The propagule doesn’t fall far from the tree, especially after short-interval, high-severity fire

Nathan S. Gill; Tyler J. Hoecker; Monica G. Turner

doi:10.1002/ecy.3194

The propagule doesn’t fall far from the tree, especially after short-interval, high-severity fire

Nathan S. Gill
, Tyler J. Hoecker
, Monica G. Turner

Forest Management

Research output: Contribution to journal › Article › peer-review

42 Scopus citations

Abstract

Subalpine forests that historically burned every 100–300 yr are expected to burn more frequently as climate warms, perhaps before trees reach reproductive maturity or produce a serotinous seedbank. Tree regeneration after short-interval (<30-yr) high-severity fire will increasingly rely on seed dispersal from unburned trees, but how dispersal varies with age and structure of surrounding forest is poorly understood. We studied wind dispersal of three conifers (Picea engelmannii, Abies lasiocarpa, and Pinus contorta var. latifolia, which can be serotinous and nonserotinous) after a stand-replacing fire that burned young (≤30 yr) and older (>100 yr) P. contorta forest in Grand Teton National Park (Wyoming, USA). We asked how propagule pressure varied with time since last fire, how seed delivery into burned forest varied with age and structure of live forest edges, what variables explained seed delivery into burned forest, and how spatial patterns of delivery across the burned area could vary with alternate patterns of surrounding live forest age. Seeds were collected in traps along 100-m transects (n = 18) extending from live forest edges of varying age (18, 30, and >100 yr) into areas of recent (2-yr) high-severity fire, and along transects in live forests to measure propagule pressure. Propagule pressure was low in 18-yr-old stands (~8 seeds/m²) and similarly greater in 30- and 100-yr-old stands (~32 seeds/m²). Mean dispersal distance was lowest from 18-yr-old edges and greatest from >100-yr-old edges. Seed delivery into burned forest declined with increasing distance and increased with height of trees at live forest edges, and was consistently higher for P. contorta than for other conifers. Empirical dispersal kernels revealed that seed delivery from 18-yr-old edges was very low (≤2.4 seeds/m²) and concentrated within 10 m of the live edge, whereas seed delivery from >100-yr-old edges was >4.9 seeds/m² out to 80 m. When extrapolated throughout the burned landscape, estimated seed delivery was low (<49,400 seeds/ha) in >70% of areas that burned in short-interval fire (<30 yr). As fire frequency increases, immaturity risk will be compounded in short-interval fires because seed dispersal from surrounding young trees is limited.

Original language	English
Article number	e03194
Journal	Ecology
Volume	102
Issue number	1
DOIs	https://doi.org/10.1002/ecy.3194
State	Published - Jan 2021

Funding

We thank K. Braziunas, W. Romme, D. Kulakowski, and two anonymous reviewers for comments that improved this manuscript, and C. Kluender, D. Abendroth, R. Steffens, J. Stephenson, K. Patronik, and L. Rios for assistance collecting data. We thank the University of Wyoming–National Park Service Research Station for logistical support, and Grand Teton National Park for facilitating this study. This work was completed under permit GRTE-2018-SCI-0039 and supported by a National Science Foundation (DEB-1719905) grant to MGT and a Michael T. Guyer Fellowship to NSG through the Department of Integrative Biology, University of Wisconsin–Madison. MGT also acknowledges support from the University of Wisconsin–Madison Vilas Trust. We declare no conflict of interest. NSG and MGT conceived the ideas and designed methods; NSG, TJH, and MGT collected, analyzed, and interpreted the data; and NSG led the writing of the manuscript, to which all authors contributed critically and gave approval for publication. We thank K. Braziunas, W. Romme, D. Kulakowski, and two anonymous reviewers for comments that improved this manuscript, and C. Kluender, D. Abendroth, R. Steffens, J. Stephenson, K. Patronik, and L. Rios for assistance collecting data. We thank the University of Wyoming–National Park Service Research Station for logistical support, and Grand Teton National Park for facilitating this study. This work was completed under permit GRTE‐2018‐SCI‐0039 and supported by a National Science Foundation (DEB‐1719905) grant to MGT and a Michael T. Guyer Fellowship to NSG through the Department of Integrative Biology, University of Wisconsin–Madison. MGT also acknowledges support from the University of Wisconsin–Madison Vilas Trust. We declare no conflict of interest. NSG and MGT conceived the ideas and designed methods; NSG, TJH, and MGT collected, analyzed, and interpreted the data; and NSG led the writing of the manuscript, to which all authors contributed critically and gave approval for publication.

