Shea (<Emphasis Type="Italic">Vitellaria paradoxa</Emphasis> C. F. Gaertn.) at the crossroads: current knowledge and research gaps

Shea (Vitellaria paradoxa C. F. Gaertn.) is arguably socio-economically and environmentally the most important plant species in the semi-arid and arid zones of Africa where it is widely distributed. Apart from the economic gains in international export markets where shea butter is valued for use in luxury cosmetic, pharmaceutical and confectionary industries, locally the fat (butter) is the main cooking oil for over 86 million inhabitants. Research during the past decades has acknowledged the chemical and nutritional composition as well as the ethnobotanical uses of shea which has resulted in its butter being used in a wide array of products. This review summarizes the current knowledge of the morphological and genetic diversity; propagation, initial growth, and management; ecology and population structure; chemical and nutritional composition as well as the socioeconomic and livelihood empowerment potential of shea. Little is known about the fruiting behaviour and the responses of shea to the inevitable changes in climate. We suggest ecophysiological and dendrochronological studies as an option to predict how the domestication of this multipurpose tree species can be sustained even under the prospects of global climate change.     

Waxy bloom on grape berry surface is one important factor for oviposition of European grapevine moths

Grapevine moths are severe pest insects in European viticulture. Oviposition by grapevine moths is largely influenced by several physical and chemical cues located on the surface of their host plant’s fruits. The contribution of waxy bloom layer on the berry surface for oviposition decision of two European grapevine moth species, Eupoecilia ambiguella and Lobesia botrana, was investigated. An experimental setup was developed to prove oviposition preferences of both species for certain grape varieties and developmental stages based on epicuticular wax extracts. Chemical analysis of epicuticular wax patterns of four different Vitis vinifera varieties revealed differences. However, oleanolic acid was the main component on berry surface waxes and its relative amount decreased between early and late phenological stages. Furthermore, oleanolic acid was responsible for the preference of earlier phenological stages for E. ambiguella oviposition. However, ovipositional variety preferences were triggered by minor components on the wax berry layer. While the oviposition decision of L. botrana was mainly triggered by oleanolic acid, additional cues like olfactory and haptic ones were also important. The ovipositional preferences were discussed in accordance with the results of the chemical analysis in order to elucidate the role of wax compounds for oviposition stimulation.     

A generalized algebraic difference approach allows an improved estimation of aboveground biomass dynamics of <Emphasis Type="Italic">Cunninghamia lanceolata</Emphasis> and <Emphasis Type="Italic">Castanopsis sclerophylla</Emphasis> forests

Key message

A generalized algebraic difference approach (GADA) developed in this study improved the estimation of aboveground biomass dynamics of Cunninghamia lanceolata (Lamb.) Hook and Castanopsis sclerophylla (Lindl.) Schott forests. This could significantly improve the fieldwork efficiency for dynamic biomass estimation without repeated measurements.

Context

The estimation of biomass growth dynamics and stocks is a fundamental requirement for evaluating both the capability and potential of forest carbon sequestration. However, the biomass dynamics of Cunninghamia lanceolata and Castanopsis sclerophylla using the generalized algebraic difference approach (GADA) model has not been made to date.

Aims

This study aimed to quantify aboveground biomass (AGB, including stem, branch and leaf biomass) dynamics and AGB increment in C. lanceolata and C. sclerophylla forests by combining a GADA for diameter prediction with allometric biomass models.

Methods

A total of 12 plots for a C. lanceolata plantation and 11 plots for a C. sclerophylla forest were selected randomly from a 100 m × 100 m systematic grid placed over the study area. GADA model was developed based on tree ring data for each stand.

Results

GADA models performed well for diameter prediction and successfully predicted AGB dynamics for both stands. The mean AGB of the C. lanceolata stand ranged from 69.4 ± 7.7 Mg ha^?1 in 2010 to 102.5 ± 11.4 Mg ha^?1 in 2013, compared to 136.9 ± 7.0 Mg ha^?1 in 2010 to 154.8 ± 8.0 Mg ha^?1 in 2013 for C. sclerophylla. The stem was the main component of AGB stocks and production. Significantly higher production efficiency (stem production/leaf area index) and AGB increment was observed for C. lancolata compared to C. sclerophylla.

