Mega‐disturbances cause rapid decline of mature conifer forest habitat in California

Ecological Applications, Journal Year: 2022, Volume and Issue: 33(2)

Published: Oct. 20, 2022

Abstract Mature forests provide important wildlife habitat and support critical ecosystem functions globally. Within the dry conifer of western United States, past management fire exclusion have contributed to forest conditions that are susceptible increasingly severe wildfire drought. We evaluated declines in cover southern Sierra Nevada California during a decade record disturbance by using spatially comprehensive structure estimates, perimeter data, eDaRT tracking algorithm. Primarily due combination wildfires, drought, drought‐associated beetle epidemics, 30% region's extent transitioned nonforest vegetation 2011–2020. In total, 50% mature 85% high density either lower or types. spotted owl protected activity centers (PAC) experienced greater canopy decline (49% 2011 cover) than non‐PAC areas (42% decline). Areas with initial without tall trees were most vulnerable declines, likely explaining disproportionate within PACs. Drought attack caused cumulative where drought mortality overlapped, both types natural far outpaced attributable mechanical activities. disproportionately affects large conifers is particularly problematic specialist species reliant on trees. However, patches degraded perimeters larger core area those outside burned areas, remnant habitats more fragmented affected alone. The percentage survived potentially benefited from severity increased over time as total declined. These some opportunity for improved resilience future disturbances, but strategic interventions also necessary mitigate worsening mega‐disturbances. Remaining may be complete loss coming decades rapid transition conservation paradigm attempts maintain static one manages sustainable dynamics.

Language: Английский

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The outsized role of California’s largest wildfires in changing forest burn patterns and coarsening ecosystem scale

Forest Ecology and Management, Journal Year: 2022, Volume and Issue: 528, P. 120620 - 120620

Published: Nov. 14, 2022

Although recent large wildfires in California forests are well publicized media and scientific literature, their cumulative effects on forest structure implications for resilience remain poorly understood. In this study, we evaluated spatial patterns of burn severity 18 exceptionally fires compared impacts to the hundreds smaller that have burned across decades. We used a atlas over 1,800 predominantly conifer between 1985 2020 calculated landscape metrics evaluate spatiotemporal unburned refugia, low-moderate-severity, high-severity post-fire effects. Total annual area burned, mean fire size, total core at high all significantly increased study period. Exceptionally (i.e., top 1% by size) were responsible 58% 42% low-moderate severities, respectively, With larger patch sizes, our results suggest coarsen pattern California’s forests, reducing fine-scale heterogeneity which supports much biodiversity as wildfire climate resilience. Thus far, most modern management has focused restoring cover minimizing ecotype conversion large, patches. These fires, however, also provided extensive areas burns where managers could leverage wildfire’s initial “treatment” with follow-up fuel reduction treatments help restore finer-scale

Language: Английский

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High‐severity burned area and proportion exceed historic conditions in Sierra Nevada, California, and adjacent ranges

Ecosphere, Journal Year: 2023, Volume and Issue: 14(1)

Published: Jan. 1, 2023

Abstract Although fire is a fundamental ecological process in western North American forests, climate warming and accumulating forest fuels due to suppression have led wildfires that burn at high severity across larger fractions of their footprint than were historically typical. These trends spiked upwards recent years are particularly pronounced the Sierra Nevada–Southern Cascades ecoregion California, USA, neighboring states. We assessed annual area burned (AAB) percentage low‐to‐moderate for seven major types this region from 1984 2020. compared values period against estimates pre‐Euro‐American settlement (EAS) prior 1850 previous study 2009. Our results show total average AAB remained below pre‐EAS levels, but gap decreasing (i.e., ~14% 1984–2009, 39% 2010–2020 [including ~150% 2020]). has low with pre‐EAS, both (AAHS) wildfire increased rapidly. The severity, which was already above 1984–2009 period, continued rise five types. Notably, between 2010 2020, AAHS exceeded first time on record. By contrast, decreased, lower elevation oak mixed conifer findings underline how forests adapted frequent being reshaped by novel proportions extents high‐severity burning. shift toward high‐severity‐dominated regime associated disruptions, including changes structure, species composition, carbon storage, wildlife habitat, ecosystem services, resilience. underscore importance finding better balance current management focus one puts greater emphasis proactive fuel reduction resilience change disturbance.

Language: Английский

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Contemporary wildfires are more severe compared to the historical reference period in western US dry conifer forests

Forest Ecology and Management, Journal Year: 2023, Volume and Issue: 544, P. 121232 - 121232

Published: July 3, 2023

Language: Английский

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Climate change is narrowing and shifting prescribed fire windows in western United States

Communications Earth & Environment, Journal Year: 2023, Volume and Issue: 4(1)

Published: Oct. 3, 2023

Abstract Escalating wildfire activity in the western United States has accelerated adverse societal impacts. Observed increases severity and impacts to communities have diverse anthropogenic causes—including legacy of fire suppression policies, increased development high-risk zones, aridification by a warming climate. However, intentional use as vegetation management tool, known “prescribed fire,” can reduce risk destructive fires restore ecosystem resilience. Prescribed implementation is subject multiple constraints, including number days characterized weather conditions conducive achieving desired outcomes. Here, we quantify observed projected trends frequency seasonality prescribed days. We find that while ~2 C global 2060 will such overall (−17%), particularly during spring (−25%) summer (−31%), winter (+4%) may increasingly emerge comparatively favorable window for especially northern states.

