A changing climate is snuffing out post‐fire recovery in montane forests

Rodman, Kyle C.; Veblen, Thomas T.; Battaglia, Michael A.; Chambers, Marin E.; Fornwalt, Paula J.; Holden, Zachary A.; Kolb, Thomas E.; Ouzts, Jessica R.; Rother, Monica T.

doi:10.1111/geb.13174

Cited by 75 publications

(45 citation statements)

References 69 publications

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“…The potential for fire-driven vegetation shifts will be enhanced by declines in the area climatically suitable for tree recruitment because of harsher post-disturbance climate (Davis et al, 2020). Moreover, a drier and warmer post-fire environment in concert with high severity fires can severely inhibit forest recovery, thereby reducing resilience of ecosystems to fire (Johnstone et al, 2016;Rodman et al, 2020).…”

Section: Discussionmentioning

confidence: 99%

Hotter Drought Escalates Tree Cover Declines in Blue Oak Woodlands of California

et al. 2021

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California has, in recent years, become a hotspot of interannual climatic variability, recording devastating climate-related disturbances with severe effects on tree resources. Understanding the patterns of tree cover change associated with these events is vital for developing strategies to sustain critical habitats of endemic and threatened vegetation communities. We assessed patterns of tree cover change, especially the effects of the 2012–2016 drought within the distribution range of blue oak (Quercus douglasii), an endemic tree species to California with a narrow geographic extent. We utilized multiple, annual land-cover and land-surface change products from the U.S. Geological Survey (USGS) Land Change Monitoring, Assessment and Projection (LCMAP) project along with climate and wildfire datasets to monitor changes in tree cover state and condition and examine their relationships with interannual climate variability between 1985 and 2016. Here, we refer to a change in tree cover class without a land-cover change to another class as “conditional change.” The unusual drought of 2012–2016, accompanied by anomalously high temperatures and vapor pressure deficit, was associated with exceptional spikes in the amount of both fire and non-fire induced tree cover loss and tree cover conditional change, especially in 2015 and 2016. Approximately 1,266 km2 of tree cover loss and 617 km2 of tree cover conditional change were recorded during that drought. Tree cover loss through medium to high severity fires was especially large in exceptionally dry and hot years. Our study demonstrates the usefulness of the LCMAP products for monitoring the effects of climatic extremes and disturbance events on both thematic and conditional land-cover change over a multi-decadal period. Our results signify that blue oak woodlands may be vulnerable to extreme climate events and changing wildfire regimes. Here, we present early evidence that frequent droughts associated with climate warming may continue to affect tree cover in this region, while drought interaction with wildfires and the resulting feedbacks may have substantial influence as well. Consequently, efforts to conserve the blue oak woodlands, and potentially other vegetation communities in the Western United States, may benefit from consideration of climate risks as well as the potential for climate-fire and vegetation feedbacks.

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Section: Discussionmentioning

confidence: 99%

Hotter Drought Escalates Tree Cover Declines in Blue Oak Woodlands of California

et al. 2021

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“…Feddema, Mast, & Savage, 2013; Petrie et al., 2017). Over the next century, AET is projected to increase across the southern Rocky Mountains, particularly at higher elevations and northern latitudes within the region (Rodman, Veblen, Battaglia, et al, 2020). Whereas these projected increases in AET have the potential to benefit growth and reproduction for some plant species and populations, substantial increases in moisture deficit may temper these potential benefits, especially at lower elevations and on south‐facing slopes (Rodman, Veblen, Battaglia, et al, 2020).…”

Section: Discussionmentioning

confidence: 99%

“…Through both an earlier age of reproductive maturity and greater seed dispersal distance (based on a much smaller individual seed mass; McCaughey et al, 1986), P. menziesii may be able to more quickly colonize large burned areas and those that have suffered early post‐fire regeneration failure. However, future climate warming is likely to limit post‐fire recovery for these two species (Rodman, Veblen, Battaglia, et al, 2020), and P. menziesii juveniles may be particularly vulnerable to drought‐induced mortality (Rother, Veblen, & Furman, 2015).…”

Section: Discussionmentioning

confidence: 99%

“…We quantified the age of established trees using increment cores collected at 20–40 cm above ground level and corrected tree age estimates for the offset from pith and time to reach coring height (Duncan, 1989; Table S3 in Appendix ). To summarize variation in climate among sites, we used average actual evapotranspiration (AET) and climatic water deficit (CWD) for the 1981–2010 period, developed at a 250‐m spatial throughout the southern Rocky Mountains (Rodman, Veblen, Battaglia, et al, 2020). AET is the total evapotranspiration constrained by moisture availability, and higher values are thought to be an indicator of greater net primary productivity (Stephenson, 1998).…”

