Heteropogon Contortus Research Articles

Soil microbial community size and composition changes along a tanglehead (Heteropogon contortus) gradient in a semiarid region

Invasive plants are a serious concern throughout many rangelands in North America because of their detrimental effects on vegetation community composition, diversity and wildlife habitat. Growing evidence shows that invasive plants affect ecosystem processes such as energy and nutrient cycling and soil microbial associations. Tanglehead (Heteropogon contortus [L.] P. Beauv. ex Roem and Schult.) is a C4, perennial caespitose grass that is rapidly increasing throughout the Coastal Sand Plain in southern Texas. In a field study, we examined the response of soil microbial community size and structure over a 3-year period (2013–2015) along a tanglehead invasion gradient represented by the natives-without-tanglehead plant communities (<15% tanglehead), natives-with-tanglehead mixtures (15–70% tanglehead), and tanglehead-dominated (>70% tanglehead) plant communities. Soil microbial size [microbial biomass carbon (MBC), nitrogen (MBN), and total fatty acid methyl esters (FAME)] differed between natives-without-tanglehead and tanglehead-dominated sites in 2013 and 2015 (dry years). MBC averaged ~200 mg kg−1 soil in natives-without-tanglehead sites but <70 mg kg−1 soil in invaded sites, and total FAME averaged 36 and 41 nmol g−1 soil in native-without-tanglehead and invaded sites, respectively, in 2013 and 44 and 55 nmol g−1 in 2015. Invaded sites had higher saprophytic fungi:bacteria ratios than sites with <15% tanglehead (0.64 vs. 0.53) over all 3 years. We conducted a separate inoculation experiment where tanglehead was planted in native soils that lacked tanglehead to investigate effects of tanglehead inoculation on soil microbial community dynamics; introduction of tanglehead to native soils did not change microbial community structure, size, or relative abundance of key microbial FAME indicators over the course of 18 months. Field study results revealed different soil microbial communities associated with tanglehead, but at what point these communities change during invasion is not clear, and how these effects are related to overall habitat degradation associated with this invasive plant requires further study.

Characteristics of Stable Hydrogen and Oxygen Isotopes of Soil Moisture under Different Land Use in Dry Hot Valley of Yuanmou

AbstractSoil moisture, stable hydrogen, and oxygen isotopes were sampled and determined in a demonstration area of soil and moisture conservation at the Laocheng Town of Yuanmou County in Chuxiong Prefecture, Yunnan of three land use types:LeucaenaBenth artificial forest,Heteropogon contortusgrass field, and farmland. The characteristics of stable hydrogen and oxygen isotopes of soil moisture in these different land use types at different soil depths were analyzed to investigate the regularities in the quantitative formation of soil moisture balance. In terms of forest land, we found that the variable coefficient of hydrogen isotopes in the 0-20 cm soil layer was the smallest, but decreased with depth under 20 cm. While in grassland, the variable coefficient in 80-100 cm was the largest, and decreased with depth above 80 cm. As for farmland, the variable coefficient in the top 20 cm was the largest, followed by 40-60 cm, and the medium 20-40 cm was the smallest. The soil moisture hydrogen isotope values of three land use type were different at surface layer, but prone to be consistent in each type. Along the soil depth in forest land, the hydrogen isotope increased first and then decreased, while increased in the end, and the maximum appeared in 80-100 cm. In grassland, the hydrogen isotope increased initially as the forest land but then decreased continuously, so the maximum was found at 20-40 cm. And in grassland, the hydrogen isotope of all depths were higher than which of forest land and farmland. In same land use type, the hydrogen isotope of soil moisture changed significantly at the surface, and the variation of hydrogen isotopes was obviously decreased along the depth. Our findings could provide reference data which would contribute to the assessment of regional groundwater resources in the dry-hot valley of Yuanmou in this study.

