts of biochar as a result of natural events such as natural fires, paleo fires [8] and land use history-deforestation, pre-industrial charcoal kilns and anthropogenic oven mounds [8,13]. The attention of the scientific community is directed to the production of biochar itself, which is then applied to the soil as a potential soil improver.…”

“…Conversely, long-term field trials are much more likely to yield results that represent these indirect effects over time. However, to study the effect of biochar application to the full extent is impossible during a human lifespan due to reported resistance of biochar to microbial decomposition and persistence in the soil for as long as 100-1000 years [26], or over millennia [8]. Overall, there is a scarcity of studies presenting the mid-term and long-term effects of biochar amendment on the soil properties and crop yields [13].…”

Statistical analysis of soil water content differences after biochar application andits repeated application during 2020 growing season

“…These soils have a high content of organic material and retain a higher production potential than the surrounding soils (Glaser et al, 2003). The soils throughout the world contain specific amounts of biochar as a result of natural events such as natural fires, paleo fires (Kuzyakov et al, 2018) and land use historydeforestation, pre-industrial charcoal kilns and anthropogenic oven mounds (Kuzyakov et al, 2018;Hardy et al, 2017). Biochar may alter the physical properties of the soil, including increasing aeration and water holding capacity of certain soils (Sohi, 2010).…”