bluuebunny/crossref_metadata_2025 huggingface dataset:
Norwegian Open Source P&A Database
Authors: Myrseth Velaug , Perez-Valdes Gerardo A. , Bakker Steffen J. , Midthun Kjetil T. , Torsæter Malin
Published: March 2016

An estimated 3000 oil wells need to be plugged and abandoned on the Norwegian Continental Shelf (NCS), with approximately 150 new wells being drilled each year. The petroleum industry estimates the total plugging costs to be almost 900 billion Norwegian kroner, and that the work will take up to 40 years to complete. Due to the current tax regulations in Norway, the state indirectly pays 78% of the costs (about 700 billion Norwegian kroner). It is therefore vital to reduce expenses by targeted research and development (R&D) of new technology, and to ensure better planning of plug and abandonment (P&A) operations in and between licenses.

The current study aims to gather available data relevant for Norwegian P&A operations in an open source database – and to develop and use a P&A planning software to derive plugging costs in various scenarios. The software may be used to identify bottlenecks in P&A operations and analyze potential efficiency gains from technology improvements both for single operations and on a system level. We will use a cross-disciplinary approach that combines the fields of operations research with technological expertise.

In this paper, we present the outline of the database and the current status of available data for P&A operations on the NCS, as well as a short literature review. Available data is categorized according to the different choices that need to be made within a single P&A operation, both with regards to technological aspects and existing regulatory framework. We also show how this database will be used to develop a first version of the P&A planning software.

Industry, government and ordinary tax payers will all benefit from knowledge sharing, optimized planning, and more targeted R&D efforts on this topic. The results from this study will be used to identify important cost drivers and to draw up a roadmap for future P&A-related R&D.
Inverse Modeling for Fluid System Characterization Through Machine Learning Algorithms
Authors: Tarrahi Mohammadali , Shadravan Arash
Published: March 2016

Inverse fluid modeling facilities designing drilling, spacer, cement or fracturing fluids. This approach uses several test data available at the laboratory databases for fluid characterization. Without machine learning algorithms it is very hard for fluid engineers to rationalize a plethora of fluid system information, transform them into knowledge and make intelligent and cost-effective decisions to design a fluid system with desired properties. Therefore, trial and error method is considered to be very costly and misleading. Today, there is a need for an expert system which uses all the available fluid design data stored in a database by which we can benefit from its insights for smart fluid designs. This predictive tool suggests a composition for drilling fluids, spacer fluids, fracturing fluids and cement slurries by implementing a machine learning algorithm on imported experimental data.

This study investigates the inverse modeling fluid characterization through machine learning algorithms. A laboratory dataset of measured fluid properties and their corresponding fluid system characteristics are employed as training data to the machine learning routine. GPR as a machine learning method considerably reduced the costs of testing, optimized the material use, integrated available experimental data and eliminated the user bias. This practical nonlinear regression method fosters an efficient and fast prediction analysis which do not require including complex physics of the underlying intricate chemical fluid behavior while integrating all available data from different databases.
Nano-Sized MgO with Engineered Expansive Property for Oil Well Cement Systems
Authors: Jafariesfad Narjes , Gong Yi , Geiker Mette Rica , Skalle Pål
Published: March 2016

The failure of cement sheaths to perform as designed in oil wells can result in loss of zonal isolation. Bulk shrinkage of the cement sheath in the annulus is one of the main causes compromising zonal isolation. Conventional cement systems without compensation for bulk shrinkage have a high risk of failure during all phases of well operation. However, when the volume reduction is compensated, without compromising the mechanical properties, the risk of failure is significantly reduced.

In this study, nano-sized MgO with designed expansive properties has been introduced to the fresh cement slurry. The expansive properties of nano-MgO were achieved by controlling the preparation condition. A dilatometer with corrugated molds was used to measure the linear strain of samples cured at 40 °C.

The reactivity of nano-MgO played a main role in controlling the expansion performance at the required time. The efficiency of nano-MgO with different reactivities for shrinkage compensation of cement system, cured at 40 °C, was studied. Addition of only 2% nano-MgO with appropriate reactivity was sufficient to maintain expansion in the cement system. Controlling the expansion performance of the additive through designing its reactivity is a promising method to limit bulk shrinkage of cement sheaths in oil wells.

The results presented show that nano-MgO with controlled expansive properties can be used to design a cement system with short- and long-term zero-bulk shrinkage.
New Insight to Wormhole Formation in Polymer Gel During Water Chasefloods Using Positron Emission Tomography PET
Authors: Brattekås B. , Steinsbø M. , Graue A. , Fernø M. A. , Espedal H. , Seright R. S.
Published: March 2016

Polymer gel is frequently used for conformance control in fractured reservoirs, where it is injected to reside in fractures or high-permeability streaks to reduce conductivity. With successful polymer gel conformance control in place, increased pressure gradients across matrix blocks may be achieved during chasefloods, diverting water, gas or EOR chemicals into the matrix to displace oil. Knowledge of gel behavior during placement and chase floods is important, because it largely controls the success of subsequent injections. Polymer gel behavior is often studied in core floods, where differential pressure and effluents from fracture and matrix outlets give information about gel deposition during placement and flow paths during chasefloods. The work presented in this paper utilize complimentary PET-CT imaging to quantify the behavior and blocking capacity of Cr(III)-Acetate HPAM gel during chase waterflooding. In-situ imaging provides information about changes that may not be extracted from pressure measurements and material balance only, such as changes in local fluid saturations and dynamic spatial flow within the fracture and within the structure of the gel network.