Regeneration pattern of medicinal plants in different vegetation landscapes of Kalbetta State Forest, Mysuru, India

Medicinal plants are valuable source for development of cost effective drugs which play a significant role in the primary healthcare. Most of the medicinal plants are subjected to unsustainable harvesting threatening for existence. The study assessed the regeneration status and pattern of the medicinal plants by documenting medicinal plants, their distribution, habit and estimating their density, dominance, diversity, species richness, similarity index and vulnerability status. The area comprises scrub and thorny forest with deciduous vegetation which hosts rich medicinal plant diversity. The stratified sampling with 285 regeneration plots indifferent vegetation landscapes was assessed. Natural vegetation landscape had a higher diversity when compared to a plantation landscape. Sorenson index of similarity revealed the occurrence of 72 species in all the three seasons indicating the high abundance of medicinal flora. Species-individual accumulation analysis showed higher species heterogeneity indifferent vegetation landscape. Dominant medicinal plants among the regeneration patterns were Hemidesmus indicus, Heteropogon contortus, Mitracarpus verticillatus, Stachytarpheta indica, Chomelia asiatica etc. The regeneration potential provides an insight for suitability of different species in different seasons across the vegetation blocks. The results of this study will help in building a comprehensive database of medicinal plants for strategizing the in-situ and ex-situ conservation measures for sustainable utilization.

Heteropogon contortusBL‐1 (Pilli Grass) and Elevated UV‐B Radiation: The Role of Growth, Physiological, and Biochemical Traits in Determining Forage Productivity and Quality

Exposure to elevated UV-B (eUV-B) is well known for its phytotoxicity, although studies made with UV-B exposure and its impact on grasses are limited especially from tropical countries including India. In this study, responses of a valuable grass species, Heteropogon contortus BL-1, were assessed under eUV-B (over ambient UV-B) at different growth stages. Damage caused by eUV-B was observed in the form of membrane damage and loss of pigments at early stages of growth, whereas tannin, phenol, and protein contents showed their increments at all the growth stages, to overcome the imposed stress. Reducing sugar showed its decline at all the growth stages, whereas starch and sucrose contents were higher mostly at later ages of plant growth. eUV-B caused a marked variations in anatomical structures with increase of mesophyll and spongy parenchymatous cells in leaves to reduce severity of irradiation, to maintain the growth and productivity. The study also highlights the significant negative influence of eUV-B on the growth of H. contortus BL-1 and its adaptive strategy to minimize the negative impacts. With the progression of age, plants although adopted to UV-B stress with maintenance of productivity, but palatability of forage was affected due to increment of tannin content.

Production of Reducing Sugars from Hydroxylated Mature Spear Grass (&lt;i&gt;Heteropogon Contortus&lt;/i&gt;)

Mature black Spear grass ( Heteropogon contortus ) was hydrolyzed using different concentrations of dilute sulphuric acid for the first time as lignocellulosic substrate for producing reducing sugars at different pH and retention time. The maximum total reducing sugar (TRS) from Spear grass hydrolysate (SGH) was 2.48g/L using 6% H 2 SO 4 at 121 o C for 4h with higher amount of xylose than glucose and arabinose. BC yield was comparable to those from reported lignocellulosic hydrolysates. The result of the study proved that mature back spear grass, commonly known as tanglehead, which is less useful as fooder due to lower nutrient, clogs animal furs and, sticks to human walker’s clothes, can be hydrolyzed with little cost to produce fermentable sugars used as substrates for producing such biotechnological products as, biofuels, biogas, and bacterial cellulose. Keywords : Reducing sugar, Spear grass hydrolysate, pH, Gluconacetobacter xylinus

Overcoming dormancy and light requirements in seeds of Heteropogon contortus, a target species for savanna restoration

As observed at a world scale, in Reunion Island Heteropogon contortus savannas face major pressure and need to be preserved and restored. However, the use of this species in restoration projects is hampered by the limited knowledge about the seed germination ecology and more specifically about dormancy and light requirements. Dormancy state and light requirements for germination of H. contortus seeds were assessed over a 3-year after-ripening period (i.e. storage). Dormancy loss was observed after one year of storage. Between one and two years of after-ripening, H. contortus seeds exhibit significantly higher mean germination percentages in daily light than in darkness, demonstrating their positive photoblasty (i.e. requires light for germination). Smoke solutions significantly enhanced germination in both daily light and darkness during the first two years of dry storage. This study also demonstrated that smoke-infused water with beekeeping smoker fuel could be an efficient method to enhance germination of H. contortus seeds. Overall, this method could be adopted for large scale restoration projects due to its efficiency, its low cost and its reproducibility.

