TY - JOUR
T1 - What Drives Reproductive Maturity and Efficiency in Serotinous Boreal Conifers?
AU - Alfaro-Sánchez, Raquel
AU - Johnstone, Jill F.
AU - Cumming, Steve G.
AU - Day, Nicola J.
AU - Mack, Michelle C.
AU - Walker, Xanthe J.
AU - Baltzer, Jennifer L.
N1 - Funding Information:
This article is part of Project 170 of the Government of the Northwest Territories (GNWT) Department of Environment and Natural Resources Cumulative Impacts Monitoring Program (awarded to JB, JJ, and SC). Additional funding was provided by Natural Science and Engineering Research Council (NSERC: Changing Cold Regions Network), Northern Scientific Training Program, NSERC Discovery to JJ, NSERC Discovery Accelerator Funding to JB, CFREF Global Water Futures funding for Northern Water Futures to JB, a National Science Foundation DEB RAPID grant (grant #1542150), and NASA Arctic Boreal and Vulnerability Experiment (ABoVE) Legacy Carbon grant (grant # NNX15AT71A) to MM. ND was supported by an NSERC Postdoctoral Fellowship and Rutherford Postdoctoral Fellowship from the Royal Society of New Zealand. In kind support was provided by the Bonanza Creek LTER program. Canadian field assistants were supported by the Northern Science Training Program. The Polar Continental Shelf Program provided helicopter support. Dedicated research time for JB was supported by the Canada Research Chairs program.
Publisher Copyright:
Copyright © 2022 Alfaro-Sánchez, Johnstone, Cumming, Day, Mack, Walker and Baltzer.
PY - 2022/7/22
Y1 - 2022/7/22
N2 - In boreal North America, much of the landscape is covered by fire-adapted forests dominated by serotinous conifers. For these forests, reductions in fire return interval could limit reproductive success, owing to insufficient time for stands to reach reproductive maturity i.e., to initiate cone production. Improved understanding of the drivers of reproductive maturity can provide important information about the capacity of these forests to self-replace following fire. Here, we assessed the drivers of reproductive maturity in two dominant and widespread conifers, semi-serotinous black spruce and serotinous jack pine. Presence or absence of female cones were recorded in approximately 15,000 individuals within old and recently burned stands in two distinct ecozones of the Northwest Territories (NWT), Canada. Our results show that reproductive maturity was triggered by a minimum tree size threshold rather than an age threshold, with trees reaching reproductive maturity at smaller sizes where environmental conditions were more stressful. The number of reproductive trees per plot increased with stem density, basal area, and at higher latitudes (colder locations). The harsh climatic conditions present at these higher latitudes, however, limited the recruitment of jack pine at the treeline ecotone. The number of reproductive black spruce trees increased with deeper soils, whereas the number of reproductive jack pine trees increased where soils were shallower. We examined the reproductive efficiency i.e., the number of seedlings recruited per reproductive tree, linking pre-fire reproductive maturity of recently burned stands and post-fire seedling recruitment (recorded up to 4 years after the fires) and found that a reproductive jack pine can recruit on average three times more seedlings than a reproductive black spruce. We suggest that the higher reproductive efficiency of jack pine can explain the greater resilience of this species to wildfire compared with black spruce. Overall, these results help link life history characteristics, such as reproductive maturity, to variation in post-fire recruitment of dominant serotinous conifers.
AB - In boreal North America, much of the landscape is covered by fire-adapted forests dominated by serotinous conifers. For these forests, reductions in fire return interval could limit reproductive success, owing to insufficient time for stands to reach reproductive maturity i.e., to initiate cone production. Improved understanding of the drivers of reproductive maturity can provide important information about the capacity of these forests to self-replace following fire. Here, we assessed the drivers of reproductive maturity in two dominant and widespread conifers, semi-serotinous black spruce and serotinous jack pine. Presence or absence of female cones were recorded in approximately 15,000 individuals within old and recently burned stands in two distinct ecozones of the Northwest Territories (NWT), Canada. Our results show that reproductive maturity was triggered by a minimum tree size threshold rather than an age threshold, with trees reaching reproductive maturity at smaller sizes where environmental conditions were more stressful. The number of reproductive trees per plot increased with stem density, basal area, and at higher latitudes (colder locations). The harsh climatic conditions present at these higher latitudes, however, limited the recruitment of jack pine at the treeline ecotone. The number of reproductive black spruce trees increased with deeper soils, whereas the number of reproductive jack pine trees increased where soils were shallower. We examined the reproductive efficiency i.e., the number of seedlings recruited per reproductive tree, linking pre-fire reproductive maturity of recently burned stands and post-fire seedling recruitment (recorded up to 4 years after the fires) and found that a reproductive jack pine can recruit on average three times more seedlings than a reproductive black spruce. We suggest that the higher reproductive efficiency of jack pine can explain the greater resilience of this species to wildfire compared with black spruce. Overall, these results help link life history characteristics, such as reproductive maturity, to variation in post-fire recruitment of dominant serotinous conifers.
KW - boreal biome
KW - cone presence
KW - post-fire regeneration
KW - reproductive age threshold
KW - reproductive size threshold
KW - serotinous species
KW - species-compositional shifts
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UR - http://www.scopus.com/inward/citedby.url?scp=85135775761&partnerID=8YFLogxK
U2 - 10.3389/fevo.2022.869130
DO - 10.3389/fevo.2022.869130
M3 - Article
AN - SCOPUS:85135775761
SN - 2296-701X
VL - 10
JO - Frontiers in Ecology and Evolution
JF - Frontiers in Ecology and Evolution
M1 - 869130
ER -