Ashe Juniper Research Articles

Crown fires remove a fire-sensitive canopy dominant from oak-juniper woodlands: results from long-term monitoring of wildfires

BackgroundIn central Texas, re-sprouting oaks (Quercus spp.) co-occur with non-resprouting Ashe juniper (Juniperus ashei) in a mosaic of fire-dependent (oak savanna) and fire-sensitive (oak-juniper woodland) habitats. The region’s mature woodlands are the only nesting habitat for the endangered golden-cheeked warbler (Setophaga chrysoparia). We studied long-term recovery of woodland structure and species composition after single and repeated crown fires on three soil types (mesa, slope, and deep savanna soils).ResultsOn once-burned sites, density and basal area of non-juniper trees (all woody species except juniper) reached or exceeded unburned levels after 14–24 years, indicating successful recruitment (24 years vs unburned, mesa: 481 ± 254 vs 155 ± 137 stems ha−1, 2 ± 1 vs 1 ± 2 m2 ha−1; slope: 910 ± 330 vs 251 ± 103 stems ha−1, 5 ± 2 vs 3 ± 2 m2 ha−1). Ashe juniper, however, remained mostly absent from burned woodlands (juniper tree density, 24 years vs unburned, mesa: 6 ± 10 vs 691 ± 410 stems ha−1; slope: 20 ± 17 vs 731 ± 183 stems ha−1) and total basal area was 47–87% lower than in unburned areas. In formerly fire-suppressed savannas, non-juniper tree density exceeded unburned levels and juniper density recovered the most (24 years vs unburned, non-juniper: 679 ± 250 vs 251 ± 103 stems ha−1; juniper: deep: 50 ± 71 vs 317 ± 297 stems ha−1). Juniper trees were still absent from twice-burned sites in year 11 and understory density was recovering more slowly, at least on slopes (one fire: 224 ± 206 stems ha−1; two fires: 26 ± 47 stems ha−1). Juniper recovery was correlated with distance to the wildfire perimeter, suggesting that regeneration is limited in part by dispersal.ConclusionsWe found successful recruitment of resprouting hardwood species after one and two crown fires, likely due to the low deer densities at Fort Cavazos. In fire-suppressed oak savannas, a single crown fire did not restore savanna structure and Ashe juniper is slowly re-establishing. Long-term restoration of a savanna on these soils will require additional treatments, like repeated prescribed fire. In oak-juniper woodlands, crown fires removed the fire-sensitive Ashe juniper from canopy co-dominance for decades, making the woodlands unsuitable as habitat for golden-cheeked warblers. Given the long-term consequences of crown fires for golden-cheeked warbler habitat, existing mature oak-juniper woodlands should be protected from crown fire.

Future Climate Change Shifts the Ranges of Major Encroaching Woody Plant Species in the Southern Great Plains, USA

AbstractWoody Plant Encroachment (WPE) is a key driver of grassland collapse in the Southern Great Plain (SGP), resulting in a series of adverse ecological and socioeconomic consequences. Climate change will interact with ongoing WPE as it will likely shift the potential ranges of WPE species. In this study, we employed an ensemble approach integrating results from multiple Species Distribution Models to project future distribution ranges of four major WPE species (Ashe juniper, honey mesquite, post oak, and eastern redcedar) in the SGP across the 21st century. The findings highlighted a noteworthy trend: under future climate conditions, the distribution ranges for these WPE species were projected to shift northward and eastward. Of particular concern is honey mesquite with significant expansion in distribution range, potentially covering up to two‐thirds of the SGP's non‐agricultural area by the end of the 21st century. Conversely, the other three WPE species were expected to experience a contraction in their distribution ranges. Ashe juniper may experience a decline in its current habitats in central Texas but gain new habitats in northern Texas, Oklahoma, and Kansas. The suitable ranges of post oak and eastern redcedar were projected to shrink eastward, primarily being restricted to eastern portions of Oklahoma and Texas under the RCP4.5 and a smaller area in eastern Oklahoma under the RCP8.5. The projected shift in WPE ranges provides a scientific basis for governments to optimize the allocation of management resources and implement timely practices to control the spread of woody plants during the early encroachment stage. Our study methodology is applicable to other regions and continents with WPE issues, including Africa, South America, and Australia.