Simultaneous determination of kaempferol and quercetin in Heteropogon Contortus (L.) Beauv. by validated high-performance thin layer chromatography

ABSTRACT Presently, the fingerprint analysis of kaempferol and quercetin has been developed simultaneously via High-Performance Thin Layer Chromatography (HPTLC) from leaves, stem, and inflorescence of Heteropogon contortus. The HPTLC method for kaempferol and quercetin was optimized with the elution of toluene: ethyl acetate: formic acid (7:3:0.5 v/v) as a mobile phase. The fingerprint analysis of kaempferol and quercetin was developed at Rf values of 0.39 and 0.24, respectively, and densitometric evaluation was done at 254 nm. The linear regression data for the calibration curve of both the compounds show a good linear relationship in the concentration range of 2–12 nanogram spot−1. The suggested method has been validated in terms of limit of detection (LOD) and limit of quantification (LOQ), precision, specificity, sensitivity, and accuracy. Present results show that maximum amount of kaempferol and quercetin is found in leaf extracts (35.80 and 17.01 milligram/gram of dry weight, respectively) of H. contortus.

High-Performance Thin-Layer Chromatography of Four Sterols in a Medicinally Important Grass Species – Heteropogon contortus (L.) Beauv.

Presently, sterols like stigmasterol, β-sitosterol, campesterol, and ergosterol are identified and quantified from leaves, stem, and inflorescence of Heteropogon contortus. (L.) Beauv (family: Poaceae) from Rajasthan, India, using high-performance thin-layer chromatography (HPTLC). H. contortus is reported with various medicinal properties. In the present study, a HPTLC–densitometric method was developed for the quantification of sterols by using toluene‒methanol‒formic acid (9:1:0.3 v/v) as the mobile phase. Post-derivatization of the plates was done by using freshly prepared anisaldehyde–sulfuric acid, heated at 110–120°C and scanned at 530 nm absorbing wavelength. The maximum contents of stigmasterol, campesterol, and ergosterol were estimated in inflorescence extracts (11.64 ± 017, 19.90 ± 0.18, and 16.64 ± 0.81 mg g−1 of dry wt. w/w, respectively), whereas β-sitosterol was found maximum in leaves, i.e., 56.52 ± 1.25 mg g−1 of dry wt (w/w). This HPTLC method is found to be simple, precise, specific, s...

Carbohydrate dynamics of three dominant species in a Chinese savanna under precipitation exclusion.

The potential impact of drought on the carbon balance in plants has gained great attention. Non-structural carbohydrate (NSC) dynamics have been suggested as an important trait reflecting carbon balance under drought conditions. However, NSC dynamics under drought and the response mechanisms of NSC to drought remain unclear, especially in water-limited savanna ecosystems. A precipitation exclusion experiment was performed to simulate different drought intensities in a savanna ecosystem in Yuanjiang valley in southwestern China. Growth, total NSC concentration and diurnal change of NSC were determined for the leaves and non-photosynthetic organs of three dominant species (Lannea coromandelica, Polyalthia cerasoides and Heteropogon contortus) throughout the growing season. Drought significantly reduced the growth of all the three species. Total NSC concentration averaged ~8.1%, varying with species, organ and sampling period, and did not significantly decrease under drought stress. By contrast, the diurnal change of NSC in these three species increased under drought stress. These results indicate that these three dominant species did not undergo carbon limitation. Thus, relative change in NSC is a more sensitive and effective indicator than carbon reserves in evaluation of plant carbon balance. These findings provide new insights for the understanding of carbon balance and the mechanisms of carbon starvation.