Section: Methodsmentioning

confidence: 99%

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A trait‐based approach to assessing resistance and resilience to wildfire in two iconic North American conifers

et al. 2020

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Ongoing changes in fire regimes have the potential to drive widespread shifts in Earth's vegetation. Plant traits and vital rates provide insight into vulnerability to fire‐driven vegetation shifts because they can be indicators of the ability of individuals to survive fire (resistance) and populations to persist (resilience) following fire. In 15 study sites spanning climatic gradients in the southern Rocky Mountains, USA, we quantified variation in key traits and vital rates of two co‐occurring, widely distributed conifers (Pinus ponderosa Douglas ex. P. Lawson & C. Lawson and Pseudotsuga menziesii (Mirb.) Franco). We used mixed‐effects models to explain inter‐ and intraspecific variation in tree growth, survival, bark thickness and seed cone production, as a function of species, tree life stage (i.e. diameter, height and age), average climate, local competition and site conditions. Pinus ponderosa was predicted to survive low‐severity fire at a 23% earlier age than P. menziesii. Pinus ponderosa had thicker bark and more rapid juvenile height growth, traits conferring greater fire resistance. In contrast, P. menziesii was predicted to produce seed cones at a 28% earlier age than P. ponderosa. For both species, larger individuals were more likely to survive fire and to produce cones. For P. ponderosa, cone production increased where average actual evapotranspiration (AET) was higher and local competition was lower. More frequent cone production on productive sites with higher AET is an important and underappreciated mechanism that may help to explain greater resilience to fire in these areas. Synthesis. Our analyses indicated that many plant traits and vital rates related to fire differed between Pinus ponderosa and Pseudotsuga menziesii, with trade‐offs between investment in traits that promote individual defence to fire and those that promote recolonization of disturbed sites. Future changes in fire regimes will act as a filter throughout North American forests, with our findings helping to infer which individuals and populations of two iconic species are most vulnerable to future change and offering a framework for future inquiry in other forests facing an uncertain future.

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“…radial growth and mortality) in many of these subalpine forest habitats (Bigler et al., 2007; Kueppers et al., 2017; Villalba et al., 1994). Warming temperatures and more frequent and extreme droughts, as well as decreasing snowpack, are expected to further increase moisture deficits in the next several decades (Rodman et al., 2020; Siler et al., 2019). The effects of a changing climate may be exacerbated or modulated by ocean–atmosphere oscillations, such as El Niño‐Southern Oscillation (ENSO), that promote episodic droughts (McCabe et al., 2004) and coarse‐scale disturbances (e.g.…”

Section: Introductionmentioning

confidence: 99%

Increasing rates of subalpine tree mortality linked to warmer and drier summers

et al. 2021

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Warming temperatures and rising moisture deficits are expected to increase the rates of background tree mortality–low amounts of tree mortality (~0.5%–2% year−1), characterizing the forest demographic processes in the absence of abrupt, coarse‐scale disturbance events (e.g. fire). When compounded over multiple decades and large areas, even minor increases in background tree mortality (e.g. <0.5% year−1) can cause changes to forest communities and carbon storage potential that are comparable to or greater than those caused by disturbances. We examine how temporal variability in rates of background tree mortality for four subalpine conifers reflects variability in climate and climate teleconnections using observations of tree mortality from 1982 to 2019 at Niwot Ridge, Colorado, USA. Individually marked trees (initial population 5,043) in 13 permanent plots—located across a range of site conditions, stand ages and species compositions—were censused for new mortality nine times over 37 years. Background tree mortality was primarily attributed to stress from unfavourable climate and competition (71.2%) and bark beetle activity (23.3%), whereas few trees died from wind (5.3%) and wildlife impacts (0.2%). Mean annualized tree mortality attributed to tree stress and bark beetles more than tripled across all stands between initial censuses (0.26% year−1, 1982–1993/1994) and recent censuses (0.82% year−1, 2008–2019). Higher rates of tree mortality were related to warmer maximum summer temperatures, greater summer moisture deficits, and negative anomalies in ENSO (La Niña), with greater effects of drought in some subpopulations (tree size, age and species). For example, in older stands (>250 years), larger and older trees were more likely to die than smaller and younger trees. Differences in tree mortality rates and sensitivity to climate among subpopulations that varied by stand type may lead to unexpected shifts in stand composition and structure. Synthesis. A strong relationship between higher rates of tree mortality and warmer, drier summer climate conditions implies that climate warming will continue to increase background mortality rates in subalpine forests. Combined with increases in disturbances and declining frequency of moist‐cool years suitable for seedling establishment, increasing rates of tree mortality have the potential to drive declines in subalpine tree populations.

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A changing climate is snuffing out post‐fire recovery in montane forests

Cited by 75 publications

References 69 publications

Hotter Drought Escalates Tree Cover Declines in Blue Oak Woodlands of California

Hotter Drought Escalates Tree Cover Declines in Blue Oak Woodlands of California

A trait‐based approach to assessing resistance and resilience to wildfire in two iconic North American conifers

Increasing rates of subalpine tree mortality linked to warmer and drier summers

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