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In response to climate warming, subalpine treelines are expected to move up in elevation since treelines are generally controlled by growing season temperature. Where treeline is advancing, dispersal differences and early life stage environmental tolerances are likely to affect how species expand their ranges. Species with an establishment advantage will colonize newly available habitat first, potentially excluding species that have slower establishment rates. Using a network of plots across five mountain ranges, we described patterns of upslope elevational range shift for the two dominant Great Basin subalpine species, limber pine and Great Basin bristlecone pine. We found that the Great Basin treeline for these species is expanding upslope with a mean vertical elevation shift of 19.1 m since 1950, which is lower than what we might expect based on temperature increases alone. The largest advances were on limber pine-dominated granitic soils, on west aspects, and at lower latitudes. Bristlecone pine juveniles establishing above treeline share some environmental associations with bristlecone adults. Limber pine above-treeline juveniles, in contrast, are prevalent across environmental conditions and share few environmental associations with limber pine adults. Strikingly, limber pine is establishing above treeline throughout the region without regard to site characteristic such as soil type, slope, aspect, or soil texture. Although limber pine is often rare at treeline where it coexists with bristlecone pine, limber pine juveniles dominate above treeline even on calcareous soils that are core bristlecone pine habitat. Limber pine is successfully "leap-frogging" over bristlecone pine, probably because of its strong dispersal advantage and broader tolerances for establishment. This early-stage dominance indicates the potential for the species composition of treeline to change in response to climate change. More broadly, it shows how species differences in dispersal and establishment may result in future communities with very different specific composition.

Aim: The persistence potential of forests under rapid climate change will depend on species‐specific tolerances to increasing growing season soil moisture stress as snowpack declines. High‐elevation tree species may be particularly vulnerable to increasing water stress and associated changes to disturbance regimes because they occur at the environmental margins of tree distributions and are considered snowpack dependent. Here, we evaluate the interacting effects of climate, disturbance, and microsite conditions on tree regeneration in high‐elevation, migration‐limited pines that have experienced recent disturbance‐induced tree mortality. Location: Great Basin (California and Nevada), USA Taxon: Gymnosperms; Pinaceae Methods: We used field observations from 70 sites that varied in climate, disturbance, and local site conditions across semi‐arid, high‐elevation forests of the Great Basin. We employed structural equation models to evaluate how climate and disturbance interact with microsite conditions to influence regeneration. Results: We found a broad range of establishment conditions for high‐elevation conifers—whitebark, limber, and bristlecone pines—across climatic and disturbance gradients in the Great Basin, but our research detected clear differences in the regeneration niche for each species that may lead to differential survival as climate and disturbance conditions continue to change. Regeneration of whitebark and bristlecone pines diverged in their responses to spring snowpack conditions, with whitebark pine increasing and bristlecone pine decreasing with greater spring snowpack. Limber pine regenerated across a range of climatic and landscape conditions, and this generalist strategy may be advantageous if future climate and disturbance conditions exceed tolerances of more specialized high‐elevation conifers. Main Conclusions: Our findings highlight the critical role that spring snowpack, and consequently growing season soil moisture, plays in determining the persistence potential of high‐elevation conifers. However, this role varies among species and thus may drive compositional changes as earlier snowmelt drives soil moisture declines across mountainous landscapes of the western United States. [ABSTRACT FROM AUTHOR]

Edmund Schulman is rightly honored for quantifying the age of bristlecone pines and discovering individuals significantly older than giant sequoias (Sequoiadendron gigantea), previously thought to be the oldest living things. However, George Engelmann inferred the potential for great age in his description of bristlecone pine (Pinus aristata) almost a century before, in 1863. Staff from Inyo National Forest re-made Engelmann's inference, and publically asserted that White Mountain bristlecones might outlive giant sequoias before Schulman had published any results of his bristlecone research. Schulman sampledWhiteMountains pines after seeing a photograph and caption associated with an article by founders of the University of California White Mountain Research Station. Although Schulman's correspondence and publications make this clear, incorrect theories regarding his decision to come to theWhite Mountains have been published and are promulgated at the Schulman Grove Visitor Center in the White Mountains. This paper places Schulman's work in its historic context by recovering forgotten information about attempts by Inyo National Forest staff and White Mountain Research Station to call attention to the trees. It also recovers details of Schulman's and C. Wesley Ferguson's activities in the White Mountains range as documented in field notes and Thomas Harlan's Bristlecone Pine Project database. [ABSTRACT FROM AUTHOR]

In 2018 Pearson et al. published a new sequence of annual radiocarbon (14C) data derived from oak (Quercus sp.) trees from Northern Ireland and bristlecone pine (Pinus longaeva) from North America across the period 1700–1500 BC. The study indicated that the more highly resolved shape of an annually based calibration dataset could improve the accuracy of 14C calibration during this period. This finding had implications for the controversial dating of the eruption of Thera in the Eastern Mediterranean. To test for interlaboratory variation and improve the robustness of the annual dataset for calibration purposes, we have generated a replicate sequence from the same Irish oaks at ETH Zürich. These data are compatible with the Irish oak 14C dataset previously produced at the University of Arizona and are used (along with additional data) to examine inter-tree and interlaboratory variation in multiyear annual 14C time-series. The results raise questions about regional 14C offsets at different scales and demonstrate the potential of annually resolved 14C for refining subdecadal and larger scale features for calibration, solar reconstruction, and multiproxy synchronization. [ABSTRACT FROM AUTHOR]