Soil carbon, nitrogen, and phosphorus storage in juniper–oak savanna: role of vegetation and geology

Abstract. Woody-plant encroachment into grasslands and savannas has been globally widespread during the past century, likely driven by interactions between grazing, fire suppression, rising atmospheric CO2, and climate change. In the southernmost US Great Plains, Ashe juniper and live oak have increased in abundance. To evaluate potential interactions between this vegetation change and the underlying soil parent material on ecosystem biogeochemistry, we quantified soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), and δ13C of SOC in soils obtained from trenches passing through grassland, juniper, and oak patches on soils lying atop the respective Edwards and Buda limestone formations in central Texas. Soils on the Edwards formation are more shallow and have more rock outcropping than those on Buda. The δ13C values of SOC under grasslands was −19 ‰, whereas those under woody patches were −21 ‰ to −24 ‰, indicating that wooded areas were relatively recent components of the landscape. Compared with grasslands, areas now dominated by juniper or oak had elevated SOC, TN, and TP storage in soils lying atop Edwards limestone. In Buda soils, only oak patches had increased SOC, TN, and TP storage compared with grasslands. Woody encroachment effects on soil nutrients were higher in soils on the Edwards formation, perhaps because root and litter inputs were more concentrated in the relatively shallow layer of soil atop the Edwards bedrock. Our findings suggest that geological factors should be considered when predicting nutrient store responses in savannas following vegetation change. Given that woody encroachment is occurring globally, our results have important implications for the management and conservation of these ecosystems. The potential interactive effects between vegetation change and soil parent material on C, N, and P storage warrant attention in future studies aimed at understanding and modeling the global consequences of woody encroachment.

Diversification deep in the heart of Texas: seven new grasshopper species and establishment of the Melanoplusdiscolor species group (Orthoptera, Acrididae, Melanoplinae).

Melanoplusdiscolor and Melanopluskendalli were previously placed in the texanus species group. Here seven new species are described from central Texas and the combined nine species placed into the discolor group based on emergence time and shape of the male terminalia and genital structures. Six of these new species are from the Edwards Plateau, a known area of high endemism. Species of the discolor group are inhabitants of shortgrass or mixed-grass prairies, Ashe juniper or oak savannas.

Urban land cover and El Niño events negatively impact population viability of an endangered North American songbird

AbstractPopulation dynamics of migratory species are influenced by land use and climate patterns experienced across the full annual cycle. Identifying environmental factors influencing productivity, survival, and their relative contributions to abundance and population growth is critical for the recovery and management of at‐risk species in the face of continuing global change. The golden‐cheeked warbler (Setophaga chrysoparia) is an endangered passerine that breeds exclusively in the mixed Ashe juniper (Juniperus ashei)–oak (Quercus) woodlands of Central Texas, USA, and winters at high elevations in Central America. We evaluated the effects of precipitation, climate, and land cover on golden‐cheeked warbler productivity, adult male survival, and territory abundance using data from a long‐term monitoring site, the Balcones Canyonlands Preserve, in Austin, Texas. We jointly analyzed annual productivity, mark–recapture, and territory count data collected on 10 plots from 2011 to 2019 in an integrated population model. The number of young fledged per male territory was negatively related to percent urban land cover within 1 km of monitoring plots, and adult male survival was negatively related to a strong El Niño event. Estimates of population growth and abundance indicated a decline in abundance across our study period. We forecasted population viability 25 years into the future given increases in urban development and frequency of El Niño events. Quasi‐extinction probability increased from 0.17 under current urban land cover conditions and El Niño frequency to 0.41 under the scenario of a 10% increase in urban development around all plots and an increase in El Niño frequency. Productivity and adult survival were positively correlated with population growth, highlighting the need for conservation and management actions to maximize these vital rates on the breeding grounds and range‐wide.

