Modelling the population dynamics of the Mt. Graham red squirrel: Can we predict its future in a changing environment with multiple threats?

The Mt. Graham red squirrel (Tamiasciurus hudsonicus grahamensis; MGRS) is among the most critically endangered mammals in the United States and is isolated on the periphery of the species’ range, potentially increasing its conservation priority. To investigate potential threats to the population and provide a tool for land managers, we developed a spatially explicit population dynamics model. We tested model predictions using available range-wide data from the literature and field work specific to the MGRS. A general model input data set using mean life history values overpredicted MGRS abundance. However, we found significant correlation with known squirrel abundance using a general data set with curtailed fecundity and survival. A model with MGRS-specific data provided the best fit to observed population size. We investigated potential impacts of two major threats to the MGRS: competition from introduced Abert’s squirrels (Sciurus aberti) and increased levels of predation. Predation and particularly competition could have significant effects on the future population of the MGRS. Careful attention must be used to model the viability of fringe populations as peripheral populations can have a different life history than populations found in the range core.     

Using Limestone to Improve Soil Fertility and Growth of Mango (Mangifera Indica L.)

Soil acidity is one of the most important factors limiting crop production. The objective of this work was to evaluate the effects of limestone application on the soil chemical properties, nutrition and yield of mango plants in an orchard under implementation. The design was randomized blocks, with five limestone doses (0; 2; 4; 6 and 8 t ha^?1) and four replications. Soil chemical analyses were performed (at 12, 24, 36 and 48 months after the experiment implementation) in the layers 0–20; 20–40 and 40–60 cm deep. Nutrition status and yield were assessed during the first and second crop seasons. The highest fruit yield was associated with the application of 3.9 and 3.8 t ha^?1 of limestone in the 2008/09 and 2009/10 seasons, respectively, that is, the dose recommended by the literature for raising base saturation to 80%, as a function of the fertility conditions of the soil initially obtained.     

Errors of kinematic-wave and diffusion-wave approximations for time-independent flows in infiltrating channels

Time-independent (or steady-state) cases of channel flow were treated and errors of the kinematic-wave and diffusion-wave approximations derived for finite flow at the upstream end. The diffusion-wave approximation was found to be in excellent agreement with the dynamic wave representation, with error magnitudes of 0.2% for values of KF ₀ ² 7.5, where K is the kinematic-wave number and f ₀ is the Froude number. Even for small values of KF ₀ ² (e.g., KF ₀ ² =0.75), the errors were typically in the range of 1.3 to 3.7%. The approximate analytical diffusion-wave solution performed poorly with error magnitudes greater than 30% even for large values of KF ₀ ² . The kinematic-wave approximation was also found to be in good agreement with the dynamic-wave representation with errors of about 1.2% for KF ₀ ² =7.5 and varying from 15 to 44% for KF ₀ ² =0.75.     

Nitrogen mineralization in a pecan (Carya illinoensis K. Koch)–cotton (Gossypium hirsutum L.) alley cropping system in the southern United States

Information on temporal and spatial patterns of N mineralization is critical in designing tree-crop mixed systems that could maximize N uptake while minimizing N loss. We quantified N mineralization rates in a pecan (Carya illinoensis K. Koch)–cotton (Gossypium hirsutum L.) alley cropping system in northwestern Florida with (non-barrier) and without tree-crop belowground interactions (barrier separating the root systems of pecan and cotton). Monthly rates of mineralization were estimated using buried bag incubations over a 15-month period. In addition, seasonal mineralization rates and cotton lint yield on soils supplied with two sources of N—inorganic fertilizer and organic poultry litter—were assessed. Results indicated that temporal variations in net NH₄ and NO₃ accumulation and mineralization rates were driven primarily by environmental factors and to a lesser degree by initial soil NH₄ and NO₃ levels. Mineralization varied by belowground interaction treatment during the initial growing season, when the non-barrier treatment exhibited a higher mineralization rate than the barrier treatment, likely due to reduced nutrient uptake by cotton in the non-barrier or a higher degree of immobilization in the barrier treatment. Mineralization during the second growing season was similar for both treatments. Source of N had no effects on N transformation in the soil. Lint yield reductions were observed in the non-barrier treatment during both years compared to the barrier treatment, likely due to interspecific competition for water. Yield differences between treatments in the second growing season were likely compounded by a diminishing pre-study fallow effect. Source of N was found to have a significant effect on cotton yield, with inorganic fertilizer resulting in 39% higher lint compared to poultry litter in the barrier treatment.     

Gingerol content of diploid and tetraploid clones of ginger (Zingiber officinale Roscoe)

Ginger (Zingiber officinale Roscoe), a monocotyledonous, sterile cultigen, is widely used as a spice, flavoring agent, and herbal medicine. The pungency of fresh ginger is due to a series of homologous phenolic ketones of which [6]-gingerol is the major one. The gingerols are thermally unstable and can be converted to their corresponding shogaols, which are present in dried ginger. Fresh rhizomes of 17 clones of Australian ginger, including commercial cultivars and experimental tetraploid clones, were assayed by HPLC for gingerols and shogaols. [6]-Gingerol was identified as the major pungent phenolic compound in all samples, while [8]- and [10]-gingerol occurred in lower concentrations. One cultivar known as "Jamaican" contained the highest concentrations of all three gingerols and was the most pungent of the clones analyzed. Gingerols were stable in ethanolic solution over a 5-month period when stored at 4 degrees C. Shogaols were not identified in the extracts prepared from fresh rhizomes at ambient temperature, confirming that these compounds are not native constituents of fresh ginger. In contrast to previous findings, this study did not find significant differences in gingerol concentrations between the tetraploid clones and their parent diploid cultivar.     

