Carbon dioxide enrichment improves growth, water relations and survival of droughted honey mesquite (Prosopis glandulosa) seedlings

Low water availability reduces the establishment of the invasive shrub Prosopis on some grasslands. Water deficit survival and traits that may contribute to the postponement or tolerance of plant dehydration were measured on seedlings of P. glandulosa Torr. var. glandulosa (honey mesquite) grown at CO(2) concentrations of 370 (ambient), 710, and 1050 micro mol mol(-1). Because elevated CO(2) decreases stomatal conductance, the number of seedlings per container in the elevated CO(2) treatments was increased to ensure that soil water content was depleted at similar rates in all treatments. Seedlings grown at elevated CO(2) had a greater root biomass and a higher ratio of lateral root to total root biomass than those grown at ambient CO(2) concentration; however, these seedlings also shed more leaves and retained smaller leaves. These changes, together with a reduced transpiration/leaf area ratio at elevated CO(2), may have contributed to a slight increase in xylem pressure potentials of seedlings in the 1050 micro mol mol(-1) CO(2) treatment during the first 37 days of growth (0.26 to 0.40 MPa). Osmotic potential was not affected by CO(2) treatment. Increasing the CO(2) concentration to 710 and 1050 micro mol mol(-1) more than doubled the percentage survival of seedlings from which water was withheld for 65 days. Carbon dioxide enrichment significantly increased survival from 0% to about 40% among seedlings that experienced the lowest soil water content. By increasing seedling survival of drought, rising atmospheric CO(2) concentration may increase abundance of P. glandulosa on grasslands where low water availability limits its establishment.     

Disease-induced losses in winter wheat in England and Wales 1985–1989

Annual surveys of winter wheat diseases in England and Wales provide information on the relative severity of the leaf and stem-base disease complex. Septoria tritici was the most damaging disease during the 5-year period 1985–1989 causing annual losses estimated to be 0.329 Mt compared with 0.251 Mt and 0.231 Mt for eyespot and mildew, the next most damaging winter wheat diseases. Annual losses during the period averaged 1.078 Mt excluding losses attributable to the fusarium diseases, for which no satisfactory yield loss relationships are available. Sowing date and length of break from cereals exert a strong influence on incidence of eyespot and losses attributable to the disease and, on the basis of these surveys, growing all winter wheat crops after a 1-year break would prevent national losses of 100 kt annually.     

Climate Change and North American Rangelands: Assessment of Mitigation and Adaptation Strategies

Recent climatic trends and climate model projections indicate that climate change will modify rangeland ecosystem functions and the services and livelihoods that they provision. Recent history has demonstrated that climatic variability has a strong influence on both ecological and social components of rangeland systems and that these systems possess substantial capacity to adapt to climatic variability. Specific objectives of this synthesis are to: 1) evaluate options to mitigate greenhouse gas emissions and future climate change; 2) survey actions that individuals, enterprises, and social organizations can use to adapt to climate change; and 3) assess options for system transformation when adaptation is no longer sufficient to contend with climate change. Mitigation for carbon sequestration does not appear economically viable, given the small and highly variable carbon dioxide fluxes of rangeland ecosystems and the high transaction costs that would be incurred. In contrast, adaptation strategies are numerous and provide a means to manage risks associated with climate change. Adaptation strategies are diverse, including altered risk perception by individuals, greater flexibility of production enterprises, and modifications to social organizations that emphasize climatic variability, rather than consistency. Many adaptations represent “no regrets” actions because their implementation can be justified without emphasis on pending climate change. Adaptations specific to livestock production systems can include flexible herd management, alternative livestock breeds or species, innovative pest management, modified enterprise structures, and geographic relocation. Social-ecological systems in which adaptation is insufficient to counter the adverse consequences of climate change might undergo transformative change to produce alternative ecosystem services, production enterprises, and livelihoods. The rangeland profession is in a pivotal position to provide leadership on this global challenge because it represents the intersection of management and scientific knowledge, includes diverse stakeholders who derive their livelihoods from rangelands, and interacts with organizations responsible for rangeland stewardship.     

A retrospective investigation of feline gastrointestinal parasites in western Canada

Between 1998 and 2008, feline fecal specimens were submitted to provincial veterinary diagnostic laboratories in Regina and Saskatoon, Saskatchewan, for sucrose centrifugation-flotation (n = 635), parasite identification (n = 17), and/or Giardia (n = 283) or Cryptosporidium (n = 266) commercial direct immunofluorescence assay (IFA). The most commonly detected parasites on flotation were Toxocara cati (4.7%), Isospora (3.8%), and taeniid eggs (Echinococcus or Taenia) (1.3%). Cats less than 2 years of age were twice as likely to have a positive parasite test as cats older than 2 years. Using IFA, Giardia was detected in 9.9% of samples, and Cryptosporidium in 2.3% of samples. Relative to IFA, flotation had sensitivity values of 39% and 50% for detection of Giardia and Cryptosporidium, respectively. Giardia and Isospora were detected in a higher proportion of samples in our study population than reported in the general cat population in western Canada. This study highlights the importance of sensitivity when interpreting diagnostic tests and provides information to guide region-specific recommendations for helminth parasite prevention and treatment.     