Experimental and numerical investigation on a solar-driven torrefaction reactor using woody waste (Ashe Juniper)

In this work, designs a novel solar-driven thermochemical conversion reactor to torrefy biomass waste (Ashe Juniper) for further pyrolysis applications. The effect of torrefaction temperature and residence time on the properties of biomass waste was investigated and results showed that torrefaction temperature dominates the properties of product compared to the effect of residence time. The highest energy yield (over 90%) was obtained at 210 ℃ while the highest energy densification (∼1.51) was achieved at 360 ℃. In addition, a two-step kinetic numerical model was used to analyze and predict the experimental process (kinetic rates) and results (C, H, and O contents) based on the experimental results. The analysis results showed that the predicted results are in good agreement with the practical results after torrefaction, indicating the feasibility of this numerical model for torrefaction and pyrolysis applications. The carbon footprint analysis showed that reduction effect of 1.3 ∼ 1.6 tCO2/ton-AJ can be obtained by torrefaction of Ashe Juniper. Finally, the prospects for future industrial applications of solar-driven torrefaction reactors discussed as one of affordable and clean energy.

Multi‐scale species density model for conserving an endangered songbird

AbstractHabitat modeling across a landscape that has gradients of habitat conditions requires potential predictor data that can be quantified at biologically relevant scales. We used remotely sensed data to develop a multi‐scale density model in 2018 for the golden‐cheeked warbler (Setophaga chrysoparia; warbler), a species that breeds in Ashe juniper (Juniperus ashei)‐oak (Quercus spp.) woodlands in central Texas, USA. We first classified Ashe juniper and broadleaf tree cover at a 1‐m resolution and used this to map potential habitat across the warbler's >67,000‐km2 breeding range. We then designed a survey for estimating warbler density based on hierarchical distance sampling. We used stratified random sampling to survey for male warblers at 1,804 points across the continuum of tree canopy cover and composition and detected 810 warblers during our surveys. We developed a suite of potential predictor variables for modeling warbler density that reflected vegetation, topography, climate, and anthropogenic land use conditions across the breeding range and developed these at 3 scales representing the territory, site, and landscape. We modeled warbler density and used the best fit model to produce a spatially explicit estimate. Predicted warbler density was influenced by tree canopy cover and canopy height at the territory scale (100‐m radius); tree canopy cover, percent of the canopy comprised of juniper, and an interaction between canopy cover and compound topographic index at the site scale (1‐km radius); and annual temperature range at the landscape scale (5‐km radius). We estimated a population size of 217,444 male warblers (95% CI = 153,917–311,965) and >3,000 males in each recovery unit. After controlling for the duration of point count surveys, our estimate of population size was similar to that reported from the only previous breeding range survey conducted in 2008–2009. Our model results indicated that management activities to increase warbler density should promote woodlands with high tree canopy cover, approximately 60–80% Ashe juniper composition, and tree heights >3 m. In contrast to a patch‐based approach, our treatment of habitat variables as continuous helped to credibly map the warbler distribution across areas with broad transitions from woodlands to shrublands. By measuring these predictor variables at biologically relevant scales, we allowed the warbler survey data to define habitat relationships instead of using anthropogenically defined habitat patches. Outcomes from our study show the benefits of developing spatial products tailored to individual species of interest for conservation and management decisions.

