Tropical dry forest succession and the contribution of lianas to wood area index (WAI)

The transmission and interception of light through the canopy is an important indicator of forest productivity in tropical forest ecosystems, and the amount of light that eventually reaches the forest floor is influenced by its interactions with leaves, branches, fruits, and flowers among many different canopy elements. While most studies of forest canopy light interception focus on leaf area index (LAI), very few studies have examined wood area index (WAI), which may account for a substantial component of light interception in tropical forests. The influence of lianas on the interception of light and their overall contribution to WAI is a potentially important factor, but it is generally overlooked because of its difficulty to assess. In this paper we evaluate the relative contribution that lianas have to the overall WAI and canopy openness as function of successional stage via a latitudinal comparison of sites across the Americas (Mexico, Costa Rica and Brazil). Our results suggest that lianas significantly increase WAI and decreases canopy openness. However, lianas were absent at all of our study sites where canopy openness exceeded 60%. Our data are the first to explicitly document the role of lianas in the estimation of WAI and, overall, they will contribute to better estimations of ecosystem level LAI in tropical environments, where there is a lack of data on WAI.     

Sources of within- and between-stand variability in specific leaf area of three ecologically distinct conifer species

Specific leaf area (SLA) is an important ecophysiological variable, but its variability within and between stands has rarely been simultaneously examined and modeled across multiple species. Extensive datasets on SLA in coastal Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirb.) Franco), hybrid spruce (Picea engelmannii Parry × Picea glauca (Moench) Voss × Picea sitchensis (Bong.) Carr.), and ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Laws.) were used to estimate variability of SLA within a canopy and its relationship to tree- and stand-level covariates, and to predict SLA at various locations in tree crowns. Also, in the case of hybrid spruce, variation in SLA due to different relative horizontal lengths from the bole was examined. In all species, SLA systematically increased from tree tip to crown base and decreased with foliage age class. Cardinal direction did not have a highly significant influence in either Douglas-fir or hybrid spruce, but SLA did significantly decrease from branch tip to bole in hybrid spruce. Tree- and stand-level (e.g. density, site index) factors had relatively little influence on SLA, but stand age did have a significant positive influence. For ponderosa pine, a significant relationship between canopy mean current-year SLA and carbon isotope discrimination was also found, suggesting the importance of water stress in this species. An equation was fitted to estimate SLA at various points in the canopy for each species and foliage age class using absolute height in the canopy, relative vertical height in the tree, and stand age.     

Energy requirements for transport and surface application of liquid pig manure in Manitoba,Canada

The objective of this study was to conduct a thorough accounting of energy used to transport liquid pig manure from farm storage to the field and to surface-apply the manure. Energy consumption was determined using both energy data from the literature plus data from field-scale research. Energy consumption was compared between two manure application systems (the drag hose and the slurry wagon systems) and two application timing treatments (single vs. twice-annual manure application). The single annual application of liquid pig manure applied at 81.5 m³ ha⁻¹ and transported 1.8 km from storage to field consumed 2180 MJ ha⁻¹ with the drag hose system and 2185 MJ ha⁻¹ with the slurry wagon system. The twice-annual manure application regime used 2726 and 2209 MJ ha⁻¹ for the drag hose and slurry wagon systems, respectively. When energy use was calculated on the basis of MJ per kg of available N, liquid pig manure applied once annually with the slurry wagon system provided N at 17.76 MJ kg⁻¹ of available N, which was 33% of the energy cost of N from anhydrous ammonia and 23% of the energy cost of N from urea. Manure transport distance could be increased to 8.4 km before the energy cost per kg of available N from pig manure was equivalent to anhydrous ammonia, and up to 12.3 km before the energy cost of manure N was equivalent to urea N. Despite the high energy cost to deliver liquid pig manure from storage to field, the much lower cost per kg of available N compared to inorganic fertilizer N highlights the opportunities that exist for improving the energy efficiency of industrial agriculture by replacing inorganic fertilizers with manure.     

Morphological and Molecular Characterization of Novel Salt-Tolerant Rice Germplasms from the Philippines and Bangladesh

To screen for new sources of salinity tolerance, 688 traditional rice varieties from the Philippines and Bangladesh were obtained, and their tolerance to hypersaline conditions at the seedling stage was examined. A total of 29 Philippine lines and 15 Bangladeshi lines were scored as salt-tolerant.Morphological assessment(plant height, biomass and Na-K ratio) revealed that among the 44 salt-tolerant accessions, Casibon, Kalagnon and Ikogan had significantly higher relative shoot length difference, relative shoot growth reduction and shoot Na-K ratio than the tolerant check FL478.Additionally, AC and Akundo exhibited significantly higher Na-K ratios than the other genotypes. The genetic diversity of the 44 genotypes was assessed using 34 simple sequence repeat markers. A total of 133 alleles were detected across all loci. Cluster analysis showed that AC, Akundo and Kuplod were clustered along with FL478, indicating a strong genetic relatedness between these genotypes. IR29(susceptible check) was singly separated. The haplotype analysis revealed that none of the 44 genotypes had a similar allele combination as FL478. These accessions are of interest since each genotype might be different from the classical salinity-tolerant Pokkali.     

