Elaeagnus angustifolia (Russian olive).

E. angustifolia is a tall shrub (up to 15 m and 1 m d.b.h.), with a dense, rounded crown, native to Europe and Asia and an important deciduous species of arid and semi-arid areas of northwestern China. It was introduced into the USA in the early 1900s, and has now become extensively naturalized in riparian areas of western states bordered on the east by North and South Dakota, Nebraska, Kansas, Oklahoma and Texas (Olson and Knopf, 1986a, 1986b; Shafroth et al., 1995). It also occurs in southern Canada from Ontario to British Columbia. It grows in some eastern USA states, but is not naturalized (Tesky, 1992). This fast-growing (up to 1.8 m per year), nitrogen-fixing species has silver-grey leaves with entire margins (4.5-9 cm), olive-shaped fruit and long thorns. The branches are flexible, pubescent (grey and scaly) and often have a short thorn at the end. The bark is brown, thin with shallow fissures, peeling in long strips. It has a deep taproot and well-developed lateral root system. The small, yellow flowers occur in late spring and have a distinctive spicy aroma. Trees produce seed after 3-5 years, with birds and small mammals dispersing them in their droppings. The seeds can remain viable for up to 3 years and are capable of germinating over a broad range of soil types (Knopf and Olson, 1984). Germination is enhanced by stratification in moist sand for 90 days at 41°C (Vines, 1960). E. angustifolia is found in a range of environments as it is tolerant of drought and saline, alkaline or infertile soils (Vines, 1960; Olson and Knopf, 1986a, 1986b), and has a well-developed root system. It is commonly found growing along floodplains, river banks, stream courses, marshes and irrigation ditches in the western states of the USA, and in desert or dry (150 mm annual rainfall) areas of Western Asia. It bears few fruits if the annual precipitation is >400 mm and also grows slowly if the water table is below 4 m. E. angustifolia is mainly established from seed, although cuttings are used in areas with sufficient moisture. It is relatively shade-tolerant once established and can withstand competition from other shrubs and trees, and can become a dominant climax species, replacing native cottonwoods and willows along water courses in the USA. E. angustifolia has been widely planted in shelterbelts, windbreaks or protective plantings as it is hardy, adaptable to a wide range of soil and moisture conditions and has a dense growth form (Brothers, 1988). It has also been used to revegetate land contaminated by paper mill wastewater (Wagner et al., 1994), potassium (Heinze and Liebmann, 1998) and bentonite (Uresk and Yamamoto, 1994), mine spoilings and as a bioindicator of heavy metal pollution (Aksoy and Sahin, 1999). The timber is hard and brownish-yellow with a beautiful grain, being similar to that of white elm (Ulmus pumila, U. americana). It can be used to make farm tools, furniture and for mining poles and civil construction. The fruits and leaves are valuable for food and animal fodder, whilst the tree is considered a good source for bee foraging. The leaves, shoots, flowers, fruits and bark have been traditionally used in Chinese medicine.

Effect of Wetting Conditions on the In Situ Density of Soil Using the Sand-Cone Method

The sand-cone method is commonly used to measure the in situ density of compacted soils. While determining field density with this method, differences in the sand-filling process between the test hole and the calibration container can cause errors. The differences can result from various in situ conditions such as the shape and size of the test hole and the moisture conditions of the filling sand and test ground. Temporary rainfall can increase the moisture content of both in situ soils and filling sand. This study examined the effect of wetting conditions on the accuracy of the sand-cone method in a laboratory. Compacted soils with different water contents (2–16%) were prepared in a small circular container in the laboratory, and the sand-filling process was simulated for cylindrical, conical, and roof-shaped test holes with depths of 10 and 15 cm. As the water content of the compacted soils increased, the sand-cone method underestimated the volume of sand accumulated in the test holes by up to 20%, resulting in the calculated density being overestimated by an identical amount. Slightly moist sand was poured into artificial test holes. When the water content of the filling sand was below 1%, no significant error was observed in the calculated volume.

Mechanistic insights from emergent landslides in physical experiments

Landslides pose a major natural hazard, and heterogeneous conditions and limited data availability in the field make it difficult to connect mapped landslide inventories to the underlying mass-failure mechanics. To test and build predictive links between landslide observations and mechanics, we monitored 67.89 h of physical experiments in which an incising and laterally migrating river generated landslides by undercutting banks of moist sand. Using overhead photos (every 20 s) and 1-mm-resolution laser topographic scans (every 15–30 min), we quantified the area, width, length, depth, volume, and time of every visible landslide, as well as the scarp angles for those within 3 min prior to a topographic scan. Both the landslide area–frequency distribution and area–volume relationship are consistent with those from field data. Cohesive strength controlled the peak in landslide area–frequency distribution. These results provide experimental support for inverting landslide inventories to recover the mechanical properties of hillslopes, which can then be used to improve hazard predictions.

