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Copyright of Fire Ecology is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Filamentous fungi associated with disease symptoms in non-native giant sequoia (Sequoiadendron giganteum) in Germany were investigated in ten cases of disease in Northwest Germany. During the study period from 2018 to 2023, a total of 81 species of Dikaria were isolated from woody tissue and needles of giant sequoia and morphotyped. Morphotypes were assigned to species designations based on ITS-sequence comparison and, in part, multi-locus phylogenetic analyses. Nine species were recognised as new reports for Germany or on giant sequoia: Amycosphaerella africana, Botryosphaeria parva, Coniochaeta acaciae, C. velutina, Muriformistrickeria rubi, Pestalotiopsis australis, P. monochaeta, Phacidiopycnis washingtonensis, and Rhizosphaera minteri. The threat posed to giant sequoia and other forest trees in Germany by certain, especially newly reported, fungal species is being discussed. The detection of a considerable number of new fungal records in the trees studied suggests that giant sequoia cultivation may be a gateway for alien fungal species in Germany. [ABSTRACT FROM AUTHOR]

The giant sequoia, a serotinous conifer naturally occurring in mixed‐conifer forests of the southern and central Sierra Nevada, California, USA, is the world's largest tree species. Giant sequoia reproduction has been severely lacking over the past century, due to fire exclusion, creating a significant conservation threat. Previous research on postfire sequoia reproduction in high‐severity fire areas, relative to low‐ and moderate‐severity areas, is limited. At 6 years postfire, we investigated giant sequoia reproduction in a high‐severity fire area, and nearby low‐/mixed‐severity fire areas, in the Nelder Grove, which burned in 2017 in the Railroad fire. Postfire giant sequoia reproduction was positively correlated with fire severity in terms of density, height (growth), and proportion (relative to other conifer species), and sequoia seedling/sapling density was positively correlated with percent shrub cover. There was no correlation between distance to live sequoia seed source and density of sequoia reproduction. More research is needed in other mixed‐severity fire areas, with larger high‐severity fire patches, to determine whether a similar postfire response occurs elsewhere. [ABSTRACT FROM AUTHOR]

Studying the species diversity and condition of monumental trees contributes to their preservation and is important for public awareness of their role in ecosystems and the country's ecological heritage. The purpose of the study was to reveal the significance of such trees for society. The task of the work was to research the characteristics of monumental trees in Ukraine. The history of environmental protection is analysed and the features of monumental tree preservation in Ukraine are presented. The beginning of environmental protection activity related to the preservation of trees in Ukraine and the most active periods have been revealed of it. The national features of the popularization of monumental trees are given. Based on the analysis of botanical natural monuments cadastres of Ukraine and Kyiv, quantitative and species composition of monumental trees were established. The most common (Quercus robur), common, less common and rare (Buxus sempervirens, Catalpa bignonioides, Metasequoia glyptostroboides, Pseudotsuga menziesii, Rhododendron myrtifolium, Sequoiadendron giganteum and others) species of monumental trees have been established, and important issues regarding their conservation are indicated. According to the types of street plantings, the majority (68%) are single trees. To assess the awareness of the population about ancient trees, the method of sociological survey of respondents was used. The most significant values of monumental trees for the population were studied. The importance of the populations' awareness of old trees through the development of an emotional connection with them, which contributes to their protection, has been established. The obtained results can be used in future environmental protection activity, exchanging of scientists' experience from different countries regarding the preservation of such trees, enrichment of information about growth characteristics, historical facts or other issues related to these trees [ABSTRACT FROM AUTHOR]

