Juniperus Osteosperma Research Articles

Dynamic regulation of water potential in Juniperus osteosperma mediates ecosystem carbon fluxes.

Some plants exhibit dynamic hydraulic regulation, in which the strictness of hydraulic regulation (i.e. iso/anisohydry) changes in response to environmental conditions. However, the environmental controls over iso/anisohydry and the implications of flexible hydraulic regulation for plant productivity remain unknown. In Juniperus osteosperma, a drought-resistant dryland conifer, we collected a 5-month growing season time series of in situ, high temporal-resolution plant water potential ( ) and stand gross primary productivity (GPP). We quantified the stringency of hydraulic regulation associated with environmental covariates and evaluated how predawn water potential contributes to empirically predicting carbon uptake. Juniperus osteosperma showed less stringent hydraulic regulation (more anisohydric) after monsoon precipitation pulses, when soil moisture and atmospheric demand were high, and corresponded with GPP pulses. Predawn water potential matched the timing of GPP fluxes and improved estimates of GPP more strongly than soil and/or atmospheric moisture, notably resolving GPP underestimation before vegetation green-up. Flexible hydraulic regulation appears to allow J. osteosperma to prolong soil water extraction and, therefore, the period of high carbon uptake following monsoon precipitation pulses. Water potential and its dynamic regulation may account for why process-based and empirical models commonly underestimate the magnitude and temporal variability of dryland GPP.

The essential oil composition of Juniperus osteosperma foliar essential oil from southern Idaho

The essential oil composition of Juniperus osteosperma foliar essential oil from southern Idaho

Metabolomic evidence of independent biotransformation pathways for terpenes in two specialist mammalian herbivores (genus Neotoma).

Herbivory is common in mammals, yet our understanding of detoxification processes used by mammals to biotransform plant secondary compounds (PSCs) is limited. Specialist herbivores are thought to have evolved detoxification mechanisms that rely more heavily on energetically cheap Phase I biotransformation reactions to process high levels of PSCs in their diets. We explored this hypothesis by comparing the urinary metabolite patterns of two specialist herbivores (genus Neotoma). Neotoma stephensi is an obligate specialist on one-seeded juniper (Juniperus monosperma). Neotoma lepida is a generalist forager across its range, yet populations in the Great Basin specialize on Utah juniper (J. osteosperma). While both juniper species have high levels of terpenes, the terpene profiles and quantities differ between the two. Individuals from both woodrat species were fed diets of each juniper in a cross-over design. Urine, collected over a 24-h period, was extracted and analyzed in an untargeted metabolomics approach using both GC-MS and HPLC-MS/MS. The obligate specialist N. stephensi excreted a unique pattern of Phase I metabolites when fed its native juniper, while N. lepida excreted a unique pattern of Phase II metabolites when fed its native juniper. Both woodrat species utilized the Phase II metabolic pathway of glucuronidation more heavily when consuming the more chemically diverse J. osteosperma, and N. stephensi utilized less glucuronidation than N. lepida when consuming J. monosperma. These results are consistent with the hypothesis that obligate specialists may have evolved unique and efficient biotransformation mechanisms for dealing with PSCs in their diet.

The importance of monsoon precipitation for foundation tree species across the semiarid Southwestern U.S.

