A laboratory method for simulating the effects of subsequent fires on pyrogenic organic matter at different exposure depths in a sand matrix

Background Across a variety of anthropogenic and natural contexts, fire can reoccur in a previously burned location. However, effects of subsequent fire on preexisting pyrogenic organic matter (PyOM) stocks are difficult to discern. Laboratory experiments offer a powerful approach to investigating how subsequent fire impacts the preexisting PyOM. Aims We aimed to design a highly repeatable laboratory method to effectively measure the impacts of subsequent fires on PyOM at different soil depths while addressing key limitations of previous methods. Methods Jack pine ( Pinus banksiana Lamb.) log burns were used to parameterize realistic heat flux profiles. Using a cone calorimeter, these profiles were applied to buried jack pine PyOM to simulate variable reburn fire intensities. Key results In general, higher heat flux and shallower depths led to more mass loss of PyOM from combustion and more heat exposure. Conclusions Our reburn method offers a highly replicable way to simulate specific fire scenarios. Conditions that result in more heat exposure (higher heat fluxes, shallower depths) are likely to lead to more loss of PyOM in subsequent fires. Implications The customizable method could simulate different fire scenarios to investigate spatial variability within a given fire event, or to study the effects of fire on different types of biomass or organisms, such as microbes. Summary text Our paper illustrates a laboratory method to better quantify loss of preexisting PyOM in soil after a fire.