Influence of Juniper on Montezuma Quail Habitat Use in Texas

ABSTRACTMontezuma quail (Cyrtonyx montezumae) inhabit oak (Quercus spp.)‐juniper (Juniperus spp.) woodlands throughout Mexico and the southwestern United States. In Texas, USA, Montezuma quail occur in the Edwards Plateau and Trans‐Pecos Mountains and Basins (Trans‐Pecos), 2 ecoregions with contrasting juniper patterns. Ashe juniper (Juniperus ashei) dominates in the Edwards Plateau and has been increasing over decades, whereas alligator juniper (Juniperus deppeana) is a co‐dominant in the Trans‐Pecos and appears to have stable Montezuma quail populations. Our objectives were to compare between ecoregions the relative abundance and habitat use of Montezuma quail in relation to juniper and quantify the influence of juniper on key features of Montezuma quail habitat (grass height, grass cover, forb cover, and forb species richness). We conducted a study from March–August 2018‒2020 in the Edwards Plateau (Kinney and Edwards counties) and Trans‐Pecos ecoregions (Jeff Davis County) to evaluate these objectives. We conducted call‐back surveys to estimate relative abundance (number of detections/hr) of Montezuma quail and identify used locations. We collected vegetation data at a micro‐scale (16‐m) at used (n = 32–30 points) and random locations (n = 70–60 points) in each ecoregion. Relative abundance of Montezuma quail was considerably lower in the Edwards Plateau (0.06 ± 0.01 detections/survey hr; ± SE) than in the Trans‐Pecos (1.10 ± 0.30 detections/survey hr). In addition, Montezuma quail selected areas of low Ashe juniper cover (<23% cover), density (<7 trees/80 m2), and height (<2 m) in the Edwards Plateau but selected areas of high alligator juniper cover (>18% cover), density (>4 trees/80 m2), and height (2–8 m) in the Trans‐Pecos. Moreover, Ashe juniper cover had a significant, negative influence on herbaceous features, whereas alligator juniper exerted little to no influence. Our results suggest that these 2 juniper species have contrasting effects on Montezuma quail space use and their habitat, possibly as a result of the contrasting influence of these junipers on herbaceous understory. Creating habitat for Montezuma quail in the Edwards Plateau generally will involve the reduction of Ashe juniper and creating patches that possess juniper trees of small stature (<2 m) with low amounts of cover (<23%) and density (<7 trees/80 m2), whereas management in the Trans‐Pecos will require site‐specific assessments based on current alligator juniper influence. © 2021 The Wildlife Society.

The influence of geographic variation in vegetation characteristics on habitat use and productivity of an endangered warbler

Understanding how geographic variation in environmental conditions influences species’ distributions and population dynamics is critical for effective management of at-risk species and can help us anticipate wildlife responses to future change. The Golden-cheeked Warbler (Setophaga chrysoparia; hereafter warbler) is an endangered migratory songbird that nests in oak-juniper woodland in Texas. From 2009 to 2013, we monitored 895 warbler territories at 90 study sites located across the warbler’s breeding range to examine how geographic variation in vegetation characteristics influenced aspects of warbler habitat selection and productivity. We found range-wide variation in the tree species composition and vegetation structure of warbler habitat. Warbler territory density decreased with increasing percent Ashe juniper (Juniperus ashei) canopy cover at study sites predominated by shin oak (Quercus sinuata) and increased with increasing percent Ashe juniper canopy cover at study sites predominated by post oak (Q. stellata), but did not vary in relation to percent Ashe juniper cover at study sites predominated by other oak species. We also found that territory size decreased with increasing percent canopy cover (all tree species), but did not find evidence that warbler pairing success or fledging success varied in relation to the vegetation characteristics of our study sites. Our results suggest that warblers breed under a wider range of conditions than identified in current management guidelines and that warbler management guidelines could be more effective if developed and applied at local or regional scales. Our study also reiterates the importance of understanding geographic variation in wildlife-habitat relationships for conservation of at-risk species.

Native tree and shrub canopy facilitates oak seedling regeneration in semiarid woodland

