Wildland fire ash: Production, composition and eco-hydro-geomorphic effects

Charcoal recognition, taphonomy and uses in palaeoenvironmental analysis

Data collected from both artificially and field (naturally) weathered biochar suggest that a potentially significant pathway of biochar disappearance is through physical breakdown of the biochar structure. Via scanning electron microscopy, we characterized this physical weathering that increased the number of structural fractures and yielded higher numbers of liberated biochar fragments. This was hypothesized to be due to the graphitic sheet expansion accompanying water sorption coupled with comminution. These fragments can be on the microscale and the nanoscale but are still carbon-rich particles with no detectable alteration in the oxygen:carbon ratio from that of the original biochar. However, these particles are now easily dissolved and could be moved by infiltration. There is a need to understand how to produce biochars that are resistant to physical degradation to maximize long-term biochar C sequestration potential within soil systems.

/pdf/physical-disintegration-of-biochar-an-overlooked-process-1stmp66stu.pdf

Physical Disintegration of Biochar: An Overlooked Process

Pyrogenic organic matter (PyOM) is considered an important soil carbon (C) sink. However, there are evidences that its addition to soil may induce a priming effect (PE) thus influencing its C abatement potential. The direction, the size and the mechanisms responsible for PyOM induced PE are far from being understood. We collected approximately 650 data points from 18 studies to analyse the characteristics of the PE induced by PyOM. The database was divided between the PE induced on the native soil organic matter and on fresh organic matter. Most of the studies were short-term incubation therefore the projections of findings on the long term may be critical. Our findings indicate that over 1 year PyOM induces an average positive PE of 0.3 mg C g−1 soil on native soil organic matter and a PE of approximately the same size but opposite direction on fresh organic matter. We studied the correlation of PE with several properties of soil, of the added PyOM, and time after PyOM addition. We found that PyOM primes positively the native soil organic matter in the first 20 days while negative PE appears in a later stage. Negative PE was correlated with the soil C content. PyOM characterized by a low C content induced a higher positive PE on native soil organic carbon. No correlation was found between the factors record in our database and the PE induced on the fresh organic matter. We reviewed the mechanisms proposed in literature to explain PE and discussed them based on findings from our meta-analysis. We believe that the presence of a labile fraction in PyOM may trigger the activity of soil microorganisms on the short term and therefore induce a positive PE, while on the long term PyOM may induce a negative PE by promoting physical protection mechanisms.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcbb.12194

A meta-analysis on pyrogenic organic matter induced priming effect

Combustion features inform archaeologists about the prehistoric use of space, subsistence behaviors, and tempo of site visitation. Their study in the field is difficult because burned sediments are susceptible to reworking and diagenesis. Microarchaeological analyses, including micromorphology, are essential for documenting the composition, preservation, and function of hearths and other burned residues. These investigations focus on the description of fuels, depositional fabrics and structures, and mineralogy. As evidenced by a literature review, microarchaeological analyses have much to offer Paleolithic archaeologists, while applications of the techniques to Late Pleistocene and Early Holocene sites and in ethnographic or experimental contexts are presently rare.

Microarchaeological Approaches to the Identification and Interpretation of Combustion Features in Prehistoric Archaeological Sites

Anthracology and taphonomy, from wood gathering to charcoal analysis. A review of the taphonomic processes modifying charcoal assemblages, in archaeological contexts

Archéobotanique et taphonomie

Identificando estrategias de adquisicion del combustible lenoso en antracologia: puede contribuir la experimentacion a determinar el calibre de los carbones en contexto arqueologico ?

Identificando estrategias de adquisición del combustible leñoso en antracología: ¿puede contribuir la experimentación a determinar el calibre de los carbones en contexto arqueológico?

We present and discuss two approaches for evaluating the diameter of carbonized wood.Results from a theoretical model and its experimental validation shows that the proportions of diameter classes predicted by the model can be recognized. Even though the measured caliber classes do not correspond to the reality of the initial diameters, the measures were sufficiently different and reproductive to be discriminated through factorial analysis. These methods are promising for documenting cultural behavior of past peoples related to firewood use and management

Julia Chrzavzez

Papers

Anthracology and taphonomy, from wood gathering to charcoal analysis. A review of the taphonomic processes modifying charcoal assemblages, in archaeological contexts

Archéobotanique et taphonomie

Identificando estrategias de adquisición del combustible leñoso en antracología: ¿puede contribuir la experimentación a determinar el calibre de los carbones en contexto arqueológico?

Charcoal analysis and wood diameter : inductive and deductive methodological approaches for the study of firewood.