The ecological significance of canopy seed storage in fire‐prone environments: a model for non‐sprouting shrubs

Enright, Neal J.; Marsula, Ralf; Lamont, Byron B.; Wissel, Christian

doi:10.1046/j.1365-2745.1998.00312.x

Cited by 175 publications

(187 citation statements)

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“…Our model allows for the manipulation of fire frequency and observation of subsequent stand-level evolutionary responses over long timescales; observations of these dynamics would be difficult or impossible in the field. Given the well-known effects of fire on the evolution of serotiny (7,(14)(15)(16)(17), such observations are required to understand the evolutionary effects of seed predation in context, and to demonstrate that selection observed in the field (Fig. 1) results in evolution (Figs.…”

Section: Discussionmentioning

confidence: 99%

“…Most studies of the evolution of serotiny have focused on the relationship between fire regime and serotiny (7,14), and both empirical and theoretical work suggest that serotiny is most common where stand-replacing fires occur predictably within the lifetime of the species (14)(15)(16). It follows that much geographical variation in serotiny is due to variation in fire regimes (17)(18)(19).…”

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confidence: 99%

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Conflicting selection from fire and seed predation drives fine-scaled phenotypic variation in a widespread North American conifer

Talluto

2014

Proc. Natl. Acad. Sci. U.S.A.

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Recent work has demonstrated that evolutionary processes shape ecological dynamics on relatively short timescales (eco-evolutionary dynamics), but demonstrating these effects at large spatial scales in natural landscapes has proven difficult. We used empirical studies and modeling to investigate how selective pressures from fire and predispersal seed predation affect the evolution of serotiny, an ecologically important trait. Serotiny is a highly heritable key reproductive trait in Rocky Mountain lodgepole pine (Pinus contorta subsp. latifolia), a conifer that dominates millions of hectares in western North America. In these forests, the frequency of serotiny determines postfire seedling density with corresponding community-and ecosystem-level effects. We found that serotinous individuals have a selective advantage at high fire frequencies and low predation pressure; however, very high seed predation shifted the selective advantage to nonserotinous individuals even at high fire frequencies. Simulation modeling suggests that spatial variation in the frequency of serotiny results from heterogeneity in these two selective agents. These results, combined with previous findings showing a negative association between the density of seed predators and the frequency of serotiny at both landscape and continental scales, demonstrate that contemporary patterns in serotiny reflect an evolutionary response to conflicting selection pressures from fire and seed predation. Thus, we show that variation in the frequency of a heritable polygenic trait depends on spatial variation in two dominant selective agents, and, importantly, the effects of the local trait variation propagate with profound consequences to the structure and function of communities and ecosystems across a large landscape.Greater Yellowstone Ecosystem | geographic selection mosaics | genes to ecosystems R ecent work has attempted to unify processes acting across spatiotemporal scales by connecting smaller-scale (e.g., individuals, patches) ecological processes to large-scale (e.g., ecosystems, landscapes) patterns via evolutionary mechanisms (1, 2). When heritable traits in foundation species have important community and ecosystem effects, ecological drivers that exert natural selection on these traits can propagate to largescale patterns in community and ecosystem function, resulting in landscape heterogeneity driven by small-scale ecological variation (1, 3). Although there is a clear conceptual link between selection acting on individuals and landscape-scale patterns, making mechanistic connections across these very different scales has proven challenging (refs. 4 and 5; but see ref. 6). Forested ecosystems in particular are difficult to study, because long generation times prevent direct observations of any response to selection. Nevertheless, attempts to elucidate the connections between individual-level genetic variation and ecosystem and landscape structure are imperative, especially given the unprecedented pace of global change.Here, we integrate empiric...

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Conflicting selection from fire and seed predation drives fine-scaled phenotypic variation in a widespread North American conifer

Talluto

2014

Proc. Natl. Acad. Sci. U.S.A.

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“…Fire can initiate seed release from all serotinous seed-bearing structures (but it is requisite for less than 5 % of serotinous species; Lamont et al, 1991). Serotiny is fire-adaptive for non-sprouting (obligate seeding) species in some fire regimes (Enright et al, 1998;Gill, 1981;Lamont and Enright, 2000;Keeley et al, 2011;Schwilk and Ackerly, 2001), as it not only provides a persistent aerial seed bank for post-fire recruitment but can also insulate seeds against heat necrosis via the thickened walls or clustering of seed-bearing structures (Mercer et al, 1994;Beaufait, 1960;Judd, 1993;Bradstock et al, 1994;Despain et al, 1996;Fraver, 1992). Theory suggests that serotiny should be favored when mean fire return intervals are longer than a species' time to reproductive maturity but shorter than its lifespan, and inter-fire recruitment is rare and/or unsuccessful at producing reproductively mature individuals (Enright et al, 1998;Lamont and Enright, 2000); conversely, non-serotiny should be favored when mean fire return intervals are longer than a species' lifespan and inter-fire recruits can survive to reproductive maturity.…”