In response to contemporary changes in climate, many tree species are shifting upslope to find favorable habitat. In the case of obligate ectomycorrhizal species, seedling growth above upper treeline depends on fungal spore availability. In the mountain ranges of the Great Basin, a recent shift in tree species stratification has been recorded, with limber pine (LP, Pinus flexilis) leapfrogging above the ancient bristlecone pine (BCP, Pinus longaeva) forest and establishing above current treeline.We compared the ability of LP and BCP to interact with soil spore banks collected at different microhabitats (next to dead trees, young live trees or in a treeless control) above current treeline in the White Mountains of California.We found an ectomycorrhizal fungal spore bank community composed of 15 species that was dominated by an undescribed and a hitherto unsequenced species of Geopora and Rhizopogon, respectively. This represents a much richer community than was found previously in this system. While both LP and BCP were able to establish ectomycorrhiza, LP was twice as likely to do so, and when comparing only seedlings that were colonized, its root system was colonized to a three‐fold greater extent. BCP seedlings grown on soils collected under young live trees were much more likely to be colonized compared to soils from the other two microhabitats.Synthesis. These differences in ectomycorrhizal receptivity might help to explain why LP is currently establishing at higher rates above the BCP treeline. Furthermore, it is possible that LP saplings above treeline can provide ectomycorrhizal facilitation for BCP seedlings, enabling the subsequent shift of BCP above treeline. [ABSTRACT FROM AUTHOR]

The article explores the history of land surveying in the U.S. West. The author reflects on the use of triangulation to locate high points and measure ground distances. Emphasis is given to the employment of environmentalist John Muir as a scout for the U.S. Coast and Geodetic Survey of 1878 in Nevada. Other topics include Muir's descriptions of bristlecone pine trees.

Trees are ubiquitous in theatre: both living and representational trees serve regularly as backdrops, scenery, props, and metaphors. Likewise, trees are ubiquitous in everyday life, frequently reduced to backdrops or resources in much the same manner. The simultaneous inclusion and overlooking of trees in theatrical and performance events prompts a need for critical attention that does not automatically objectify trees or recruit them solely to symbolize human stories. Covering the history and use of trees in theatre, then moving to living trees as beings engaged in arboreal repertoire, this essay introduces and makes visible the nonhuman participation in embodied human/nonhuman performance events. Three case studies illustrate instances where trees can be seen as participants in performances of human history, memory, and witnessing: the Anne Frank Tree and its saplings; the ancient bristlecone pine known as Methuselah; and carved quaking aspen groves. Establishing trees and plants as co-participants in performance events takes an imaginative leap forward, towards an understanding of human/nonhuman encounters as mutual and based in shared experience. Such a perspective, the essay argues, shifts theatrical criticism and analysis from inherently privileging the human to a mode of critical engagement that acknowledges and values the contributions that nonhumans, such as trees, make in performance events. [ABSTRACT FROM AUTHOR]

The preference-performance hypothesis states that ovipositing phytophagous insects will select host plants that are well-suited for their offspring and avoid host plants that do not support offspring performance (survival, development and fitness). The mountain pine beetle (Dendroctonus ponderosae), a native insect herbivore in western North America, can successfully attack and reproduce in most species of Pinus throughout its native range. However, mountain pine beetles avoid attacking Great Basin bristlecone pine (Pinus longaeva), despite recent climate-driven increases in mountain pine beetle populations at the high elevations where Great Basin bristlecone pine grows. Low preference for a potential host plant species may not persist if the plant supports favorable insect offspring performance, and Great Basin bristlecone pine suitability for mountain pine beetle offspring performance is unclear. We infested cut bolts of Great Basin bristlecone pine and two susceptible host tree species, limber (P. flexilis) and lodgepole (P. contorta) pines with adult mountain pine beetles and compared offspring performance. To investigate the potential for variation in offspring performance among mountain pine beetles from different areas, we tested beetles from geographically-separated populations within and outside the current range of Great Basin bristlecone pine. Although mountain pine beetles constructed galleries and laid viable eggs in all three tree species, extremely few offspring emerged from Great Basin bristlecone pine, regardless of the beetle population. Our observed low offspring performance in Great Basin bristlecone pine corresponds with previously documented low mountain pine beetle attack preference. A low preference-low performance relationship suggests that Great Basin bristlecone pine resistance to mountain pine beetle is likely to be retained through climate-driven high-elevation mountain pine beetle outbreaks. [ABSTRACT FROM AUTHOR]

The article reveals the mysteries of Great Basin bristlecone pine trees in the Patriarch Grove of California's White Mountains. They have been identified as the oldest living trees on Earth. Scientists have been studying the trees in order to understand how the climate has behaved through millennia. The difference between the Great Basin bristlecone pine tree and the Rocky Mountain bristlecone pine is discussed.