This article explores the lessons that can be learned from plants, specifically in relation to stress recognition and response. The author observes signs of stress in certain plants within a prairie community and contrasts how humans tend to focus on personal deficits when individuals exhibit stress, while plants prioritize identifying and addressing environmental factors. The author suggests that adopting a mindset of growth and thriving when engaging with fellow humans, similar to how we approach plants, could lead to positive transformations in human communities. The article also delves into the science of dendrochronology, which involves reading tree rings to understand climate patterns and tree age. It examines the historical and cultural significance of ancient trees and their veneration in various periods and cultures. The author expresses concerns about the modern tendency to quantify and measure trees, emphasizing the need to value trees beyond their instrumental use. The text further discusses the importance of preserving old trees in urban environments and designing cities that can support the growth of large and old trees in the face of climate change. It introduces the concept of "elderflora" and explores the factors contributing to tree longevity, highlighting the bias in dendrochronology towards certain plants and the exclusion of succulents. The text also emphasizes the significance of small-scale care for trees in cultural sites like temples and shrines. It discusses the role of botanic gardens in conservation and education, particularly in preserving genetic diversity. The article mentions California's efforts to preserve giant sequoias and touches on the aesthetics of longevity in bonsai. It acknowledges [Extracted from the article]

Fire is a critical driver of giant sequoia (Sequoiadendron giganteum [Lindl.] Buchholz) regeneration. However, fire suppression combined with the effects of increased temperature and severe drought has resulted in fires of an intensity and size outside of the historical norm. As a result, recent mega‐fires have killed a significant portion of the world's sequoia population (13%–19%), and uncertainty surrounds whether severely affected groves will be able to recover naturally, potentially leading to a loss of grove area. To assess the likelihood of natural recovery, we collected spatially explicit data assessing mortality, crown condition, and regeneration within four giant sequoia groves that were severely impacted by the SQF‐ (2020) and KNP‐Complex (2021) wildfires within Sequoia and Kings Canyon National Parks. In total, we surveyed 5.9 ha for seedlings and assessed the crown condition of 1104 giant sequoias. To inform management, we used a statistical methodology that robustly quantifies the uncertainty in inherently "noisy" seedling data and takes advantage of readily available remote sensing metrics that would make our findings applicable to other recently burned groves. A loss of giant sequoia grove area would be a consequence of giant sequoia tree mortality followed by a failure of natural regeneration. We found that areas that experienced very high‐severity fire (above ~800 RdNBR) are at substantial risk for the loss of grove area, with tree mortality rapidly increasing and giant sequoia seedling density simultaneously decreasing with fire severity. Such high‐severity areas comprised 17.8, 142.0, 14.6, 1.6 ha and ~90%, ~14%, ~53%, and ~27% of Board Camp, Redwood Mountain, Suwanee, and New Oriole Lake groves, respectively. In all sampling areas, we found that seedling densities fell far below the average density measured after prescribed fires, where seedling numbers were almost certainly adequate to maintain giant sequoia populations and postfire conditions were more in keeping with historical norms. Importantly, spatial pattern is also important in assessing the risk of grove loss, and in two groves, Suwanee and New Oriole Lake, the high‐severity patches were not always contiguous, potentially making some areas more resilient to regeneration failure due to the proximity of surviving trees. [ABSTRACT FROM AUTHOR]

Sequoiadendron giganteum (giant sequoia) has a fragmented distribution of 75 groves found along the western slope of the Sierra Nevada Mountains, California, USA. Outplanting and range expansion or assisted migration of this iconic species for the objectives of genetic conservation and timber production would be supported by information on growth and morphology to guide seed-collection decisions. We measured and assessed giant sequoia planted as seedlings and clonal stock originating from 22 groves in two common-garden experiments at Foresthill, California, north of the current species range, after 29 growing seasons. Traits examined were tree-size parameters, fluting and asymmetry of the lower stem, basal swelling, fullness of the live crown, epicormic sprouting, and heartwood decay resistance in cut stumps. Performance in terms of tree size after 29 years varied widely among genotypes with different grove origins. Morphology and decay resistance also exhibited some variation according to grove origins. The seedling stock outperformed the clonal stock of the same grove origins in terms of size and is therefore recommended when faster early growth is desired to outcompete other trees or for other management objectives. However, more fluting was exhibited by the larger fast-growing giant sequoia, while fewer seedlings had epicormic sprouts than the clonal stock of the same grove origins. At our warm low-elevation study site, giant sequoia from Mountain Home, Giant Forest, and Converse Basin consistently exhibited above-average growth among other giant sequoia in a pure planting and in an intimate mixture with five common conifer associates. Therefore, seed collected from these three groves should perform relatively well at other locations with a similar climate. When conservation of the species and its genetic diversity is the primary objective, we recommend collecting from a wide range of groves and undertaking assisted migration by planting at multiple locations inside and outside giant sequoia’s range as a hedge against the loss of native groves.