AbstractOaks (Quercus spp.) are currently declining worldwide due to a multitude of threats. Woodland management is often heavily focused on thinning and burning nontarget species to reduce competition and promote oak dominance in the overstory. These techniques have typically been developed in temperate regions, such as eastern U.S. forests, but whether they are the most effective strategy for promoting oak regeneration in semiarid woodlands has not been sufficiently examined. We conducted our study on the eastern Edwards Plateau in central Texas, where several oak species are codominant with Ashe juniper (Juniperus ashei) over karst limestone terrane. These juniper‐oak woodlands provide habitat for many endemic species and play an essential role in the maintenance of key aquifers. A history of canopy clearing and a severe drought in 2011 generated patches of living and dead juniper‐oak canopy interspersed with canopy gaps in our study area. In November 2013, we planted 200 shin oak (Quercus sinuata var. breviloba) acorns in each of three habitat treatments, replicated six times: (1) live canopy, (2) dead canopy, and (3) open invasive grassland. We monitored emergence and survival each year, harvesting five seedlings from each replicate in October 2017 to assess shoot height, rooting depth, biomass, ectomycorrhizal colonization, and foliar nutrients. Canopy trees, living or dead, significantly enhanced seedling emergence and survival. Survival was positively associated with increasing Ashe juniper and oak basal area, shrub cover, and soil organic matter, and negatively associated with increasing canopy gap size (complete mortality in gaps >220 m2). Seedling biomass increased significantly in dead and open treatments along with foliar nutrients N, P, and S (dead treatments) or S and Fe (open treatments), whereas ectomycorrhizal colonization and foliar nutrients Ca, Mg, and Mn increased under living canopy. Our findings suggest that oak regeneration in these juniper‐oak woodlands closely resembles that of Mediterranean regions, where canopy facilitates seedling survival. Both living and dead trees and shrubs enhanced oak regeneration, with seedling survival depending on proximity to larger trees, living roots, shrubs, and juniper‐oak canopy. Planting acorns under canopy is an inexpensive, sustainable, and effective restoration practice in drought‐prone ecosystems.

Spatial Use and Survivorship of Translocated Wild‐Caught Texas Horned Lizards

ABSTRACTThe Texas horned lizard (Phrynosoma cornutum), a state threatened species in Texas, USA, appears to be declining throughout much of its distribution. Because of popular interest in restoring lizard populations, we conducted a 3‐year radio‐telemetric study to evaluate the feasibility of reintroducing Texas horned lizards into previously occupied areas with suitable habitat characteristics. We translocated lizards from natural populations in western Texas to the McGillivray and Leona McKie Muse Wildlife Management Area (MWMA) in the Cross Timbers and Prairies of north‐central Texas, an ecoregion that has experienced apparent local extirpations of horned lizards. We translocated lizards after partly restoring a 32.5‐ha portion of the MWMA from ashe juniper (Juniperus ashei)‐honey mesquite (Prosopis glandulosa) woodland to mid‐grass prairie. After a 10‐day acclimation period and soft release, we tracked 57 horned lizards from March 2014 to October 2016 to evaluate daily movements, spatial use, sources of mortality, reproduction, and changes in body condition. Daily movement averages (1.16–174.18 m) and area used by individuals (<0.01–6.81 ha) were similar to those recorded for natural populations, with peaks in movement occurring in May and June. Annual survivorship for individuals (1.1–47.2%) was also similar to that reported from natural populations; however, survivorship declined across the 3 active seasons. Although mortality of translocated lizards was high, body condition remained relatively stable across active seasons, and reproduction occurred each year, indicating that translocation could be a viable option for restoring horned lizard populations to previously occupied parts of their range. © 2019 The Wildlife Society.

Postbreeding Habitat Use by Golden-Cheeked Warblers (Setophaga chrysoparia)

The period following breeding but prior to migration is an important, though understudied, component of the avian annual life cycle. We quantified habitat use by endangered Golden-cheeked Warblers (Setophaga chrysoparia) during the postbreeding period in Golden-cheeked Warbler breeding habitat (i.e., oak-juniper [Quercus-Juniperus] woodlands) predominated by Texas oak (Quercus buckleyi) or post oak (Q. stellata), as well as in immediately adjacent oak woodland, oak savanna, and riparian vegetation not usually associated with breeding activity for this species. Most (87%) of the Golden-cheeked Warblers we detected were in oak-juniper woodlands, especially in Texas oak sites, but we also detected warblers in each of the other vegetation types we surveyed. Adults and family groups used breeding and nonbreeding habitat similarly, as did males and females, but juveniles used nonbreeding habitat more than adults did. Neither canopy cover nor territory density during the breeding season influenced postbreeding habitat use by warblers, regardless of vegetation type. We detected warblers 82% less often in post oak breeding habitat than in Texas oak breeding habitat despite similar densities of breeding territories, suggesting that warblers left post oak sites earlier during the postbreeding period. However, we found no evidence that warblers that bred in post oak sites were more likely to move into adjacent nonbreeding habitat than those that bred in Texas oak sites. Ashe juniper (Juniperus ashei) was the most consistently used woody substrate during the postbreeding period, regardless of warbler sex, warbler age, habitat type, or predominant oak species. Our results emphasize the continued importance of oak-juniper woodlands to Golden-cheeked Warblers during the postbreeding period but suggest that other vegetation types may also have conservation value for this species.