Quantifying the spatial and temporal distribution of tanglehead (Heteropogon contortus) on South Texas rangelands

IntroductionTanglehead is a grass native to southwestern US rangelands; however, its prevalence as a native invasive on South Texas rangelands has increased rapidly during the last decade. Large areas of monotypic stands have emerged in Jim Hogg, Duval, Brooks, and Kleberg counties. The aim of this research is to understand the spatial and temporal dynamics of these invasions as a model for the assessment of native invasive species. Our specific objectives were to (1) evaluate the feasibility of classifying tanglehead using 1-m resolution imagery data, (2) assess the spatial and temporal distribution of tanglehead in relation to soil type and distance from roads, and (3) quantify the temporal and spatial distribution of tanglehead on our study sites. We combined remote sensing approaches with landscape metrics to quantify the spatial and temporal distribution of tanglehead in five locations across our study area. We calculated the normalized difference vegetation index and combined it with the original aerial imagery to conduct an unsupervised classification with the following land cover classes: woody vegetation, tanglehead, non-tanglehead herbaceous, and bare ground. Soil type and the distance from roads were assessed to determine the relationship between these factors and tanglehead spatial distribution.ResultsWe were able to successfully map tanglehead using the 1-m imagery. Our image classification approach resulted in accuracies greater than 85% for all sites. Tanglehead occurred in sandy, loamy sand, and sandy loam soils. Over 70% of tanglehead cover occurred within the first 150 m from the edge of roads. This cover increased from 7.1% (SE = 1.1%) in 2008 to 17.8% (SE = 5.4%) in 2014. Once established, small patches of tanglehead began aggregating or coalescing with existing stands, thereby creating larger patches over larger areas.ConclusionsOur study has shown the value of analyzing spatiotemporal dynamics of tanglehead with remote sensing techniques and landscape metrics to improve our understanding of establishment and dispersal processes of a native invasive. This study provides useful information to improve rangeland management decisions as well as assessing native invasive dynamics with potential applications for assessing its effects on wildlife habitat, livestock operations, and habitat restoration strategies.

Effect of Feeding Tanniferous Oak Leaves on Nutrient Utilization, Serum Mineral Profile and Biochemical Indices in Goats

A 120 days growth study was conducted to assess the effect of tanniniferous oak leaves (Quercus semecarpifolia) on nutrient utilization, mineral bioavailability, and biochemical indices in goats. Eighteen growing kids (13.13 ± 0.99 kg; 7–9 months) were randomly divided into three homogenous groups of six each in a completely randomized design and fed native grass hay (Heteropogon contortus) in T1 (control), oak leaves (Quercus semecarpifolia) in T2 and supplemental tannic acid with grass hay in T3 keeping the concentrate mixture constant in all the treatments. At 90 days post feeding, a metabolism trial of six days duration was conducted. Blood was collected on day 0, 60 and 120. The nutrient intake per unit metabolic body size was higher (P < 0.05) in T2 than T1 and T3 without any alteration in plane of nutrition. Balance of Ca, Co, Cu, and Mn was higher (P < 0.05) in oak leaves fed goats, which was further reflected as higher (P < 0.05) serum mineral level of Ca and Mn in those animals. Serum urea level was lower (P < 0.05) in the oak leaves fed group (T2), whereas the serum cholesterol values were lower (P < 0.05) in T2 and T3. The levels of different serum enzymes viz. alkaline phosphatase and alkaline transaminase were higher (P < 0.05) in tannic acid supplemented group. These results suggest that feeding of oak leaves (condensed tannin, 0.85% and hydrolysable tannin, 4.4% in diet) improved bioavailability of Ca and Mn in goats as compared to animals fed local grass hay with or without supplementation of tannic acid.

TO QUANTIFY THE LUTEOLIN CONTENT FROM THE AERIAL PARTS OF HETEROPOGON CONTORTUS (L.) BEAUV. (SPEAR GRASS) THROUGH HIGH-PERFORMANCE THIN-LAYER CHROMATOGRAPHY