• Seedlings were highly aggregated 0 – 2.5 m around deadwood and mature adult trees. • Distance to deadwood was the most influential factor for Pinus flexilis seedlings. • Distance to mature Pinus longaeva was highly influential for P. longaeva seedlings. • Mature trees had similar habitat requirements and spatial patterns as seedlings. The spatial patterns of trees are a defining feature of forests, yet because of the long lifespan of trees, the full origins of these spatial patterns remain unclear. We used 15.6 ha of a mapped forest plot to assess the local habitat characteristics and spatial structure of 1,550 naturally established seedlings and 1,955 adults of Pinus flexilis (limber pine) and Pinus longaeva (Great Basin bristlecone pine) in southern Utah, USA. For both species, proximity to deadwood (large end diameter ≥ 10 cm) and mature trees were key parameters of habitat, likely indicating abiotic or biotic facilitation. Both seedlings and mature trees were highly aggregated 0.0–2.5 m around large pieces of deadwood, which can persist in this ecosystem for centuries or millennia. Seedlings were most often located around deadwood 15–22 cm in diameter, though deadwood size had little influence on the distance at which seedlings established. Seedlings of both P. flexilis and P. longaeva were abundant near heterospecific adult Pinus. The elevational distribution of seedlings and adults of both species were not different, indicating a regeneration niche similar to the niche of mature trees and also that changing climate at this site has not yet affected species distributions. Low amounts of manganese and higher levels of pH and potassium in the mineral soil were associated with P. longaeva seedlings but were less important for P. flexilis. Edaphic patterns combined with the presence of deadwood define the overlap between seedling and mature species habitat and identify the key drivers influencing the spatial structure in this high-elevation, old-growth forest. Likely, persistence of these two Pinus species as well as regeneration or site colonization is more favorable in the presence of large deadwood. [ABSTRACT FROM AUTHOR]

In the Great Basin, limber pine is a sub-alpine tree species that is colonizing newly available habitat above treeline in greater numbers than treeline-dominating Great Basin bristlecone pine, especially on dolomite soil, where few plants are able to grow and where limber pine adults are rare. To examine the role of soil type on germination and establishment of limber pine, I sowed limber pine seeds in containers of the three main White Mountains soil types in one location while measuring soil moisture and temperature. I found that dolomite soil retains water longer, and has higher soil water content, than quartzite and granite soils and has the coolest maximum growing season temperatures. Limber pine germination and survival were highest in dolomite soil relative to quartzite and granite where limber pine adults are more common. While adult limber pines are rare on dolomite soils, young limber pines appear to prefer them. This indicates that limber pine either has only recently been able to survive in treeline climate on dolomite or that bristlecone pine has some long-term competitive advantage on dolomite making limber pine, a species with 1500 year old individuals, an early succession species in Great Basin sub-alpine forests. [ABSTRACT FROM AUTHOR]

Over the last two decades, mountain pine beetle ( Dendroctonus ponderosae ) populations reached epidemic levels across much of western North America, including high elevations where cool temperatures previously limited mountain pine beetle persistence. Many high-elevation pine species are susceptible hosts and experienced high levels of mortality in recent outbreaks, but co-occurring Great Basin bristlecone pines ( Pinus longaeva ) were not attacked. Using no-choice attack box experiments, we compared Great Basin bristlecone pine resistance to mountain pine beetle with that of limber pine ( P. flexilis ), a well-documented mountain pine beetle host. We confined sets of mountain pine beetles onto 36 pairs of living Great Basin bristlecone and limber pines and recorded beetle status after 48 h. To test the role of induced defenses in Great Basin bristlecone pine resistance, we then repeated the tests on 20 paired sections of Great Basin bristlecone and limber pines that had been recently cut, thereby removing their capacity for induced defensive reactions to an attack. In tests on cut trees, we also investigated the potential for population-level differences in mountain pine beetle host selection behavior by testing beetles from two separate geographic regions. Beetles placed on Great Basin bristlecone pine rarely initiated attacks relative to those placed on limber pine in both studies, regardless of the beetle population source. Our results indicate that Great Basin bristlecone pine has a high level of resistance to mountain pine beetle due at least in part to stimuli that repel pioneering attackers from initiating attacks, even when induced defenses are compromised. [ABSTRACT FROM AUTHOR]

Little is known about fuel characteristics and dynamics in GBBP communities, and current monitoring programs inadequately quantify the surface and canopy fuels of this system. Using the Forest Inventory Analysis (FIA) plot variables of tree species, height, diameter at breast height (DBH), canopy base height (CBH), coarse (CWD) and fine (FWD) woody debris counts, and canopy fuels measurements, this paper examines the effects of climate-induced changes to fuel loading, fire hazard and risk on predicted changes in fire behavior and severity. Field transects were installed using FIA protocols along environmental gradients. Plots were located every 22 chains or ∼440 m along random transects on Mt. Washington in the Great Basin National Park (GBNP) and in the nearby Mt. Moriah Wilderness, NV. Additional plots were installed at Notch Peak (UT), Cave Mountain (NV), and Wheeler Peak (GBNP, NV). Linear regression showed that all classes of FWD decreased with elevation, and only 1000-h fuels remained constant across elevational transects. This, combined with lower CBH and foliar moisture and increasing temperatures due to climate change, increases fire potential at the Great Basin bristlecone pine treeline, threatening the oldest individuals of this iconic species. New information about discontinuous fuels will aid in management of high elevation alpine treeline forests. [ABSTRACT FROM AUTHOR]

In this paper, we provide the first documented evidence of Pinus longaeva from the Tushar Mountain range in central Utah. The P. longaeva trees, initially noticed at the end of September, and further surveyed during the first week of October 2016 are present on 6 small sites on the north-facing slopes of the North Fork of North Creek in the Tushar Mountains of the Fishlake National Forest. We estimate that there are currently up to 179 live individuals that range in age from seedlings to approximately 1400 years. Our data indicate these are particularly slow-growing specimens on very steep sites, in soil of igneous origin. Though many of the trees are infested with dwarf mistletoe, there is little indication that the population is currently at risk from fire, bark beetle attack, or many other common pathogens characteristic of other Pinus species. Nonetheless, there may be reasons for concern associated with future changes to the climate of southern Utah, as well as the impact of invasive species such as white pine blister rust ( Cronartium ribicola). We see opportunities for additional research on this unique population and its associated plant community. We also see the need for management strategies to conserve these P. longaeva stands, as well as a possible need to preserve its seeds and/or other genetic materials. [ABSTRACT FROM AUTHOR]

