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1.
Ecol Appl ; 31(7): e02395, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34164888

RESUMO

Between 2012 and 2016, California suffered one of the most severe droughts on record. During this period Sequoiadendron giganteum (giant sequoias) in the Sequoia and Kings Canyon National Parks (SEKI), California, USA experienced canopy water content (CWC) loss, unprecedented foliage senescence, and, in a few cases, death. We present an assessment of the vulnerability of giant sequoia populations to droughts that is currently lacking and needed for management. We used a temporal trend of remotely sensed CWC obtained between 2015 and 2017, and recently georeferenced giant sequoia crowns to quantify the vulnerability of 7,408 individuals in 10 groves in the northern portion of SEKI. CWC is sensitive to changes in liquid water in tree canopies; therefore, it is a useful metric for quantifying the response of sequoia trees to drought. Temporal trends indicated that 9% of giant sequoias had a significant decline or consistently low CWC, suggesting these trees were likely operating at low photosynthetic capacity and potentially at high risk to drought stress. We also found that 20% of the giant sequoias had an increase or consistently high level of CWC, indicating these trees were at low risk to drought stress. These vulnerability categories were used in a random forest model with a combination of topographic, fire-related, and climate variables to generate high-resolution vulnerability risk maps. These maps show that higher risk is associated with lower elevation and higher climate water deficit. We also found that sequoias at higher elevations but located near meadows had higher vulnerability risk. These results and the vulnerability maps can identify vulnerable sequoias that may be difficult to save or locations of refugia to be protected, and thus may aid forest managers in preparation for future droughts.


Assuntos
Secas , Sequoiadendron , California , Clima , Incêndios , Tecnologia de Sensoriamento Remoto
2.
G3 (Bethesda) ; 10(11): 3907-3919, 2020 11 05.
Artigo em Inglês | MEDLINE | ID: mdl-32948606

RESUMO

The giant sequoia (Sequoiadendron giganteum) of California are massive, long-lived trees that grow along the U.S. Sierra Nevada mountains. Genomic data are limited in giant sequoia and producing a reference genome sequence has been an important goal to allow marker development for restoration and management. Using deep-coverage Illumina and Oxford Nanopore sequencing, combined with Dovetail chromosome conformation capture libraries, the genome was assembled into eleven chromosome-scale scaffolds containing 8.125 Gbp of sequence. Iso-Seq transcripts, assembled from three distinct tissues, was used as evidence to annotate a total of 41,632 protein-coding genes. The genome was found to contain, distributed unevenly across all 11 chromosomes and in 63 orthogroups, over 900 complete or partial predicted NLR genes, of which 375 are supported by annotation derived from protein evidence and gene modeling. This giant sequoia reference genome sequence represents the first genome sequenced in the Cupressaceae family, and lays a foundation for using genomic tools to aid in giant sequoia conservation and management.


Assuntos
Sequoiadendron , Cromossomos , Genoma , Sequenciamento de Nucleotídeos em Larga Escala , Anotação de Sequência Molecular , Árvores
3.
Int J Mol Sci ; 21(9)2020 May 09.
Artigo em Inglês | MEDLINE | ID: mdl-32397436

RESUMO

The influences of (1) a high fiber content, (2) the arrangement of fibers in fiber groups, and (3) a layered hierarchical composition of the bark of the giant sequoia (Sequoiadendron giganteum) on its energy dissipation capability are analyzed and discussed regarding the relevance for an application in bioinspired components in civil engineering. The giant sequoia is native to the Sierra Nevada (USA), a region with regular rockfalls. It is thus regularly exposed to high-energy impacts, with its bark playing a major protective role, as can be seen in the wild and has been proven in laboratory experiments. The authors quantify the fundamental biomechanical properties of the bark at various length scales, taking into account its hierarchical setup ranging from the integral level (whole bark) down to single bark fibers. Microtensile tests on single fibers and fiber pairs give insights into the properties of single fibers as well as the benefits of the strong longitudinal interconnection between single fibers arranged in pairs. Going beyond the level of single fibers or fiber pairs, towards the integral level, quasistatic compression tests and dynamic impact tests are performed on samples comprising the whole bark (inner and outer bark). These tests elucidate the deformation behavior under quasistatic compression and dynamic impact relevant for the high energy dissipation and impact-damping behavior of the bark. The remarkable energy dissipation capability of the bark at the abovementioned hierarchical levels are linked to the layered and fibrous structure of the bark structurally analyzed by thin sections and SEM and µCT scans.