Polymer gel was placed in core plugs with longitudinal fractures that connected the inlet and outelt, and chase water was subsequently injected to measure the gel blocking capacity. The water phase was labelled with a positron emitting radiopharmaceutical (F-18) to visualize and quantify local flows with positron emission tomography (PET) during gel rupture and subsequent flooding. Using PET, we study gel rupture and the development of wormholes during gel erosion after rupture as a function of flow rate. A particular strength with access to dynamic, local flow patterns is the direct comparison to global measurements, such as differential pressure and production rate, to verify existing gel behavior models.
Integrity of Downscaled Well Models Subject to Cooling
Authors: Todorovic Jelena , Gawel Kamila , Lavrov Alexandre , Torsæter Malin
Published: March 2016

The annular cement is often subject to temperature variations, for example heating during steam injection, or cooling during CO2 injection or hydraulic fracturing. Fractures caused by thermal stresses may create flow paths through the cement sheath thereby jeopardizing the well integrity. The objective of this work was to experimentally and numerically investigate the effect of thermal cycles and harsh cooling on downscaled wellbore sections with a focus on the cement sheath failure.

Downscaled wellbore sections were each prepared by cementing a casing section within a hollow cylinder of Berea sandstone. One specimen was subjected to a thermal cycling program that included cooling to −50 °C and heating to 80 °C. Two other specimens (dry and wet) were used in harsh cooling experiments with solid CO2 and liquid nitrogen. CT scanning was performed before the onset of, during and after the completion of the thermal cycling program or harsh cooling experiments.

No differences in the distribution of voids and fractures in the cement before and after the thermal cycling were observed. This indicates that the applied temperature range was not sufficient to cause damage in the cement sheath. On the other hand, the harsh cooling experiment using liquid nitrogen resulted in fracturing of both the cement and rock in the water-saturated specimen.

Finite-element simulations reproducing the thermal cycling program used in the laboratory experiment were performed. The simulations have shown that thermal radial stresses at cement/casing and cement/sandstone interfaces were relatively low, i.e., from 0.5 to 1.0 MPa, which might explain the lack of thermal-induced damage in CT images. The simulations also suggest that the radial fracture in the water-saturated specimen subject to harsh cooling was caused by a combined effect of tensile hoop stresses and stresses due to water freezing. The fracture was most likely initiated in the sandstone followed by further propagation into the cement. It is likely that well construction materials and the surrounding formation are water-saturated. Thus, cooling well below 0 °C, which may occur during a CO2 blowout, would increase chances for cement and formation failure.
A Numerical Study of Gas Kick Migration Velocities and Uncertainty
Authors: Fjelde K. K. , Frøyen J. , Ghauri A. A.
Published: March 2016

There has quite recently been some discussion regarding the accuracy of gas kick slippage models used in transient flow models. This is not necessarily easy to give a correct answer on. However if pressure build up gradients for a migrating kick in a closed well is used for predicting the kick migration velocity, one can easily obtain a misinterpretation due to the fact that parts of the kick can become suspended in the mud. This was discussed in a paper presented two decades ago (Johnson et al., 1995). The purpose of the paper presented here is to show what kind of uncertainties that are involved in the transient flow modelling process and how that affects the pressure build up gradients.

In this paper, a transient numerical model that can be used for simulating two-phase flow will be presented. It is based on the Drift flux model and the one dimensional advection upstream splitting method hybrid scheme (AUSMV). When using transient models for predicting the kick migration time, there are two sources of errors. The first is obvious in the sense that the gas slip parameters are uncertain. However, a less known potential source of error can be numerical diffusion and discretization errors caused by the numerical solver itself. The paper will show how the AUSMV scheme can be made less diffusive by using the slopelimiter concept.

The paper will demonstrate that the effect of numerical diffusion can be quite substantial. This will be done by simulating pressure build up in a closed well varying both the slip parameters but also the degree of numerical diffusion. In addition, the simulated effect on the pressure build up when gas get trapped in the mud for lower gas concentrations will also be demonstrated.

This paper aims at showing that the uncertainty caused by numerical diffusion can be of the same order as uncertainty in the slip parameters. It will also confirm the results reported in Johnson et al. (1995) by the use of a transient low diffusion flow model.
Long-Term Integrity of Well Cements at Downhole Conditions
Authors: Vrålstad Torbjørn , Todorovic Jelena , Saasen Arild , Godøy Rune
Published: March 2016

The objective of plug and abandonment of wells can be described as "restoring the cap rock". In that respect, the long-term integrity of the plugging material is crucial. I.e. it is important that the plugging material can resist downhole chemicals and otherwise withstand downhole conditions. In this paper, we have performed ageing tests with cement samples at relevant downhole conditions to determine the long-term integrity of well cement as plugging material. Portland cement samples with and without silica flour as additive have been separately exposed to crude oil, brine and H2S (in brine) at 100 °C and 500 bar for 1, 3, 6 and 12 months. The long-term integrity of the samples was determined by measuring changes in weight, volume, mechanical strength and permeability, as well as physical appearance.

