Shin Oak Research Articles

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.

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.

Direct and indirect effects of petroleum production activities on the western fence lizard (Sceloporus occidentalis) as a surrogate for the dunes sagebrush lizard (Sceloporus arenicolus).

The dunes sagebrush lizard (Sceloporus arenicolus) is a habitat specialist of conservation concern limited to shin oak sand dune systems of New Mexico and Texas (USA). Because much of the dunes sagebrush lizard's habitat occurs in areas of high oil and gas production, there may be direct and indirect effects of these activities. The congeneric Western fence lizard (Sceloporus occidentalis) was used as a surrogate species to determine direct effects of 2 contaminants associated with oil and gas drilling activities in the Permian Basin (NM and TX, USA): herbicide formulations (Krovar and Quest) and hydrogen sulfide gas (H2S). Lizards were exposed to 2 concentrations of H2 S (30 ppm or 90 ppm) and herbicide formulations (1× or 2× label application rate) representing high-end exposure scenarios. Sublethal behavioral endpoints were evaluated, including sprint speed and time to prey detection and capture. Neither H2S nor herbicide formulations caused significant behavioral effects compared to controls. To understand potential indirect effects of oil and gas drilling on the prey base, terrestrial invertebrate biomass and order diversity were quantified at impacted sites to compare with nonimpacted sites. A significant decrease in biomass was found at impacted sites, but no significant effects on diversity. The results suggest little risk from direct toxic effects, but the potential for indirect effects should be further explored.

Texas Today: A Sea of the Wrong Grasses

“In the ’60s when I bought this place and moved here from Houston, we had so many quail that you didn’t even need a bird dog to find them,” mused my 85-year-old hill country neighbor. “Then,” he paused, his satirical glance drifting toward the mantle to a dust-covered 20-gauge double-barreled shotgun and a faded John Cowan Print of a quail hunt on a shin oak mountaintop of the Texas hill country, “by the early ’80s, the quail were gone.” “Well,” I interjected in a smug biologist’s refrain, “what changed?” “Hell, I dunno, but just before that time everybody planted all the maize fields to coastal (bermudagrass), and that damn KR bluestem came in from the highway when they redid it.” “I’ll bet that’s part of it,” added the old man. What ran through agronomist Nick Diaz’s mind on a hot, dry Gulf Coast summer day in 1939, when he first laid eyes on the maroon, glistening seedheads of Dichanthium annulatum growing in a King Ranch pasture, was probably a lot different than what raced through mine on April 26, 2009. As the one who first noticed the accidentally introduced African grass, and the one who helped select, increase, and release what would come to be known as Kleberg bluestem, Mr. Diaz had high hopes for transforming dried up, grass-poor ranges into lush seas of grass. He probably envisioned pastures full of fat cattle and a buffered annual bonus check, courtesy of this grass that could grow so well, and so aggressively, in the hellish windblown sands and cracked black clays of the Wild Horse Desert of south Texas. Today’s biologists look upon Kleberg bluestem, and its African, Asian, and Australian grass cousins brought to Texas, with a nauseating suspicion of an ecological nightmare. It is akin to a viral pandemic, swallowing up chunks of what few can accurately describe with words, few thoroughly understand, but what used to be waves of bluebonnets and paintbrushes in the spring, crimson stands of native prairie grasses in the fall, and carpets of yellow flowers interspersed by funny looking grasses whose seeds stick in socks and shoestrings. The native Texas landscape is disappearing before our eyes, under a sea of the wrong grasses. What ran through my mind on April 26, 2009, when I saw those maroon seedheads blowing in the breeze alongside U.S. 183 was much different than what Nick Diaz must have pictured in 1939. I wondered aloud what the hell a grass that I work to rid south Texas of on a daily basis was doing on a highway right-of-way in one of the most rural counties of central Texas a hundred miles from where it ever grew in the past. In my 20 years of being a plant maniac, and my father’s 40 of ranching, we’d never seen it here before. Scarier still, those ripe seeds, like a pandemic land virus, ended up washing down two different creeks in the six inch rain we had two days later. I didn’t envision a pasture full of cattle, but in my mind’s eye, I can imagine one further void of quail, with fewer wildflowers and all the things that make the native Texas landscape special. I bet that my father and I will see more Kleberg bluestem again in central Texas, and I suspect that my grandchildren will see more of it than I care to imagine. If action isn’t taken now, there’s a good chance that what’s left of the Texas rural landscape will be a sea of the wrong grasses.