Language: Английский

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Frequent, heterogenous fire supports a forest owl assemblage

Ecological Applications, Journal Year: 2025, Volume and Issue: 35(1)

Published: Jan. 1, 2025

Abstract Fire shapes biodiversity in many forested ecosystems, but historical management practices and anthropogenic climate change have led to larger, more severe fires that threaten animal species where such disturbances do not occur naturally. As predators, owls can play important ecological roles biological communities, how changing fire regimes affect individual assemblages is largely unknown. Here, we examined the impact of severity, history, configuration over past 35 years on an assemblage six forest owl Sierra Nevada, California, using ecosystem‐scale passive acoustic monitoring. While negative impacts this appeared be ephemeral (1–4 duration), spotted avoided sites burned at high‐severity for up two decades after a fire. Low‐ moderate‐severity benefited small cavity‐nesting great horned owls. Most study adapted within region's natural range variation, characterized by higher proportions low‐ relatively less some may resilient wildfire than others, novel “megafires” are frequent, contiguously limit distribution reducing prevalence eliminating habitat closed‐canopy multiple decades. Management strategies restore with patches promote mosaic conditions will likely facilitate conservation predators.

Language: Английский

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Tradeoffs in growth and fuel reduction when using prescribed fire in young mixed conifer stands

Fire Ecology, Journal Year: 2025, Volume and Issue: 21(1)

Published: Feb. 6, 2025

Language: Английский

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Forest restoration and fuels reduction work: Different pathways for achieving success in the Sierra Nevada

Ecological Applications, Journal Year: 2023, Volume and Issue: 34(2)

Published: Nov. 10, 2023

Abstract Fire suppression and past selective logging of large trees have fundamentally changed frequent‐fire‐adapted forests in California. The culmination these changes produced that are vulnerable to catastrophic change by wildfire, drought, bark beetles, with climate exacerbating this vulnerability. Management options available address problem include mechanical treatments (Mech), prescribed fire (Fire), or combinations (Mech + Fire). We quantify forest structure composition, fuel accumulation, modeled behavior, intertree competition, economics from a 20‐year restoration study the northern Sierra Nevada. All three active (Fire, Mech, Mech Fire) conditions were much more resistant wildfire than untreated control. included lowest surface duff loads hazards. low hazards beginning 7 years after initial treatment had lower tree growth controls. only competition somewhat similar historical California mixed‐conifer was Fire, indicating stands under would likely be resilient enhanced stressors. While reduced hazard reintroduced fundamental ecosystem process, it done at net cost landowner. Using mastication thinning resulted positive revenues also relatively strong as an investment reducing hazard. represents compromise between desire sustain financial feasibility reintroduce fire. One key component long‐term conservation will continued maintain improve restoration. Many Indigenous people speak “active stewardship” one principles land management aligns well need for increased western US forests. If we do not use knowledge 20+ research longer tradition cultural practices knowledge, frequent‐fire continue degraded lost.

Language: Английский

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Surviving in Changing Forests: Abiotic Disturbance Legacy Effects on Arthropod Communities of Temperate Forests

Current Forestry Reports, Journal Year: 2023, Volume and Issue: 9(4), P. 189 - 218

Published: May 8, 2023

Language: Английский

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The magnitude and pace of photosynthetic recovery after wildfire in California ecosystems

Proceedings of the National Academy of Sciences, Journal Year: 2023, Volume and Issue: 120(15)

Published: April 3, 2023

Wildfire modifies the short- and long-term exchange of carbon between terrestrial ecosystems atmosphere, with impacts on ecosystem services such as uptake. Dry western US forests historically experienced low-intensity, frequent fires, patches across landscape occupying different points in fire-recovery trajectory. Contemporary perturbations, recent severe fires California, could shift historic stand-age distribution impact legacy uptake landscape. Here, we combine flux measurements gross primary production (GPP) chronosequence analysis using satellite remote sensing to investigate how last century California impacted dynamics fire-affected A GPP recovery trajectory curve more than five thousand forest since 1919 indicated that fire reduced by [Formula: see text] g C m[Formula: y[Formula: text]([Formula: text]) first year after fire, average prefire conditions y. The largest forested (n = 401) took two decades recover. Recent increases severity time have led nearly MMT CO[Formula: (3-y rolling mean) cumulative forgone due landscape, complicating challenge maintaining California's natural working lands a net sink. Understanding these changes is paramount weighing costs benefits associated fuels management for climate change mitigation.

Language: Английский

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