Two radiocarbon excursions (AD 774–775 and AD 993–994) occurred due to an increase of incoming cosmic rays on a short timescale. The most plausible cause of these events is considered to be extreme solar proton events (SPE). It is possible that there are other annual 14C excursions in the past that have yet to be confirmed. In order to detect more of these events, we measured the 14C contents in bristlecone pine tree-ring samples during the periods when the rate of 14C increase in the IntCal data is large. We analyzed four periods every other year (2479–2455 BC, 4055–4031 BC, 4465–4441 BC, and 4689–4681 BC), and found no anomalous 14C excursions during these periods. This study confirms that it is important to do continuous measurements to find annual cosmic-ray events at other locations in the tree-ring record. [ABSTRACT FROM AUTHOR]

Tree-ring growth records from bristlecone pines reveal an irregular pattern of fluctuations that have been linked to climatic change but otherwise have remained poorly understood. We find within these records evidence for a temporally related variance to mean power law, 1/f noise and multifractality that empirically resembles a fractal stochastic process and could be attributed to self-organized criticality. These growth records, however, also conformed to a non-Gaussian statistical distribution (the Tweedie compound Poisson distribution) characterized by an inherent variance to mean power law, that by itself implies 1/f noise. This distribution has a fundamental role in statistical theory as a focus of convergence for many types of random data, much like the Gaussian distribution has with the central limit theorem. The growth records were also multifractal, with the dimensional exponent of the Tweedie distribution critically balanced near the transition point between fractal stochastic processes and gamma distributed data, possibly consequent to a related convergence effect. Non-Gaussian random systems, like those related to bristlecone pine tree growth, may express 1/f noise and multifractality through mathematical convergence effects alone, without the dynamical assumptions of self-organized criticality. [ABSTRACT FROM AUTHOR]

Mountain pine beetle ( MPB, Dendroctonus ponderosae) is a significant mortality agent of Pinus, and climate-driven range expansion is occurring. Pinus defenses in recently invaded areas, including high elevations, are predicted to be lower than in areas with longer term MPB presence. MPB was recently observed in high-elevation forests of the Great Basin ( GB) region, North America. Defense and susceptibility in two long-lived species, GB bristlecone pine ( Pinus longaeva) and foxtail pine ( P. balfouriana), are unclear, although they are sympatric with a common MPB host, limber pine ( P. flexilis)., We surveyed stands with sympatric GB bristlecone-limber pine and foxtail-limber pine to determine relative MPB attack susceptibility and constitutive defenses., MPB-caused mortality was extensive in limber, low in foxtail and absent in GB bristlecone pine. Defense traits, including constitutive monoterpenes, resin ducts and wood density, were higher in GB bristlecone and foxtail than in limber pine., GB bristlecone and foxtail pines have relatively high levels of constitutive defenses which make them less vulnerable to climate-driven MPB range expansion relative to other high-elevation pines. Long-term selective herbivore pressure and exaptation of traits for tree longevity are potential explanations, highlighting the complexity of predicting plant-insect interactions under climate change. [ABSTRACT FROM AUTHOR]

Dendroclimatic proxies can be generated from the analysis of wood cellular structures, allowing for a more complete understanding of the physiological mechanisms that control the climatic response of tree species. Century-long (1870-2013) time series of anatomical parameters were developed for Great Basin bristlecone pine (Pinus longaeva D.K. Bailey) by capturing strongly contrasted microscopic images through a Confocal Laser Scanning Microscope. Environmental information embedded in wood anatomical series was analyzed in comparison with ring-width series using measures of empirical signal strength. Response functions were calculated against monthly climatic variables to evaluate climate sensitivity of cellular features (e.g., lumen area; lumen diameter) for the period 1950-2013. Calibration-verification tests were used to determine the potential to generate long climate reconstructions from these anatomical proxies. A total of eight tree-ring parameters (two ring-width and six chronologies of xylem anatomical parameters) were analyzed. Synchronous variability among samples varied among tree-ring parameters, usually decreasing from ring-width to anatomical features. Cellular parameters linked to plant hydraulic performance (e.g., tracheid lumen area and radial lumen diameter) showed empirical signal strength similar to ring-width series, while noise was predominant in chronologies of lumen tangential width and cell wall thickness. Climatic signals were different between anatomical and ring-width chronologies, revealing a positive and temporally stable correlation of tracheid size (i.e., lumen and cell diameter) with monthly (i.e., March) and seasonal precipitation. In particular, tracheid lumen diameter emerged as a reliable moisture indicator and was then used to reconstruct total March-August precipitation from 1870 to 2013. Wood anatomy holds great potential to refine and expand dendroclimatic records by allowing estimates of plant physiological adaptations to external stressors. Integrating xylem cellular features with ring-width chronologies can widen our understanding of past climatic variability (including annual extreme events) and improve the evaluation of long-term plant response to drought, especially in connection with future warming scenarios. [ABSTRACT FROM AUTHOR]