Growth rate and survivorship of drought: CO2 effects on the presumed tradeoff in seedlings of five woody legumes

Traits that promote rapid growth and seedling recruitment when water is plentiful may become a liability when seedlings encounter drought. We tested the hypothesis that CO2 enrichment reinforces any tradeoff between growth rate and drought tolerance by exaggerating interspecific differences in maximum relative growth rate (RGR) and survivorship of drought among seedlings of five woody legumes. We studied invasive species of grasslands that differ in distribution along a rainfall gradient. Survivorship of drought at ambient CO2 concentration ([CO2]) was negatively related to RGR in well-watered seedlings in one of two experiments, but the relationship was weak because interspecific differences in RGR were small. Contrary to our hypothesis, there was no significant relationship among well-watered seedlings between RGR at ambient [CO2] and either the relative or absolute increase in RGR at elevated [CO2]. As predicted, however, CO2 enrichment reinforced interspecific differences in survivorship of seedlings exposed to similar rates of soil water depletion. Doubling [CO2] improved seedling survivorship of the most drought-tolerant species throughout the period of soil water depletion, but did not consistently affect survivorship of more drought-sensitive species. Midday xylem pressure potentials of drought-treated seedlings were less negative at elevated [CO2] than at ambient [CO2], but no other measured trait was consistently correlated with improved survivorship at high [CO2]. Carbon dioxide enrichment may not reinforce species differences in RGR, but could exaggerate interspecific differences in drought tolerance. To the extent that seedling persistence in grasslands correlates with drought survivorship, our results indicate a positive effect of CO2 enrichment on recruitment of woody legumes that are currently tolerant of drought.     

Acclimation of whole-plant Acacia farnesiana transpiration to carbon dioxide concentration

Transpiration per unit leaf area of Acacia farnesiana (L.) Willd. plants grown at a CO2 concentration ([CO2]) of 385 micromol x mol(-1) was about twice that of plants grown at 980 micromol x mol(-1). However, whes plants grown for more than a year at 980 micromol x mol(-1) were exposed to 380 micromol x mol(-1) for 9 days, they transpired at half the rate of those that had been grown at 380 micromol x mol(-1)1. Similarly, plants grown at 380 micromol x mol(-1), when exposed to 980 micromol x mol(-1), transpired at twice the rate of those grown at 980 micromol x mol(-1). Thus, the effects of elevated [CO2] on whole-plant transpiration, like those on photosynthesis, respiration and stomatal conductance, cannot reliably be extrapolated from measurements made during short-term exposure to elevated [CO2].     

Visceral larva migrans and alveolar hydatid disease. Dangers real or imagined.

For both visceral larva migrans and alveolar hydatid diseases, it is the feces of companion animals that are the primary source of human infection. Clearly, whatever is done to reduce this form of environmental contamination and the prevalence of the parasites' infective stages will help to protect the health of the human population in the United States and Canada, particularly the children. Very important are appropriate anthelmintic treatment programs, especially for T. canis, and proper control of close associations between pets and people. Probably the known incidence of visceral larva migrans in humans and the range of its known pathogenicity will increase as better diagnostic methods become available. In addition, other animal helminths, for instance Toxocara cati and Toxascaris leonina, may become more substantially documented as causes of human visceral larva migrans. Until more is known of the geographical distribution and prevalence of Echinococcus multilocularis among animals in North America, it will be difficult to assess accurately the future significance of alveolar hydatid disease in the continent's human population. Another important advance would be the development of anthelmintics that are effective for somatic second stage larvae of T. canis, and others effective for adult or larval Echinococcus species. Meanwhile it is a most important responsibility of the veterinary profession to educate its clients thoroughly concerning these dangerous helminths.     

Predicting likelihood of in vivo chemotherapy response in canine lymphoma using ex vivo drug sensitivity and immunophenotyping data in a machine learning model

We report a precision medicine platform that evaluates the probability of chemotherapy drug efficacy for canine lymphoma by combining ex vivo chemosensitivity and immunophenotyping assays with computational modelling. We isolated live cancer cells from fresh fine needle aspirates of affected lymph nodes and collected post‐treatment clinical responses in 261 canine lymphoma patients scheduled to receive at least 1 of 5 common chemotherapy agents (doxorubicin, vincristine, cyclophosphamide, lomustine and rabacfosadine). We used flow cytometry analysis for immunophenotyping and ex vivo chemosensitivity testing. For each drug, 70% of treated patients were randomly selected to train a random forest model to predict the probability of positive Veterinary Cooperative Oncology Group (VCOG) clinical response based on input variables including antigen expression profiles and treatment sensitivity readouts for each patient's cancer cells. The remaining 30% of patients were used to test model performance. Most models showed a test set ROC‐AUC > 0.65, and all models had overall ROC‐AUC > 0.95. Predicted response scores significantly distinguished (P < .001) positive responses from negative responses in B‐cell and T‐cell disease and newly diagnosed and relapsed patients. Patient groups with predicted response scores >50% showed a statistically significant reduction (log‐rank P < .05) in time to complete response when compared to the groups with scores <50%. The computational models developed in this study enabled the conversion of ex vivo cell‐based chemosensitivity assay results into a predicted probability of in vivo therapeutic efficacy, which may help improve treatment outcomes of individual canine lymphoma patients by providing predictive estimates of positive treatment response.