| 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). Pre-fire and for two growing seasons post-fire (2012 and 2013), we measured thaw depth to determine severity effects on active layer depth and permafrost thaw. Thaw depth was measured at five locations (until late summer 2013, and at four locations afterwards) within each burn plot by inserting a hand-held metal probe until resistance was felt. Measurements were acquired weekly while at the field station and bi-monthly during the remainder of the growing season.
|
|---|