Old School and High Tech: A Comparison of Methods to Quantify Ashe Juniper Biomass as Fuel or Forage

• Ashe juniper invasion is a widespread issue on Texas and Oklahoma rangelands. Increased densities of Ashe juniper trees increase the risk of wildfire and decrease herbaceous forage production. • Browsing animals, such as goats, are one tool that can be used to effectively reduce juniper fuel. • In order to estimate the available biomass, allometric measurements were compared against three-dimensional Light Detection and Ranging (LiDAR) scans of whole juniper plants. • Accurate measurements of standing juniper browse and fuel load can be vital information for decision support of grazing management and wildland fire mitigation, especially in the ever-growing wildland-urban interface.

The economical production of functionalized Ashe juniper derived-biochar with high hazardous dye removal efficiency

High adsorption capacity is crucial for the commercial application of biochar in contaminant removal. Here, we produced a functionalized biochar with high adsorption capacity for high concentration dye chemicals higher than 300 mg/L in which sulfuric acid treatment was implicated for functionalization. This study presents the effects of the concentration of sulfuric acids (50, 70, and 90%) on the physical and chemical properties of the biochar produced by conventional pyrolysis from Ashe juniper. We found that the high concentration of sulfuric acid was crucial for developing biochar with a high degree of sulfonation and oxidation on the biochar surface and highly developed porosity, resulting in approximately 200 times improved adsorption capacity compared to raw biochar. The implications of the design of experiment (DOE) confirm the significant effects of dosage which also have quadratic effect and initial dye concentration on the adsorption capacity. An adsorption isotherm study revealed that the methylene blue adsorption followed Langmuir isotherm, meaning that the homogeneous surface of the functionalized biochar. By multicomponent adsorption experiment, the functionalized biochar showed a higher affinity to methylene blue than methyl orange, indicating the potential of our products as a promising separator of methylene blue. Furthermore, techno-economic analysis revealed the economic feasibility of functionalized biochar for a dye chemical removal from aqueous solution.

Tree Mortality After a Hot Drought: Distinguishing Density-Dependent and -Independent Drivers and Why It Matters

Hot drought is a climate phenomenon that has lately received much attention for its potential to disrupt forest function worldwide. A sharp increase in tree mortality associated with this climate pattern are often cast as a disturbance, in which high temperature is responsible for causing exceptional rates of mortality. The alternative interpretation is simply that drought kills trees in a density-regulating manner and within the bounds of normal forest function. To evaluate the evidence for disturbance versus regulating dynamics, we conducted censuses across 30 plots in the Edwards Plateau region of central Texas, USA, four years after the hot drought of 2011. The purpose was to explain variation in population responses to drought, including crown mortality, resprouting rate and sapling survivorship in terms of physical site factors, community characteristics and local climate data. Through model selection analysis, we identified the most parsimonious binomial regression models for the three most common species. In Ashe juniper populations, overall crown mortality was 20% and all predictive factors indicated the influence of population-regulating dynamics. In live oak (Quercus virginiana & Q. fusiformis), which had a crown mortality rate of 23%, the influence of regulating factors was less prominent, but there was also no evidence that crown death was linked to heat exposure. However, resprouting in both species appeared to be inhibited by heat exposure, as was crown mortality in the understory species Texas persimmon (Diospyros texana). Along with overall high levels of sapling survivorship, these patterns suggest that Ashe juniper woodlands, despite having been relatively hard hit by the 2011 drought, are not particularly threatened by hot drought events, although some subordinate species may be. Density-regulating mechanisms of forest drought response are often underplayed, but they are far easier to represent in vegetation models than disturbance dynamics.

