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Carol A. Brewer - One of the best experts on this subject based on the ideXlab platform.
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Effects of Short-term, High Exposure to Chlorine Gas on Morphology and Physiology of Pinus ponderosa andPseudotsuga menziesii
Annals of Botany, 2001Co-Authors: Maarten D. J. Schreuder, Carol A. BrewerAbstract:Following an accidental spill, acute morphological and physiological eAects of chlorine gas exposurewere evaluated on two conifer species, Pseudotsuga menziesii (Mirb.) Franco and Pinus ponderosa (L.), growing in a montane, coniferous forest in the Rocky Mountains, USA. Foliar injury, consisting of chlorosis, necrotic mottling and necrosis was observed only on foliage that was directly exposed to chlorine gas. Necrotic needles of both species defoliated during the months immediately following exposure. Buds of both species within 50 m of the gas release were killed; this gave rise to secondary shoot growth for Pseudotsuga menziesii. Cuticular injury was assessed by measuring droplet contact and retention angles on 1-year-old foliage (directlyexposed) and current-year foliage (which flushed after the gas cloud had subsided). Chlorine gas exposure led to smaller droplet contact angles on needles in both age classes of Pseudotsuga menziesii (P 5 0.0001), but not on Pinus ponderosa. Moreover, exposure led to increased cuticular water loss and decreased total water content of needles in both age classes of Pseudotsuga menziesii, and for 1-year-old needles of Pinus ponderosa (P 5 0.0001). On exposed trees, needles in both age classes had lower Fv/Fm ratios (P 5 0.0001), suggesting reductions in photosynthetic eAciency. Thus, exposure of needles to chlorine gas may lead to increased drought susceptibility and damage to chloroplast membranes in conifers, and may have a negative influence on tree growth. Importantly, plant responses to chlorine gas are species-specific and are influenced by variation between sites and the stochastic movement of chlorine gas clouds. # 2001 Annals of Botany Company
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Persistent Effects of Short-term, High Exposure to Chlorine Gas on Physiology and Growth of Pinus ponderosa andPseudotsuga menziesii
Annals of Botany, 2001Co-Authors: Maarten D. J. Schreuder, Carol A. BrewerAbstract:Following a single acute exposure to chlorine gas, persistent eAects on epicuticular waxes, cuticular transpiration, tree growth and mortality were studied in foliage of Pinus ponderosa and Pseudotsuga menziesii for three growing seasons. Chlorine gas exposure caused foliar injury to both exposed foliage and foliage that flushed after exposure (P 5 0.05). The tendency to form films of water rather than droplets was greater in directly exposed foliage (P 5 0.001). Rates of cuticular transpiration were higher for directly and indirectly exposed foliage of Pinus ponderosa up to 1 year after exposure and up to 6 months after exposure for directly exposed Pseudotsuga menziesii (P 5 0.001), after which P. menziesii needles defoliated. Total water content (TWC) and relative water content were significantly correlated with foliar injury (P 5 0.05). TWC was lower for directly exposed foliage up to 1 year after exposure (P 5 0.001). There was no persistent negative eAect on Fv/Fm ratios after 1 year. Exposure to chlorine gas did not aAect needle length or annual shoot increment growth, but exposure was correlated with increased bud production. Needle longevity of foliage that flushed 2 months after exposure was reduced significantly (P 5 0.001). Annual stem increment growth for both species decreased over at least three growing seasons following chlorine gas exposure (P 5 0.001), and depended on distance from the spill site. Cone production was lower for exposed Pinus ponderosa trees compared to controls (P 5 0.05), and tree mortality was higher within approx. 50 m of the release site for Pseudotsuga menziesii. Growth responses for both conifers agreed well with predicted patterns of carbon allocation after defoliation caused by chlorine gas exposure. # 2001 Annals of Botany Company
Maarten D. J. Schreuder - One of the best experts on this subject based on the ideXlab platform.