Giant sequoia groves, located on the western slope of the central and southern Sierra Nevada mountains in California, USA, have been experiencing regeneration failure for more than a century due to the exclusion of wildfires. Giant sequoias are serotinous conifers and have evolved a strong relationship between high-severity fire and reproduction. While this relationship is widely recognized, only one previous peer-reviewed study has directly investigated giant sequoia reproduction and fire severity, and that study used different fires for each severity class. We conducted a study of giant sequoia reproduction and fire severity in a single fire, the KNP Complex fire of 2021, within the Redwood Mountain Grove in Sequoia and Kings Canyon National Park. We found that giant sequoia seedlings are more dominant relative to other conifer species and are growing faster in a large high-severity fire area than in adjacent low/moderate-severity areas. Distance to the nearest live sequoia seed source was not a significant factor in sequoia seedling density. Our results call into question the basis for widespread plans and projects designed to prevent high-severity fires and should reevaluate moving forward with proposed tree planting activities in high-severity fire areas within giant sequoia groves. [ABSTRACT FROM AUTHOR]

Sequoiadendron giganteum (giant sequoia) has a fragmented distribution of 75 groves found along the western slope of the Sierra Nevada Mountains, California, USA. Outplanting and range expansion or assisted migration of this iconic species for the objectives of genetic conservation and timber production would be supported by information on growth and morphology to guide seed-collection decisions. We measured and assessed giant sequoia planted as seedlings and clonal stock originating from 22 groves in two common-garden experiments at Foresthill, California, north of the current species range, after 29 growing seasons. Traits examined were tree-size parameters, fluting and asymmetry of the lower stem, basal swelling, fullness of the live crown, epicormic sprouting, and heartwood decay resistance in cut stumps. Performance in terms of tree size after 29 years varied widely among genotypes with different grove origins. Morphology and decay resistance also exhibited some variation according to grove origins. The seedling stock outperformed the clonal stock of the same grove origins in terms of size and is therefore recommended when faster early growth is desired to outcompete other trees or for other management objectives. However, more fluting was exhibited by the larger fast-growing giant sequoia, while fewer seedlings had epicormic sprouts than the clonal stock of the same grove origins. At our warm low-elevation study site, giant sequoia from Mountain Home, Giant Forest, and Converse Basin consistently exhibited above-average growth among other giant sequoia in a pure planting and in an intimate mixture with five common conifer associates. Therefore, seed collected from these three groves should perform relatively well at other locations with a similar climate. When conservation of the species and its genetic diversity is the primary objective, we recommend collecting from a wide range of groves and undertaking assisted migration by planting at multiple locations inside and outside giant sequoia's range as a hedge against the loss of native groves. [ABSTRACT FROM AUTHOR]

Abstract The giant sequoia, a serotinous conifer naturally occurring in mixed‐conifer forests of the southern and central Sierra Nevada, California, USA, is the world's largest tree species. Giant sequoia reproduction has been severely lacking over the past century, due to fire exclusion, creating a significant conservation threat. Previous research on postfire sequoia reproduction in high‐severity fire areas, relative to low‐ and moderate‐severity areas, is limited. At 6 years postfire, we investigated giant sequoia reproduction in a high‐severity fire area, and nearby low‐/mixed‐severity fire areas, in the Nelder Grove, which burned in 2017 in the Railroad fire. Postfire giant sequoia reproduction was positively correlated with fire severity in terms of density, height (growth), and proportion (relative to other conifer species), and sequoia seedling/sapling density was positively correlated with percent shrub cover. There was no correlation between distance to live sequoia seed source and density of sequoia reproduction. More research is needed in other mixed‐severity fire areas, with larger high‐severity fire patches, to determine whether a similar postfire response occurs elsewhere.