The timing of wood formation is crucial to determine how environmental factors affect tree growth. The long-lived bristlecone pine (Pinus longaeva D. K. Bailey) is a foundation treeline species in the Great Basin of North America reaching stem ages of about 5000 years. We investigated stem cambial phenology and radial size variability to quantify the relative influence of environmental variables on bristlecone pine growth. Repeated cellular measurements and half-hourly dendrometer records were obtained during 2013 and 2014 for two high-elevation stands included in the Nevada Climate-ecohydrological Assessment Network. Daily time series of stem radial variations showed rehydration and expansion starting in late April-early May, prior to the onset of wood formation at breast height. Formation of new xylem started in June and lasted until mid-September. There were no differences in phenological timing between the two stands, or in the air and soil temperature thresholds for the onset of xylogenesis. A multiple logistic regression model highlighted a separate effect of air and soil temperature on xylogenesis, the relevance of which was modulated by the interaction with vapor pressure and soil water content. While air temperature plays a key role in cambial resumption after winter dormancy, soil thermal conditions coupled with snowpack dynamics also influence the onset of wood formation by regulating plant-soil water exchanges. Our results help build a physiological understanding of climate-growth relationships in P. longaeva, the importance of which for dendroclimatic reconstructions can hardly be overstated. In addition, environmental drivers of xylogenesis at the treeline ecotone, by controlling the growth of dominant species, ultimately determine ecosystem responses to climatic change. [ABSTRACT FROM AUTHOR]

Limber pine seeds were potentially a valuable food resource for native occupants of the high mountains of the intermountain west. The seeds are rich in fats and proteins, with a greater caloric content by weight than pinyon pine seeds. The seeds are available in late summer, and collecting them is fairly easy, yielding large returns per time spent collecting. If the seeds are eaten whole or ground into meal without hand-hulling, return rates are very high, similar to rates for large and small game animals. The kernels are difficult to remove from their hulls, however, resulting in very low return rates if hand-hulled. Energetic considerations indicate that whole or ground limber pine seeds could have served as an important storable late summer food for prehistoric high-altitude occupants. [ABSTRACT FROM AUTHOR]

Microsites created by live plants and non-living structures can be important for plant establishment where abiotic stress is high. The activity of herbivores and resulting pattern of seedling survival also affects plant distributions. We investigated factors thought to influence survival of bristlecone pine ( Pinus longaeva Bailey) seedlings in the White Mountains, California, USA, with two field experiments in which microsite and exposure to herbivory were manipulated. In the microsite experiment, we planted seedlings underneath wooden shade structures, underneath sagebrush plants, and in exposed locations. In the herbivory experiment, we tested the effects of herbivore exclusion in three different habitat types. We planted seedlings in full wire cages (herbivores excluded), in half cages (herbivores allowed while enabling assessment of possible non-herbivore effects of cages on seedling survival), or with no cage (herbivores allowed), and repeated these treatments in three habitats: below, within, and above a bristlecone woodland. Over three growing seasons, seedlings planted under wooden shade structures had higher survival (28.9%) than seedlings growing under sagebrush (10%) or in exposed areas (3.3%). We found a significant treatment by habitat interaction in the herbivory experiment ( χ 2 = 12.056, P = 0.017), driven by a clear pattern of high herbivory inside the bristlecone woodland, but not above or below it. Our results suggest that biologically-derived microsites (shelter from dead wood and live shrubs), as well as herbivore-mediated density-dependent mortality, are important determinants of bristlecone pine seedling survival. [ABSTRACT FROM AUTHOR]

The giant sequoia and the bristlecone pine trees are capable of living up to several hundreds or even thousands of years. Plants achieve this longevity by regenerating stem cells capable of giving rise to all differentiated cells. Plant stem cells reside in specific niches with high mitotic activity that are known as meristems. Remarkably, at the center of the root stem cell niche (SCN) resides a group of mitotically inactive cells known as the quiescent center (QC). Recent studies suggest that stress-related phytohormones and DNA damage can initiate QC cell division, resulting in the replenishment of stem cells surrounding the QC. We therefore propose that the QC represents a pool of backup cells that serve to replace damaged stem cells, thereby contributing to plant longevity. [ABSTRACT FROM AUTHOR]

The instrumental temperature record is of insufficient length to fully express the natural variability of past temperature. High elevation tree-ring widths from Great Basin bristlecone pine ( Pinus longaeva) are a particularly useful proxy to infer temperatures prior to the instrumental record in that the tree-rings are annually dated and extend for millennia. From ring-width measurements integrated with past treeline elevation data we infer decadal- to millennial-scale temperature variability over the past 4,500 years for the Great Basin, USA. We find that twentieth century treeline advances are greater than in at least 4,000 years. There is also evidence for substantial volcanic forcing of climate in the preindustrial record and considerable covariation between high elevation tree-ring widths and temperature estimates from an atmosphere-ocean general circulation model over much of the last millennium. A long-term temperature decline of ~−1.1 °C since the mid-Holocene underlies substantial volcanic forcing of climate in the preindustrial record. [ABSTRACT FROM AUTHOR]

