Molecular Mechanisms of Raccoon Rabies Virus Progression in Its Natural Host

Rabies virus presents a global public health problem. Our current understanding of the molecular determinants of rabies virulence stems from rodent models and laboratory strains of the virus, however, it is unclear how well rodent models represent viral response in natural reservoirs. Here, we examined interactions between the raccoon variant of rabies virus (RRV) and its natural host, raccoons, to gain a better understanding of molecular determinants of virulence in this system. We found expression patterns of RRV genes under tight control until the virus reached the central nervous system where replication increased significantly. Further, our examination of viral variants within an individual revealed that variant diversity may have an effect on virulence. We found that a mutation at a region of a T helper cell epitope on the nucleoprotein was associated with viral challenge outcomes and could be associated with RRV pathogenicity.

Photoperiod and Nitrogen Supply Limit the Scope of Northward Migration and Seed Transfer of Black Spruce in a Future Climate Associated with Doubled Atmospheric CO2 Concentration

The predicated changes in precipitation and temperature associated with the continued elevation of atmospheric CO2 concentration will trigger the northward shift of the Climate Envelopes for 130 North America tree species by as much as 10 degrees. However, climate envelope models do not take into account changes in other factors that may also influence the survival and growth of plants at the predicted new locations, such as photoperiod and nutrient regimes. This study investigated how photoperiod and nitrogen supply would affect the ecophysiological traits of black spruce (Picea mariana (Mill) B. S. P.) that are critical for survival and growth at new locations predicted by climate envelope models. We exposed black spruce seedlings to the photoperiod regime at the seed origin (PS) and that 10° north of the seed origin (PNM) as predicted by climate envelope models under the current and doubled atmospheric CO2 concentration and different levels of N supply (30 vs. 300 μmol·mol-1 N). We found that the PNM and the 30 μmol·mol-1 N supply both had negative impact on the development of seedling cold hardiness in the fall, and led to earlier burst of the terminal bud and greater rate of mortality in the following growing season. While the PNM stimulated seedling growth in the first growing season, the effect was not sustained in the second growing season. Our results suggest that the photoperiod regimes and poor nutrient conditions at higher latitudes will likely constrain the scope of the northward migration or seed transfer of black spruce.

Morphological Response of Jack Pine to the Interactive Effects of Carbon Dioxide, Soil Temperature and Photoperiod

Responding to the predicted shift in climate envelope jack pine, (Pinus banksiana Lamb.) might migrate 10° northward between 2071 and 2100 and will be exposed to a different photoperiod regime. Successful migration of the species might depend on the initial acclimating capability to the conditions of new location. The impacts of elevated carbon dioxide concentration [CO2], soil temperature and photoperiod on the phenological traits, growth and biomass responses in jack pine seedlings were investigated. Seedlings were grown in greenhouses under two [CO2] (400 and 950 μmol•mol-1), two soil temperatures (ambient soil temperature at seed origin and 5°C warmer) and three photoperiod regimes (photoperiods at seed origin, 5° north of the seed origin and 10° north of the seed origin). Budburst and bud setting time were recorded and the seedling height (Ht), root collar diameter (RCD), root biomass, stem biomass and leaf biomass were measured after six months of treatment. It was observed that under elevated [CO2], ambient Tsoil and photoperiods associated with 10° northward migrations budburstis advanced by 10 days. Photoperiods toward north significantly prolonged the bud setting time. However, tri-factor interactive effect on bud set was not statistically significant. Elevated [CO2] significantly (P < 0.05) increased the RCD, volume of the seedlings and total biomass and longer growing season photoperiods towards north significantly increased the seedling heights. Though elevated [CO2] significantly increased the projected leaf area, it had no significant effect on specific leaf area. Elevated [CO2] significantly reduced the shoot to root ratio, which indicated higher biomass allocation in roots under elevated [CO2]. However, all these growth and biomass responses were statistically insignificant under tri-factor interactive effects. The results suggest that climate change induced northward migration will not affect the growth of jack pine. However, a long distance migration (e.g. 10° north) will expose the species to late-spring frost damage.

N/P/K Ratios and CO₂Concentration Change Nitrogen-Photosynthesis Relationships in Black Spruce

The relationship between photosynthesis and leaf nitrogen concentration is often used to model forest carbon fixation and ratios of different nutrient elements can modify this relationship. However, the effects of nutrient ratios on this important relationship are generally not well understood. To investigate whether N/P/K ratios and CO2 concentration ([CO2]) influence relationships between photosynthesis and nitrogen, we exposed one-year-old black spruce seedlings to two [CO2] (370 and 720 μmol·mol-1), two N/P/K ratio regimes (constant (CNR) and variable (VNR) nutrient ratio) at 6 N supply levels (10 to 360 μmol·mol-1). It was found that photosynthesis (Pn) was more sensitive to nitrogen supply and N/P/K ratios under the elevated [CO2] than under ambient [CO2];under the elevated [CO2], Pn declined with increases in N supplies above 150 μmol·mol-1 in the CNR treatment but was relatively insensitive to N supplies of the same range in the VNR treatment. Further, our data suggest that the nutrient ratio and the CO2 elevation effects on photosynthesis were via their effects on the maximum rate of carboxylation (Vcmax) but not electron transport (Jmax) or triose phosphate utilization (TPU). The results suggest that the CO2 elevation increased the demand for all three nutrient elements but the increase was greater for N than for P and K. The CO2 elevation resulted in greater photosynthetic use efficiencies of N, P and K, but the increases varied with the nutrient ratio treatments. The results suggest that under elevated [CO2], higher net photosynthetic rates demand different optimal N-P-K ratios than under the current [CO2].