Abstract Fire is a critical driver of giant sequoia (Sequoiadendron giganteum [Lindl.] Buchholz) regeneration. However, fire suppression combined with the effects of increased temperature and severe drought has resulted in fires of an intensity and size outside of the historical norm. As a result, recent mega‐fires have killed a significant portion of the world's sequoia population (13%–19%), and uncertainty surrounds whether severely affected groves will be able to recover naturally, potentially leading to a loss of grove area. To assess the likelihood of natural recovery, we collected spatially explicit data assessing mortality, crown condition, and regeneration within four giant sequoia groves that were severely impacted by the SQF‐ (2020) and KNP‐Complex (2021) wildfires within Sequoia and Kings Canyon National Parks. In total, we surveyed 5.9 ha for seedlings and assessed the crown condition of 1104 giant sequoias. To inform management, we used a statistical methodology that robustly quantifies the uncertainty in inherently “noisy” seedling data and takes advantage of readily available remote sensing metrics that would make our findings applicable to other recently burned groves. A loss of giant sequoia grove area would be a consequence of giant sequoia tree mortality followed by a failure of natural regeneration. We found that areas that experienced very high‐severity fire (above ~800 RdNBR) are at substantial risk for the loss of grove area, with tree mortality rapidly increasing and giant sequoia seedling density simultaneously decreasing with fire severity. Such high‐severity areas comprised 17.8, 142.0, 14.6, 1.6 ha and ~90%, ~14%, ~53%, and ~27% of Board Camp, Redwood Mountain, Suwanee, and New Oriole Lake groves, respectively. In all sampling areas, we found that seedling densities fell far below the average density measured after prescribed fires, where seedling numbers were almost certainly adequate to maintain giant sequoia populations and postfire conditions were more in keeping with historical norms. Importantly, spatial pattern is also important in assessing the risk of grove loss, and in two groves, Suwanee and New Oriole Lake, the high‐severity patches were not always contiguous, potentially making some areas more resilient to regeneration failure due to the proximity of surviving trees.

Water availability in mountain forests affects vegetation response to drought, which in turn changes evapotranspiration (ET). We investigated water-balance indicators based on precipitation (P) minus ET to assess Mediterranean-climate forest vulnerability to multi-year droughts. We used the drought-vulnerable dense mixed-conifer forests of California's Sierra Nevada, which includes 78 groves of giant sequoia as study area. With long-term Landsat-based ET data during 1985–2018, water-stress patterns at 30-m resolution during two historical droughts (1987–92 and 2012–15) were analyzed. Canopy moisture loss and tree mortality were used as indices of drought vulnerability. Using cumulative multi-year P–ET as an indicator, groves that were water stressed in 1987–92 were more vulnerable in California's unprecedented 2012–15 drought. Historical-minimum annual P–ET is an indicator of water stress, explaining 32% and 29% of the variances of canopy moisture loss and tree mortality, respectively. As an extreme test to explore potential vegetation response, we trained a deep-learning Long Short-Term Memory (LSTM) model to project ET during hypothetical extended-drought scenarios. The LSTM model reasonably predicted ET with r2 of 0.72 for the testing period. Annual P–ET using LSTM-based ET agreed (r2 = 0.99) with that using ET values from Landsat. Historical water-stress-prone areas were projected to suffer larger ET decreases and to experience more-severe stress during a 12-yr drought scenario. Water stress is more severe in lower-elevation forests, versus mid-to-high areas that have higher precipitation and shorter growing season under current climate. Our study provides water-balance-based indicators to project drought vulnerability and assess effects of disturbance in forests in a warming climate.