• Great Basin bristlecone pine (GBBP) is revered for its longevity. • Hotter droughts and bark beetles contributed to recent mortality. • We show, however, that GBBP is a population sink for bark beetles. • Attacks that killed GBBP likely originated from adults emerging from co-occurring pines. • New management strategies to protect this iconic species are needed. High-elevation five-needle pines are foundational species and iconic components of subalpine forests across western North America. Because they often grow at environmental extremes, high-elevation pines are vulnerable to changing climate conditions. In addition to the direct effects of recent climatic changes, these species are increasingly threatened by biotic disturbances that thrive in the warming and drying conditions now occurring at higher elevations. Among the high-elevation pines, Great Basin bristlecone pine (Pinus longaeva) is revered for its extreme longevity and has been considered an icon of stability during periods of change. Life history strategies of Great Basin bristlecone pine that contribute to its longevity include physiological traits that enhance survival in harsh and dry habitats, and defensive traits that make it less vulnerable than other high-elevation pines to tree-killing bark beetles. Recent increases in growing degree days with no associated increase in precipitation is causing temperature-amplified tree drought stress, while warming temperatures positively influence bark beetle population growth. We report on preliminary investigations into recent and unexpected Great Basin bristlecone pine mortality at two sites, including the potential roles of weather-induced stress and bark beetles. At both sites climatic water deficit (CWD), a cumulative measure of moisture stress, and mean annual temperature increased during the 2010 decade and CWD was the highest in 2020 relative to any time during the past 40 years. Although Great Basin bristlecone pine mortality has not previously been attributed to bark beetles, we observed recent (i.e., 2013 to 2020) bark beetle-attacked trees at both sites, coincident with the timing of increasing temperature and CWD. Few adult beetles were produced, however, and our results support previous research that Great Basin bristlecone pine is a population sink for bark beetles. Because bark beetles are likely not self-sustaining in Great Basin bristlecone pine, bark beetle-caused mortality of this iconic species will most likely occur when it grows mixed with or near other pine species that support bark beetle population growth. We found Ips confusus and Dendroctonus ponderosae attacking Great Basin bristlecone pine in areas where their host trees, P. monophylla and P. flexilis , were also growing. These results suggest that the presence of these infested conifers likely contributed to Great Basin bristlecone pine mortality. We highlight several factors that may be used for prioritizing future research and monitoring to facilitate development of management strategies for protecting this iconic species. [ABSTRACT FROM AUTHOR]

Abstract: AMS-based 14C measurements have been obtained on 53 dendrochronologically-dated Bristlecone pine (Pinus longaeva) wood samples in decadal increments spanning 2300–2750cal BP with particular interest focused on the decades centered on 2405cal BP and 2625cal BP. In general, there is overall agreement with the current IntCal04/09 consensus calibration curve for this period. For the 2400–2410cal BP interval, our Bristlecone-based 14C value is consistent with the 14C value obtained by Belfast on Irish oak for that decade but not on German oak values obtained by Seattle. Our 14C value for the 2620–2630cal BP interval is consistent with the German oak (Heidelberg)-based 14C decadal value. The 10Be-based reconstruction of 14C variations over the 2620–2630cal BP interval also supports the Heidelberg data although clearly additional clarifications are required before the current tree ring-based 14C and ice core-based 10Be data for this interval can be accurately interpreted and valid inferences obtained. [Copyright &y& Elsevier]

Abstract: We present the first near millennium-length, annually resolved stable isotope record from bristlecone pines (Pinus longaeva, D.K Bailey). The carbon isotope ratios from the cellulose of seven trees from the White Mountains of California, corrected for anthropogenic changes in atmospheric chemistry, are used to reconstruct growing season (June through August) precipitation back to AD 1085. Extremely negative isotope results are strongly correlated with proposed severest El Niño events over the last 500yr, and similar values in the first half of the millennium are used to reconstruct a further 13 strong El Niño events, concentrated in the 12th Century and the mid 13th and 14th Centuries. Ring-width chronologies from adjacent sites in the White Mountains demonstrate a high degree of decadal covariance with the δ13C series, although there are several periods of notable divergence. [Copyright &y& Elsevier]

Abstract: Bristlecone pine trees are exceptionally long-lived, and with the incorporation of remnant material have been used to construct multi-millennial length ring–width chronologies. These chronologies can provide valuable information about past temperature and moisture variability. In this study, we outline a method to build a moisture-sensitive bristlecone chronology and assess the robustness and consistency of this sensitivity over the past 1200yr using new reconstructions of Arkansas River flow (AD 1275–2002 and 1577–2002) and the summer Palmer Drought Sensitivity Index. The chronology, a composite built from parts of three collections in the central Rocky Mountains, is a proxy for decadal-scale moisture variability for the past 18 centuries. Since the sample size is small in some portions of the time series, the chronology should be considered preliminary; the timing and duration of drought events are likely the most robust characteristics. This chronology suggests that the region experienced increased aridity during the medieval period, as did much of western North America, but that the timing and duration of drought episodes within this period were somewhat different from those in other western locations, such as the upper Colorado River basin. [Copyright &y& Elsevier]

The absolutely dated bristlecone pine (Pinus longaeva) tree-ring chronology spans almost 9000 years, offering great potential for inferring past environmental change. Existing ring width chronologies have been widely used to produce some of the most influential millennial length temperature reconstructions for the Northern Hemisphere. A recently published ™18O record from two bristlecone pine trees growing at Methuselah Walk in the White Mountains of California showed a dramatic decrease in ™18O between AD 1850 and 1920 (c. 13‰), interpreted as indicating a major shift in Pacific storm tracks over the past 300 years. Here we present new bristlecone pine ™18O time series from 15 trees at three White Mountains sites, including two series from Methuselah Walk. Whilst occasional high interannual variability is observed in our ™18O series, none of our chronologies exhibit an equivalent pronounced or sustained twentieth-century decrease, suggesting the earlier results are anomalous and may require palaeoclimatic re-interpretation. [ABSTRACT FROM AUTHOR]