Section: Introductionmentioning

confidence: 99%

Timing of fire relative to seed development may enable non-serotinous species to recolonize from the aerial seed banks of fire-killed trees

et al. 2013

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Abstract. The existence of non-serotinous, non-sprouting species in fire regimes where serotiny confers an adaptive advantage is puzzling, particularly when these species recruit poorly from soil seed banks or from burn edges. In this paper, white spruce (Picea glauca (Moench) Voss) was used to show how the timing of fire relative to seed development may permit non-serotinous species to recolonize burned areas from the aerial seed banks of fire-killed trees. To estimate survival of seeds within closed cones during crown fires, cone heating was simulated using a one-dimensional conduction model implemented in a three-dimensional computational fluid dynamics fire behavior model. To quantify the area burned when germinable seed would be contained within closed cones during a mast year, empirical fire occurrence and seed development (germinability and cone opening) data were compared for multiple locations across the white spruce range. Approximately 12% of cones contained viable seed following crown fire simulations (0.072 m s−1 mean spread rate; 9147 kW m−1 mean intensity), and roughly half of the historical area burned resulted from fires that occurred when closed cones would contain germinable seed. Together, these results suggest that non-serotinous species may recolonize burned areas from in situ aerial seed banks, and that this may be an important cause of their existence in fire regimes to which they otherwise seem poorly suited.

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“…Thus, fire intervals as long as those that appear to be required for A. morroensis maintenance could eliminate these obligate seeders. The fire interval that optimizes populations of one such serotinous shrub, Banksia hookeriana, has been found to be 16 years, based on detailed understanding of the dynamics of seed production, storage, and loss in relation to plant age (Enright et al 1996(Enright et al , 1998. This reflects a regime of fairly frequent fire thought to be common over evolutionary time scales in much of South Africa and Australia (Pyne 1991, Bond andvan Wilgen [1996] and references therein).…”

Section: Conservation and Management Implicationsmentioning

confidence: 99%

Are Long Fire-free Periods Needed to Maintain the Endangered, Fire-recruiting Shrub Arctostaphylos morroensis(Ericaceae)?

Odion¹,

Tyler²

2002

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ABSTRACT. Morro manazanita (Arctostaphylos morroensis) is a distinctive shrub restricted to a small area along the coast of California, USA. This endangered species faces two opposing fire-related extinction risks: (1) adults are killed by fire, and (2) recruitment opportunities only occur with fire. These strongly limit the capacity of this, as well as other obligate-seeding species, to recover from a population decline, which may result if there is an inadequate amount of time between fires for replenishment of sufficient seed populations. Using a prescribed burn, we tested whether the size of the seed bank that had accumulated in a 40-yr-old stand would prove adequate for maintaining A. morroensis population sizes through fire. Prior to the burn, we found ~11,000 seeds/m 2 in the soil, mostly in the top 5 cm. However, the number of viable seeds was substantially lower (334 seeds/m 2 ), and less than one-third of these survived the experimental fire (99 seeds/m 2 ). Germination occurred only in the first two wet seasons after the fire, and may have been adequate to replace the number of A. morroensis present before the burn. However, most seedlings did not survive their initial summer drought. After three years, the new population of A. morroensis was less than half the size of the parent population. Further mortality is expected because the remaining seedlings are highly clumped. We conclude that A. morroensis may require considerably longer than 40 years to establish an adequate seed bank to compensate for mortality and prevent population decrease or local extinction. This prolonged risk is perhaps explained by specialization of this species to a historic regime of relatively infrequent fire. There are many obligate-seeding species in fire-prone shrublands that may not be resilient to a regime of fire more frequent than that with which they evolved.

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The ecological significance of canopy seed storage in fire‐prone environments: a model for non‐sprouting shrubs

Cited by 175 publications

References 32 publications

Conflicting selection from fire and seed predation drives fine-scaled phenotypic variation in a widespread North American conifer

Conflicting selection from fire and seed predation drives fine-scaled phenotypic variation in a widespread North American conifer

Timing of fire relative to seed development may enable non-serotinous species to recolonize from the aerial seed banks of fire-killed trees

Are Long Fire-free Periods Needed to Maintain the Endangered, Fire-recruiting Shrub Arctostaphylos morroensis(Ericaceae)?

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