It is seen from the results that the addition of a pozzolan such as silica has a significant impact on the long-term integrity of Portland cement, especially in a corrosive environment such as H2S. All the samples were affected by most of the different chemical environments, but the cement samples without silica were considerably more affected than the samples with silica as additive. Furthermore, the exposure to H2S in brine resulted in the formation of an unexpected white deposit, which precipitated both inside and outside the samples.
Depositional, Diagenetic, Production, and Seismic Characteristics of a Mid-Dip Tuscaloosa Point Bar Complex, Little Creek Field, Mississippi
Authors: Shew R. D. , Werren E. G. , Adams E. R. , Stancliffe R. J.
Published: March 2016

Little Creek field is oil productive from a structurally and stratigraphically trapped sandstone within the Upper Cretaceous lower Tuscaloosa Formation (Mid-Dip trend of southwestern Mississippi). The field was discovered in 1958 based on the seismic interpretation of simple closure at the lower Tuscaloosa horizon at a depth of 10,750 ft. Interpretation of core and log data indicates that the objective is a series of point-bar deposits and channel abandonment facies formed by the lateral migration of a north-to-south-flowing meandering river system. Development drilling, based on geologic concepts of point-bar architectures, occurred on 40-ac spacing with a total of 208 wells drilled; 162 were successful. New seismic data across the field have shown that the sandstone is a mappable "soft" seismic event; similar techniques have been successfully used for discovery and delineation elsewhere within the Mid-Dip Tuscaloosa trend. Little Creek has undergone primary recovery, waterflood, a carbon dioxide pilot, and recent initiation of a field-scale carbon dioxide flood. Approximately 70% of the original oil in place (102 million bbl) is estimated to be recovered by all processes.

Reservoir quality and continuity are generally high and are controlled by both depositional and diagenetic processes. Average porosity and permeability are 24% and 100 md, respectively. Depositional controls-include slightly reduced vertical to horizontal permeability, local shale drapes, and channel abandonment facies. Diagenetic controls include compaction, chlorite grain coatings, and quartz and ankerite cements. The chlorite is most important in controlling the observed petrophysical properties of the sandstone including the water saturation, porosity, and bimodal pore system.
Injection and Nitrification Inhibitor Improve the Recovery of Pig Slurry Ammonium Nitrogen in Grain Crops in Brazil
Authors: Gonzatto Rogério , Chantigny Martin H. , Aita Celso , Giacomini Sandro J. , Rochette Philippe , Angers Denis A. , Pujol Stefen B. , Zirbes Emerson , De Bastiani Géssica G. , Ludke Roberto C.
Published: March 2016

Efficient management practices are needed for no‐till (NT) cropping systems fertilized with pig slurry (PS). We evaluated the effect of application mode (surface broadcasting vs. injection) with or without the nitrification inhibitor dicyandiamide (DCD), on the recovery of PS ammonium nitrogen (NH4–N) in 2‐yr crop succession (corn [Zea mays L.]/oat [Avena strigosa L.]/corn/wheat [Triticum aestivum L.]) under NT and irrigation. Each crop received PS at planting. The NH4‐N fraction of PS was enriched with 15N to discriminate the contribution of current vs. past applications to crop N uptake. Compared to surface application, injection increased corn uptake of PS NH4–N by 22 kg N ha−1 under low precipitation regime, likely because it efficiently reduced ammonia volatilization; the effect was small under high precipitation regime and in winter crops in general. To the contrary, DCD doubled the uptake of PS NH4–N in corn (+24 kg N ha−1) under high precipitation regime, likely because it reduced losses through N leaching, whereas the gain was smaller under drier conditions and in winter crops in general. Because of this complementary response to injection and DCD, the retention of PS NH4–N in the soil–plant system for the whole crop succession was maximized where PS was injected in combination with DCD, being 19 to 23% greater than injection or DCD alone. The injection of DCD‐treated PS is therefore recommended to maximize crop uptake of PS NH4–N and minimize environmental losses under irrigated NT conditions in southern Brazil.

Core Ideas

Injection of dicyandiamide‐treated pig slurry is a recommendable practice to maximize crop uptake of pig slurry NH4–N.

Injection of dicyandiamide‐treated pig slurry is a recommendable practice to minimize environmental N losses.

Injection was more efficient under dryer than wetter conditions.

Dicyandiamide added to pig slurry improved the retention of pig slurry NH4–N only under wet conditions.
Cytochemical features of olfactory receptor cells in benthic and pelagic Sculpins (Cottoidei) from Lake Baikal
Authors: Klimenkov Igor , Sudakov Nikolay , Pastukhov Mikhail , Kositsyn Nikolay
Published: March 2016