Multiscale Nest‐Site Selection by Black‐Capped Vireos

Abstract: We used an information‐theoretic approach to investigate nest‐site selection by black‐capped vireos (Vireo atricapilla) at the landscape and habitat‐patch scales on Fort Hood Military Reservation in central Texas, USA, during 2003 and 2004. We used a use‐availability sampling design and logistic regression to compare woody cover characteristics at nests to random points in the landscape to determine habitat selection at the landscape scale. At the habitat‐patch scale, we used matched case‐control logistic regression to compare habitat measures at nests and random non‐nest points to evaluate support for hypotheses concerning the influence of woody cover, nest‐patch, and nest‐site characteristics on black‐capped vireo nest‐site selection. At the landscape scale, we found strong support (Akaike wt [wj] = 1.0) for a model with a cubic effect of percent woody cover and woody cover edge density. Sites with the greatest predicted probabilities of use had woody cover values between 30% and 60% and increasing amounts of edge. We found strong support (wi = 0.93) for the global model at the habitat‐patch scale that included characteristics of the nest site, nest patch, and woody cover within 25 m. Based on odds ratios and confidence limits, percent woody cover, cover below 2 m, cover type, and substrate height had the greatest effect on nest‐site selection. The predicted probability a site was selected for a nest site increased with foliage cover below 2 m, taller substrates, deciduous cover, and decreased at high levels of percent woody cover (especially >80%). Texas red oak (Quercus buckleyi) was the most used nest substrate (100 of 358 nests), followed by shin oak (Q. sinuata var. breviloba; 86 of 358 nests) and Ashe juniper (Juniperus ashei; 44 of 358 nests). Black‐capped vireos used Texas red oak and shin oak in greater proportion to their availability, whereas Ashe juniper was used less in proportion to its availability, suggesting vireos avoided this species. We suggest that managers promote dense deciduous cover for nesting habitat and maximize edge‐to‐area ratios to maintain spatial and structural heterogeneity.

The venomous hair structure, venom and life cycle of Lagoa crispata, a puss caterpillar of Oklahoma

The presence of a unique population of Lagoa crispata, puss caterpillar, in western Oklahoma is reported. A detailed microscopic examination shows the structure of the L. crispata spines resemble the type 4 spines described by [Kawamoto, F., Kumada, N., 1984. Biology and venoms of lepidoptera. In: Tu, A.T. (Ed.), Handbook of Natural Toxins, Insect Poisons, Allergens and other invertebrate venoms, vol. 2, pp. 291–332 (ch. 9)]. The major food source of L. crispata are the leaves of oak (shin oak). The high tannin content of this food source results in spine extracts high in oak tannins. These extracts have activity but enzyme and toxin activity is lost with time. The gel filtration protein fractions are colored from brown to yellow and are inactive as enzymes or toxins. No hyaluronidase, protease or phosphohydrolase activity is detected in these protein fractions. The life cycle shows these caterpillars have 6 instars. Characterizations and annual emerging times of each instar are included.

Canopy Light Reflectance and Remote Sensing of Shin Oak (Quercus havardii) and Associated Vegetation

Shin oak is a deciduous shrub that forms dense stands of brush on sandy soils in rangeland areas of the Rolling and High Plains of Texas. Plant canopy reflectance measurements made on shin oak showed that it had both low visible (0.63- to 0.69-μm waveband) and nearinfrared (0.76- to 0.90-μm waveband) reflectance values, a characteristic generally not shared by associated plant species or mixtures of species. The low reflectance values of shin oak caused it to have dark-red, reddish-brown, or brown image tones on color-infrared photographic, videographic, and SPOT satellite images that made it distinguishable from associated vegetation and other land use features. The optimum time to remotely distinguish this noxious shrub is during the mature phenological stage from June to September. Computer-based image analyses of video and satellite images showed that shin oak populations could be quantified. This technique can permit “percent land area” estimates of shin oak on rangelands. The aerial imagery is useful for detecting shin oak on smaller rangeland areas, whereas the satellite imagery is applicable in mapping large areas of shin oak distribution.

Seasonal Deer Diets in Central Texas and Their Response to Brush Control

The diets of female white-tailed deer in central Texas were examined over a 12- month period to determine variations in diets in response to brush removal and seasonality of forage species. Five intensities of mechanical brush removal were applied. No consistent trends in diets were detected relative to intensity of brush removal. The annual diet consisted of 102 species and was comprised of 56% browse, 35% forbs, and 9% grass. Nineteen species comprised 85% of the annual diet. The effect of precipitation on herbaceous forage availability seemed to be the major factor influencing forage selection. ha ranch is surrounded by a 2.3-m deer-proof fence. Soils in this region are shallow stony clays of limestone origin. Topography is characterized by gently rolling hills. Annual precipitation averages 63.5 cm. Arborescent vegetation is predominantly a mixture of white shin oak (Quercus breviloba), blackjack oak (Q. marilandica), post oak (Q. stellata), Spanish oak (Q. texana), live oak (Q. virginiana), juniper (Juniperus spp.), and mesquite (Prosopis spp.). Ashe juniper (J. ashei) is the dominant woody species. Common grasses and forbs are common curlymesquite (Hilaria belangeri), Wrights' threeawn (Aristida wrightii), grama grasses (Bouteloua spp.), Texas wintergrass (Stipa leucotricha), upright prairie coneflower (Ratibida columnaris), arrowleaf sida (Sida rhombifolia), yellow woodsorrel (Oxalis dillenii), plantains (Plantago spp.), verbenas (Verbena spp.), one-seeded croton (Croton monanthogynus), and two-leafed senna (Cassia roemeriana) (Rollins, 1983).