Flammability Ranking of Major Species of Trees and Shrubs in Daxing'anling Area of Northeastern China

Factor analysis and expert scoring methods were used to rank flammability of 16 major species of trees and shrubs in Daxing'anling area of northeastern China,based on 6 flammability variables,i.e.,air dry moisture content,absolute dry moisture content,ignition point,ash content,heat of combustion and extractive content measured on leaves,barks and twigs.Out of 16 species evaluated,for leaves' flammability,Larix gmelini was the smallest and Pinus sylvestris var.mongolica was the biggest;for barks' flammability,Salix koreensis was the smallest and P.sylvestris var.mongolica was the biggest;and for twigs' flammability,Populus davidiana was the smallest and Ledum palustre var.dilatatum was the biggest.The flammability ranking based on the integrated scores of leaves,barks and twigs suggested that Prunus padus,Betula dahurica,and L.gmelini were the top 3 less flammable species and that L.palustre var.dilatatum,P.sylvestris var.mongolica,and R.simsii were the top 3 more flammable species.This ranking agreed well with current standards and experience and should help the species selection for building fire-break forest belts in the study region.

北方针叶树CO_(2)的刺激和响应机制随光强而变化

黑云杉(Picea mariana[Mill.]B.S.P.)和白云杉(Picea glauca[Moench]Voss.)是同属物种,两者都是适度耐阴,并且在北美北方针叶林中广泛分布。为了了解光照对CO_(2)浓度升高的生理生态反应的影响,在三种光照条件下(温室中光照设置为100%、50%和30%)将一年生的两种幼苗暴露在360和720µmol mol–1浓度的CO_(2)环境中,测定了其中后期叶面气体交换量。研究结果表明,CO_(2)的浓度升高提高了净光合速率(Pn)和光合水分利用效率,但降低了气孔导度和蒸腾作用。CO_(2)对光合作用的刺激在50%光照下最大,在100%光照下最小。光合作用、最大羧化速率(Vcmax)和光饱和电子传递速率(Jmax)均随光照强度的降低而降低。升高的CO_(2)在所有光照处理中显著降低了Vcmax,在生长季节中期,两种云杉的Vcmax均显著降低,但在生长季节后期,当光照达到30%时,这一影响变得不明显,而且黑云杉的响应大于白云杉。CO_(2)浓度升高也降低了白云杉的Jmax,但在生长季后期30%光照时,这种影响变得不显著。但CO_(2)浓度升高对黑云杉的影响随时间而变化。在所有光照处理中,CO_(2)浓度升高降低了黑云杉生长中期的Jmax,且在生长后期30%光照时影响不显著,但在100%和50%光照时,Jmax升高。这些研究结果表明,两个树种植物都受益于CO_(2)浓度的升高,但它们的响应机制随着光照的增加而变化:即在100%和50%光照下,它们的响应主要是生理上的,而在30%光照下,它们的响应主要是形态上的。

Towards a downstream passage solution for out-migrating American eel (Anguilla rostrata) on the St. Lawrence River

There is a need to develop safe and effective downstream passage for diadromous anguillid eels on large rivers,where the combination of physical screening and bypass structures that is used to protect eel on smaller rivers is infeasible.The Eel Passage Research Center was established in 2013 to address the challenge of providing safe passage for out-migrating silver-stage American eel(Anguilla rostrata)on the St.Lawrence River,the outflow of the Laurentian Great Lakes,which is spanned by two large,mainstem hydroelectric generating stations.The Center’s goal is to develop the technology to behaviorally guide eel to a collection point for capture and transfer around the two generating stations.To achieve this goal,three parallel initiatives were undertaken;1)research into behavioral guidance techniques suitable for guiding out-migrating eel on large,high flow rivers,2)the evaluation of sonar technologies for detection of eel,necessary for assessing in situ guidance,and 3)the commissioning of literature reviews for the most promising guidance technologies.A number of behavioral guidance stimuli,including electricity,flow,sound and electromagnetic fields were examined in laboratory and flume settings for their utility in guiding out-migrating silver-stage eel.Of the techniques examined,only sound showed any promise for guidance.Three sonar technologies(Simrad 120 kHz EK60 echosounder,Sound Metrics ARIS Explorer 1800 sonar,and the Kongsberg Mesotech 500 kHz M3 multi-mode multibeam sonar)were evaluated to determine if existing acoustic technologies could be used to estimate the relative abundance and distribution of out-migrating silver-phase American eel in the St.Lawrence River.Only the ARIS unit could successfully identify eel targets,and only over a short(<15 m)range.The immense volume of sonar data accumulated over a portion of a single outmigration season contributed to the successful development of machine learning tools to automate the identification of American eel targets.Based on previous research on the St.Lawrence River identifying light as a promising deterrent,and the potential for sound as a deterrent in this study,full literature reviews were commissioned for these two stimuli.Lessons learned to date have resulted in the design of a subscale,prototype guidance structure that is expected to be deployed in 2022.