Control of Meloidogyne incognita in three-dimensional model systems and pot experiments by the attract-and-kill effect of furfural acetone

Meloidogyne incognita causes large-scale losses of agricultural crops worldwide. The natural metabolite furfural acetone has been reported to attract and kill M. incognita, but whether the attractant and nematicidal activities of furfural acetone on M. incognita function simultaneously in the same system, especially in three dimensions or in soil, is still unknown. Here, we used 23% pluronic F-127 gel and a soil simulation device to demonstrate that furfural acetone has a significant attract-and-kill effect on M. incognita in both three-dimensional model systems. At 24 h, the chemotaxis index and corrected mortality of nematodes exposed to 60 mg/mL furfural acetone in 23% pluronic F-127 gel were as high as 0.82 and 74.44%, respectively. Soil simulation experiments in moist sand showed that at 48 h, the chemotaxis index and corrected mortality of the nematode towards furfural acetone reached 0.63 and 82.12%, respectively, and the effect persisted in the presence of tomato plants. In choice experiments, nematodes selected furfural acetone over plant roots and were killed subsequently. In pot studies, furfural acetone had a control rate of 82.80% against M. incognita. Collectively, these results provide compelling evidence for further investigation of furfural acetone as a novel nematode control agent.

Microsclerotial Granular Formulation of the Entomopathogenic Fungus Metarhizium brunneum and Its Combinations With Hydrogel and Imidacloprid Against the Annual Bluegrass Weevil (Coleoptera: Curculionidae)

We determined the potential of the entomopathogenic fungus Metarhizium brunneum Petch (Hypocreales: Clavicipitaceae) F52 strain, and of a microsclerotial formulation, for the control of the annual bluegrass weevil, Listronotus maculicollis Kirby, which is a major pest of golf course turf in eastern North America with widespread insecticide resistance. Under laboratory conditions in Petri dishes with moist sand, the microsclerotia (23–46 kg granules/ha) caused high rates of mortality (85–100%) and infection (67–80%) in annual bluegrass weevil adults, but these levels did not occur until after 9 d at constant 26°C and 12–15 d at 14 h at 23°C and 10 h at 17°C. Production of viable conidia was marginally higher at the higher temperature regime (7.3 vs. 5.2 × 109 per gram of granules). Application of microsclerotia did not provide significant control and infection of adults in pots with grass in the greenhouse. In field trials targeting spring generation larvae, microsclerotia application (50–100 kg granules/ha) was ineffective, and coapplication of hydrogel to stabilize soil moisture did not increase larval control. A liquid M. brunneum F52 conidial formulation (4.75–9.5 × 1013 colony forming units/ha) provided up to 51% control. Combinations of M. brunneum F52 with the neonicotinoid insecticide imidacloprid provided additive control with up to 70% control with the conidial formulation. Field efficacy was probably limited by suboptimal temperatures for the fungus, and future tests need to examine whether higher control rates can be achieved in applications targeting the summer generation larvae.

EFFECT OF COLD STRATIFICATION ON SEED GERMINATION OF THE MULTIPURPOSE FRUIT SHRUB, ZIZIPHUS LOTUS (L.) LAM. (RHAMNACEAE)

Shrubs and trees of the genus Ziziphus are a good example of naturally occurring multipurpose plant species with great potential in arid regions. This study was conducted to investigate the effect of cold stratification on seed germination and seedling growth of Ziziphus lotus (L.) Lam. Seeds were subjected to 0, 45, 90 and 120 days of cold stratification at 5°C. We also examined fruit, kernel and seed morphology. For each treatment period, four replicates of 50 seeds were incubated in plastic containers between two layers of moist sand at 15% and under greenhouse conditions for 15-day period. At the end of the experiment, the final germination percentage (FGP), shoot length and root length were assessed. The results clearly indicated that increasing duration of cold stratification improved seed germination. The most effective stratification period was 120 days where Z. lotus recorded 83% of FGP and 16.5 cm of total seedling length. Cold stratification treatments significantly increased shoot height, root length, as well as seedling total length. 120 days stratification treatment resulted in the highest shoot and root length (6.80 cm and 9.75 cm, respectively). An overview on the emergence of Z. lotus seedlings during a 15-day period was also illustrated.