Assuntos
Casca de Planta/fisiologia , Sequoiadendron/fisiologia , Estresse Mecânico , Árvores/fisiologia , Ailanthus/fisiologia , Parede Celular/ultraestrutura , Módulo de Elasticidade , Microscopia Eletrônica de Varredura , Casca de Planta/ultraestrutura , Resistência à Tração , Microtomografia por Raio-X
4.
Am J Bot ; 107(1): 45-55, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31883111

RESUMO

PREMISE: Patterns of genetic structure across a species' range reflect the long-term interplay between genetic drift, gene flow, and selection. Given the importance of gene flow in preventing the loss of diversity through genetic drift among spatially isolated populations, understanding the dynamics of gene flow and the factors that influence connectivity across a species' range is a major goal for conservation of genetic diversity. Here we present a detailed look at gene flow dynamics of Sequoiadendron giganteum, a paleoendemic tree species that will likely face numerous threats due to climate change. METHODS: We used microsatellite markers to examine nineteen populations of S. giganteum for patterns of genetic structure and to estimate admixture and rates of gene flow between eight population pairs. Also, we used Generalized Dissimilarity Models to elucidate landscape factors that shape genetic differentiation among populations. RESULTS: We found minimal gene flow between adjacent groves in the northern disjunct range. In most of the southern portion of the range, groves showed a signal of connectivity which degrades to isolation in the extreme south. Geographic distance was the most important predictor of genetic dissimilarity across the range, with environmental conditions related to precipitation and temperature explaining a small, but significant, portion of the genetic variance. CONCLUSIONS: Due to their isolation and unique genetic composition, northern populations of S. giganteum should be considered a high conservation priority. In this region, we suggest germplasm conservation as well as restoration planting to enhance genetic diversity.


Assuntos
Fluxo Gênico , Sequoiadendron , Ecossistema , Variação Genética , Genética Populacional , Repetições de Microssatélites
5.
Tree Physiol ; 37(10): 1312-1326, 2017 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-28985377

RESUMO

In tall trees, the mechanisms by which foliage maintains sufficient turgor pressure and water content against height-related constraints remain poorly understood. Pressure-volume curves generated from leafy shoots collected crown-wide from 12 large Sequoiadendron giganteum (Lindley) J. Buchholz (giant sequoia) trees provided mechanistic insights into how the components of water potential vary with height in tree and over time. The turgor loss point (TLP) decreased with height at a rate indistinguishable from the gravitational potential gradient and was controlled by changes in tissue osmotica. For all measured shoots, total relative water content at the TLP remained above 75%. This high value has been suggested to help leaves avoid precipitous declines in leaf-level physiological function, and in giant sequoia was controlled by both tissue elasticity and the balance of water between apoplasm and symplasm. Hydraulic capacitance decreased only slightly with height, but importantly this parameter was nearly double in value to that reported for other tree species. Total water storage capacity also decreased with height, but this trend essentially disappeared when considering only water available within the typical range of water potentials experienced by giant sequoia. From summer to fall measurement periods we did not observe osmotic adjustment that would depress the TLP. Instead we observed a proportional shift of water into less mobile apoplastic compartments leading to a reduction in hydraulic capacitance. This collection of foliar traits allows giant sequoia to routinely, but safely, operate close to its TLP, and suggests that gravity plays a major role in the water relations of Earth's largest tree species.


Assuntos
Gravitação , Folhas de Planta/fisiologia , Sequoiadendron/fisiologia , Água/fisiologia , Estações do Ano , Árvores/fisiologia
6.
Oecologia ; 182(3): 713-30, 2016 11.
Artigo em Inglês | MEDLINE | ID: mdl-27553681

RESUMO

Optimality theory states that whole-tree carbon gain is maximized when leaf N and photosynthetic capacity profiles are distributed along vertical light gradients such that the marginal gain of nitrogen investment is identical among leaves. However, observed photosynthetic N gradients in trees do not follow this prediction, and the causes for this apparent discrepancy remain uncertain. Our objective was to evaluate how hydraulic limitations potentially modify crown-level optimization in Sequoiadendron giganteum (giant sequoia) trees up to 90 m tall. Leaf water potential (Ψ l ) and branch sap flow closely followed diurnal patterns of solar radiation throughout each tree crown. Minimum leaf water potential correlated negatively with height above ground, while leaf mass per area (LMA), shoot mass per area (SMA), leaf nitrogen content (%N), and bulk leaf stable carbon isotope ratios (δ(13)C) correlated positively with height. We found no significant vertical trends in maximum leaf photosynthesis (A), stomatal conductance (g s), and intrinsic water-use efficiency (A/g s), nor in branch-averaged transpiration (E L), stomatal conductance (G S), and hydraulic conductance (K L). Adjustments in hydraulic architecture appear to partially compensate for increasing hydraulic limitations with height in giant sequoia, allowing them to sustain global maximum summer water use rates exceeding 2000 kg day(-1). However, we found that leaf N and photosynthetic capacity do not follow the vertical light gradient, supporting the hypothesis that increasing limitations on water transport capacity with height modify photosynthetic optimization in tall trees.