Forest dynamics in arid and semiarid regions are sensitive to water availability, which is becoming increasingly scarce as global climate changes. The timing and magnitude of precipitation in the semiarid southwestern U.S. (“Southwest”) has changed since the 21st century began. The region is projected to become hotter and drier as the century proceeds, with implications for carbon storage, pest outbreaks, and wildfire resilience. Our goal was to quantify the importance of summer monsoon precipitation for forested ecosystems across this region. We developed an isotope mixing model in a Bayesian framework to characterize summer (monsoon) precipitation soil water recharge and water use by three foundation tree species (Populus tremuloides [aspen], Pinus edulis [piñon], and Juniperus osteosperma [Utah juniper]). In 2016, soil depths recharged by monsoon precipitation and tree reliance on monsoon moisture varied across the Southwest with clear differences between species. Monsoon precipitation recharged soil at piñon-juniper (PJ) and aspen sites to depths of at least 60 cm. All trees in the study relied primarily on intermediate to deep (10-60 cm) moisture both before and after the onset of the monsoon. Though trees continued to primarily rely on intermediate to deep moisture after the monsoon, all species increased reliance on shallow soil moisture to varying degrees. Aspens increased reliance on shallow soil moisture by 13% to 20%. Utah junipers and co-dominant ñons increased their reliance on shallow soil moisture by about 6% to 12%. Nonetheless, approximately half of the post-monsoon moisture in sampled piñon (38-58%) and juniper (47-53%) stems could be attributed to the monsoon. The monsoon contributed lower amounts to aspen stem water (24-45%) across the study area with the largest impacts at sites with recent precipitation. Therefore, monsoon precipitation is a key driver of growing season moisture that semiarid forests rely on across the Southwest. This monsoon reliance is of critical importance now more than ever as higher global temperatures lead to an increasingly unpredictable and weaker North American Monsoon.

Seasonal Trap Abundance of Two Species of Psilochalcis Kieffer (Hymenoptera: Chalcididae) in Rangelands of the Eastern Great Basin of Utah, USA

Two species of Psilochalcis (Hymenoptera: Chalcididae) wasps occurring in the Great Basin region of the western United States were sampled from three locations in central Utah (USA) over a two-year period using Malaise traps. Each location is composed of four contiguous habitat types: pinyon/juniper (Pinus edulis or P. monophylla and Juniperus osteosperma), sagebrush (Artemisia tridentata), cheatgrass (Bromus tectorum), and crested wheatgrass (Agropyron cristatum). Seasonal trap abundance for each Psilochalcis species was determined. Psilochalcis minuta Petersen and Psilochalcis quadratis Petersen occur in highest abundance from mid-May to early August. Psilochalcis minuta demonstrates a significant association with pinyon/juniper habitat, specifically at the Utah; Juab County, Yuba Valley sample site, whereas P. quadratis demonstrates a significant association with cheatgrass (Bromus tectorum) habitat at the same location.

Epigaeic spider response to sagebrush steppe restoration treatments

Epigaeic (ground-active) spiders are dominant predators of arthropods and are important prey for vertebrates in sagebrush steppe systems. As part of the Sagebrush Steppe Treatment Evaluation Project (SageSTEP), the response of epigaeic spiders to sagebrush steppe restoration treatments was evaluated. Spiders were pitfall trapped pre-treatment and for up to 7 years post-treatment at 20 sites in the interior western United States. Spider species, functional groups, and communities were analyzed as regards site conditions and in response to treatments (prescribed fire, mechanical, and herbicide) designed to restore sagebrush steppe lands encroached by piñon–juniper woodlands (Pinus and Juniperus spp.) and invaded by cheatgrass (Bromus tectorum). A total of 10,149 epigaeic spiders were caught during the 8-year sampling period (2006–2014), comprising 18 families, 51 genera, and 109 species. Ten species are currently undescribed, including two species of jumping spiders (Salticidae), two species of funnel spiders (Agelenidae), and a species of trapdoor spider (Euctenizidae). Nearly 70% of adult catch comprised the 10 most commonly collected species; 50 species were caught fewer than five times. Spiders of the family Gnaphosidae (ground spiders) dominated the collection (65% of adults), followed by wolf spiders (Lycosidae; 12%), jumping spiders (8%), and crab spiders (Thomisidae; 4%). Fewer gnaphosids were caught in plots with higher tree cover, and this pattern was reversed by tree removal. There was no significant epigaeic spider response to the broadleaf herbicide tebuthiuron, nor to mowing or clear-cutting. Mastication caused a subtle increase in epigaeic spider richness at Utah juniper sites. Prescribed fire decreased abundance and richness of epigaeic spiders in the short term (1 year post-treatment), with catch at most sites converging to control levels by Year 2 post-treatment; application of the annual herbicide imazapic at treeless sites may have amplified this effect slightly in the short term. In general, gnaphosid catch and richness closely paralleled litter and bunchgrass cover. These patterns suggest that while gnaphosid spiders are not sagebrush-obligate species per se, these spiders prefer habitat conditions that provide more hiding cover, in the form of litter and vegetation, found more often in treeless sagebrush steppe plant communities and in woodland communities that have relatively lower tree cover.