Variability in Predicting Edible Browse from Crown Volume

Biomass estimates were made with regression techniques using crown volume and weight relationships. The log-log function yielded the highest coefficient of determination for Vasey shin oak, plateau oak, Texas persimmon, and honey mesquite. A quadratic function was best for woollybucket bumelia, littleleaf sumac, agarito, and pricklyash. Sugar hackberry showed equally high coefficients with either the linear or quadratic. Coefficients of determination for catclaw acacia, elbowbush, and skunkbush sumac generally were low regardless of the type of regression equation used. When sampled at various periods over the year, predictive accuracy declined for Vasey shin oak and plateau oak through fall and winter but rose again in spring and early summer. For both species, the log-log function was best from late summer to winter but during spring and early summer the quadratic function was best. Browse biomass commonly is recognized as one of the most difficult of all vegetation components to measure (Blair 1958). Even so, the information has been valuable to foresters for measuring potential flammability (Brown 1976) and to range scientists for estimating utilization by herbivores (Dalrymple et al. 1965; Ferguson and Marsden 1977), forage available to herbivores (Bryant 1977), productivity of herbivores (Leigh et al. 1970), or the response to brush control (Bentley et al. 1970; Scifres et al. 1974). Thus, numerous methods have been developed for inventory of browse or shrub yield. Some of these different methods have been reported by Hamiss and Murray (1976). Recently, techniques used for predicting browse yield have included linear regressions of crown volume on the weight of plants to predict yield. Crown volume requires at least two measurements of the plant in addition to weight, and is well suited because a combination of measurements is usually better than any single measurement (Cook 1960). Also, volume generally yields a better relationship to weight than surface area to weight (Lyon 1968). These volume-weight relationships have usually included only one species (Lyon 1968; Scifres et al. 1974; Rittenhouse and Sneva 1977). Only Bentley et al. (1970) has dealt with more than one shrub species. Previous studies have not examined the same species at different sampling dates within a 1-year period to determine the impact of defoliation on the precision of the predictive equations. Lyon (1968) has, however, found that the precision of regression equations varied with range site for the single species being studied. The authors are assistant professor, Range and Wildlife Management, Texas Tech University; and associate professor, Department of Range Science, Texas A&M University. At the time of this research, Bryant was research assistant, Range Science, Texas A&M University. Financial support from the Texas Agr. Exp. Sta. at Sonora is gratefully acknowledged. This article is TA 14210 from the Texas Agricultural Experiment Station. Manuscript received April 28, 1978. The objective of this research was to evaluate the use of various regression functions for the prediction of biomass from crown volume for several browse species and for selected species at different sampling dates. Methods and Materials Crown volume and weight relationships were used on several browse species to estimate the availability of edible browse to herbivores. Two of the species were evaluated at different sampling dates over a 1-year period. An 8-ha study site was selected at the Texas Agricultural Experiment Station, Sonora, Texas (Fig. 1). The site had been rootplowed 7 years prior. All available browse was in a young age class and less than 2.2 m tall. Since 1970, the browse had received light used by cattle, sheep, Angora goats, and white-tailed deer (Odocoileus virginianus L.). In August, 1975, the density for each species was estimated using either point-center-quarter (Cottam and Curtis 1956) or the correctedpoint-distance technique (Laycock and Batcheler 1975), depending on the degree of aggregation. Two transects, 322 m long, were used and points were established every 30.5 m. The distance to the nearest individual of each species was measured and its height and diameter at the widest point were recorded. Height and diameter measurements were converted to conical volume using the formula

