Natural range of variation of red fir and subalpine forests in the Sierra Nevada Bioregion

Meyer, Marc D.; North, Malcolm P.

doi:10.2737/psw-gtr-263

Cited by 19 publications

(30 citation statements)

References 131 publications

(330 reference statements)

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“…2002) or less than (Meyer et al. 2019, Meyer and North 2019) those found in pure stands at similar or higher elevations, respectively, and A. concolor abundances were slightly less than those found in pure stands at similar elevations (Barbour et al. 2002) and in mixed‐conifer stands at lower elevations (Knapp et al.…”

Section: Discussionmentioning

confidence: 85%

“…Climate change‐induced effects on disturbance activity will be a compounding driver of forest composition change, as shifts in climate are anticipated to amplify fire and bark beetle activity in montane and subalpine forests, affecting A. concolor and A. magnifica (Meyer and North 2019). Montane forest densification due to fire suppression has predisposed forests to greater disturbance risk and severity through the build‐up of fuels and increased competition for limited resources (Young et al.…”

Section: Discussionmentioning

confidence: 99%

“…Departures from historical fire frequencies are less pronounced in the A. magnifica zone and, while upper elevation A. magnifica forest composition and structure still reside within their natural range of variation, canopy decline and tree mortality are expected to increase with rising fire and beetle activity under future climates (Meyer et al. 2019, Meyer and North 2019). Local shifts in forest trajectories are expected to be catalyzed by disturbance (Smith et al.…”

Section: Discussionmentioning

confidence: 99%

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Persistent yet vulnerable: resurvey of an Abies ecotone reveals few differences but vulnerability to climate change

Nelson

O’Dean

Knapp

et al. 2021

Ecology

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Climate change is shifting forest tree species distributions across elevational and latitudinal gradients, and these changes are often pronounced at ecotones where species meet their climatic bounds and are replaced by other species. Using an extensive ecotone composed of lower‐montane white fir (Abies concolor var. lowiana) and upper‐montane red fir (Abies magnifica var. magnifica) in the central Sierra Nevada range of California, USA, we (1) examined how the demographics of the ecotone have responded to recent climate using a field observational study and a historical dataset, (2) quantified climate drivers across species life stages using contemporary demographic data, and (3) tested the potential impacts of future climate on species‐specific seedling survival and growth in a fully factorial growth chamber experiment that varied temperature, growing season length, and water availability. A re‐examination of the ecotone midpoint after 35 yr suggested a reduction in A. concolor sapling and tree densities and a rise in A. magnifica proportional dominance between surveys. Seedling abundances across the ecotone indicated that A. magnifica tends to dominate the regeneration layer and currently forms an important component of the seedling community at elevations below those where A. magnifica saplings or trees begin to co‐dominate stands. Observational and experimental assessments suggest that temperature and precipitation serve as important drivers, differentiating A. concolor vs. A. magnifica distributions, and are primary stressors at the seedling stage. Seedlings of both species were adversely affected by experimental climate treatments, although A. concolor exhibited greater survival and a more conservative growth strategy under extreme climatic stress than A. magnifica. Projections indicate that historical climate conditions will rise by an amount greater than the ecotone’s current elevational extent by the end of the 21st century. Differential drivers of species abundances suggest that the projected climate will expand conditions that promote A. concolor abundance and impede A. magnifica abundance across the ecotone; however, disturbance activity and microclimatic conditions will also influence regeneration and overstory tree dynamics. Our study demonstrates the importance of quantifying species‐specific responses to climate and indicates that widespread regeneration failure may be one possible consequence in which species exhibit strong sensitivity to projected climate conditions.