Successes and limitations of quantitative diet metabarcoding in a small, herbivorous mammal.

DNA metabarcoding is widely used to determine wild animal diets, but whether this technique provides accurate, quantitative measurements is still under debate. To test our ability to accurately estimate the abundance of dietary items using metabarcoding, we fed wild-caught desert woodrats (Neotoma lepida) diets consisting of constant amounts of juniper (Juniperus osteosperma, 15%) and varying amounts of creosote (Larrea tridentata, 1%-60%), cactus (Opuntia sp., 0%-100%) and commercial chow (0%-85%). Using metabarcoding, we compared the representation of items in the original diet samples to that in the faecal samples to test the sensitivity and accuracy of diet metabarcoding, the performance of different bioinformatic pipelines and our ability to correct sequence counts. Metabarcoding, using standard trnL primers, detected creosote, juniper and chow. Different pipelines for assigning taxonomy performed similarly. While creosote was detectable at dietary proportions as low as 1%, we failed to detect cactus in most samples, probably due to a primer mismatch. Creosote read counts increased as its proportion in the diet increased, and we could differentiate when creosote was a minor and major component of the diet. However, we found that estimates of juniper and creosote varied. Using previously suggested methods to correct these errors did not improve accuracy estimates of creosote, but did reduce error for juniper and chow. Our results indicate that metabarcoding can provide quantitative information on dietary composition, but may be limited. We suggest that researchers use caution when quantitatively interpreting diet metabarcoding results unless they first experimentally determine the extent of possible biases.

Phylogenetic Position of a New Trisetacus Mite Species (Nalepellidae) Destroying Seeds of North American Junipers and New Hypotheses on Basal Divergence of Eriophyoidea.

Simple SummaryEriophyoid mites are microscopic herbivores associated with higher plants. Some of them are serious pests due to their ability to vector viruses and cause other damage to host plants. Mites of the genus Trisetacus are widespread parasites of conifers. They usually live in buds, cones, and rarely within needles of Pinaceae (pine family) and Cupressaceae (cypress family). We discovered a new species, Trisetacus indelis n. sp., severely damaging seeds of three North American junipers in the western USA. This species possesses two morphologically different forms of females and has two deletion mutations in the gene cytochrome oxidase subunit I (Cox1). Such mutations are rare in eriophyoids and were previously detected only in two pestiferous species from palms and hazelnut. Our molecular-phylogenetic analyses determine the closest known relatives of the new species and suggest that Old and New World Trisetacus independently transitioned to living in seeds of junipers. Additionally we show that reconstruction of the phylogeny of Eriophyoidea based on one gene, Cox1, produces a poorly-resolved but biologically consistent tree topology to hypothesize the evolution of Eriophyoidea. Overall, our study improves our understanding of the diversity of conifer-inhabiting mites and indicates further needs in investigating the phylogeny of Eriophyoidea.Eriophyoid mites of the genus Trisetacus Keifer are widespread parasites of conifers. A new oligophagous species, T. indelis n. sp., was discovered severely damaging seeds of North American junipers (Juniperus osteosperma, J. occidentalis, and J. californica) in the western USA. It has two codon deletions in the mitochondrial gene Cox1 rarely detected in Eriophyoidea and includes distinct morphological dimorphism of females. A phylogenetic analysis based on amino acid alignment of translated Cox1 sequences using a large set of out-groups (a) determined that two North American congeners, T. batonrougei and T. neoquadrisetus, were the closest known relatives of T. indelis n. sp., and (b) indicated that Old and New World seed-inhabiting Trisetacus from junipers do not form a distinct clade, suggesting a possible independent transition to living in seeds of junipers in America and Eurasia by Trisetacus spp. Our analysis produced a new topology consistent with a scenario assuming gradual reduction of prodorsal shield setation in Eriophyoidea and an ancient switch from gymnosperms to other hosts. Additionally, our analysis did not support monophyly of Trisetacus; recovered a new host-specific, moderately supported clade comprising Trisetacus and Nalepellinae (Nalepella + Setoptus) associated with Pinaceae; and questioned the monophyly of Trisetacus associated with Cupressaceae.

