Cone allometry and seed protection from fire are similar in serotinous and nonserotinous conifers.

Serotiny is an adaptive trait that allows certain woody plants to persist in stand-replacing fire regimes. However, the mechanisms by which serotinous cones avoid seed necrosis and nonserotinous species persist in landscapes with short fire cycles and serotinous competitors remain poorly understood. To investigate whether ovulate cone traits that enhance seed survival differ between serotinous and nonserotinous species, we examined cone traits in 24 species within Pinaceae and Cupressaceae based on physical measurements and cone heating simulations using a computational fluid dynamics model. Fire-relevant cone traits were largely similar between cone types; those that differed (e.g. density and moisture) conferred little seed survival advantage under simulated fire. The most important traits influencing seed survival were cone size and seed depth within the cone, which was found to be an allometric function of cone mass for both cone types. Thus, nonserotinous cones should not suffer significantly greater seed necrosis than serotinous cones of equal size. Closed nonserotinous cones containing mature seeds may achieve substantial regeneration after fire if they are sufficiently large relative to fire duration and temperature. To our knowledge, this is the most comprehensive study of the effects of fire-relevant cone traits on conifer regeneration supported by physics-based fire simulation.

Non-serotinous woody plants behave as aerial seed bank species when a late-summer wildfire coincides with a mast year.

ABSTRACT: Trees which lack obvious fire-adaptive traits such as serotinous seed-bearing structures or vegetative resprouting are assumed to be at a dramatic disadvantage in recolonization via sexual recruitment after fire, because seed dispersal is invariably quite constrained. We propose an alternative strategy in masting tree species with woody cones or cone-like structures: that the large clusters of woody tissue in a mast year will sufficiently impede heat transfer that a small fraction of seeds can survive the flaming front passage; in a mast year, this small fraction would be a very large absolute number.In Kootenay National Park in British Columbia, we examined regeneration by Engelmann spruce (Picea engelmannii), a non-serotinous conifer, after two fires, both of which coincided with mast years. Coupling models of seed survivorship within cones and seed maturation schedule to a spatially realistic recruitment model, we show that (1) the spatial pattern of seedlings on a 630 m transect from the forest edge into the burn was best explained if there was in situ seed dissemination by burnt trees; (2) in areas several hundred meters from any living trees, recruitment density was well correlated with local prefire cone density; and (3) spruce was responding exactly like its serotinous codominant, lodgepole pine (Pinus contorta).We conclude that non-serotinous species can indeed behave like aerial seed bank species in mast years if the fire takes place late in the seed maturation period. Using the example of the circumpolar boreal forest, while the joint probability of a mast year and a late-season fire will make this type of event rare (we estimate P = 0.1), nonetheless, it would permit a species lacking obvious fire-adapted traits to occasionally establish a widespread and abundant cohort on a large part of the landscape.

Emergence of morel (Morchella) and pixie cup (geopyxis carbonaria) ascocarps in response to the intensity of forest floor combustion during a wildfire.

We studied the density of ascocarps (mushrooms) of morels (Morchella) and pixie cups (Geo-pyxis carbonaria) as a function of postfire duff (forest floor organic layer) depth in the first 4 y after a wildfire. The great majority of ascocarps of both species appeared in the first summer (2004) after an Aug 2003 fire in predominantly pine-spruce montane stands in Kootenay National Park, British Columbia. The spatial distribution of the ascocarps of both species was strongly biased toward (i) microsites with thin postfire duff and (ii) proximity to standing burned tree trunks. The bases of ascocarps of both species invariably were found just below the surface of the mineral soil. A field experiment in nearby intact forest showed that complete or partial duff removal in the absence of damage to the roots or crown did not lead to ascocarps of either species. We conclude that for both fungal species an unusually large abundance of ascocarps simultaneously requires damage to the associated trees and major duff reduction.