Objective: The objective of this study was to quantify the luteolin content present in the extracts from different aerial plants (leaves, stem, and inflorescence) of Heteropogon contortus through high-performance thin-layer chromatography.Methods: The chromatographic fingerprint analysis of the different plant extracts has been developed using optimized mobile phase toluene: ethyl acetate: formic acid (5:5:0.7 v/v) and the developed plate is derivatized with freshly prepared anisaldehyde-sulfuric acid. Then, the plate is heated at 110–120°C. The plate is scanned for densitometry measurements and to record the overlay spectra at 366 nm absorbance/reflectance wavelength. Quantification of luteolin marker compound in different extracts of H. contortus is estimated using 2–12 ng/spot.Results: The yellow colored bands appearing on the chromatogram confirm the presence of luteolin marker compound in the different plant samples of H. contortus. Further, the presence of the luteolin marker is confirmed by comparing the Rf values (0.21) of the standard and the samples and from densitometry measurements by scanning the plate at 366 nm absorbance/reflectance. Line-to-line overlay spectra are obtained.Conclusion: From this, it is concluded that leaf sample of H. contortus contains maximum amount of luteolin, i.e., 37.13 ± 0.11 mg/g of dry wt. than inflorescence (1.60 ± 0.013 mg/g of dry wt.) and stem (0.53 ± 0.014 mg/g of dry wt.). The leaves are good source of luteolin and can be used as an alternate natural source to synthesize herbal drugs to cure cancer, hypertension, and inflammatory diseases.

Spring fire effects on two Aristida/Bothriochloa native pastures in central Queensland, Australia

Controlled burns are commonly used to suppress woody plant regrowth and to remove accumulated unpalatable pasture from rangelands and occasionally to alter pasture composition in native pastures in central Queensland, Australia. Outcomes can be somewhat unpredictable and short-term, and reliable evidence is needed to confirm the likely long-term efficacy of such fires. We imposed a regime of repeated spring burns on native Aristida/Bothriochloa pastures growing in two contrasting eucalypt woodlands of central Queensland to determine the effects on pasture composition, ground cover, landscape stability and woody plant recruitment, all in the absence of grazing. The sites selected were a silver-leaved ironbark (Eucalyptus melanophloia F.Muell.) woodland and a poplar box (E. populnea F.Muell.) woodland. Weather conditions precluded spring burns in 3 years out of 7 at the silver-leaved ironbark site and in 2 years out of 8 at the poplar box site. The burn intensity was variable, and frequent fires produced a marked change in abundance of only a few pasture species. Depending on the site, fires significantly increased the frequency of Enneapogon spp., Bothriochloa bladhii (Retz.) S.T.Blake and Dichanthium sericeum (R.Br.) A.Camus and reduced the frequency of some minor components such as Cymbopogon spp., Panicum effusum R.Br., Cenchrus ciliaris L. and, ephemerally, that of some forbs. Contrary to expectation, only Aristida calycina R.Br. declined in abundance among the many Aristida species present, and the abundance of Heteropogon contortus (L.) P.Beauv. ex Roem. &amp; Schult. barely increased under regular spring fires. The total germinable seeds of herbaceous species in the soil each spring was significantly reduced by burning in the previous spring. Repeated spring fires rarely reinforced any initial change induced by burning, and slightly lowered average ground cover as well as various indices of landscape stability and ecosystem functionality. Changes produced were not always consistent across the two communities. Though prescribed burning is often important for maintaining grazing productivity and landscape values, very regular use is not recommended.

TO QUANTIFY THE LUTEOLIN CONTENT FROM THE AERIAL PARTS OF HETEROPOGON CONTORTUS (L.) BEAUV. (SPEAR GRASS) THROUGH HIGH-PERFORMANCE THIN-LAYER CHROMATOGRAPHY