Mesopredator frugivory has no effect on seed viability and emergence under experimental conditions

AbstractMembers of the orderCarnivoraare a unique and important seed disperser who consume and deposit undamaged seeds while providing regular long‐distance seed dispersal opportunities. Some members ofCarnivora, such as coyotes (Canis latrans), are undergoing range expansions which may help the plant species they consume colonize new locations or replace dispersal services provided by recently extirpated species. In this study, we evaluated aspects of the seed dispersal effectiveness of coyotes and gut passage time to determine the potential dispersal distances for three commonly consumed and commonly occurring plant species (Amelanchier alnifolia, Celtis ehrenbergiana, andJuniperus osteosperma). We also investigated the potential effects of secondary dispersal of seeds away from scats by comparing seedling emergence from whole scats to those where seeds were first removed from scats. We found that seeds generally took between 4 and 24 h to pass through the digestive tract of coyotes, which could result in regular seed dispersal up to 7 km. Gut passage through coyotes had no effect on seed viability or emergence for any of the three plant species, including that gut passage forA. alnifoliaandJ. osteospermadoes not replace cold stratification for breaking physiological dormancy. By simulating secondary dispersal, we found that 22% (±8.2%) moreC. ehrenbergianaseedlings emerged when seeds were removed from scats and those seedlings emerged 7 d earlier (±5 d) compared to seeds that remained in the coyote scat. Coyotes are effective seed dispersers, with the potential for regular long‐distance dispersal services and for providing opportunities for secondary seed dispersal, which could aid in climate migration or serve to replace extirpated dispersal mutualists.

Temperature memory and non-structural carbohydrates mediate legacies of a hot drought in trees across the southwestern USA.

Trees are long-lived organisms that integrate climate conditions across years or decades to produce secondary growth. This integration process is sometimes referred to as 'climatic memory.' While widely perceived, the physiological processes underlying this temporal integration, such as the storage and remobilization of non-structural carbohydrates (NSC), are rarely explicitly studied. This is perhaps most apparent when considering drought legacies (perturbed post-drought growth responses to climate), and the physiological mechanisms underlying these lagged responses to climatic extremes. Yet, drought legacies are likely to become more common if warming climate brings more frequent drought. To quantify the linkages between drought legacies, climate memory and NSC, we measured tree growth (via tree ring widths) and NSC concentrations in three dominant species across the southwestern USA. We analyzed these data with a hierarchical mixed effects model to evaluate the time-scales of influence of past climate (memory) on tree growth. We then evaluated the role of climate memory and the degree to which variation in NSC concentrations were related to forward-predicted growth during the hot 2011-2012 drought and subsequent 4-year recovery period. Populus tremuloides exhibited longer climatic memory compared to either Pinus edulis or Juniperus osteosperma, but following the 2011-2012 drought, P. tremuloides trees with relatively longer memory of temperature conditions showed larger (more negative) drought legacies. Conversely, Pinus edulis trees with longer temperature memory had smaller (less negative) drought legacies. For both species, higher NSC concentrations followed more negative (larger) drought legacies, though the relevant NSC fraction differed between P. tremuloides and P. edulis. Our results suggest that differences in tree NSC are also imprinted upon tree growth responses to climate across long time scales, which also underlie tree resilience to increasingly frequent drought events under climate change.