Electron and laser confocal microscopy were used to analyze the adaptive
cytochemical features of the olfactory epithelium in three genetically close
deep-water Cottoidei species endemic to Lake Baikal ? golomyanka (Baikal
oilfish) Comephorus baicalensis, longfin Baikal sculpin Cottocomephorus
inermis and fat sculpin Batrachocottus nikolskii ? whose foraging strategies
are realized under different hydrostatic pressure regimes. Hypobaric hypoxia
that developed in B. nikolskii (a deep-water benthic species) upon delivery
to the surface caused distinct destructive changes in cells of the olfactory
epithelium. In C. baicalensis and C. inermis, whose foraging behavior
involves daily vertical migrations between deep and shallow layers, these
cells are characterized by a significantly higher structural and functional
stability than in deep-water B. nikolskii. The results of morphological
study and quantitative analysis of functionally active mitochondria in cells
of the olfactory epithelium of closely related deep-water fish species with
different modes of life provide evidence that tolerance of the olfactory
apparatus to hypobaric hypoxia is different in pelagic and benthic species.
These results help elucidate the mechanisms responsible for the consistent
functioning of the olfactory system in animals evolutionarily adapted to
extreme environmental factors, and provide theoretical and practical
implications in different fields of biology, neurology and extreme medicine.
Edaphic characteristics of Austrian pine (Pinus nigra Arn.) forests in the Visegrad area
Authors: Blagojevic Velibor , Knezevic Milan , Kosanin Olivera , Kapovic-Solomun Marijana , Lucic Radovan , Eremija Sasa
Published: March 2016

This paper presents the results of soil research in Austrian pine (Pinus
nigra Arn.) forest communities in the Visegrad area, carried out to determine
the basic soil characteristics and eco-production potential of forest
habitats as an important basis and framework for the successful management of
these forests on the principles of sustainable development. Austrian pine
forests in this region are an important and ecologically valuable community.
The complexity of the geological structure and relief dynamics are dominant
environmental factors that condition the expressed variability of soils in
the study area. Forest communities of Austrian pine are formed on the
peridotites and serpentinites, eutric ranker (haplic leptosol), eutric
cambisol (haplic cambisols) and pseudogley (haplic planosol), dense granular
and marl limestones calcomelanosol (mollic leptosol), rendzina (rendzic
leptosol) and calcocambisol (leptic cambisol). The productivity of these
soils is highly correlated with depth and texture composition, and the impact
of these factors is linked with soil type, climate and other site conditions.
In the research area, soil types with low production potential such as
rankers, rendzinas, limestone and dolomite calcomelanosol are dominant.
Deeper variants of eutric cambisol, pseudogley and calcocambisol can be
classified as soils with moderate to high production potential.
Catalytic steam reforming of ethanol for hydrogen production: Brief status
Authors: Bineli Aulus , Tasic Marija , Filho Rubens
Published: March 2016

Hydrogen represents a promising fuel since it is considered as a cleanest
energy carrier and also because during its combustion only water is emitted.
It can be produced from different kinds of renewable feedstocks, such as
ethanol, in this sense hydrogen could be treated as biofuel. Three chemical
reactions can be used to achieve this purpose: the steam reforming (SR), the
partial oxidation (POX) and the autothermal reforming (ATR). In this study,
the catalysts implemented in steam reforming of ethanol were reviewed. A wide
variety of elements can be used as catalysts for this reaction, such as base
metals (Ni, Cu and Co) or noble metals (Rh, Pt and Ru) usually deposited on a
support material that increases surface area and improves catalytic function.
The use of Rh, Ni and Pt supported or promoted with CeO2, and/or La2O3 shows
excellent performance in ethanol SR catalytic process. The ratio of water to
ethanol, reaction temperatures, catalysts loadings, selectivity and activity
are also discussed as they are extremely important for high hydrogen yields.
Achievements in management and utilization of southern grasslands
Authors: Hoveland C. S. ,   Society for Range Management
Published: March 2016

Grasslands in the humid southern USA are utilized primarily for grazing on improved pastures, most of which were developed since the 1930s and 1940s. Virtually all of these grasslands were developed from species introduced from other areas of the world. Major achievements in successful developing these grasslands, often on eroded cropland, were: (a) introduction of Kentucky 31 tall fescue (Festuca arundinacea Schreb.); (b) introduction of Pensacola bahiagrass (Paspalum notatum Flugge); (c) breeding of Coastal bermudagrass [Cynodon dactylon (L.) Pers.]; (d) fertilizer and lime use along with availability of low-cost N; (e) no-till planting of winter annual grasses; (f) pasture renovation with legumes; (g) herbicides for weed control; (h) recycling of agricultural wastes in forage production; (i) development of round hay baler; (j) controlled grazing; (k) discovery of the tall fescue fungal endophyte and its effect on livestock and the grass plant; (1) development of grazing-tolerant alfalfa; (m) improved cool season annual grasses and legumes for winter grazing; and (n) near infrared reflectance spectroscopy for rapid and low-cost forage analysis. Future areas of emphasis in improvement of these grasslands may include: (a) greater use of grazing-tolerant grasses and legumes; (b) stress-tolerant tall fescue with "friendly" non-toxic endophytes; (c) feed antidotes to the toxins of endophyte-infected tall fescue; (d) use of herbicide-and pest-resistant biotechnology genes in forage plants; (e) use of gypsum to alleviate subsoil acidity and improve rooting depth of aluminum-sensitive forage cultivars; (f) greater use of computers in information access and decision making by livestock producers; (g) greater use of forages for wildlife food; (h) breeding of pasture plants with greater winter productivity; (i) development of a perennial grass biomass energy industry for electrical generation and liquid fuel production.
Activated charcoal attenuates bitterweed toxicosis in sheep
Authors: Poage G. W. , Scott C. B. , Bisson M. G. ,   Society for Range Management
Published: March 2016