Assuntos
Sequoiadendron , Árvores , Fotossíntese , Folhas de Planta , Transpiração Vegetal , Água
7.
Am J Bot ; 103(5): 796-807, 2016 05.
Artigo em Inglês | MEDLINE | ID: mdl-27208348

RESUMO

PREMISE OF THE STUDY: Leaves respond to environmental signals and acclimate to local conditions until their ecological limits are reached. Understanding the relationships between anatomical variation in leaves and the availability of water and light improves our ability to predict ecosystem-level impacts of foliar response to climate change, as it expands our knowledge of tree physiology. METHODS: We examined foliar anatomy and morphology of the largest plant species, Sequoiadendron giganteum, from leafy shoot samples collected throughout crowns of trees up to 95 m tall and assessed the functionality of within-crown variation with a novel drought/recovery experiment. KEY RESULTS: We found phenotypic variation in response to water availability in 13 anatomical traits of Sequoiadendron leaves. Shoot expansion was constrained by the hydrostatic gradient of maximum water potential, while functional traits supporting succulence and toughness were associated with sites of peak hydraulic limitation. Water-stress tolerance in experimental shoots increased dramatically with height. CONCLUSION: We propose a heat-sink function for transfusion tissue and uncover a suite of traits suggesting rapid hydraulic throughput and flexibility in water-stress tolerance investments as strategies that help this montane species reach such enormous size. Responses to water stress alter the amount of carbon stored in foliage and the rate of the eventual release of carbon.


Assuntos
Adaptação Fisiológica , Folhas de Planta/fisiologia , Estresse Fisiológico , Traqueófitas/fisiologia , Água/fisiologia , Secas , Fenótipo , Brotos de Planta/anatomia & histologia , Brotos de Planta/fisiologia , Sequoiadendron/fisiologia , Traqueófitas/anatomia & histologia
9.
Tree Physiol ; 35(5): 453-69, 2015 May.
Artigo em Inglês | MEDLINE | ID: mdl-25787330

RESUMO

We compared the physiology and growth of seedlings originating from different Sequoia sempervirens (D. Don.) Endl. (coast redwood) and Sequoiadendron giganteum (Lindl.) Buchh. (giant sequoia) populations subjected to progressive drought followed by a recovery period in a controlled greenhouse experiment. Our objective was to examine how multiple plant traits interact to influence the response of seedlings of each species and seed population to a single drought and recovery cycle. We measured soil and plant water status, leaf gas exchange, stem embolism and growth of control (well-watered) and drought-stressed (water withheld) seedlings from each population at the beginning, middle and end of a 6-week drought period and again 2 weeks after re-watering. The drought had a significant effect on many aspects of seedling performance, but water-stressed seedlings regained most physiological functioning by the end of the recovery period. Sequoiadendron seedlings exhibited a greater degree of isohydry (water status regulation), lower levels of stem embolism, higher biomass allocation to roots and lower sensitivity of growth to drought compared with Sequoia. Only minor intra-specific differences were observed among populations. Our results show that seedlings of the two redwood species exhibit contrasting drought-response strategies that align with the environmental conditions these trees experience in their native habitats, and demonstrate trade-offs and coordination among traits affecting plant water use, carbon gain and growth under drought.


Assuntos
Secas , Sequoia/fisiologia , Sequoiadendron/fisiologia , Estresse Fisiológico , California , Clima , Plântula/genética , Plântula/crescimento & desenvolvimento , Plântula/fisiologia , Sequoia/genética , Sequoia/crescimento & desenvolvimento , Sequoiadendron/genética , Sequoiadendron/crescimento & desenvolvimento , Especificidade da Espécie
11.
Mycologia ; 104(5): 988-97, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22492401

RESUMO

Interactions with soil microbiota determine the success of restoring plants to their native habitats. The goal of our study was to understand the effects of restoration practices on interactions of giant sequoia Sequoiadendron giganteum with arbuscular mycorrhizal (AM) fungi (Glomeromycota). Natural regeneration of Sequoiadendron is threatened by the absence of severe fires that create forest canopy gaps. Generating artificial canopy gaps offers an alternative tool for giant sequoia restoration. We investigated the effect of regeneration practices, including (i) sapling location within gaps, (ii) gap size and (iii) soil substrate, on AM fungal colonization of giant sequoia sapling roots in a native giant sequoia grove of the Sierra Nevada, California. We found that the extent of AM fungal root colonization was positively correlated with sapling height and light availability, which were related to the location of the sapling within the gap and the gap size. While colonization frequency by arbuscules in saplings on ash substrate was higher relative to saplings in mineral soil, the total AM fungal root colonization was similar between the substrates. A negative correlation between root colonization by Glomeromycota and non-AM fungal species indicated antagonistic interactions between different classes of root-associated fungi. Using DNA genotyping, we identified six AM fungal taxa representing genera Glomus and Ambispora present in Sequoiadendron roots. Overall, we found that AM fungal colonization of giant sequoia roots was associated with availability of plant-assimilated carbon to the fungus rather than with the AM fungal supply of mineral nutrients to the roots. We conclude that restoration practices affecting light availability and carbon assimilation alter feedbacks between sapling growth and activity of AM fungi in the roots.