Quantifying the demographic vulnerabilities of dry woodlands to climate and competition using rangewide monitoring data.

Climate change is expected to alter the distribution and abundance of tree species, impacting ecosystem structure and function. Yet, anticipating where this will occur is often hampered by a lack of understanding of how demographic rates, most notably recruitment, vary in response to climate and competition across a species range. Using large-scale monitoring data on two dry woodland tree species (Pinus edulis and Juniperus osteosperma), we develop an approach to infer recruitment, survival, and growth of both species across their range. In doing so, we account for ecological and statistical dependencies inherent in large-scale monitoring data. We find that drying and warming conditions generally lead to declines in recruitment and survival, but the strength of responses varied between species. These climate conditions point to geographic regions of high vulnerability for particular species, such as Pinus edulis in northern Arizona, where both survival and recruitment are low. Our approach provides a path forward for leveraging emerging large-scale monitoring and remotely sensed data to anticipate the impacts of global change on species distributions.

Prey Specialization by Cougars on Feral Horses in a Desert Environment

ABSTRACTNatural controls on the distribution, abundance, or growth rates of exotic species are a desirable mode of intervention because of lower costs compared to anthropogenic controls and greater social acceptance. In the Great Basin, cougars (Puma concolor) are the most widely distributed carnivore capable of killing large ungulate prey. Populations of feral horses (Equus ferus) are widely distributed throughout the Great Basin and can grow at rates up to 20%/year. Although cougars exhibit distributional overlap with horses, it has been assumed that predation is minimal because of differences in habitat use and body‐size limitations. To evaluate this hypothesis, we monitored the diets of 21 global positioning system (GPS)‐collared cougars in the western Great Basin (5 males, 8 females) and eastern Sierra Nevada (2 males, 6 females) from 2009–2012. We investigated 1,310 potential kill sites and located prey remains of 820 predation events. We compared prey composition and kill rates of cougars inhabiting the Sierra Nevada and Great Basin, and among male and female cougars across seasons. We used generalized linear mixed models (GLMMs) to examine the effects of prey availability and habitat characteristics on the probability of predation on horses by cougars. Mule deer (Odocoileus hemionus) comprised 91% of prey items killed on the Sierra Nevada reference site but only comprised 29% of prey items in the Great Basin study area. Average annual kill rates for deer differed between the Sierra Nevada ( = 0.85 deer/week, range = 0.44–1.3) and Great Basin ( = 0.21 deer/week, range = 0.00–0.43). Diets of cougars in the Great Basin were composed predominantly of horses (59.6%, n = 460 prey items; 13 individuals). Ten cougars regularly consumed horses, and horses were the most abundant prey in the diet of 8 additional individuals in the Great Basin. Cougars on average killed 0.38 horses/week in the Great Basin (range=0.00–0.94 horses/week). Differences in predation on horses between the sexes of cougars were striking; Great Basin females incorporated more horses across all age classes year‐round, whereas male cougars tended to exploit neonatal young during spring and summer before switching to deer during winter. Within GLMM models, the probability of predation on horses compared to other prey species increased with elevation, horse density, and decreasing density of mule deer on the landscape, and was more likely to occur in sagebrush (Artemesia spp.) than in pinyon (Pinus monophylla)–juniper (Juniperus osteosperma) forests. Behavior of individual cougars accounted for more than a third of the variation explained by our top models predicting predation on horses in the Great Basin. At landscape scales, cougar predation is unlikely to limit the growth of feral horse populations. In the Great Basin ecosystem, however, cougars of both sexes successfully preyed on horses of all age classes. Moreover, some reproductive, female cougars were almost entirely dependent on feral horses year‐round. Taken together, our data suggest that cougars may be an effective predator of feral horses, and that some of our previous assumptions about this relationship should be reevaluated and integrated into management and planning. © 2021 The Wildlife Society.