Development of the Safe Tractor Assessment Rating System

We describe the development of the Safe Tractor Assessment and Rating System (STARS), a design-based tractor safety rating system that can be applied to new or used tractors to provide an objective assessment of their inherent safety features. A predictive rating system model, based on technical inspection, was used. Key principles underlying the system included the potential for design features to reduce the risk of an injury event occurring, and to reduce the risk of injury if such an event did occur. The rating system was based on current standards, research literature, injury and fatality data, and farmer input via focus groups. Development was an iterative process involving field, pilot, and inter-rater reliability tests. The final system was divided into six domains: rollover protection, runover protection, user protection, information and controls, pedestrian protection, and options. Within each domain, optimum design features were described for the common or serious potential injury risks, and a score was assigned for each feature. Scores were translated into a star rating, from zero stars for virtually no inherent safety features to five stars for the highest inherent safety, for each of the six domains. STARS distinguished well between older tractor models known to have few inherent safety features and newer tractor models known to have higher levels of inherent safety. STARS can provide tractor manufacturers, dealers, and users with information critical for managing tractor-associated injury risk. In Australia, it is initially being implemented within the curriculum of the technical education and training sector.     

Part 2: A Field Study of Enhanced Remediation of Toluene in the Vadose Zone Using a Nutrient Solution

The objective of this study was to test the effectiveness of a nitrate-rich nutrient solution and hydrogen peroxide (H₂O₂) to enhance in-situ microbial remediation of toluene in the unsaturated zone. Three sand-filled plots were tested in three phases (each phase lasting approximately 2 weeks). During the control phase, toluene was applied uniformly via sprinkler irrigation. Passive remediation was allowed to occur during this phase. A modified Hoagland nutrient solution, concentrated in 150 L of water, was tested during the second phase. The final phase involved addition of 230 moles of H₂O₂ in 150 L of water to increase the available oxygen needed for aerobic biodegradation. During the first phase, measured toluene concentrations in soil gas were reduced from 120 ppm to 25 ppm in 14 days. After the addition of nutrients during the second phase, concentrations were reduced from 90 ppm to about 8 ppm within 14 days, and for the third phase (H₂O₂), toluene concentrations were about 1 ppm after only 5 days. Initial results suggest that this method could be an effective means of remediating a contaminated site, directly after a BTEX spill, without the intrusiveness and high cost of other abatement technologies such as bioventing or soil-vapor extraction. However, further tests need to be completed to determine the effect of each of the BTEX components.     

Bio-economic evaluation of farmers’ perceptions of viable farms in western Kenya

Arable land in western Kenya is under considerable pressure from increasing human population. Rural households depend on farming for at least part of their livelihood, and poverty rates are among the highest in Kenya. Land is often depleted of nutrients, and for most farmers, access to inputs and markets is poor. There is a need to identify options that are manageable within the context of the farmer’s resource base and the household’s objectives that could improve farm household well-being. In this study we integrated qualitative informal participatory approaches with quantitative mathematical programming and biophysical simulation modelling. Households in four sub-locations in Vihiga District were clustered and pilot cases identified. Meetings were held with farmers to elicit their perceptions of what their ideal farm would look like, and how its performance might compare with their own farm’s performance. With farmers’ help, a range of scenarios was analysed, relating to changes in current enterprise mixes, changes in current farm sizes, and changes in prices of staples foods and cash crops. A considerable mismatch was found between farmers’ estimates of their own farm’s performance, and what was actually produced. There seems to be a threshold in farm size of 0.4 ha, below which it is very difficult for households to satisfy their income and food security objectives. Even for larger farms whose households are largely dependent on agriculture, the importance of a cash crop in the system is critical. There is a crucial role for extension services in making farmers aware of the potential impacts on farm revenue of modest changes in their farm management systems. We are monitoring nine households in the district, whose farmers have made some changes to their system in an attempt to increase household income and enhance food security.     

Subsurface drip irrigation for corn production: a review of 10 years of research in Kansas

Kansas State University initiated studies in 1989 to develop the methodology for successful application of subsurface drip irrigation (SDI) for corn production on the deep silt loam soils of the Central Great Plains, USA. Irrigation water use for corn can be reduced by 35–55% when using SDI compared with more traditional forms of irrigation in the region. Irrigation frequency has not been a critical issue when SDI is used for corn production on the deep silt loam soils of the region. A dripline spacing of 1.5 m has been found to be most economical for corn grown in 0.76 m spaced rows. Nitrogen fertigation was a very effective management tool with SDI, helping to maximize corn grain yield, while obtaining high efficiencies of nitrogen and water use. The research SDI systems have been utilized since 1989 without replacement or major degradation. SDI systems lasting 10–20 years are cost competitive for corn production with the more traditional forms of irrigation in the Great Plains for certain field sizes.Communicated by P. Thorburn