We assessed the potential of activated charcoal to attenuate bitterweed (Hymenoxys odorata DC.) toxicosis in 3 trials. In Trial 1, lambs were offered a subacute level (.264% BW) of bitterweed and received either 0, .5, 1, or 1.5 g/kg BW of activated charcoal. In Trial 2, lambs were dosed (by gavage) with .264% BW of bitterweed and varying levels of activated charcoal followed by feeding milo (Sorghum sp.) immediate after dosing. A decrease in milo intake, which indicates aversive postingestive feedback, was interpreted to indicate that toxicosis occurred. In Trial 3, lambs were fed a 20% CP supplement with or without activated charcoal and then exposed to bitterweed and other forage species growing in pots; we counted the number of bites of each. In Trial 1, lambs refused to eat bitterweed after 10 days of exposure, thus the study was stopped. In Trial 2, lambs that received 1 or 1.5 g/kg BW of activated charcoal consumed more (p < 0.05) milo than those receiving 0 g/kg BW. In Trial 3, lambs supplemented with activated charcoal took more (p < 0.05) bites of bitterweed than lambs receiving a protein supplement alone. Lambs readily ate activated charcoal when added to a 20% crude protein supplement in a 10% mixture. Collectively, these results suggest activated charcoal will result in continued consumption of bitterweed which suggests avoidance of toxicosis. Activated charcoal also may be effective in preventing bitterweed toxicosis when combined with a supplement.
Breed and stocking rate effects on Chihuahuan Desert cattle production
Authors: Winder J. A. , Bailey C. C. , Thomas M. ,   Society for Range Management
Published: March 2016

Productivity of Barzona, Brangus, and Beefmaster cattle was evaluated on conservatively (n=2) (40 ha AU-1) and moderately (28.5 ha AU-1) stocked pastures (n=2) in the Chihuahuan Desert of south-central New Mexico. Equivalent numbers of suckled, first-calf heifers of each breed (n=31) weighing 333+/-11 kg were randomly assigned to the study pastures in the spring of 1992. Pastures were grazed continuously and herd productivity data were collected from 1992-1994. In late August 1994, all pastures were destocked due to onset of severe drought. No effect of breed (P > 0.10) was detected in the analyses, so data were pooled across breeds and compared between the stocking rates. Calf crop percentages (1993, 1994) were higher in conservative than moderate stocked pastures (82 vs 62%, respectively, P < 0.01). Financial analyses standardized to a hypothetical medium size (8,094 ha) New Mexico Chihuahuan Desert cattle range showed net returns per ha did not differ (P > 0.10) between stocking rates. However, the main effect of year and stocking rate X year interaction were significant (P < 0.05). These analyses suggest that the drought in 1994 lowered returns per ha compared to 1993 when precipitation was near average and that conservative stocking may present less financial risk than moderate stocking when drought occurs. These data are consistent with other studies from arid and semi-arid rangelands demonstrating that conservative stocking can give financial returns from cattle production equal to or greater than those from moderate stocking.
Broom snakeweed establishment following fire and herbicide treatments
Authors: McDaniel K. C. , Carroll D. B. , Hart C. R. ,   Society for Range Management
Published: March 2016

Broom snakeweed (Gutierrezia sarothrae [Pursh] Britt Rusby) propagation was monitored from 1990 through 1998 following burning and herbicide control practices conducted on blue grama (Bouteloua gracilis [H. B. K. Lag.]) grasslands near Corona, N.M. Broom snakeweed usually germinated in April, May, or June (83% of 394 total) and mostly in 1991 and 1992 (81% of total) when spring moisture was sufficient. The majority of broom snakeweed seedlings (52% of total) emerged the first or second year after summer burning, especially in areas where grass yield and cover declined and bare ground exposure increased as a result of intense fires. Spring fires caused less damage to blue grama than summer fires, and the number of broom snakeweed seedlings produced (18% of total) was similar to non-treated rangeland (22% of total), but lower than numbers on areas burned in the summer. Grass yield and cover increased within a year of herbicide spraying and treated plots had significantly (P 0.05) fewer broom snakeweed seedlings (8% of total) than burned and non-treated areas.
Are Namibia's grasslands desertifying?
Authors: Ward D. , Ngairorue B. T. ,   Society for Range Management
Published: March 2016

We compared the herbage standing crop on 31 farms along a rainfall gradient in Namibia (southwestern Africa) in 1997 with the results attained for the same gradient by Walter (1939). We found that the slope for the regression of herbage yield on mean annual rainfall in 1997 was 5.93, i.e. 5.93 kg herbage was produced per hectare for every 1 mm increase in rainfall along the gradient. This regression slope is considerably lower than that in Walter's (1939) study (slope = 10.34). Thus, current grassland productivity per unit of rainfall in Namibia is about half that of 50 years ago. There is no evidence of a change in annual rainfall over this period, nor is there any evidence that either short-term (current) or longer-term (11 years) stocking densities affect current herbage yield. We conclude that, while desertification has taken place, grazing over the last decade has not been the cause of this reduced productivity.
Late season toxic alkaloid concentrations in tall larkspur (Delphinium spp.)
Authors: Gardner D. R. , Pfister J. A. ,   Society for Range Management
Published: March 2016