Carbohydrate Reserves in Roots of Sand Shin Oak in West Texas

Carbohydrate Reserves in Roots of Sand Shin Oak in West Texas

Comparative Food Habits of Deer and Three Classes of Livestock

To observe forage competition between deer and livestock, the forage selections of a tame deer (Odocoileus virginianus), a goat, a sheep, and a cow were observed under four range conditions, using both stocked and unstocked experimental pastures, on the Kerr Wildlife Management Area in the Edwards Plateau region of Texas in 1959. The animals were trained in 2 months of preliminary testing. The technique employed consisted of recording the number of bites taken of each plant species by each animal during a 45-minute grazing period in each pasture each week for 1 year. Results indicated moderate to heavy competition for browse and mast between the deer and goat in all pastures during all seasons, and between the deer and all three classes of livestock in the winter. Browse and mast comprised over 50 percent of the deer's diet, except in the spring and summer, and over 50 percent of the goat's diet in all seasons. Following a decrease in available browse, sheep become competitive with deer for forbs. Forbs formed an average of 68 percent of the deer's diet and 65 percent of the sheep's diet in the ungrazed control pasture in the summer; the animals generally were grazing the same species. The added factors of bearing and nursing fawns, and growing antlers, contribute to the nutritional stresses on deer in the summer, the period when extensive die-offs of deer most frequently occur in the Edwards Plateau region. Competition for grass between deer and livestock probably is important only when grass is in a succulent stage in the spring and no other forage is available in quantity. Continuous grazing by animals tends to remove the most palatable species and concentrates competition on fewer, less palatable ones. Observations from the numerous replications of feeding times and places allow the conclusion that this technique provides a reliable index to preferred foods and staple foods. In the Edwards Plateau region of Texas, most of the rangelands are grazed by two or more classes of livestock along with deer. Research on the Kerr Wildlife Management Area, near Hunt, Texas, indicates that deer when managed and harvested properly can provide economic returns comparable to those from domestic livestock. But a study of the economic feasibility of management for livestock and deer in combination revealed the need for more exact knowledge of their competition for forage. To provide such information, a study of the food habits of cattle, sheep, goats, and deer was initiated in May, 1959, and concluded in May, 1960. The Kerr Wildlife Management Area is a research facility of the Texas Parks and Wildlife Department located in Kerr County in the eastern portion of the Edwards Plateau. This region, encompassing some 26,000 square miles of central Texas, probably is unique in its combined productivity of deer and livestock in high densities (Hahn 1945, Taylor and Hahn 1947). Previous studies of its vegetation in relation to deer and livestock were reported by Buechner (1944), Taylor and Beuchner (1943), and Whisenhunt (1949). On the Kerr Area, particularly the pastures involved in this study, the prominent vegetal expression is a savannah of live oak, in which Ashe juniper (Juniperus ashei) and shin oak are conspicuous. Part of the Kerr Wildlife Management Area contains 10, 96-acre deer-proof pastures which are used for a long-term study of the influence of combined sheep, goat, and cattle grazing rates on deer production. Each species of animal obviously has a different influence on the welfare of the others and on the forage resource in general, but the experimental design had revealed only the gross influence of combinations of animals. Performances of deer in experimental pas-

A Preliminary Study of the Shinnery in Oklahoma

Shinnery is scattered throughout the western third of Oklahoma principally on coarse soils derived from materials of the Pliocene and Pleistocene epochs. It occurs on sandy soils (Brownfield and Nobscott series) throughout the mixed prairie and short grass plains in a region of low precipitation (20 in. to 25 in.). The most common species is Havardi, although Q. stellata, Q. Margaretta and Q. Mohriana are present. The shinnery constitutes an oak population of extreme hybridity with Q. Havardi x Q. stellata being the most common hybrids. Most stands of shinnery are two to four feet high, although the height may vary from one to 40 feet. Since no germination of acorns was observed, it is assumed that reproduction is accomplished largely by rhizomes. Fire is utilized to control the height of the shin oaks and to promote an increase in forage whereas the herbicide, 2,4,5-T, when used for three successive years, eliminates much of the shinnery. Early explorers in western Oklahoma commented on areas of dwarf oaks and several shrubs, variously designated as chaparral, shin oak or shinnery (Gregg, 1839; Marcy, 1853 and others). The term shinnery, which is employed in this discussion, is derived from the French word cheniere. Shinnery does not refer to dwarf oaks which are about shin-high as is generally believed. Shinnery is a vegetation type which comprises diminutive oaks (shin oaks) from two to four feet tall with islands (mottes), of the same shin oak species, up to twenty feet above the general level of the stand (Fig. 1). In his report on 'The Vegetation of Oklahoma', Bruner (1931) states that the chaparral . . is represented in the central part of western Oklahoma by communities of the 'shin oak'. According to Bruner, the shin oaks include Quercus mohriana, Q. stellata palmeri, Q. stellata rufescens, and Q. vaseyana ... In addition, the shinnery often comprises Artemisia filifolia, Rhus trilobata, Celtis reticulata, Cornus drummondii, and Prunus angustifolia. According to Duck and Fletcher (1948) a total of 1173 square miles of the shinnery-grassland type occurs in western Oklahoma, principally in Woodward, Ellis, Roger Mills, Beckham, and Harmon Counties. This study was limited to Oklahoma only. It includes the area from * Nomenclature follows Waterfall's catalogue of the flora of Oklahoma.

Live Oak and Shin Oak as Desirable Plants on Edwards Plateau Ranges

Live Oak and Shin Oak as Desirable Plants on Edwards Plateau Ranges