RESTORATION OF FORMER GRASSLAND IN SOUTH-CENTRAL TEXAS

AbstractIn the past, grasslands and savannas were common in many areas of south-central Texas, including the San Antonio area. With the advent of European settlers and their livestock, much of this area was converted to agriculture and rangeland. Today, most of San Antonio is developed, but some preservation has occurred. Restored grassland, mechanically cleared of Juniperus ashei (juniper, Ashe juniper) and other woody species in 2013, was examined and compared to adjacent non-cleared woodland. The woodland examined was dominated by Diospyros texana (Texas persimmon) and Juniperus ashei. Richness in the woodland canopy was 15 species. The understory below the canopy had 25 woody species. In the restored grassland area, herbaceous plant cover was 41.8%, woody plant cover 5.8%, bare soil 2.9%, and litter cover 49.5%. Species richness was 71, with 60 herbaceous and 11 woody species (percent cover of each from <0.1–7.1%). The most common species in the restored grassland in descending order were Nassella leucotricha (Texas winter grass), Calyptocarpus vialis (straggler daisy), Carex planostachys (cedar sedge), Sporobolus crypandrus (sand dropseed), D. texana, and Verbesina virginica (frost weed). Several C4 grass species were present with low cover but may increase in abundance over time. Four of the six most common restored grassland species were present below the woodland canopy and 12 woody species were present in the restored grassland as juveniles. Cost of restoration was approximately $38,500 ($7,500 supplies, $31,000 labor).

Tree Species Use and Seasonal Response to Food Availability of Black-Capped Vireo

The ability of songbirds to survive and reproduce depends on many factors, one of which is the ability to acquire enough food. We quantified foraging behavior, nestinghabitat vegetation composition, and available arthropod prey of the Vireo atricapilla (Black-capped Vireo) in Texas during 2010 and 2011. We used observational surveys of foraging behavior and vegetation time-use to quantify the Black-capped Vireos' foraging behavior and vegetative use versus availability (i.e., mean proportion of use vs. vegetative species availability). We collected descriptive data on the Black-capped Vireos' foraging use of available vegetative species and compared among vegetative species, year, and within-season sampling periods. In 2010 and 2011, we identified and mapped 49 and 63 breeding territories and repeatedly surveyed 30 and 58 territories for foraging activity, respectively. Data analysis focused on the foraging use of the 3 most commonly used and available tree species: Juniperus ashei (Ashe Juniper), Quercus sinuata (Shin Oak), and Q. fusiformis (Live Oak). Ashe Juniper, Shin Oak, and Live Oak together made up 78.8% and 83.6% of total proportion of substrate for foraging efforts in 2010 and 2011, respectively. Ashe Juniper had the highest proportion (~28–50%) of foraging effort in 2010, 2011, and all but 1 sampling period for both years. We also repeatedly collected branch clippings from within a random subset of surveyed Black-capped Vireo territories to identify potentially available arthropod foods. We evaluated by order richness, total abundance, and dry biomass to make comparisons among vegetative species, year, and within-season sampling periods. We found significant differences in the biomass of arthropod orders Acari and Thysanoptera in 2010 and between orders Acari and Hymenoptera in 2011 among the 3 focal vegetative species. Examination of additional descriptive data suggests seasonal changes in potentially available arthropod foods. Our research underscores the importance of vegetation composition to Black-capped Vireos that may help habitat managers select for potential vegetative species distributions to optimize food resources throughout the breeding season for this species.