Conclusion

Dynamic GADA models could overcome the limitations posed by within-stand competition and limited biometric data, can be applied to study AGB dynamics and AGB increment, and contribute to improving our understanding of net primary production and carbon sequestration dynamics in forest ecosystems.

     

Knots in trees: strain distribution in a naturally optimised structure

Electronic speckle pattern interferometry was applied to directly measure the distribution of longitudinal, tangential, and shear strains in small boards of Norway spruce (Picea abies (L.) Karst.) exposed to tensile load in longitudinal direction. A sample with a central intergrown knot and one with an equivalent loose knot were compared with reference samples made of clear wood with an artificial central circular or square hole, respectively. The observed measurements were compared with a finite element (FE) simulation. The FE model was based on a geometric model to quantify the local fibre orientation and a micromechanical model to estimate elastic constants of clear wood and knot tissue. Both the measurements and simulation clearly illustrate a rather homogenous strain distribution around the intergrown knot. In comparison, the natural optimisation of dispersing strain peaks is less efficient in the case of loose knots. The artificial circular and square holes in samples with parallel fibre orientation lead to high gradients in the strain field and peak values in vicinity of the disturbance.     

An in vitro biomechanical comparison of a locking compression plate fixation and kerf cut cylinder fixation for ventral arthrodesis of the fourth and the fifth equine cervical vertebrae

Objectives: To (1) define mechanical properties in flexion, extension, and left lateral bending of cadaveric equine 4th and 5th cervical (C4–C5) articulations, (2) compare biomechanical properties of C4–C5 when stabilized with a kerf cut cylinder (KCC) compared with a ventrally placed 4.5 mm locking compression plate (LCP). Study Design: In vitro biomechanical investigation. Sample Population: Cadaveric adult equine cervical vertebral columns (n=54). Methods: Cervical vertebrae aged by horse dentition and size measured from radiographs were divided into 3 age groups then randomly allocated to 3 groups. The C4–C5 articulation was treated differently in each of the groups: KCC group; KCC‐implanted LCP group; 8‐hole 4.5 mm LCP implanted and intact group; no implant. Specimens were randomly subdivided into 1 of 3 loading conditions, before testing to failure under 4‐point bending. Stiffness, yield bending moment, failure bending moment, and failure mode were recorded. General linear models were performed to analyze associations between biomechanical properties and test variables. Results: All specimens failed at the C4–C5 intervertebral articulation. The cervical vertebrae with the LCP construct had significantly higher stiffness, yield bending moment, and failure bending moment than the KCC‐implanted cervical vertebrae. Failure modes differed between groups and varied with loading direction: KCC group, fractures of C5 associated with the KCC were common; LCP group, screw pull out or fractures (of C4 and C5 bodies, during extension and the caudal aspect of C4 during left lateral bending) were common; and intact group, subluxations were most common. Conclusions: In this model, LCP constructs had superior biomechanical properties compared with KCC constructs. Further research investigating the effect of repetitive loading is indicated.     

Wood net primary production resilience in an unmanaged forest transitioning from early to middle succession

The mixed deciduous forests of the upper Midwest, USA are approaching an ecological threshold in which early successional canopy trees are reaching maturity and beginning to senesce, giving way to a more diverse canopy of middle and late successional species. The net primary production (NPP) of these forests is generally considered past peak and in decline, but recent studies show a striking resilience in the NPP trajectories of some middle and late successional forests; yet, the mechanisms controlling such temporal changes in NPP are largely unknown. At the University of Michigan Biological Station in northern Michigan, we used a ≥9-year continuous record of wood net primary production (NPP), leaf area index (LAI), canopy composition, and stem mortality in 30 forested plots to identify the constraints on wood NPP as a mixed forest transitions from early to middle succession. Although wood NPP decreased over time in most stands, the rate of decline was attenuated when the canopy comprised a more diverse assemblage of early and middle/late successional species. The mechanism for sustained NPP in stands with more species diverse canopies was the proliferation of LAI by intact later successional tree species, even as stem mortality rates of early successional trees increased. We conclude that projections of carbon sequestration for the aging mixed forests of the upper Midwest should account for species composition shifts that affect the resilience wood NPP.     