Objective: The objective of this study was to quantify the luteolin content present in the extracts from different aerial plants (leaves, stem, and inflorescence) of Heteropogon contortus through high-performance thin-layer chromatography.Methods: The chromatographic fingerprint analysis of the different plant extracts has been developed using optimized mobile phase toluene: ethyl acetate: formic acid (5:5:0.7 v/v) and the developed plate is derivatized with freshly prepared anisaldehyde-sulfuric acid. Then, the plate is heated at 110–120°C. The plate is scanned for densitometry measurements and to record the overlay spectra at 366 nm absorbance/reflectance wavelength. Quantification of luteolin marker compound in different extracts of H. contortus is estimated using 2–12 ng/spot.Results: The yellow colored bands appearing on the chromatogram confirm the presence of luteolin marker compound in the different plant samples of H. contortus. Further, the presence of the luteolin marker is confirmed by comparing the Rf values (0.21) of the standard and the samples and from densitometry measurements by scanning the plate at 366 nm absorbance/reflectance. Line-to-line overlay spectra are obtained.Conclusion: From this, it is concluded that leaf sample of H. contortus contains maximum amount of luteolin, i.e., 37.13 ± 0.11 mg/g of dry wt. than inflorescence (1.60 ± 0.013 mg/g of dry wt.) and stem (0.53 ± 0.014 mg/g of dry wt.). The leaves are good source of luteolin and can be used as an alternate natural source to synthesize herbal drugs to cure cancer, hypertension, and inflammatory diseases.

In vitro sunscreen activity of Methanolic root extract of a Sri Lankan grass Heteropogon contortus

<i>In vitro</i> sunscreen activity of Methanolic root extract of a Sri Lankan grass <i>Heteropogon contortus</i>

Effects of inundation and stranding on leaf litter decomposition and chemical transformation

Inundation and stranding are important processes of the riparian ecosystem due to water level fluctuation. Plant litter decomposition is a key process that determines the accumulation of soil organic matter in riparian ecosystems, but little is known about the alternating effects of inundation and stranding on this process. Using litters of the grass species Heteropogon contortus, we studied how the remaining mass and nitrogen (N), δ13C and δ15N, and 13C-CPMAS NMR spectra responded to permanent inundation, temporary inundation and drying over a period of twelve months. Inundation (permanent or temporary) and stranding altered litter C and N dynamics. The δ13C declined in the immersed litters and was stable after the litters were transported to the grassland plots, while δ15N in the litters that were decomposing continually in the water rapidly increased during the earlier stage of decomposition. We observed a significant increase in the proportion of ketone, carboxyl, and alkyl in the permanently inundated litter samples compared with those of litters decomposed at terrestrial habitats at the final harvest. These results indicated that the effects of inundation on the decay of labile and recalcitrant litter components were asynchronous. The decomposing litters in the inundation treatment differed chemically from those in the terrestrial habitat treatments and were characterized by greater relative abundances of ketone C and carboxyl C. The higher values of alkyl/O-alkyl for the stranding litters that had higher mass remaining and C/N as compared to those of inundated litters that had lower mass remaining and C/N in the final harvest, suggested a relatively higher contribution of the recalcitrant components to the litter residues. Likewise, the effects of transient inundation depend on the timing of immersion and stranding.

Nutritional study of local fodder species in Ahmednagar district of western Maharashtra

The locally grown forage grasses are main fodder source for maintaining the indigenous livestock breeds like Dangi cattle and Sangamneri goat in Ahmednagar district. Most commonly observed fodder grass and tree species grazed by livestock were collected from the field. The nutritional quality of these grasses and tree species was determined by undertaking proximate analysis in the laboratory. The local fodder species include Dicanthium annulatum, Setaria intermedia, Themeda triandra, Heteropogon contortus, Indigofera cordifolia, Apluda mutica, Cymbopogon martini, Tephrosia purpurea. Among the tree species Melia azedarach, Azadirachta indica, Prosopis julifera, Grewia asiatica, Clerodendrum multiflorum were the major tree species commonly available as fodder source. The nutritional analysis indicated that crude protein content ranged from 5.61 to 15.46%, crude fiber 18.09 to 34.87%, ether extract 1.00 to 3.24%, Ash 6.44 to 21.56 % and silica was less than 5.31%. The grass and tree species found in hilly regions are showing tremendous variation in nutritional composition. This study highlighted the importance of local fodder species including grasses, legumes, bushes and trees in rearing the livestock with low inputs at field conditions.