Five-needle pines provide some of the world’s longest chronologies of paleoclimate interest. We examined 66 five-needle pine growth chronologies from 1896 to their end years using linear trend, correlation, and cluster analyses. Chronologies were categorized based on the sites’ proximity to upper treeline. A significant positive trend in ring width over the post-1896 interval was most common in upper treeline chronologies, but positive linear trend was found in all elevational proximity classes and all species. Cluster analysis of climate response patterns identified four groups exhibiting strong associations with (i) positive response to previous autumn, winter, and spring precipitation, (ii) positive response to spring and (or) summer precipitation coupled with an inverse relationship with summer temperature, (iii) positive response to winter and (or) spring precipitation coupled with an inverse relationship with spring temperature, and (iv) positive associations with temperature in all seasons except spring and no appreciative precipitation response. Most chronologies positively associated with temperatures were from sites located near upper treeline and also contain significant positive linear trend. Our results suggest that some five-needle pine treeline chronologies may be reliable predictors of past temperatures, but careful site selection is required. [ABSTRACT FROM AUTHOR]

Great Basin bristlecone pine (Pinus longaeva) at 3 sites in western North America near the upper elevation limit of tree growth showed ring growth in the second half of the 20th century that was greater than during any other 50-year period in the last 3,700 years. The accelerated growth is suggestive of an environmental change unprecedented in millennia. The high growth is not overestimated because of standardization techniques, and it is unlikely that it is a result of a change in tree growth form or that it is predominantly caused by CO2 fertilization. The growth surge has occurred only in a limited elevational band within ≈150 m of upper treeline, regardless of treeline elevation. Both an independent proxy record of temperature and high-elevation meteorological temperature data are positively and significantly correlated with upper-treeline ring width both before and during the high-growth interval. Increasing temperature at high elevations is likely a prominent factor in the modern unprecedented level of growth for Pinus Iongaeva at these sites. [ABSTRACT FROM AUTHOR]

Abstract: The oxygen isotope ratio of alpha-cellulose produced by Bristlecone Pine trees from the White Mountains of California was measured for three different 10-year tree-ring sections at near-weekly resolution to investigate how the growing season climate cycle influences the annual to inter-annual isotopic variability of whole-ring samples. We selected sections of wood that grew under periods of generally reduced (155–172 BC) and increased (AD 1106–1122; AD 1827–1834) growth to assess whether or not the environmental parameters that are responsible for ring-width variability, including water availability, also influence the intra-annual cellulosic isotope variability. Each annual ring is characterized by a parabolic function of intraseasonal δ18O change that reflects humidity and temperature-dependent fractionations of H2 18O utilized by the tree during the growth period. Subtle shifts in the shape and amplitude of the seasonal δ18O cycle are attributed to changing growing season length but the differences are not large enough to bias a whole-ring isotopic value. We model the isotope fractionations based on growing season climate variables and tree physiology and find that the measured δ18O is in close agreement with the model-predicted values. The model retains no information on previous winter conditions and thus confirms that these trees draw upon an isotopically homogenized water source. The intraseasonal δ18O cycle arises entirely from fractionations due to summer season temperature and humidity. A persistent issue with dendroclimatic reconstructions is addressing seasonal biases in the record, we find that in this environment where growth and precipitation are separated by many months we are able to capture distinct information on both seasons by coupling average annual values with information on sub-seasonal variability. [Copyright &y& Elsevier]

Abstract: Archeologists recognize that prehistoric human populations were a significant variable in the operation of past California ecosystem processes, and that a changing environment created constraints and opportunities for prehistoric cultural adaptation. The tie between paleoclimatology and archeology is an evolving interdisciplinary field of study that aims to facilitate a better understanding of prehistoric subsistence-settlement patterns relative to climate variability. A paleoclimatic model based on temperature inferences and precipitation reconstruction from tree-ring widths of bristlecone pine in the White Mountains of California is used to explain the distribution of prehistoric alpine villages in the White Mountains. The paleoclimatic model is visually and statistically compared with calendar ages converted from calibrated 14C dates from the village sites. Results elucidate the role of water availability in the frequency and intensity of settlement, as 88% of the calendar dates associated with 14C dates fall within wet periods (α=0.05, p=0.005). The coincidence of the calendar dates around above average precipitation periods confirms that long-term available resources are contingent on the availability of moisture, the key to life in the desert environment. [Copyright &y& Elsevier]

Abstract: Many years of low growth identified in a western USA regional chronology of upper forest border bristlecone pine (Pinus longaeva and Pinus aristata) over the last 5000 yr coincide with known large explosive volcanic eruptions and/or ice core signals of past eruptions. Over the last millennium the agreement between the tree-ring data and volcano/ice-core data is high: years of ring-width minima can be matched with known volcanic eruptions or ice-core volcanic signals in 86% of cases. In previous millennia, while there is substantial concurrence, the agreement decreases with increasing antiquity. Many of the bristlecone pine ring-width minima occurred at the same time as ring-width minima in high latitude trees from northwestern Siberia and/or northern Finland over the past 4000–5000 yr, suggesting climatically-effective events of at least hemispheric scale. In contrast with the ice-core records, the agreement between widely separated tree-ring records does not decrease with increasing antiquity. These data suggest specific intervals when the climate system was or was not particularly sensitive enough to volcanic forcing to affect the trees, and they augment the ice core record in a number of ways: by providing confirmation from an alternative proxy record for volcanic signals, by suggesting alternative dates for eruptions, and by adding to the list of years when volcanic events of global significance were likely, including the mid-2nd-millennium BC eruption of Thera. [Copyright &y& Elsevier]