Assessment of first-year veterinary students' clinical skills using objective structured clinical examinations

The DVM program at the University of Calgary offers a Clinical Skills course each year for the first three years. The course is designed to teach students the procedural skills required for entry-level general veterinary practice. Objective Structured Clinical Examinations (OSCEs) were used to assess students' performance on these procedural skills. A series of three OSCEs were developed for the first year. Content was determined by an exam blueprint, exam scoring sheets were created, rater training was provided, a mock OSCE was performed with faculty and staff, and the criterion-referencing Ebel method was used to set cut scores for each station using two content experts. Each station and the overall exam were graded as pass or fail. Thirty first-year DVM students were assessed. Content validity was ensured by the exam blueprint and expert review. Reliability (coefficient α) of the stations from the three OSCE exams ranged from 0.0 to 0.71. The three exam reliabilities (Generalizability Theory) were, for OSCE 1, G=0.56; OSCE 2, G=0.37; and OSCE 3, G=0.32. Preliminary analysis has suggested that the OSCEs demonstrate face and content validity, and certain stations demonstrated adequate reliability. Overall exam reliability was low, which reflects issues with first-time exam delivery. Because this year was the first that this course was taught and this exam format was used, work continues in the program on the teaching of the procedural skills and the development and revision of OSCE stations and scoring checklists.     

Effects of Halide Ions on the Carbamidocyclophane Biosynthesis in Nostoc sp. CAVN2

In this study, the influence of halide ions on [7.7]paracyclophane biosynthesis in the cyanobacterium Nostoc sp. CAVN2 was investigated. In contrast to KI and KF, supplementation of the culture medium with KCl or KBr resulted not only in an increase of growth but also in an up-regulation of carbamidocyclophane production. LC-MS analysis indicated the presence of chlorinated, brominated, but also non-halogenated derivatives. In addition to 22 known cylindrocyclophanes and carbamidocyclophanes, 27 putative congeners have been detected. Nine compounds, carbamidocyclophanes M−U, were isolated, and their structural elucidation by 1D and 2D NMR experiments in combination with HRMS and ECD analysis revealed that they are brominated analogues of chlorinated carbamidocyclophanes. Quantification of the carbamidocyclophanes showed that chloride is the preferably utilized halide, but incorporation is reduced in the presence of bromide. Evaluation of the antibacterial activity of 30 [7.7]paracyclophanes and related derivatives against selected pathogenic Gram-positive and Gram-negative bacteria exhibited remarkable effects especially against methicillin- and vancomycin-resistant staphylococci and Mycobacterium tuberculosis. For deeper insights into the mechanisms of biosynthesis, the carbamidocyclophane biosynthetic gene cluster in Nostoc sp. CAVN2 was studied. The gene putatively coding for the carbamoyltransferase has been identified. Based on bioinformatic analyses, a possible biosynthetic assembly is discussed.     

Soil type, management history, and soil amendments influence the development of soil-borne (Rhizoctonia solani, Pythium ultimum) and air-borne (Phytophthora infestans, Hyaloperonospora parasitica) diseases

The impact of soil type, long-term soil management, and short-term fertility input strategies on the suppressiveness of soils against soil-borne (Ocimum basilicum – Rhizoctonia solani, Lepidium sativum – Pythium ultimum) as well as air-borne (Lycopersicon esculentum – Phytophthora infestans, Arabidopsis thaliana – Hyaloperonospora parasitica) diseases was studied. Soils from field trials established in five European sites with contrasting pedo-climatic conditions were examined. Sites included (i) a long-term management field trial comparing organic and conventional farming systems (DOK-trial, Therwil, Switzerland) (ii) a short-term fertility input field trial comparing mineral and organic matter fertilisation regimes (Bonn (BON), Germany) (iii) two short-term fertility input field trials (Stockbridge (STC) and Tadcaster (TAD), UK) comparing the impact of farmyard manure, composted farmyard manure, and chicken manure pellet amendements and (iv) soil from a site used as a reference (Reckenholz (REC), Switzerland). Soil type affected disease suppressiveness of the four pathosystems signficantly, indicating that soils can not only affect the development of soil-borne, but also the resistance of plants to air-borne diseases at relevant levels. Suppressiveness to soil- and air-borne diseases was shown to be affected by soil type, but also by long-term management as well as short-term fertility inputs.