Characterization of New Natural Cellulosic Fiber from Heteropogon Contortus Plant

ABSTRACTNatural fibers are one of effective substitute for switching artificial fiber and concentrating to reinforce polymer matrixes due to their decomposable character. This study was implied to realize physico-chemical properties of bio fiber obtained from Heteropogon contortus (HC) plant. Heteropogon contortus fibers (HCFs) had cellulose (64.87 wt. %), hemicellulose (19.34 wt. %), lignin (13.56 wt. %), and low density (602 kg/m3). The chemical functional group of HCFs was established by Fourier transform infrared spectroscopy, thermal stability of the fiber up to 220°C discovered by thermogravimetric analysis. Further the assets of HCFs proved that it can act as an excellent reinforcement material as a bio composite. Finally, the tensile properties were carried out through single fiber tensile tests, such as tensile strength, tensile modulus and microfibrillar angle.

Effects of Tanglehead Expansion on Bobwhite Habitat Use in South Texas

Usable space for northern bobwhite (Colinus virginianus) has been reduced across a large portion of South Texas rangelands due to the spread of non-native, invasive grasses. A native grass, tanglehead (Heteropogon contortus) has rapidly expanded its dominance in the western Sand Sheet of South Texas within the last 10-15 years. It has formed high-density monocultures, similar to non-native grasses, which are associated with losses of forb and grass diversity as well as bare ground, which are key components of bobwhite habitat. The objectives of our research were to 1) determine selection-avoidance of habitat features by bobwhites, and 2) determine the effects of tanglehead cover on vegetation characteristics. We detected 488 coveys across 20,103 ha on helicopter surveys conducted December 2014 in South Texas. We measured 6 vegetation characterstics (grass and forb species richness, vegetation height, woody-plant cover, tanglehead cover, and non-native grass cover) at all covey detections and an equal number of random locations. We developed continuous selection ratios based on probability density functions of used and random points derived using Simple Saddlepoint Approximations to determine habitat selection by bobwhites. We also used quantile regression at the 10th, 50th, and 90th quantiles to determine relationships between tanglehead and vegetation factors. Bobwhite avoided areas of high canopy cover (>20%) of all invasive grasses measured. Brush cover was selected for up to 47%, after which it was avoided. We found significant negative relationships between tanglehead cover and forb and grass species richness, bare ground, and shrub cover, and a positive relationship with vegetation height at all quantiles modeled. Our results demonstrate the negative effects of increased tanglehead cover on native rangeland habitats. Further expansion by tanglehead has the potential to significantly reduce usable space for bobwhites in South Texas.

Efficiency of rumen microbial protein synthesis in cattle grazing tropical pastures as estimated by a novel technique

The efficiency of microbial protein synthesis (EMPS) in cattle grazing a range of tropical pasture types was examined using a new method of intra-jugular infusion of chromium–EDTA to estimate urinary excretion of purine derivatives. Seven pasture types were studied in south-eastern Queensland, Australia, over a 13-month period. These included native tropical grass (C4) pasture (major species Heteropogon contortus and Bothriochloa bladhii) studied in the early wet, the wet–dry transition and the dry season; introduced tropical grass (C4) pasture (Bothriochloa insculpta) in the mid-wet season; two introduced tropical legume species (C3; Lablab purpureus and Clitoria ternatea); and the temperate-grass (C3) pasture, ryegrass (Lolium multiflorum). There was a large range in EMPS across pasture types, with a range of 26–209 g microbial crude protein per kilogram digestible organic matter intake (DOMI). Estimated rumen-degradable protein (RDP) supply (42–525 g/kg DOMI) was the major factor associated with EMPS across the range of pasture types studied. EMPS in steers grazing all tropical grass pastures was low (&amp;lt;130 g/kg DOMI) and limited by RDP supply. Negative linear relationships (P &amp;lt; 0.05) between EMPS and concentrations of both neutral detergent fibre and acid detergent fibre in extrusa were evident. However, non-fibre carbohydrate in extrusa, total non-structural carbohydrate concentration in plucked pasture leaf, rumen fluid and particle dilution rate, protozoal concentration in rumen fluid and rumen fluid pH were not correlated with EMPS. It was concluded that EMPS was well below 130 g microbial crude protein per kilogram DOMI when cattle grazed unfertilised, tropical grass pastures in south-eastern Queensland and that RDP was the primary limiting nutrient. High EMPS was associated with a very high RDP, vastly in excess of RDP requirements by microbes.