TaqMan Multiplex Real-Time qPCR assays for the detection and quantification of Barley yellow dwarf virus, Wheat dwarf virus and Wheat streak mosaic virus and the study of their interactions

The phytopathogenic fungus Sclerotinia sclerotiorum forms dormant structures (termed sclerotia) that germinate myceliogenically under certain environmental conditions. During myceliogenic germination, sclerotia produce hyphae, which can infect leaves or stems of host plants directly from the ground; this is termed basal infection. This study determined which abiotic conditions were most important for promoting myceliogenic germination of sclerotia in vitro. A high sclerotium hydration level and low incubation temperature (15°C) improved mycelial growth in the presence of a nutrient source. Sclerotia incubated without a nutrient source on moist sand, vigorously myceliogenically germinated most frequently (63%) when they had been previously imbibed and then conditioned at −20°C. By far the most consistent amount of vigorous myceliogenic germination (>75%) was produced when sclerotia were heat-dried before being submerged in water. The hyphae of these sclerotia were shown to infect and proliferate on leaves of intact Brassica napus plants. This research provides a better understanding of the abiotic conditions that are likely to increase the risk of basal infection by S. sclerotiorum.

Heat-dried sclerotia of Sclerotinia sclerotiorum myceliogenically germinate in water and are able to infect Brassica napus

The phytopathogenic fungus Sclerotinia sclerotiorum forms dormant structures (termed sclerotia) that germinate myceliogenically under certain environmental conditions. During myceliogenic germination, sclerotia produce hyphae, which can infect leaves or stems of host plants directly from the ground; this is termed basal infection. This study determined which abiotic conditions were most important for promoting myceliogenic germination of sclerotia in vitro. A high sclerotium hydration level and low incubation temperature (15°C) improved mycelial growth in the presence of a nutrient source. Sclerotia incubated without a nutrient source on moist sand, vigorously myceliogenically germinated most frequently (63%) when they had been previously imbibed and then conditioned at −20°C. By far the most consistent amount of vigorous myceliogenic germination (>75%) was produced when sclerotia were heat-dried before being submerged in water. The hyphae of these sclerotia were shown to infect and proliferate on leaves of intact Brassica napus plants. This research provides a better understanding of the abiotic conditions that are likely to increase the risk of basal infection by S. sclerotiorum.

Bioarchaeological Analysis of Remains

Presumably in constructing the sidewalk, the bones from these shallow burials were disposed of elsewhere. Remains of five adults and one child were excavated. Seven subadult teeth were surface-collected around a hole at the western edge of the site. Being buried in moist sand meant that most bones excavated were fragmented. Bones and teeth were examined for evidence of pathologies. This small sample is not representative of the community, but the pathologies provide insight on these persons’ lives. The linea aspera on the only femur excavated is fairly robust. The individual’s sex was indeterminate, but this ambiguity reinforced the point that both men and women in this community engaged in physically demanding work. Cranial fragments from two individuals were thickened, an indicator of anemia resulting from nutritional deficiency or disease. Cribra orbitalia was noted in the eye socket of one individual, another indicator of nutritional deficiency. Two of the child’s incisors have transverse lines, evidence of enamel hypoplasia, an indicator of infectious disease and nutritional stress. Individuals buried in this cemetery were likely of low social status, living in congested and unsanitary conditions with limited food. These pathologies raise questions about the extent these conditions existed among African-Bahamian communities. Economic opportunities for free and enslaved workers would have been limited.

Soil restraints on buried pipelines subjected to reverse-fault displacement

The interaction between a buried pipeline and surrounding soil during large ground displacements is typically simulated using numerical nonlinear soil-restraint springs aligned with the longitudinal axis of the pipeline and in the two directions orthogonal to it. There are only very limited experimental data available to characterize the soil springs for simulating pipelines crossing reverse faults where large oblique soil displacements relative to the pipe could occur. Full-scale model testing was undertaken to evaluate this complex soil–pipe interaction problem. The tests simulated the performance of ∼400 mm diameter (nominal pipe size, NPS 16) pipe specimens buried in moist sand and crushed limestone trench backfill. The peak normalized oblique soil restraint (Nθ) values for oblique pipe movement angles (θ), when θ = 0° (horizontal movement) and θ = 90° (vertical movement), estimated based on state-of-practice approaches, were in agreement with those from full-scale testing. The value of Nθ was found to depend significantly on the peak friction angle of soil ([Formula: see text]) when θ was closer to 0°, whereas Nθ was less sensitive to [Formula: see text] when θ was beyond about 35°. The theoretical values of Nθ based on limit-equilibrium approaches compared well with the experimental findings.