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Effects of Short-term, High Exposure to Chlorine Gas on Morphology and Physiology of Pinus ponderosa andPseudotsuga menziesii
Annals of Botany, 2001Co-Authors: Maarten D. J. Schreuder, Carol A. BrewerAbstract:Following an accidental spill, acute morphological and physiological eAects of chlorine gas exposurewere evaluated on two conifer species, Pseudotsuga menziesii (Mirb.) Franco and Pinus ponderosa (L.), growing in a montane, coniferous forest in the Rocky Mountains, USA. Foliar injury, consisting of chlorosis, necrotic mottling and necrosis was observed only on foliage that was directly exposed to chlorine gas. Necrotic needles of both species defoliated during the months immediately following exposure. Buds of both species within 50 m of the gas release were killed; this gave rise to secondary shoot growth for Pseudotsuga menziesii. Cuticular injury was assessed by measuring droplet contact and retention angles on 1-year-old foliage (directlyexposed) and current-year foliage (which flushed after the gas cloud had subsided). Chlorine gas exposure led to smaller droplet contact angles on needles in both age classes of Pseudotsuga menziesii (P 5 0.0001), but not on Pinus ponderosa. Moreover, exposure led to increased cuticular water loss and decreased total water content of needles in both age classes of Pseudotsuga menziesii, and for 1-year-old needles of Pinus ponderosa (P 5 0.0001). On exposed trees, needles in both age classes had lower Fv/Fm ratios (P 5 0.0001), suggesting reductions in photosynthetic eAciency. Thus, exposure of needles to chlorine gas may lead to increased drought susceptibility and damage to chloroplast membranes in conifers, and may have a negative influence on tree growth. Importantly, plant responses to chlorine gas are species-specific and are influenced by variation between sites and the stochastic movement of chlorine gas clouds. # 2001 Annals of Botany Company
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Persistent Effects of Short-term, High Exposure to Chlorine Gas on Physiology and Growth of Pinus ponderosa andPseudotsuga menziesii
Annals of Botany, 2001Co-Authors: Maarten D. J. Schreuder, Carol A. BrewerAbstract:Following a single acute exposure to chlorine gas, persistent eAects on epicuticular waxes, cuticular transpiration, tree growth and mortality were studied in foliage of Pinus ponderosa and Pseudotsuga menziesii for three growing seasons. Chlorine gas exposure caused foliar injury to both exposed foliage and foliage that flushed after exposure (P 5 0.05). The tendency to form films of water rather than droplets was greater in directly exposed foliage (P 5 0.001). Rates of cuticular transpiration were higher for directly and indirectly exposed foliage of Pinus ponderosa up to 1 year after exposure and up to 6 months after exposure for directly exposed Pseudotsuga menziesii (P 5 0.001), after which P. menziesii needles defoliated. Total water content (TWC) and relative water content were significantly correlated with foliar injury (P 5 0.05). TWC was lower for directly exposed foliage up to 1 year after exposure (P 5 0.001). There was no persistent negative eAect on Fv/Fm ratios after 1 year. Exposure to chlorine gas did not aAect needle length or annual shoot increment growth, but exposure was correlated with increased bud production. Needle longevity of foliage that flushed 2 months after exposure was reduced significantly (P 5 0.001). Annual stem increment growth for both species decreased over at least three growing seasons following chlorine gas exposure (P 5 0.001), and depended on distance from the spill site. Cone production was lower for exposed Pinus ponderosa trees compared to controls (P 5 0.05), and tree mortality was higher within approx. 50 m of the release site for Pseudotsuga menziesii. Growth responses for both conifers agreed well with predicted patterns of carbon allocation after defoliation caused by chlorine gas exposure. # 2001 Annals of Botany Company
Daniel M. Johnson - One of the best experts on this subject based on the ideXlab platform.
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Short- and long-term effects of fire on stem hydraulics in Pinus ponderosa saplings
Plant cell & environment, 2020Co-Authors: Raquel Partelli-feltrin, Henry D. Adams, Crystal A. Kolden, Alistair M. S. Smith, Daniel M. JohnsonAbstract:Understanding tree physiological responses to fire is needed to accurately model post-fire carbon processes and inform management decisions. Given trees can die immediately or at extended time periods after fire, we combined two experiments to assess the short- (one-day) and long-term (21-months) fire effects on Pinus ponderosa sapling water transport. Native percentage loss of conductivity (nPLC), vulnerability to cavitation, and xylem anatomy were assessed in unburned and burned saplings at lethal and non-lethal fire intensities. Fire did not cause any impact on nPLC and xylem cell wall structure in either experiment. However, surviving saplings evaluated 21-months post-fire were more vulnerable to cavitation. Our anatomical analysis in the long-term experiment showed that new xylem growth adjacent to fire scars had irregular-shaped tracheids and many parenchyma cells. Given conduit cell wall deformation was not observed in the long-term experiment, we suggest that the irregularity of newly grown xylem cells nearby fire wounds may be responsible for decreasing resistance to embolism in burned plants. Our findings suggest that hydraulic failure is not the main short-term physiological driver of mortality for Pinus ponderosa saplings. However, the decrease in embolism resistance in fire-wounded saplings could contribute to sapling mortality in the years following fire. This article is protected by copyright. All rights reserved.
