Abstract
Fire is an important driver of change in most forest, savannah, and prairie ecosystems and fire-altered organic matter, or pyrogenic carbon (PyC), conveys numerous functions in soils of fire maintained terrestrial ecosystems. Although an exceptional number of recent review articles and books have addressed agricultural soil application of charcoal or biochar, few reviews have addressed the functional role of naturally formed PyC in fire maintained ecosystems. Recent advances in molecular spectroscopic techniques have helped strengthen our understanding of PyC as a ubiquitous, complex material that is capable of altering soil chemical, physical, and biological properties and processes. The uniquely recalcitrant nature of PyC in soils is partly a result of its stable C=C double bonded, graphene-like structure and C-rich, N-poor composition. This attribute allows it to persist in soils for hundreds to thousands of years and represent net ecosystem C sequestration in fire maintained ecosystems. The rapid formation of PyC during wildfire or anthropogenic fire events short circuits the normally tortuous pathway of recalcitrant soil C formation. Existing literature also suggests that PyC provides an essential role in the cycling of certain nutrients, greatly extending the timeframe by which fires influence soil processes, and facilitating recovery in ecosystems where organic matter inputs are low and post-fire surface soil bacterial and fungal activity is reduced. The high surface area of PyC allows for the adsorption a broad spectrum of organic compounds that directly or indirectly influence microbial processes after fire events. Adsorption capacity and microsite conditions created by PyC yields a ‘charosphere’ effect with heightened microbial activity in the vicinity of PyC. In this mini-review, we explore the function of PyC in natural and semi-natural settings, provide a mechanistic approach to understanding these functions, and examine examples of such mechanisms in published literature.
Highlights
In recent years, naturally occurring and anthropogenic pyrogenic carbon (PyC) in the environment have become a prominent area of research across scientific disciplines (Zhu et al, 2005; Hammes et al, 2007; Ding et al, 2014; Lehmann and Joseph, 2015; Alam et al, 2016), and yet, to date, there has been little effort to provide a broad ranging synthesis of this unique material that transcends individual disciplines and ecosystems (Sohi et al, 2010; Hart and Luckai, 2013)
Function of Pyrogenic Carbon in Soils emphasis on the importance of PyC in the global carbon (C) cycle and as an amendment for agricultural soils has resulted in a rapid increase in the number of studies across managed, semi-natural, and natural environmental conditions affording a multi-disciplinary framework for improving our mechanistic understanding of PyC (Barrow, 2012; Santín et al, 2015; Dietrich et al, 2017)
Applications of molecular spectroscopic analyses to PyC studies in natural environments complement the absolute quantification of PyC and any known information on molecular changes associated with wood pyrolysis (Nishimiya et al, 1998), transport and oxidation of PyC particles (Hockaday et al, 2006; Cheng et al, 2008; Inoue et al, 2017), change in soil organic matter quality due to wildfires (Miesel et al, 2015), and interactions of PyC surfaces with the surrounding soil environment (Archanjo et al, 2017)
Summary
Naturally occurring and anthropogenic pyrogenic carbon (PyC) in the environment have become a prominent area of research across scientific disciplines (Zhu et al, 2005; Hammes et al, 2007; Ding et al, 2014; Lehmann and Joseph, 2015; Alam et al, 2016), and yet, to date, there has been little effort to provide a broad ranging synthesis of this unique material that transcends individual disciplines and ecosystems (Sohi et al, 2010; Hart and Luckai, 2013). Function of Pyrogenic Carbon in Soils emphasis on the importance of PyC in the global carbon (C) cycle and as an amendment for agricultural soils has resulted in a rapid increase in the number of studies across managed, semi-natural, and natural environmental conditions affording a multi-disciplinary framework for improving our mechanistic understanding of PyC (Barrow, 2012; Santín et al, 2015; Dietrich et al, 2017). We describe these potential functions and explore the mechanisms underlying PyC functionality in natural and semi-natural environments for the advancement of multi-disciplinary research endeavors (see Figure 1)
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