Differing Fine-Scale Responses of Vegetation and Bare Soil to Moisture Variation in a Pinyon-Juniper Woodland Underlie Landscape-Scale Responses Observed from Remote Sensing

Pinyon juniper woodlands in the American southwest face an uncertain ecological future with regard to climate altered precipitation. Although satellite remote sensing will be relied upon to assess the overall health of these plant communities more fine scaled information is needed to elucidate the mechanisms shaping the broader scaled regional assessments. We conducted a study to assess the NDVI response at the plant canopy level (insitu sensors placed over the canopies) of three tree and one shrub species to changes in precipitation, reference evapotranspiration and soil volumetric water content. Landsat data was used to compare stand integrated and satellite NDVI values. We also provided supplemental water in the amount of 10.85 cm over the study period to additional trees and shrubs which also had insitu NDVI sensors placed over their canopies. NDVI at the canopy level separated statistically by species and when contrasted with bare soil (p<0.001). Spring early summer dry down events were inversely related to increasing ETref-precipitation with a steeper dry down slope in the first year associated with no rainfall occurring in May and June. All three-tree species did not show any significant difference in canopy NDVI based on supplemental water, however the shrub species did reveal a significant response to water (p<0.001). Although all of the three-tree species revealed a one-month period in which they responded to precipitation in July of the first year after 11.2 cm of precipitation, no immediate (day of or next day) response was observed to precipitation or supplemental water events. Snowberry was unique in its NDVI response during the spring green up period in the second year revealing a highly linear shift over a 40-day period with a clear separation between treatments (p<0.001) with those plants receiving supplemental water having a higher more positive slope. Landsat NDVI values revealed an inverse sinusoidal relationship with ETref-precipitation (R2=0.59 p=0.012). Landsat values (0.19+/- 0.01) were found to have no significant difference with bare soil NDVI (0.17+/- 0.01) but were significantly different from all four tree and shrub species. Integrated NDVI based on sensor weighted % cover estimates (0.37+/-0.03) were nearly double Landsat values (0.19+/-0.01). Both NDVI values of pinyon pine and Utah juniper were found to be linear correlated with Landsat NDVI in the second Year (R2>0.75, p<0.001). Multiple regression analysis revealed that 95% of the variation in Landsat NDVI in the second year could be accounted for based on bare soil NDVI and pinyon pine NDVI (p<0.001). et al., NDVI interspace (bare soil) of pinyon juniper woodlands dominated the nature of the Landsat curve. Our results demonstrate the value of ground sensors to help fill the gap between what can be inferred at the forest canopy level and what is occurring at the plant level.

Long-term noise pollution affects seedling recruitment and community composition, with negative effects persisting after removal.

Noise pollution can affect species' behaviours and distributions and may hold significant consequences for natural communities. While several studies have researched short-term effects of noise, no long-term research has examined whether observed patterns persist or if community recovery can occur. We used a long-term study system in New Mexico to examine the effects of continuous natural gas well noise exposure on seedling recruitment of foundational tree species (Pinus edulis, Juniperus osteosperma) and vegetation diversity. First, we examined seedling recruitment and vegetation diversity at plots where current noise levels have persisted for greater than 15 years. We then examined recruitment and diversity on plots where noise sources were recently removed or added. We found support for long-term negative effects of noise on tree seedling recruitment, evenness of woody plants and increasingly dissimilar vegetation communities with differences in noise levels. Furthermore, seedling recruitment and plant community composition did not recover following noise removal, possibly due in part to a lag in recovery among animals that disperse and pollinate plants. Our results add to the limited evidence that noise has cascading ecological effects. Moreover, these effects may be long lasting and noise removal may not lead to immediate recovery.