To determine whether the terpene composition of the resins of Metasequoia and Sequoiadendron genera is useful for chemotaxonomic discrimination, extracts of resins from trunks, needles, and female cones were analysed by gas chromatography. High levels of a-pinene and trace amounts of sesqui- and diterpenes were typical for resins from trunks and needles of M. glyptostroboides. Resins from cones contained also a higher level of (E)-ß-caryophyllene. In resins of S. giganteum, the levels of monoterpenes and diterpenes were nearly balanced. The resins from cones were an exception: 14-isopropylpodocarpa-8,11,13-trien-13-ol predominates noticeably over a-pinene. Using cluster analysis of the terpenes from needle resins, a distinct proximity of Sequoiadendron from USA and Metasequoia from Japan and Sequoiadendron from France and Metasequoia from the Czech Republic was proven. This proximity was caused by the presence of the monoterpene a-pinene in a very high quantity. On the contrary, great differences among S. giganteum growing in Corsica, Croatia, and the Czech Republic were caused by the presence of high levels of different terpenes such as elemicin, safrole, and 14-isopropylpodocarpa-8,11,13-trien-13-ol, each of them being detected only in a single study. The results therefore indicated that there is a proximity between Metasequoia and Sequoiadendron genera but only in some populations. [ABSTRACT FROM AUTHOR]

Copyright of Montes is the property of Colegio y Asociación de Ingenieros de Montes and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Trees play a vital role in enhancing public open spaces, such as city parks, gardens, inter-block spaces of greenery, urban forests, and recreational areas, providing green spaces and leisure opportunities for both residents and visitors. Their research reveals the alarming impact of ash dieback symptoms on various I Fraxinus i taxa, including native species and introduced North American and Asian ash species. However, the well-being of urban trees is under constant threat from various pests and pathogens, both native and invasive species. We strongly encouraged studies focusing on cutting-edge research in the realm of insect, plant, and pathogen interactions, research on the innovative tools used for detecting and identifying tree pests and pathogens, as well as ecological and field studies conducted in urban tree environments. [Extracted from the article]

Copyright of Fire Ecology is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Janssen, Merck, Roche, Takeda Research funding: AbbVie, AstraZeneca, BeiGene, CSL Behring, Gilead. ZANUBRUTINIB (ZANU) VERSUS BENDAMUSTINE + RITUXIMAB (BR) IN PATIENTS (PTS) WITH TREATMENT-NAïVE (TN) CLL/SLL: EXTENDED FOLLOW-UP OF THE SEQUOIA STUDY B Introduction: b Zanu, a next-generation Bruton tyrosine kinase inhibitor (BTKi), demonstrated superior progression-free survival (PFS) by independent review versus BR in pts with TN CLL/SLL without (w/o) del(17p) in the SEQUOIA study (NCT03336333) at a median follow-up of 26.2 mo; pts with del(17p) treated with zanu in a separate cohort had similar outcomes to pts w/o del(17p). [Extracted from the article]

We examine major reorganizations of the terrestrial ecosystem around Mono Lake, California during the last deglacial period from 16,000– 9,000 cal yr BP using pollen, microcharcoal, and coprophilous fungal spores (Sporormiella) from a deep-water sediment core. The pollen results record the assemblage, decline, and replacement of a mixed wooded community of Sierran and Great Basin taxa with Alkali Sink and Sagebrush Steppe biomes around Mono Lake. In particular, the enigmatic presence of Sequoiadendron-type pollen and its extirpation during the early Holocene hint at substantial biogeographic reorganizations on the Sierran-Great Basin ecotone during deglaciation. Rapid regional hydroclimate changes produced structural alterations in pine–juniper woodlands facilitated by increases in wildfires at 14,800 cal yr BP, 13,900 cal yr BP, and 12,800 cal yr BP. The rapid canopy changes altered the availability of herbaceous understory plants, likely putting pressure on megafauna populations, which declined in a stepwise fashion at 15,000 cal yr BP and 12,700 cal yr BP before final extirpation from Mono Basin at 11,500 cal yr BP. However, wooded vegetation communities overall remained resistant to abrupt hydroclimate changes during the late Pleistocene; instead, they gradually declined and were replaced by Alkali Sink communities in the lowlands as temperature increased into the Early Holocene, and Mono Lake regressed. [ABSTRACT FROM AUTHOR]