Effect of metal salts impregnation and microwave-assisted solvent pretreatment on selectivity of levoglucosenone and levoglucosan from vacuum pyrolysis of ashe juniper waste

Levoglucosenone (LGO), furfural (FF) and levoglucosan are high value-added chemical components of bio-oil derived by thermal deconstruction of biomass. However, separation of these chemicals from bio-oil is challenging due to low selectivity. Impregnation of metal salts for catalytic pyrolysis or microwave treatment for altering chemical composition in biomass are potential methods to enhance selectivity of these high value-added chemicals. In the current study, Ashe juniper waste was pretreated with metal salts prior to vacuum pyrolysis and investigated the effects of metal salt type and its concentration on product yield and properties. The results showed that Levoglucosenone, which was attributed to dehydration of levoglucosan, was obtained only with the biomass pretreated with CuSO4 and ZnSO4. Metal salt type and concentration also affected the selectivity of levoglucosenone (LGO) and furfural (FF) by catalytic vacuum pyrolysis. Microwave-assisted organosolv treatment also affected biomass chemical composition, pyrolysis characteristics and promoted the selectivity of levoglucosan.

Projected drought effects on the demography of Ashe juniper populations inferred from remote measurements of tree canopies

Tree mortality from drought is anticipated to increase as climate change promotes more frequent or severe water limitation. Ecosystem impacts of woody mortality depend on both the number and sizes of trees that die, but a limited capacity to predict mortality risk for individual trees hinders the capacity to forecast drought effects on tree population demography and ecosystem processes. We remotely measured leaf area of living Ashe juniper trees at three savanna sites in central Texas, USA to characterize the frequency-size distribution (FSD) of juniper populations and evaluate mortality risk from drought as a function of tree size. Mortality risk of individuals was assessed from the deviation in leaf area per tree from that of a similarly sized individual with near maximal leaf area using correlations among leaf area, growth rate, and mortality measured during a prior drought. We found that the FSD of juniper trees is bell-shaped at each site. Mortality risk from drought exceeded 25% of emergent (> 4 m height) trees in savanna juniper populations, but was highest for largest trees. Mortality risk was greatest at a grazed savanna, exceeding 50% of trees with projected canopy area > 20 m2. Results imply that severe drought could kill a large fraction (18–85%) of intermediate- to large-sized Ashe juniper trees in central Texas savannas. Our analysis demonstrates a novel use of remote measurements of canopy foliation to link mortality risk from drought to the demography of Ashe juniper populations through properties of individual trees.

Effects of Brush Management on the Reproductive Ecology of Endangered Black-capped Vireos

Terrestrial habitats are frequently managed to improve perceived economic or aesthetic value of the land and to improve habitat quality for wildlife species. In central Texas, removal of native Juniperus asheii (Ashe Juniper) is a common landscape-management practice due to the species' propensity for invasion of rangeland, vigorous growth leading to dominance of habitats, and reputation for high water-use. Ashe Junipers provide habitat for wildlife species of economic (e.g., Odocoileus virginianus [White-tailed deer], Meleagris gallopavo [Wild Turkey]) and conservation concern (e.g., the endangered Setophaga chrysoparia [Golden-cheeked Warbler]); however, the relationship between Ashe Junipers and the federally endangered Vireo atricapilla (Black-capped Vireo) is less clear. Blackcapped Vireos breed in early successional shrublands where Ashe Junipers are often able to invade, grow quickly, and shade out the deciduous shrubby vegetation preferred by vireos. Although Ashe Juniper removal in Black-capped Vireo habitat is common practice, relatively little is known about the impacts of brush management on Black-capped Vireo use and reproductive success. Here we present results of a study on the effects of an Ashe Juniper removal treatment, in which juniper trees were removed but surrounding deciduous vegetation was largely left intact, on Black-capped Vireo habitat use and reproductive success. Comparing before and after Ashe Juniper removal, we found that the number of Blackcapped Vireos settling in manipulated habitats remained similar, and we saw no significant changes in the size of the average territory or reproductive success. We conclude that, when the amount of damage to the surrounding deciduous vegetation is limited, selective Ashe Juniper removal is unlikely to negatively affect Black-capped Vireos.