Effects of Recent Wildfires in Piñon-Juniper Woodlands of Mesa Verde National Park, Colorado, USA

Pinus edulis–Juniperus osteosperma (pinon-juniper) woodlands in the southwestern United States are of high conservation value and are threatened by changing climate and increasing frequency of large, severe fires. We followed vegetation development after three recent fires (1989, 1996, and 2000) in Mesa Verde National Park (MEVE). Two types of pinon-juniper vegetation are found in MEVE: sprouting woodlands (SPW), dominated by species that resprout after injury, and obligate seeding woodlands (OSW), dominated by non-sprouting species. SPW stands showed greater resilience than OSW in terms of recovery of pre-fire structure and species composition, and vulnerability to invasion by nonnative plant species. After all three fires, plant cover increased more rapidly in SPW stands; all major pre-fire species were present within 2 y, and fewer nonnative species became established. Plant cover developed more slowly in OSW stands; nonnative plant species proliferated, in places being more abundant than the newly germinating native species. No reestablishment of pinon or juniper trees has been observed. If current trends persist, some portions of the burned SPW may be converted to a persistent shrubland type, while much of the burned OSW may be converted to a persistent, novel herbaceous vegetation type with a large component of nonnative species. Similar changes after fire can be expected in pinon-juniper woodlands like those in MEVE, which are widely distributed throughout the region.

Temporal controls on crown nonstructural carbohydrates in southwestern US tree species.

In trees, large uncertainties remain in how nonstructural carbohydrates (NSCs) respond to variation in water availability in natural, intact ecosystems. Variation in NSC pools reflects temporal fluctuations in supply and demand, as well as physiological coordination across tree organs in ways that differ across species and NSC fractions (e.g., soluble sugars vs starch). Using landscape-scale crown (leaves and twigs) NSC concentration measurements in three foundation tree species (Populus tremuloides, Pinus edulis, Juniperus osteosperma), we evaluated in situ, seasonal variation in NSC responses to moisture stress on three timescales: short-term (via predawn water potential), seasonal (via leaf δ13C) and annual (via current year's ring width index). Crown NSC responses to moisture stress appeared to depend on hydraulic strategy, where J. osteosperma appears to regulate osmotic potentials (via higher sugar concentrations), P. edulis NSC responses suggest respiratory depletion and P. tremuloides responses were consistent with direct sink limitations. We also show that overly simplistic models can mask seasonal and tissue variation in NSC responses, as well as strong interactions among moisture stress at different timescales. In general, our results suggest large seasonal variation in crown NSC concentrations reflecting the multiple cofunctions of NSCs in plant tissues, including storage, growth and osmotic regulation of hydraulically vulnerable leaves. We emphasize that crown NSC pool size cannot be viewed as a simple physiological metric of stress; in situ NSC dynamics are complex, varying temporally, across species, among NSC fractions and among tissue types.

Rapid and surprising dieback of Utah juniper in the southwestern USA due to acute drought stress

For nearly two decades, the American Southwest has been in the grips of a long-term ‘megadrought’, punctuated by a number of short and severe ‘global change type droughts’ (i.e., negative precipitation anomalies co-occurring with high temperature). These events have caused widespread mortality of the drought-sensitive piñon pine (Pinus edulis) while co-dominant Juniperus spp. have historically been much more drought tolerant and thus have rarely died. However, a severe drought occurred in 2018 that rapidly (<1 year) caused canopy dieback of Juniperus osteosperma across a vast area of southeastern Utah. In order to uncover the etiology behind this surprising dieback event, we set up a series of survey plots that captured gradients in microclimate, topography, and dieback severity. We also quantified xylem hydraulic damage and assessed the presence of various biotic agents in declining junipers to identify the primary causes of this dieback. We observed that juniper canopy dieback was most severe (>60% canopy dieback) at hot, dry, low elevation sites, and was associated with drought-induced hydraulic damage. There was no evidence that biotic agents could be the primary drivers of this dieback, implicating the acute effects of drought as the main causal agent. The speed and scale of this drought-induced juniper dieback seems to be historically unprecedented in the region and foreshadows an uncertain future for piñon-juniper woodlands as the region continues to get warmer and drier.