Absorption of water across the surfaces of leaves is an ecologically important aspect of tree physiology. Variation in foliar water uptake capacity depends on environmental conditions when traits associated with the uptake pathway respond to climatic signals. Using a series of experiments, we verify that water enters Sequoia sempervirens (D. Don) Endl. leaves by crossing the cuticle, and show that surface-trait acclimation alters the kinetic parameters of foliar water uptake. Under our experimental conditions, the cuticle was the primary pathway for water entry into the leaf. Exposure to climatic variation may induce surface acclimations, such as increased waxiness, that reduce water-film formation over stomata at the expense of dry-season foliar uptake rates. We found that water uptake is negatively associated with the interaction of leaf-surface wax coverage and stomatal density, and provide an accessible protocol to measure these key traits in Sequoia. Linking absorptive pathways and trait acclimation to physiological performance can provide a foundation for range-wide or genomic investigations of forest interactions with water and a mechanism-centered means to monitor canopy hydraulic parameters over time. [ABSTRACT FROM AUTHOR]

Giant sequoia groves, located on the western slope of the central and southern Sierra Nevada mountains in California, USA, have been experiencing regeneration failure for more than a century due to the exclusion of wildfires. Giant sequoias are serotinous conifers and have evolved a strong relationship between high-severity fire and reproduction. While this relationship is widely recognized, only one previous peer-reviewed study has directly investigated giant sequoia reproduction and fire severity, and that study used different fires for each severity class. We conducted a study of giant sequoia reproduction and fire severity in a single fire, the KNP Complex fire of 2021, within the Redwood Mountain Grove in Sequoia and Kings Canyon National Park. We found that giant sequoia seedlings are more dominant relative to other conifer species and are growing faster in a large high-severity fire area than in adjacent low/moderate-severity areas. Distance to the nearest live sequoia seed source was not a significant factor in sequoia seedling density. Our results call into question the basis for widespread plans and projects designed to prevent high-severity fires and should reevaluate moving forward with proposed tree planting activities in high-severity fire areas within giant sequoia groves.

A novel approach has been adopted for synthesizing green silver nanoparticles (AgNPs) over hemp/cotton blended woven fabrics. The nanosilvers were synthesized from the bark of mammoth pines (Sequoiadendron giganteum) through ensuring in situ synthesis protocol. The synthesized AgNPs displayed brilliant color appearances on the surfaces of fabrics due to LSPR (localized surface plasmon resonance) effects. The deposited AgNPs were quantified by X-ray fluorescence (XRF) tests for the solid samples and found significant presence of metallic silvers on the surfaces. The control and colored materials were characterized in terms of scanning electron microscopy (SEM) analysis, SEM-deployed EDX (energy-disruptive X-ray) and associated elemental mapping investigations and provided the explicit signal of AgNPs presence in the coated materials. The colorimetric data of the developed products were also investigated for the confirmation of developed color in the fabric samples. The perceived colorimetric data also shown the brilliant, bright, and stable coloration effects on nanosilver incorporated specimens. Moreover, the color fastness results also demonstrates a stable coloration effects on the fabrics due to the strong binding of AgNPs with the cellulosic materials. Statistically, coefficient of variations (R2) for all the colorimetric data also investigated to identify their relationship with nanosilver concentrations and found they are significant. Overall, this current research is going to report a novel, innovative, and sustainable coloration approach on hemp/cotton blended woven fabrics, which would facilitate the dyeing industries significantly. [ABSTRACT FROM AUTHOR]