Tall larkspurs [Delphinium barbeyi (L. Huth), D. occidentale (Wats.), D. glaucescens (Rydb.), D. glaucum (Wats.)] pose a serious poisoning threat to cattle on many summer ranges. Livestock producers often defer grazing until larkspur is mature, but specific information is lacking on toxic alkaloid concentrations in larkspur from pod stage to senescence. Tall larkspur leaves and seed pods were collected about every 2 weeks during the pod stage to senescence from marked plants in locations in Utah (Logan and Salina), Idaho (Ashton, Humphrey, and Oakley), Colorado (Yampa and Montrose), and California (Carson Pass) from 1995 to 1997. Toxic alkaloid concentions in pods (average= 2.9mg/g) exceeded leaf alkaloid concentrations (average= 1.5 mg/g in all species, but the magnitude of the difference varied among the 4 species. Leaves showed a more rapid decrease in toxic alkaloid concentration with plant maturity compared to pods. Seed pods did not begin to lose substantial amounts of toxic alkaloid until larkspur matured and pods began to dessicate. At seed shatter, D. glaucescens pods retained more toxic alkaloid than the other species, and alkaloid concentration was sufficiently high after pods had shattered (3.5 mg/g) to pose a moderate grazing risk. After seed shatter, the toxic alkaloid concentrations in leaves and pods of D. barbeyi, D. occidentale, and D. glaucum were generallyless than 2 mg/g; thus, risk of losing cattle would be low for the remainder of the grazing season
Herbivore dunging and endozoochorous seed deposition in a Mediterranean dehesa
Authors: Malo J. E. , Jiménez B. , Suarez F. ,   Society for Range Management
Published: March 2016

Spatial patterns of herbivore defecation within grazing systems are important as they directly affect pasture growth and composition. These effects are partially linked to seed dispersal in dung, a little studied process. This paper focuses on: (i) quantification of dung and seeds deposited by herbivores in a Mediterranean grazing system, and (ii) analysis of the spatial variability of dung and seeds deposited within and among plant communities. We carried out year-long monthly quantifications of the depositions of rabbit (Oryctolagus cuniculus), fallow deer (Dama dama), red deer (Cervus elaphus), and cow (Bos taurus) dung to 32 plots distributed in Quercus rotundifolia Lam. and Fraxinus angustifolia Vahl woodlands, mixed scrub, and Cistus ladanifer L. scrub. We also quantified the germinable seed content of dung. The results revealed differences (p < 0.05) in dung deposition, varying (I) among the 4 species, (ii) within species (except for the red deer) among plant communities, and (iii) within plant communities. An average of 735 seeds/m2 were returned to the soil via dung, with the highest numbers in open woodlands (870–1,888 seeds/m2) and the lowest numbers in scrubs (83–315 seeds/m2). Cows dispersed the most seeds (68%), followed by red deer (20%), rabbits (7%), and fallow deer (5%). Spatial variability in deposition led to accumulations of up to several thousand seeds at points covered by the dung. The effect of seed input to the seed bank and on vegetation may be low at large and medium-sized spatial scales, but it can be very important at small scales and for colonization processes.
Grassland biomass dynamics along an altitudinal gradient in the Pampa
Authors: Pérez C. A. , Frangi J. L. ,   Society for Range Management
Published: March 2016

Above and below-ground biomass and necromass dynamics were assessed for 3 grassland sites located at 550, 850, and 1,025 m elevation in Sierra de la Ventana range (38 degrees 1'S 62 degrees 2'W) in Argentina. The objective was to determine if differences existed in dry matter structure, mycorrhizae infection, net primary productivity (NPP) partitioning to aboveground and belowground tissues, senescence and litter fall, and seasonal patterns of dry matter fluxes with altitude. Soil properties, water budgets and temperature at the sites were also assessed. Biomass plus necromass (without litter) was 1,184 +/- 41, 1,208 +/- 70, and 1,507 +/- 63 gDM m-2 for the lower, intermediate and upper sites, respectively. The below:aboveground biomass ratio increased with elevation. Total NPP was 1,131, 1,280, and 1,157 gDM m-2 year-1, respectively, for the 3 grassland sites. belowground allocation of net productivity increased with altitude. Both mass and proportion of thin roots increased with elevation, and so did mycorrhizae infection. The aboveground and belowground turnover rates decreased with altitude, but rates were faster for aboveground tissues. We found different temporal patterns in productivity, senescence and disappearance among grassland sites despite similar total NPP. Water holding capacity of soils and temperature were important factors related to several of the observed trends in structure and function. Differences in grassland structure and fluxes are discussed as related to soils and local climate at each site.
Seed production in sideoats grama populations with different grazing histories
Authors: Smith S. E. , Mosher R. , Fendenheim D. ,   Society for Range Management
Published: March 2016