Funders	Funder number
GRTE‐2018‐SCI‐0039
DEB‐1719905
University of Wisconsin-Madison

Keywords

Engelmann spruce
Greater Yellowstone Ecosystem
dispersal kernel
fire frequency
fire-regime change
forest structure
lodgepole pine
resilience
seed dispersal
subalpine fir

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10.1002/ecy.3194

Cite this

@article{4bb1d9d503fd48089d459e09310229c5,

title = "The propagule doesn{\textquoteright}t fall far from the tree, especially after short-interval, high-severity fire",

abstract = "Subalpine forests that historically burned every 100–300 yr are expected to burn more frequently as climate warms, perhaps before trees reach reproductive maturity or produce a serotinous seedbank. Tree regeneration after short-interval (<30-yr) high-severity fire will increasingly rely on seed dispersal from unburned trees, but how dispersal varies with age and structure of surrounding forest is poorly understood. We studied wind dispersal of three conifers (Picea engelmannii, Abies lasiocarpa, and Pinus contorta var. latifolia, which can be serotinous and nonserotinous) after a stand-replacing fire that burned young (≤30 yr) and older (>100 yr) P. contorta forest in Grand Teton National Park (Wyoming, USA). We asked how propagule pressure varied with time since last fire, how seed delivery into burned forest varied with age and structure of live forest edges, what variables explained seed delivery into burned forest, and how spatial patterns of delivery across the burned area could vary with alternate patterns of surrounding live forest age. Seeds were collected in traps along 100-m transects (n = 18) extending from live forest edges of varying age (18, 30, and >100 yr) into areas of recent (2-yr) high-severity fire, and along transects in live forests to measure propagule pressure. Propagule pressure was low in 18-yr-old stands (\textasciitilde{}8 seeds/m2) and similarly greater in 30- and 100-yr-old stands (\textasciitilde{}32 seeds/m2). Mean dispersal distance was lowest from 18-yr-old edges and greatest from >100-yr-old edges. Seed delivery into burned forest declined with increasing distance and increased with height of trees at live forest edges, and was consistently higher for P. contorta than for other conifers. Empirical dispersal kernels revealed that seed delivery from 18-yr-old edges was very low (≤2.4 seeds/m2) and concentrated within 10 m of the live edge, whereas seed delivery from >100-yr-old edges was >4.9 seeds/m2 out to 80 m. When extrapolated throughout the burned landscape, estimated seed delivery was low (<49,400 seeds/ha) in >70\% of areas that burned in short-interval fire (<30 yr). As fire frequency increases, immaturity risk will be compounded in short-interval fires because seed dispersal from surrounding young trees is limited.",

keywords = "Engelmann spruce, Greater Yellowstone Ecosystem, dispersal kernel, fire frequency, fire-regime change, forest structure, lodgepole pine, resilience, seed dispersal, subalpine fir",

author = "Gill, \{Nathan S.\} and Hoecker, \{Tyler J.\} and Turner, \{Monica G.\}",

note = "Publisher Copyright: {\textcopyright} 2020 by the Ecological Society of America",

year = "2021",

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doi = "10.1002/ecy.3194",

language = "English",

volume = "102",

journal = "Ecology",

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T1 - The propagule doesn’t fall far from the tree, especially after short-interval, high-severity fire

AU - Gill, Nathan S.

AU - Hoecker, Tyler J.

AU - Turner, Monica G.