Variations in clinical presentation and anatomical distribution of gross lesions of African swine fever in domestic pigs in the southern highlands of Tanzania: a field experience

African swine fever is a contagious viral disease responsible for up to 100% mortality among domestic pigs. A longitudinal study was carried out to determine the clinical presentation and anatomical distribution of gross lesions in affected pigs in Mbeya region, Tanzania during the 2010 to 2014 outbreaks. Data were collected during clinical and postmortem examination by field veterinarians and using a structured questionnaire. A total of 118 respondents (100%) showed awareness about African swine fever. During previous outbreaks, the mortality rate was almost 100%, while in 2014 it was estimated to be less than 50%.The clinical picture of the 2010–2012 outbreaks was characterized by high fever, depression, inappetance, mucosal congestion, hemorrhages, erythematous lesions in different body parts, and abortion. Several internal organs including the kidneys, spleen, and liver were congested and edematous. During the 2014 outbreak, a number of pigs (49.7%) were asymptomatic when brought to slaughter slabs but were found to have African swine fever gross lesions at postmortem examination as compared to 12.3% in 2010–2012. Bluish discoloration, which is normally distributed on the non-hairy parts of the body, was not apparent in some pigs except at postmortem examination. Some pigs (36.1%) presented nasal and/or oral bloody discharges which were uncommon (9.1%) during previous outbreaks. Moreover, other gross features included enlarged dark red renal lymph nodes and spleen. Clinical signs such as anorexia, diarrhea, and pyrexia were mainly observed when affected pigs reached moribund stage. The majority of pregnant sows died without presenting abortions. In some litters, suckling piglets (3–6 weeks) survived from the disease. These findings indicated that in 2014, African swine fever outbreak in Mbeya region was characterized by a different clinical picture.     

Seroprevalence and Risk Factors for Leptospira Seropositivity in Beef Cattle,Sheep and Deer Farmers in New Zealand

Leptospirosis is a global zoonosis that in New Zealand affects primarily people occupationally exposed to livestock. The objective of this study was to estimate the seroprevalence of five Leptospira serovars in farmers working on cattle, sheep and deer farms that had the serological status of animals previously assessed and to identify risk factors for farmer seropositivity. A total of 178 farmers from 127 properties participated in the study. Blood samples were tested using the microscopic agglutination test (MAT) for the presence of antibodies to Leptospira. Samples with a MAT titre ≥48 were considered seropositive. Using Bayesian statistical analysis, the median seroprevalence of Leptospira, all serovars combined, was estimated to be 6.6% (95% probability interval (PI) 3.6–10.9%). Risk factors associated with seropositivity were assisting deer or cattle calving, farming deer, having ≥25% of flat terrain and high abundance of wild deer on farm, while high possum abundance on farm was negatively associated with seropositivity. No association was observed between farmer serostatus and previously recorded livestock serology. Leptospira seropositivity was associated with influenza‐like illness of farmers (RR = 1.7; 95% PI 1.0–2.5). Assuming a causal relationship, this suggested an annual risk of 1.3% (95% PI 0.0–3.0%) of influenza‐like illnesses due to Leptospira infection in the population of farmers. The association between seropositivity and disease can be used to estimate the public health burden of leptospirosis in New Zealand. Identifying and understanding risk factors for Leptospira seropositivity can inform preventive measures, hence contributing to the reduction of leptospirosis incidence in farmers.     

Validation of environmental DNA (eDNA) as a detection tool for at‐risk freshwater pearly mussel species (Bivalvia: Unionidae)

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Copepod dynamics across warm and cold periods in the eastern Bering Sea: Implications for walleye pollock (Gadus chalcogrammus) and the Oscillating Control Hypothesis

Differences in zooplankton populations in relation to climate have been explored extensively on the southeastern Bering Sea shelf, specifically in relation to recruitment of the commercially important species walleye pollock (Gadus chalcogrammus). We addressed two research questions in this study: (i) Does the relative abundance of individual copepod species life history stages differ across warm and cold periods and (ii) Do estimated secondary production rates for copepods differ across warm and cold periods? For most copepod species, warmer conditions resulted in increased abundances in May, the opposite was observed in colder conditions. Abundances of smaller‐sized copepod species did not differ significantly between the warm and cold periods, whereas abundances of larger‐sized Calanus spp. increased during the cold period during July and September. Estimated secondary production rates in the warm period were highest in May for smaller‐sized copepods; production in the cold period was dominated by the larger‐sized Calanus spp. in July and September. We hypothesize that these observed patterns are a function of temperature‐driven changes in phenology combined with shifts in size‐based trophic relationships with primary producers. Based on this hypothesis, we present a conceptual model that builds upon the Oscillating Control Hypothesis to explain how variability in copepod production links to pollock variability. Specifically, fluctuations in spring sea‐ice drive regime‐dependent copepod production over the southeastern Bering Sea, but greatest impacts to upper trophic levels are driven by cascading July/September differences in copepod production.     

Ultrasound-guided vessel catheterization in adult Yorkshire cross-bred pigs

Objective

To describe an ultrasound-guided approach for venous and arterial vascular access and catheterization in anesthetized adult Yorkshire cross-bred pigs.