Frequent and intense defoliation of grasses has been associated with the evolution of "grazing morphotypes" that exhibit a variety of vegetative traits correlated with improved grazing resistance. While recovery from a seed bank is not considered an important grazing resistance mechanism, relatively little is actually known regarding seed (caryopsis) production in grazing morphotypes of caespitose grasses. The goal of this research was to compare components of seed production in 2 populations of sideoats grama (Bouteloua curtipendula var. caespitosa Gould Kapadia) from nearby sites with different histories of livestock grazing. This was done using vegetative propagules of genotypes from both populations in a greenhouse study. The study was conducted in 2 flowering seasons under conditions considered favorable for seed production. The population exposed to livestock grazing showed a genetically based decrease in seed production relative to the ungrazed population. Lower seed production per plant in the grazed population was at least partially due to reduced numbers of tillers and panicles per plant and spikes per panicle that may be associated with selection for grazing tolerance. The grazed population also exhibited lower average seed production per spike indicating lower inherent floral fertility. Seed production was not closely correlated with vegetative traits associated with increased grazing tolerance, nor was there evidence of obvious physiological trade-offs related to decreased seed production in the grazed population. Lower seed production potential in populations of sideoats grama intensively grazed by livestock may lead to reduced potential for seedling colonization.
Grassland fire effects on corroded barbed wire
Authors: Engle D. M. , Weir J. R. ,   Society for Range Management
Published: March 2016

Fire effects on rangeland ecosystems have been studied extensively. Few studies have investigated effects of fire on rangeland developments. Only 1 study has investigated the effects of fire on barbed wire with an intact coating of corrosion-resistant zinc and no studies have investigated wire that has lost the protective coating. A common perception is that grass fire causes older wire to break more easily and become more brittle. In the present study, we determined the influence of grassland fire on wire that was 20 and 30-years old and had sufficient loss of the zinc coating to have undergone corrosion of the underlying steel. We found that regardless of age, wire subjected to grass fire did not differ (P > 0.05) in breaking strength, elongation, or ductility from the same wire that was not subjected to fire. We conclude that the problems experienced when repairing breaks in old barbed wireare not a result of fire, but rather brittle and weak wire resulting from exposure to the corrosive elements of the environment.
Herbage productivity and ungulate use of northeastern Nevada mountain meadows
Authors: Beck Jeffrey L. , Peek James M. ,   Society for Range Management
Published: March 2016

The effects of grazing by cattle (Bos taurus) and recently reestablished elk (Cervus elaphus) on mountain meadows in northeastern Nevada are poorly understood. We evaluated production, use, and species richness of herbage standing crop in and outside 3 meadow exclosures in northeastern Nevada's Jarbidge Mountains across 3 seasons in 1999 and 2000. Treatments included control, wildlife (mainly big game), and cattle. There was less forb standing crop in fall than in early or mid-summer, but no difference in forb standing crop from early to mid-summer across all treatments. There were no differences in graminoid standing crop among treatments in 1999, while there was significantly less graminoid crop in cattle treatments in 2000 than in the control or wildlife treatments. Species lists in exclosures and cattle treatments overlapped 48.9-68.4%. Clipping treatments to evaluate effects of use on yearly productivity were light use (13.3-24.7%) and total use (clipped to ground) in early and mid-summer, and control. There was no difference in fall or graminoid herbage between controls and quadrats clipped lightly in early summer and mid-summer and there was no difference in forb or graminoid yield (seasonally clipped herbage plus end of growing season herbage) in clipped quadrats and controls. Across years, forbs and graminoids clipped to ground in early summer and mid-summer regrew by fall to no more than 19.2, 4.2, 24.7, and 10.0%, respectively, of the amount in control quadrats. Managers should consider delaying cattle grazing until late summer on mountain meadows used consistently by elk in early summer.
Spatial patterns of light gaps in mesic grasslands
Authors: Derner Justin D. , Wu X. Ben ,   Society for Range Management
Published: March 2016

The spatial pattern of light gaps in mesic grasslands in central Texas with contrasting disturbance histories was assessed using patch-based landscape metrics determined from a threshold level (25% of full sunlight), as light intensities below this threshold substantially decrease survival of honey mesquite (Prosopis glandulosa var. glandulosa Torr.) seedlings. The spatial pattern of light gaps, with the exception of edge density, were significantly different between annually-disturbed and non-disturbed grasslands on all sample dates (2 April, 30 April, 29 May, and 26 June 1998). Differences in patch metrics did not occur between non-disturbed grasslands despite contrasting vegetation composition [perennial forbs and perennial bunch (tussock) grasses]. Patch-based landscape metrics of light gaps did vary temporally in both annually-disturbed and non-disturbed grasslands. The structure and spatial configuration of light gaps were distinctly different between annually-disturbed and non-disturbed grasslands: a low density of large patches characterized light gaps in annually-disturbed grassland, whereas non-disturbed grasslands had a high density of small patches. Our findings demonstrate that the current disturbance regime is the principal environmental driver influencing species dominance and composition, and indirectly vegetation structure, which collectively contribute to the observed dynamics of light gap patches in these mesic grasslands. Incorporating spatially explicit consideration of light gap structure and dynamics into experimental studies addressing invasion of weedy plant species such as honey mesquite may be an effective approach to address mechanisms and the ecological significance of disturbance operating as a driver facilitating woody plant invasions in mesic grasslands.
Economic implications of brush treatments to improve water yield
Authors: Olenick Keith L. , Conner J. Richard , Wilkins R. Neal ,   Society for Range Management
Published: March 2016