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Y1 - 2021/1

N2 - Subalpine forests that historically burned every 100–300 yr are expected to burn more frequently as climate warms, perhaps before trees reach reproductive maturity or produce a serotinous seedbank. Tree regeneration after short-interval (<30-yr) high-severity fire will increasingly rely on seed dispersal from unburned trees, but how dispersal varies with age and structure of surrounding forest is poorly understood. We studied wind dispersal of three conifers (Picea engelmannii, Abies lasiocarpa, and Pinus contorta var. latifolia, which can be serotinous and nonserotinous) after a stand-replacing fire that burned young (≤30 yr) and older (>100 yr) P. contorta forest in Grand Teton National Park (Wyoming, USA). We asked how propagule pressure varied with time since last fire, how seed delivery into burned forest varied with age and structure of live forest edges, what variables explained seed delivery into burned forest, and how spatial patterns of delivery across the burned area could vary with alternate patterns of surrounding live forest age. Seeds were collected in traps along 100-m transects (n = 18) extending from live forest edges of varying age (18, 30, and >100 yr) into areas of recent (2-yr) high-severity fire, and along transects in live forests to measure propagule pressure. Propagule pressure was low in 18-yr-old stands (~8 seeds/m2) and similarly greater in 30- and 100-yr-old stands (~32 seeds/m2). Mean dispersal distance was lowest from 18-yr-old edges and greatest from >100-yr-old edges. Seed delivery into burned forest declined with increasing distance and increased with height of trees at live forest edges, and was consistently higher for P. contorta than for other conifers. Empirical dispersal kernels revealed that seed delivery from 18-yr-old edges was very low (≤2.4 seeds/m2) and concentrated within 10 m of the live edge, whereas seed delivery from >100-yr-old edges was >4.9 seeds/m2 out to 80 m. When extrapolated throughout the burned landscape, estimated seed delivery was low (<49,400 seeds/ha) in >70% of areas that burned in short-interval fire (<30 yr). As fire frequency increases, immaturity risk will be compounded in short-interval fires because seed dispersal from surrounding young trees is limited.

AB - Subalpine forests that historically burned every 100–300 yr are expected to burn more frequently as climate warms, perhaps before trees reach reproductive maturity or produce a serotinous seedbank. Tree regeneration after short-interval (<30-yr) high-severity fire will increasingly rely on seed dispersal from unburned trees, but how dispersal varies with age and structure of surrounding forest is poorly understood. We studied wind dispersal of three conifers (Picea engelmannii, Abies lasiocarpa, and Pinus contorta var. latifolia, which can be serotinous and nonserotinous) after a stand-replacing fire that burned young (≤30 yr) and older (>100 yr) P. contorta forest in Grand Teton National Park (Wyoming, USA). We asked how propagule pressure varied with time since last fire, how seed delivery into burned forest varied with age and structure of live forest edges, what variables explained seed delivery into burned forest, and how spatial patterns of delivery across the burned area could vary with alternate patterns of surrounding live forest age. Seeds were collected in traps along 100-m transects (n = 18) extending from live forest edges of varying age (18, 30, and >100 yr) into areas of recent (2-yr) high-severity fire, and along transects in live forests to measure propagule pressure. Propagule pressure was low in 18-yr-old stands (~8 seeds/m2) and similarly greater in 30- and 100-yr-old stands (~32 seeds/m2). Mean dispersal distance was lowest from 18-yr-old edges and greatest from >100-yr-old edges. Seed delivery into burned forest declined with increasing distance and increased with height of trees at live forest edges, and was consistently higher for P. contorta than for other conifers. Empirical dispersal kernels revealed that seed delivery from 18-yr-old edges was very low (≤2.4 seeds/m2) and concentrated within 10 m of the live edge, whereas seed delivery from >100-yr-old edges was >4.9 seeds/m2 out to 80 m. When extrapolated throughout the burned landscape, estimated seed delivery was low (<49,400 seeds/ha) in >70% of areas that burned in short-interval fire (<30 yr). As fire frequency increases, immaturity risk will be compounded in short-interval fires because seed dispersal from surrounding young trees is limited.

KW - Engelmann spruce

KW - Greater Yellowstone Ecosystem

KW - dispersal kernel

KW - fire frequency

KW - fire-regime change

KW - forest structure

KW - lodgepole pine

KW - resilience

KW - seed dispersal

KW - subalpine fir

UR - https://www.scopus.com/pages/publications/85092131615

U2 - 10.1002/ecy.3194

DO - 10.1002/ecy.3194

M3 - Article

C2 - 32910502

AN - SCOPUS:85092131615

SN - 0012-9658

VL - 102

JO - Ecology

JF - Ecology

IS - 1

M1 - e03194

ER -

The propagule doesn’t fall far from the tree, especially after short-interval, high-severity fire

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