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Drought Increases Vulnerability of Pinus ponderosa Saplings to Fire-Induced Mortality
Fire, 2020Co-Authors: Raquel Partelli-feltrin, Daniel M. Johnson, Aaron M. Sparks, Henry D. Adams, Crystal A. Kolden, Andrew S. Nelson, Alistair M. S. SmithAbstract:The combination of drought and fire can cause drastic changes in forest composition and structure. Given the predictions of more frequent and severe droughts and forecasted increases in fire size and intensity in the western United States, we assessed the impact of drought and different fire intensities on Pinus ponderosa saplings. In a controlled combustion laboratory, we exposed saplings to surface fires at two different fire intensity levels (quantified via fire radiative energy; units: MJ m−2). The recovery (photosynthesis and bud development) and mortality of saplings were monitored during the first month, and at 200- and 370-days post-fire. All the saplings subjected to high intensity surface fires (1.4 MJ m−2), regardless of the pre-fire water status, died. Seventy percent of pre-fire well-watered saplings recovered after exposure to low intensity surface fire (0.7 MJ m−2). All of the pre-fire drought-stressed saplings died, even at the lower fire intensity. Regardless of the fire intensity and water status, photosynthesis was significantly reduced in all saplings exposed to fire. At 370 days post-fire, burned well-watered saplings that recovered had similar photosynthesis rates as unburned plants. In addition, all plants that recovered or attempted to recover produced new foliage within 35 days following the fire treatments. Our results demonstrate that the pre-fire water status of saplings is an important driver of Pinus ponderosa sapling recovery and mortality after fire.
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Impacts of fire radiative flux on mature Pinus ponderosa growth and vulnerability to secondary mortality agents
International Journal of Wildland Fire, 2017Co-Authors: Aaron M. Sparks, Crystal A. Kolden, Alistair M. S. Smith, Alan F. Talhelm, Kara M. Yedinak, Daniel M. JohnsonAbstract:Recent studies have highlighted the potential of linking fire behaviour to plant ecophysiology as an improved route to characterising severity, but research to date has been limited to laboratory-scale investigations. Fine-scale fire behaviour during prescribed fires has been identified as a strong predictor of post-fire tree recovery and growth, but most studies report these metrics averaged over the entire fire. Previous research has found inconsistent effects of low-intensity fire on mature Pinus ponderosa growth. In this study, fire behaviour was quantified at the tree scale and compared with post-fire radial growth and axial resin duct defences. Results show a clear dose–response relationship between peak fire radiative power per unit area (W m–2) and post-fire Pinus ponderosa radial growth. Unlike in previous laboratory research on seedlings, there was no dose–response relationship observed between fire radiative energy per unit area (J m–2) and post-fire mature tree growth in the surviving trees. These results may suggest that post-fire impacts on growth of surviving seedlings and mature trees require other modes of heat transfer to impact plant canopies. This study demonstrates that increased resin duct defence is induced regardless of fire intensity, which may decrease Pinus ponderosa vulnerability to secondary mortality agents.
Frank W. Telewski - One of the best experts on this subject based on the ideXlab platform.
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Pinus ponderosa: A checkered past obscured four species
American journal of botany, 2016Co-Authors: Ann Willyard, Frank W. Telewski, Kevin M Potter, Valerie D Hipkins, Mary F Mahalovich, David S. Gernandt, Paula E. Marquardt, Stephen K. Langer, Blake Cooper, Connor DouglasAbstract:PREMISE OF THE STUDY: Molecular genetic evidence can help delineate taxa in species complexes that lack diagnostic morphological characters. Pinus ponderosa (Pinaceae; subsection ponderosae ) is recognized as a problematic taxon: plastid phylogenies of exemplars were paraphyletic, and mitochondrial phylogeography suggested at least four subdivisions of P. ponderosa. These patterns have not been examined in the context of other ponderosae species. We hypothesized that putative intraspecific subdivisions might each represent a separate taxon. METHODS: We genotyped six highly variable plastid simple sequence repeats in 1903 individuals from 88 populations of P. ponderosa and related ponderosae (P. arizonica, P. engelmannii, and P. jeffreyi). We used multilocus haplotype networks and discriminant analysis of principal components to test clustering of individuals into genetically and geographically meaningful taxonomic units. KEY RESULTS: There are at least four distinct plastid clusters within P. ponderosa that roughly correspond to the geographic distribution of mitochondrial haplotypes. Some geographic regions have intermixed plastid lineages, and some mitochondrial and plastid boundaries do not coincide. Based on relative distances to other species of ponderosae, these clusters diagnose four distinct taxa. CONCLUSIONS: Newly revealed geographic boundaries of four distinct taxa (P. benthamiana, P. brachyptera, P. scopulorum, and a narrowed concept of P. ponderosa) do not correspond completely with taxonomies. Further research is needed to understand their morphological and nuclear genetic makeup, but we suggest that resurrecting originally published species names would more appropriately refl ect the taxonomy of this checkered classifi cation than their current treatment as varieties of P. ponderosa.