Abstract: The relative greenness and wetness of Giant Sequoia (Sequoiadendron giganteum) groves and the surrounding Sierra Nevada, California forests were investigated using patterns in vegetation indices from Landsat imagery for the period 1985–2015. Vegetation greenness (normalized difference vegetation index) and thus forest biomass in groves increased by about 6% over that 30 year period, suggesting a 10% increase in evapotranspiration. No significant change in the surrounding nongrove forest was observed. In this period, local temperature measurements showed an increase of about 2.2°C. The wetness of groves (normalized difference wetness index) showed no overall long‐term trend but responded to changes in annual water‐year precipitation and temperature. The long‐term trends of grove greenness and wetness varied by elevation, with the lower rain‐snow transition elevation zone (1,700–2,100 m) marking a change from an increasing trend at lower elevations to a decreasing trend at higher elevations. The 2011–2015 drought brought an unprecedented drop in grove wetness, over 5 times the 1985–2010 standard deviation, and wetness in SEGI groves dropped 50% more than in nongrove areas. Overall, the wetness and greenness of SEGI groves showed a larger response to the warming climate and drought than nongrove areas. The influence of droughts on the wetness of SEGI groves reflected effects of both the multidecadal increase in forest biomass and the effects of warmer drought‐year temperatures on the evaporative demand of current grove vegetation, plus sufficient regolith water storage of rain and snowmelt to sustain that vegetation through seasonal and multiyear dry periods.

Many forests globally are experiencing increases in large, high-severity wildfires, often with increasingly inadequate post-fire tree regeneration. To identify areas that might need post-fire planting, forest managers have a growing need for seedling reference densities – the natural seedling densities expected to be adequate to regenerate a forest – to compare with observed post-fire seedling densities. The most useful reference densities will meet five criteria: they will (1) be specific to natural post-fire reproduction rather than planted seedlings (because planted seedlings can have substantially greater survival than natural seedlings, thus underestimating adequate natural reproduction), (2) apply to the first few years following fire (when management decisions and actions are most likely), (3) be specific to each of those post-fire years (because post-fire seedling densities can change rapidly with time since fire), (4) be associated with estimates of uncertainty, and (5) include consideration of novel environmental conditions during management applications (because most reference densities will be based on data collected under more environmentally benign conditions). The world's most massive tree species, the giant sequoia (Sequoiadendron giganteum) of California's Sierra Nevada, recently experienced historically unprecedented wildfires that killed an estimated 13–19% of mature sequoias across their native range. Seedlings germinating after these fires then experienced exceptional summer heat and the two most severe summer droughts of the 121-year historical record. To help inform management responses to these events, we used seedling censuses from past fires (mostly prescribed fires) to calculate sequoia seedling reference densities meeting the five criteria. The reference densities had three striking features, which are partly attributable to giant sequoia's status as a pioneer species. First, despite being inherently conservative, the reference densities were quite high. For example, mean first-year reference density was 172,599 seedlings ha−1. Second, reference densities declined precipitously with time since fire: the mean fifth-year reference density was only 5% of the mean first-year density. Third, the reference densities were associated with relatively substantial uncertainty, a consequence of density variations among seedling plots; for example, the 95% credible interval for first-year reference density was 64,377 to 313,438 seedlings ha−1. Despite this uncertainty, a case-study sequoia grove that recently burned in a high-severity wildfire had second-year post-fire seedling densities that were significantly (and dramatically) lower than the corresponding second-year reference density, suggesting inadequate post-fire reproduction. Our results highlight the value of the five criteria for reference densities – criteria that, in current practice, are rarely all met. • We propose five characteristics for useful seedling reference (stocking) densities. • Reference densities should derive from natural post-fire reproduction, not plantings. • A separate reference density may be needed for each year post-fire. • We develop and apply a probabilistic approach to using reference densities. • Reference densities must be assessed in the context of novel environmental conditions. [ABSTRACT FROM AUTHOR]