One possible method of increasing water yield in some water-poor areas is through brush management. Economic modeling of brush control programs designed to improve water yield has been performed for numerous Texas watersheds. These studies assumed a single criteria brush control program. This single criteria program may have negative impacts on certain wildlife habitats, is likely unacceptable to landowners, and does not incorporate additional restoration practices. Our study analyzed the economic consequences of 3 brush management/restoration scenarios for the Edwards Aquifer recharge zone and Twin Buttes watersheds and the drainage basins contained within. Economic measures included total public cost () and public cost of producing additional water (/1000 m3 of added water). Because of its larger size, estimated total public cost was higher for the Twin Buttes watershed than for the Edwards Aquifer recharge zone watershed, despite the fact that the Twin Buttes had lower cost per ha of treated brush. Public cost of additional water is lower for basins within the Edwards Aquifer recharge zone watershed (ranging from 26 to 44 per 1000 m3 of added water) than in the Twin Buttes watershed (ranging from 51 to 129) which suggests that public investment in brush management efforts are likely to be more economically efficient in the Edwards Aquifer area. Within individual basins, public cost of additional water were similar for all 3 brush management/restoration scenarios.
Cross-cultural Adaptation and Validation of the Victorian Institute of Sport Assessment-Patella Questionnaire for French-Speaking Patients With Patellar Tendinopathy
Authors: Kaux Jean-François , Delvaux François , Oppong-Kyei Julian , Beaudart Charlotte , Buckinx Fanny , Croisier Jean-Louis , Forthomme Bénédicte , Crielaard Jean-Michel , Bruyère Olivier
Published: March 2016

Study Design

Clinical measurement study.

Background

The Victorian Institute of Sport Assessment-Patella (VISA-P), originally developed in English, assesses the severity of patellar tendinopathy symptoms. To date, no French version of the questionnaire exists.

Objectives

The aim of our study was to translate the VISA-P into French and verify its psychometric properties.

Methods

The translation and cultural adaptation were performed according to international recommendations in 6 steps: initial translation, translation merging, back translation to the original language, use of an expert committee to reach a prefinal version, test of the prefinal version, and expert committee appraisal of a final version. Afterward, the psychometric properties of the final French version (VISA-PF) were assessed in 92 subjects, divided into 3 groups: pathological subjects (n = 28), asymptomatic subjects (n = 22), and sports-risk subjects (n = 42).

Results

All members of the expert committee agreed with the final version. On a scale ranging from 0 to 100, with 100 representing an asymptomatic subject, the average ± SD scores on the VISA-PF were 53 ± 17 for the pathological group, 99 ± 2 for the healthy group, and 86 ± 14 for the sports-risk group. The test-retest reliability of the VISA-PF was excellent, with good internal consistency. Correlations between the VISA-PF and divergent validity of the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36) were low, and the correlation coefficient values measured between the VISA-PF scores and converged items of the SF-36 were higher.

Conclusion

The VISA-PF is understandable, valid, and suitable for French-speaking patients with patellar tendinopathy. J Orthop Sports Phys Ther 2016;46(5):384–390. Epub 21 Mar 2016. doi:10.2519/jospt.2016.5937
Comparing the Predictive Value of Task Performance and Task-Specific Sensitivity During Physical Function Testing Among People With Knee Osteoarthritis
Authors: Wideman Timothy H. , Edwards Robert R. , Finan Patrick H. , Haythornthwaite Jennifer A. , Smith Michael T.
Published: March 2016

Study Design

Cross-sectional cohort.

Background

Knee osteoarthritis (OA) is a leading cause of pain and mobility restriction. Past research has advocated the use of brief, functional tasks to evaluate these restrictions, such as the six-minute-walk test and the timed up-and-go test. Typically, only task performance (ie, walking distance, completion time) is used to inform clinical practice. Recent research, however, suggests that individual variance in how people feel while completing these tasks (ie, task sensitivity) might also have important clinical value.

Objective

To compare the predictive value of task performance and task-specific sensitivity in determining OA-related physical function (measured by the Western Ontario and McMaster Universities Osteoarthritis Index) and pain-related interference (measured by the Multidimensional Pain Inventory).

Methods

One hundred eight participants with chronic knee OA completed the six-minute-walk test and the timed up-and-go test, and reported levels of discomfort and affective response (mood) associated with each test.

Results

In separate regression models, both task performance and task-specific sensitivity predicted OA-related physical function and pain-related interference. A final regression model including all significant predictors showed that task-specific sensitivity (specifically, post-six-minute-walk discomfort) emerged as a unique predictor of both outcomes.

Conclusion

These findings highlight the value of a novel clinical assessment strategy for patients with knee OA. While clinicians commonly focus on how patients perform on standardized functional tasks, these results highlight the value of also considering levels of posttask sensitivity. Measures of task-specific sensitivity relate to Maitland's concept of pain irritability, which may be a useful framework for future research on sensitizing factors and pain-related disability. J Orthop Sports Phys Ther 2016;46(5):346–356. Epub 21 Mar 2016. doi:10.2519/jospt.2016.6311