Are mineral soils exposed by severe wildfire better seedbeds for conifer regeneration?

Abstract

We examined jack pine (Pinus banksiana Lamb.), black spruce (Picea mariana (Mill.) BSP), and white spruce (Picea glauca (Moench) Voss) seed germination and seedling recruitment in aspen (Populus tremuloides Michx.) and conifer mixedwood stands following the 1999 Black River fire in southeastern Manitoba, Canada. Three postfire seedbed types were tested: scorched (surface litter only partially consumed), lightly burned (surface litter consumed with little or no duff consumption), and severely burned (complete consumption of litter and duff exposing mineral soil). Seeds were sown in 1999, 2000, and 2001, and each cohort was monitored for 3 years. In 1999, severely burned seedbeds had poor germination, while scorched seedbeds had the highest germination. The reverse was true in 2001. After the first growing season, continued survival of seedlings was greater on severely burned seedbeds for all three cohorts. However, better survival on severely burned seedbeds was not sufficient to overcome poor germination in 1999 and 2000. When using artificial seeding to promote conifer regeneration, we recommend a delay of one full year after a severe spring fire for jack pine and two full years for black spruce and white spruce on boreal aspen and conifer mixedwood sites.

Persistent effects of fire severity on early successional forests in interior Alaska

“…Charron and Greene, 2002;Kemball et al, 2006;Johnstone and Chapin, 2006;Johnstone et al, 2010a). A gap remains in our understanding of whether the effects of fire severity on boreal forest communities are solely driven by the response of seedling recruitment to variations in organic layer depths, or are also shaped by subsequent effects of fire on soil conditions that affect the growth of established individuals.…”

Fire Effects on Soils in Lake States Forests: A Compilation of Published Research to Facilitate Long-Term Investigations

“…Reports of high fire severity included fires that consumed the entire organic layer or left only a layer of ash [73] as well as those that resulted in minimal impact to soil where the organic layer was not consumed [55]. Within-fire severity level has a measureable influence on soil properties; for example, soil pH was greater in areas of high fire severity than in areas of lower severity in a boreal forest [73]. The specific effects of fire as a function of severity level have not been well-investigated in the fire effects literature regardless of regional location.…”

Effects of substrate availability and competing vegetation on natural regeneration of white spruce on logged boreal mixedwood sites

“…On upland mixedwood sites that support healthy growth of both coniferous and broadleaf species (MacDonald 1995), white spruce tends to function as a later successional species eventually gaining dominance over the early successional canopy of deciduous (i.e., broadleaf) trees (Bergeron et al 2014). White spruce dominated forests across Canada have mostly originated following fire (Kemball et al 2006;Gärtner et al 2011), and the coincidence of wildfire with mast seed years is key to successful natural regeneration of this species (Peters et al 2005). While the factors affecting the early establishment of natural regeneration on unmanaged sites are well studied (e.g., Gärtner et al 2011 and citations therein), we know much less about natural regeneration of white spruce following harvesting.…”