Assuntos
Glomeromycota/fisiologia , Micorrizas/crescimento & desenvolvimento , Sequoiadendron/crescimento & desenvolvimento , Sequoiadendron/microbiologia , California , Carbono/metabolismo , Ecossistema , Glomeromycota/genética , Glomeromycota/crescimento & desenvolvimento , Glomeromycota/metabolismo , Minerais/metabolismo , Micorrizas/efeitos dos fármacos , Micorrizas/metabolismo , Sequoiadendron/metabolismo , Solo , Árvores
12.
Food Chem Toxicol ; 48(7): 1945-9, 2010 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-20435080

RESUMO

In an attempt to isolate bioactive substances, ethyl acetate cone extract of Metasequoia glyptostroboides was subjected to a column chromatographic analysis that resulted in isolation of an abietane type diterpenoid, taxoquinone. Its structure was elucidated by spectroscopic means. In further, taxoquinone showed potential antibacterial effect as diameters of zones of inhibition against foodborne pathogenic bacteria such as Listeria monocytogenes ATCC 19166, Salmonella typhimurium KCTC 2515, Salmonella enteritidis KCTC 2021, Escherichia coli ATCC 8739, E. coli O157:H7 ATCC 43888, Enterobacter aerogenes KCTC2190, Staphylococcus aureus ATCC 6538 and S. aureus KCTC 1916, which were found in the range of 10.6-15.8mm. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of taxoquinone against the employed bacterial pathogens were found in the range of 62.5-250 and 125-500 microg/ml. Also the compound had strong antibacterial effect on the viable counts of the tested bacteria. Further, scanning electron microscopic study demonstrated potential detrimental effect of taxoquinone on the morphology of E. coli ATCC 8739. These findings indicate that bioactive compound taxoquinone present in M. glyptostroboides could be used as a promising antibacterial agent in food industry to inhibit the growth of certain important foodborne pathogens.


Assuntos
Antibacterianos/farmacologia , Contaminação de Alimentos/análise , Microbiologia de Alimentos , Sequoiadendron/química , Bactérias/efeitos dos fármacos , Carga Bacteriana , Escherichia coli/efeitos dos fármacos , Escherichia coli/ultraestrutura , Testes de Sensibilidade Microbiana , Microscopia Eletrônica de Varredura , Extratos Vegetais/farmacologia , Quinonas/farmacologia
13.
Plant Cell Environ ; 32(7): 743-57, 2009 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-19210642

RESUMO

We examined changes in branch hydraulic, leaf structure and gas exchange properties in coast redwood (Sequoia sempervirens) and giant sequoia (Sequoiadendron giganteum) trees of different sizes. Leaf-specific hydraulic conductivity (k(L)) increased with height in S. sempervirens but not in S. giganteum, while xylem cavitation resistance increased with height in both species. Despite hydraulic adjustments, leaf mass per unit area (LMA) and leaf carbon isotope ratios (delta(13)C) increased, and maximum mass-based stomatal conductance (g(mass)) and photosynthesis (A(mass)) decreased with height in both species. As a result, both A(mass) and g(mass) were negatively correlated with branch hydraulic properties in S. sempervirens and uncorrelated in S. giganteum. In addition, A(mass) and g(mass) were negatively correlated with LMA in both species, which we attributed to the effects of decreasing leaf internal CO(2) conductance (g(i)). Species-level differences in wood density, LMA and area-based gas exchange capacity constrained other structural and physiological properties, with S. sempervirens exhibiting increased branch water transport efficiency and S. giganteum exhibiting increased leaf-level water-use efficiency with increasing height. Our results reveal different adaptive strategies for the two redwoods that help them compensate for constraints associated with growing taller, and reflect contrasting environmental conditions each species faces in its native habitat.


Assuntos
Folhas de Planta/fisiologia , Caules de Planta/fisiologia , Transpiração Vegetal/fisiologia , Sequoia/fisiologia , Sequoiadendron/fisiologia , Isótopos de Carbono , Fotossíntese/fisiologia , Árvores/fisiologia , Água/fisiologia , Xilema/fisiologia
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