| Summary: | Global change models predict an increase in fire activity in boreal forests as climate continues to warm and dry. Because fire consumes the soil organic layer (SOL), the layer of undecomposed mosses and roots atop the permafrost, we hypothesized that increased fire severity will increase permafrost thaw by reducing the depth, and therefore insulating capacity, of the SOL. To test this hypothesis, we conducted plot-level (2-m2) experimental burns in July 2012 in a low-density, mature larch stand located near the Northeast Science Station in Cherskii, Siberia. Dried fuels comprised of naturally occurring vegetation were added to plots to achieve four burn treatments based on residual SOL depths: control, low severity (> 8 cm), moderate severity (5-8 cm), and high severity (2-5 cm). Seeds were collected in fall 2012, sowed on plots (100 seeds/m2) in fall 2012, and counted in July 2013. Larch recruitment was measured during July 2013 within each burn plot by counting number of new larch seedlings on a weekly basis. Seedling were tagged and numbered for later identification.
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