Fire-Environment Analysis: An Example of Army Garrison Camp Williams, Utah

The planning of fuel treatments for ecological or societal purposes requires an in-depth understanding of the conditions associated with the occurrence of free-burning fire behavior for the area of concern. Detailed fire-environment analysis for Army Garrison Camp Williams (AGCW) in north-central Utah was completed as a prerequisite for fuel treatment planning, using a procedure that could be generally applied. Vegetation and fuels data, topographic and terrain features, and weather and climate data, were assessed and integrated into predictive fuel models to aid planning. A fire behavior fuel model map was developed from biophysical variables, vegetation type, and plot survey data using random forests, and resulted in an overall classification rate of 72%. The predominate vegetation type-fuel complex was grass, followed by lesser amounts of Gambel oak, Wyoming big sagebrush and Utah juniper. The majority of AGCW is mountainous in nature, characterized by slopes less than 40% in steepness with slightly more northerly and easterly aspects than south and west, and elevations that ranged from 1650 to 1950 m above mean sea level. Local fire weather data compiled from the three nearest remote automated weather stations indicated that average temperature maxima (32 °C) and relative humidity minima (12%) usually occurred between 1400 to 1500 h daily, and from July to August, seasonally. The semi-arid climate at AGCW, coupled with the corresponding preponderance of flashy fuel types and sloping terrain, constitutes a formidable fire environment in which to plan for mitigating against adverse fire behavior.

Holocene vegetation and climate change on the Colorado Plateau in southern Utah, USA

AbstractPollen, plant macrofossils, and sedimentary analyses from archaeological deposits at North Creek Shelter (NCS) on the Colorado Plateau provide data on vegetation and climate change during the Holocene. From 11,300–10,200 cal yr BP, NCS was embedded in a mixed conifer forest of cool-adapted species (e.g.,Abies,Pseudotsuga menziesii, andPinus ponderosa) with anArtemisiaunderstory. During this interval, NCS pollen corresponds to modern pollen fromPicea–Abiesforests that reside 950 m higher in elevation. Rapid deposition rates of NCS sediments indicate that climatic conditions during the Early Holocene were more mesic than today, with increased precipitation. The onset of warmer conditions at NCS began at 10,200 cal yr BP, and pollen and plant macrofossils indicate that a semiarid woodland and scrub mosaic dominated byPinus edulis,Juniperus osteosperma, and Amaranthaceae surrounded NCS by 9300 cal yr BP. This is corroborated by fossil pollen that is similar to modern pollen fromP. edulis–J. osteospermawoodlands and Amaranthaceae scrub that currently surround NCS. Sedimentary analyses suggest that during this time, accumulation rates were very low due to low precipitation and a drier climate overall. Migration ofP. edulisinto southern Utah is directly dated to 8100 cal yr BP, thus confirming recently proposed patterns of northward expansion.

Devils playground, Box Elder County

Why take your kids to the neighborhood playground, when you can visit a playground that inspires their sense of geologic adventure? Devils Playground is not your ordinary community playground, but a wonderland of granitic rock weathered into fantastic forms and weird shapes. Occupying an assortment of Bureau of Land Management, state, and private land in the Bovine Mountains, Devils Playground is a relatively unknown geologic curiosity found in a remote corner of northwestern Utah. Devils Playground is situated in the physiographic region known as the Great Basin province that extends across western Utah, Nevada, and to the Sierra Nevada Mountains in eastern California. The area is composed mostly of granitic rocks of the Emigrant Pass intrusion. A combination of granitic rock, faulting, and weathering under a semiarid climate created favorable conditions for the creation of Devils Playground. Desert plants such as sagebrush,Utah juniper, pinyon pine, Mormon tea, and cheatgrass are common throughout the area.