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Section: Discussionmentioning

confidence: 85%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Persistent yet vulnerable: resurvey of an Abies ecotone reveals few differences but vulnerability to climate change

Nelson

O’Dean

Knapp

et al. 2021

Ecology

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“…At higher elevations, red fir forests burned slightly less frequently (40‐year mean fire return interval) and with greater percentage of high severity (10%–20%; Mallek et al., 2013; Safford & Water, 2014). The historic spatial patterns of fire severity is less certain, but high‐severity patches were likely relatively small (mostly <10 ha) in the yellow pine and mixed conifer forests (Safford & Stevens, 2017), and contemporary reference sites show 86% of high‐severity patches in red fir and subalpine forests are less than 15 ha in size (Meyer & North, 2019).…”

Section: Methodsmentioning

confidence: 99%

When bigger isn’t better—Implications of large high‐severity wildfire patches for avian diversity and community composition

Steel

Fogg

Burnett

et al. 2021

Diversity and Distributions

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Aim Wildfires increasingly create large high‐severity patches with interior areas far from less disturbed habitats. We evaluated how these trends impact bird communities by investigating the effect of internal distance from lower‐severity areas, high‐severity patch size, and years since fire on avian alpha and beta diversity. Location Sierra Nevada, California, USA. Methods Bird occurrence data were collected during 2009–2017 within high‐severity patches of 27 wildfires representing 1–30 years since disturbance. A two‐step multispecies occupancy method was used to account for imperfect detection of 94 species and estimate effects of patch characteristics on community richness and dissimilarity. Results Community richness decreased with distance from patch edge and with patch size. Richness increased with years since fire, but this pattern was dependent on distance from edge with higher peak richness (23 species) near edges than interiors (18 species). Community dissimilarity was not associated with distance, indicating that large high‐severity patch interiors contain subsets of, rather than complements to, edge communities. Dissimilarity peaked later with increasing patch size. Guild richness of tree and primary cavity nesters was negatively associated with distance and patch size. Richness of ground and shrub nesters was insensitive to distance, while shrub nester richness increased somewhat with patch size. Due to declines among other species, ground and shrub nesters made up a greater percentage of the avian community within the interiors of large high‐severity patches. Main conclusions As fire activity increases due to accumulating forest fuels and accelerating climate change, high‐severity patches and their resulting early‐seral habitats are becoming more extensive with less edge and more interior area. Such changes are likely to decrease avian diversity locally and shift community composition away from forest‐associated species. Management actions that promote the full range of fire effects but limit high‐severity patch size may best conserve bird diversity within fire‐adapted ecosystems.

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“…This article is protected by copyright. All rights reserved Here, we study how productivity influences the effects of fire severity on understory species diversity in Mediterranean-type subalpine forest in California, where mountainous terrain drives local variation in productivity via steep temperature and moisture gradients (Meyer and North 2019). We sampled understory plant richness in 13 subalpine fires that spanned nearly 500 km in latitude and included both fire severity and productivity gradients (Appendix S1: Fig.…”

Section: Accepted Articlementioning

confidence: 99%

Productivity modifies the effects of fire severity on understory diversity

Brodie¹,

Miller

Safford

2021

Ecology

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High severity fire may promote or reduce plant understory diversity in forests. However, few empirical studies test long-standing theoretical predictions that productivity may help to explain observed variation in post-fire plant diversity. Support for the influence of productivity on disturbance-diversity relationships is found predominantly in experimental grasslands, while tests over large areas with natural disturbance and productivity gradients are few and have yielded inconsistent results. Here, we measured the response of post-fire understory plant diversity to natural gradients of fire severity and productivity in a large-scale observational study in California's subalpine forests. We found that plant species richness increased with increasing fire severity and that this trend was stronger at high productivity. We used plant traits to investigate whether release from competition might contribute to increasing diversity and found that short-lived and far-dispersing species benefited more from high severity fire than their long-lived and near-dispersing counterparts.For far-dispersing species only, the benefit from high severity fire was stronger in high productivity plots where unburned species richness was lowest. Our results support theoretical connections between fire severity, productivity and plant communities that are key to predicting the consequences of increasing fire severity and frequency on diversity in the coming decades.

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Natural range of variation of red fir and subalpine forests in the Sierra Nevada Bioregion

Cited by 19 publications

References 131 publications

Persistent yet vulnerable: resurvey of an Abies ecotone reveals few differences but vulnerability to climate change

Persistent yet vulnerable: resurvey of an Abies ecotone reveals few differences but vulnerability to climate change

When bigger isn’t better—Implications of large high‐severity wildfire patches for avian diversity and community composition

Productivity modifies the effects of fire severity on understory diversity

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