Normal somatic cells have a finite replicative capacity. With each cell division, telomeres (the physical ends of linear chromosomes) progressively shorten until they reach a critical length, at which point the cells enter replicative senescence. Some cells maintain telomere length by the action of the telomerase enzyme. The bristlecone pine, Pinus longaeva, is the oldest known living eukaryotic organism, with the oldest on record turning 4770 years old in 2005. To determine what changes occur, if any, in telomere length and telomerase activity with age, and what roles, if any, telomere length and telomerase activity may play in contributing to the increased life-span and longevity of P. longaeva with age, as well as in other tree species of various life-spans, we undertook a detailed investigation of telomere length and telomerase activity in such trees. The results from this study support the hypothesis that both increased telomere length and telomerase activity may directly/indirectly contribute to the increased life-span and longevity evident in long-lived pine trees (2000–5000 year life-spans) compared to medium-lived (400–500 year life-span) and short-lived (100–200 year life-span) pine trees, as well as in P. longaeva with age. [ABSTRACT FROM AUTHOR]

Compares the genetic diversity estimated from allozyme and from random amplified polymorphic DNA (RAPD) in a sample of 210 Great Basin bristlecone pines from three groves in White Mountains, California. Limitations of RAPD; Factors that may have enabled the pines to maintain a level of genetic diversity; Pros and cons of the results from allozymes and RAPD for population genetic studies in bristlecone pine.

Presents a study which tested the hypothesis that tree size affects the frequency of bark stripping in Pinus aristata. Materials and methods; Environmental factors; Discussion.

Intersite variation in ectomycorrhizal (ECM) inoculum potential in soils from 16 sites located in arid subalpine areas of the White Mountains of California was quantified. The study sites included valleys dominated by big sagebrush (Artemisia tridentata Nutt.) and mountainsides dominated by ancient Great Basin bristlecone pine (Pinus longaeva Bailey). ECM inoculum potential was not detected at three of four valley sites nor in 42% of forest soil samples. Only 10 mycorrhizal species were detected in bioassays, and four of those accounted for 94.5% of all colonized seedlings, in order of decreasing abundance these were Pyronemataceae sp., Rhizopogon sp., Wilcoxina rehmii Yang & Korf, and Cenococcum sp. These species were identified also from in situ mycorrhizal roots. The abundance of the dominant Pyronemataceae sp. was significantly positively correlated with pH, which at all forest sites was high compared with typical conifer forest soils. Our results show that the ECM inoculum potential of soils is low, homogeneous, and spatially restricted in these ancient high-elevation forests.Key words: fungal community, molecular ecology, spore dispersal.Les auteurs ont quantifié la variation, entre les sites, du potentiel inoculant ectomycorhizien (ECM) de sols provenant de 16 sites isolés des régions subalpines des White Mountains, en Californie. Les sites d'étude incluent des vallées dominées par la grande armoise, Artemisia tridentata Nutt., et les flancs de montagnes dominées par le pin des anciens Great Basin, Pinus longaeva Bailey. Aucun inoculum ECM n'a été détecté sur trois des quatre sites des vallées, non plus que de 42 % des échantillons de sols forestiers. On n'a retrouvé que 10 espèces mycorrhiziennes dans les bio-essais, et quatre de ces espèces colonisent à elles seules 94,5 % de tous les plants mycorhizés. Ce sont, en ordre décroissant d'abondance : une Pyronématacée sp., un Rhizopogon sp., le Wilcoxina rehmii Yang & Korf, et un Cenococcum sp. Ces espèces ont également été identifiées à partir de racines mycorhizées récoltées in situ. L'abondance de la Pyronématacée sp. est significativement et positivement corrélée avec le pH, lequel sur tous les sites forestiers est élevé, comparativement aux sols typiques des forêts conifériennes. Les résultats indiquent que le potentiel ECM inoculant est faible, homogène, et spatialement restreint dans ces vieilles forêts de haute altitude.Mots clés : communauté fongique, écologie moléculaire, dispersion des spores.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

• Fungal communities differ on roots of Pinus flexilis and Pinus longaeva. • Fungal communities in soil were similar around Pinus flexilis and Pinus longaeva. • Advanced tree age was associated with different fungal communities. • Advanced tree age did not influence fungal diversity. The long-lived five-needle pines, Pinus flexilis (limber pine) and Pinus longaeva (Great Basin bristlecone pine) can co-occur and may form symbiotic partnerships with the same species of ectomycorrhizal fungi. These shared symbiotic relationships may facilitate the persistence of these pine species. Throughout their lives, P. flexilis and P. longaeva may also assemble unique belowground fungal communities, adding to the conservation value of ancient trees. We used MiSeq sequencing of fungal rDNA to compare fungal community similarity for co-occurring P. flexilis and P. longaeva roots and soils in an old-growth forest at the Utah Forest Dynamics Plot, Utah, USA. We cored trees to measure their age and determine whether fungal communities change with advanced tree age. We found 720 amplicon sequence variants associated with P. flexilis roots, 736 with P. longaeva roots, and 199 that were shared between the two pines. Root-associated fungal communities were significantly different between P. flexilis and P. longaeva despite similar soil communities. The fungal community composition on P. flexilis roots and around P. longaeva soil was associated with advanced tree age up to 1340 years. The root-associated fungal community of P. flexilis and the soil community of P. longaeva increased in dissimilarity with tree age, indicating that age heterogeneity within old-growth stands promotes fungal diversity. The significant differences in root-associated fungal communities between the two pine species highlights that they are likely engaged in different bi-directional selection with fungal communities. [ABSTRACT FROM AUTHOR]