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Spatial pattern of allozyme variation in a contact zone of Pinus ponderosa and P. arizonica (Pinaceae)
American journal of botany, 2003Co-Authors: Bryan K. Epperson, Myong Gi Chung, Frank W. TelewskiAbstract:The spatial distribution of genotypes for nine polymorphic allozyme loci was examined in a contact zone between Pinus ponderosa var. scopulorum and another tree regarded as either a separate species, Pinus arizonica, or variety, Pinus ponderosa var. arizonica ,i n southern Arizona. Previous work had identified a steep elevational cline for a key taxonomic trait, number of leaf-needles per fascicle, on the south slope of Mt. Lemmon. The present results indicate that the taxa are not fully interbreeding in this contact zone, because allozyme genotypes are considerably more spatially structured than expected for the dispersal characteristics of pines. The amount of spatial differentiation is also much less than that observed for needle number. It appears that this is due to the lack of differentiation for allozyme gene frequencies for the two types of trees, which is further evidenced by analysis of samples from two other populations away from the contact zone. It is likely that if the two taxa were isolated in the past, it was not for long enough nor complete enough to allow mutation-drift to create substantial differentiation between them. Another possible explanation is that introgression after recontact is so advanced that any differences have been erased throughout the Santa Catalina mountain range. ponderosa pine (Pinus ponderosa Law.) has a broad range throughout much of the western United States, and it extends south along the Rocky Mountains into the southwestern United States, where it reaches a transition zone. Whereas in the broad plateau country in northern Arizona and New Mexico, ponderosa pine is generally considered to occur as a single taxon, Pinus ponderosa var. scopulorum Engelm., in southern Arizona it co-occurs with and possibly interbreeds with another tree, variously regarded as a separate species, Pinus arizonica Engelm. (Perry, 1991; Farjon and Styles, 1997), or variety, Pinus ponderosa var. arizonica (Engelm) Shaw (Kearney and Peebles, 1964). Taxa in this region differ by a number of highly heritable seed cone and leaf-needle traits, including numbers of needles per fascicle (Rehfeldt et al., 1996; Rehfeldt, 1999). Pinus ponderosahas three needles whereas arizonica is a fiveneedle pine (e.g., Niebling and Conkle, 1990). Pinus arizonica’s distribution extends much farther south, well into the central mountains of Mexico. The five-needle form may be better adapted to warmer conditions. In certain regions of Arizona, New Mexico, and northwestern Mexico the ranges of the two taxa overlap (Perry, 1991; Flora of North America Editorial
Connor Douglas - One of the best experts on this subject based on the ideXlab platform.
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Pinus ponderosa: A checkered past obscured four species
American journal of botany, 2016Co-Authors: Ann Willyard, Frank W. Telewski, Kevin M Potter, Valerie D Hipkins, Mary F Mahalovich, David S. Gernandt, Paula E. Marquardt, Stephen K. Langer, Blake Cooper, Connor DouglasAbstract:PREMISE OF THE STUDY: Molecular genetic evidence can help delineate taxa in species complexes that lack diagnostic morphological characters. Pinus ponderosa (Pinaceae; subsection ponderosae ) is recognized as a problematic taxon: plastid phylogenies of exemplars were paraphyletic, and mitochondrial phylogeography suggested at least four subdivisions of P. ponderosa. These patterns have not been examined in the context of other ponderosae species. We hypothesized that putative intraspecific subdivisions might each represent a separate taxon. METHODS: We genotyped six highly variable plastid simple sequence repeats in 1903 individuals from 88 populations of P. ponderosa and related ponderosae (P. arizonica, P. engelmannii, and P. jeffreyi). We used multilocus haplotype networks and discriminant analysis of principal components to test clustering of individuals into genetically and geographically meaningful taxonomic units. KEY RESULTS: There are at least four distinct plastid clusters within P. ponderosa that roughly correspond to the geographic distribution of mitochondrial haplotypes. Some geographic regions have intermixed plastid lineages, and some mitochondrial and plastid boundaries do not coincide. Based on relative distances to other species of ponderosae, these clusters diagnose four distinct taxa. CONCLUSIONS: Newly revealed geographic boundaries of four distinct taxa (P. benthamiana, P. brachyptera, P. scopulorum, and a narrowed concept of P. ponderosa) do not correspond completely with taxonomies. Further research is needed to understand their morphological and nuclear genetic makeup, but we suggest that resurrecting originally published species names would more appropriately refl ect the taxonomy of this checkered classifi cation than their current treatment as varieties of P. ponderosa.