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An epidemic can cause enormous damage through financial and economic losses in addition to impaired health and loss of life. Good epidemic models can provide insights into ongoing waves that may facilitate public health responses and other readiness. Epidemic systems can undergo or consist of more than two driving forces; actually, they involve several. This paper deals with the modeling epidemics with two wave dynamics. We present a mathematical model with three driving forces, which is more compatible with the biology of the epidemic than conventional bilogistic and bi‐Richards ones, which have two driving forces. Simulation results show that our proposed model can predict turning points (waves) and cumulative case numbers during the two waves of epidemics satisfactorily. As a sample examination of our proposed model against real data, we show that the second phase of a typical epidemic can be detected by using less case data past the beginning of the epidemic than the bi‐Richards model. [ABSTRACT FROM AUTHOR]

Examines the phase coupling and synchrony in the spatiotemporal dynamics of muskrat and mink populations in Canada. Correlation between amplitudes and time-series; Identification of the cyclic minima; Causes of differences in regional phase dynamics.

Biomass burning activities can produce large quantities of smoke and result in adverse air quality conditions in regional environments. In Canada, the Environment and Climate Change Canada (ECCC) operational FireWork (v1.0) air quality forecast system incorporates near-real-time biomass burning emissions to forecast smoke plumes from fire events. The system is based on the ECCC operational Regional Air Quality Deterministic Prediction System (RAQDPS) augmented with near-real-time wildfire emissions using inputs from the Canadian Forest Service (CFS) Canadian Wildland Fire Information System (CWFIS). Recent improvements to the representation of fire behaviour and fire emissions have been incorporated into the CFS Canadian Forest Fire Emissions Prediction System (CFFEPS) v2.03. This is a bottom-up system linked to CWFIS in which hourly changes in biomass fuel consumption are parameterized with hourly forecasted meteorology at fire locations. CFFEPS has now also been connected to FireWork. In addition, a plume-rise parameterization based on fire-energy thermodynamics is used to define the smoke injection height and the distribution of emissions within a model vertical column. The new system, FireWork v2.0 (FireWork–CFFEPS), has been evaluated over North America for July–September 2017 and June–August 2018, which are both periods when western Canada experienced historical levels of fire activity with poor air quality conditions in several cities as well as other fires affecting northern Canada and Ontario. Forecast results were evaluated against hourly surface measurements for the three pollutant species used to calculate the Canadian Air Quality Health Index (AQHI), namely PM 2.5 , O3 , and NO2 , and benchmarked against the operational FireWork v1.0 system (FireWork-Ops). This comparison shows improved forecast performance and predictive skills for the FireWork–CFFEPS system. Modelled fire-plume injection heights from CFFEPS based on fire-energy thermodynamics show higher plume injection heights and larger variability. The changes in predicted fire emissions and injection height reduced the consistent over-predictions of PM 2.5 and O3 seen in FireWork-Ops. On the other hand, there were minimal fire emission contributions to surface NO2 , and results from FireWork–CFFEPS do not degrade NO2 forecast skill compared to the RAQDPS. Model performance statistics are slightly better for Canada than for the US, with lower errors and biases. The new system is still unable to capture the hourly variability of the observed values for PM 2.5 , but it captured the observed hourly variability for O3 concentration adequately. FireWork–CFFEPS also improves upon FireWork-Ops categorical scores for forecasting the occurrence of elevated air pollutant concentrations in terms of false alarm ratio (FAR) and critical success index (CSI). [ABSTRACT FROM AUTHOR]

Individual-tree basal area increment (BAI) models were developed for major tree species in the boreal forest of Ontario, Canada. A composite distance-independent individual-tree BAI model was structured based on the log-linearized gamma base function using a dataset derived from a network of ∼1800 permanent growth plots. A suite of fixed effects covariates that included basal area of trees larger than the subject tree, diameter at breast height, stand basal area and latitude, along with ecological land classification ecosites used as a random effect parameter, were found to be significant covariates in the model. A model fitted with the intercept designated as a mixed-effects parameter had a smaller Akaike's information criterion compared with other competing models. The mixed-effects modelling approach allowed us to select the best suite of covariates by correctly specifying the covariance structure according to the hierarchy of the fitting data. Furthermore, inclusion of ecosite as a random effect parameter increased ecological resolution in the BAI model by localizing its prediction and improves compatibility between growth and yield modelling and other important management tools such as the forest resources inventory. [ABSTRACT FROM AUTHOR]

Summary AimTo investigate effects of within-season and interannual climate variability on the behaviour of boreal forest ecosystems as simulated by the FORSKA2 patch model. LocationEleven climate station locations distributed along a transect across the boreal zone of central Canada. MethodsFORSKA2′s water balance submodel was modified to enable it to behave more realistically under a varying climate. Long-term actual monthly time-series of temperature and precipitation data were detrended and used to drive the modified model. Long-term monthly averages of the same detrended data were used to drive the unmodified model. ResultsModifications created significant improvements when simulating species composition at sites in boreal Canada. Simulated forest biomass values were slightly higher than those obtained from the unmodified model using averaged climate records, but resembled the observed distribution of vegetation more closely. Main conclusionsModified FORSKA2 suggests that boreal forest composition and distribution may be more sensitive to changes in monthly rainfall data than to changes in temperature. Climate variability affects seasonal water balances and should be considered when using patch models to forecast vegetation dynamics during and following a period of climate transition. The modified model provided improved representation of the latitudinal trend in spatially averaged biomass density in this region. [ABSTRACT FROM AUTHOR]

Over the past two decades, partial harvesting has been increasingly used in boreal forests as an alternative to clearcutting to promote irregular stand structures and maintain a balance between biodiversity preservation and continued timber production. However, relatively little is still known about the silvicultural potential of partial harvesting in Canada's boreal forest, especially in areas prone to organic matter accumulation (paludification), and most prior research has focused on biodiversity responses. In this study, we assess the effects of partial harvesting on stand development (recruitment, growth, and mortality) ten years after harvesting in previously unmanaged black spruce stands and quantify its effectiveness in reducing the impacts on ecosystem structures. Our analyses revealed that pre-harvest stand structure and site characteristics, especially initial basal area, sapling density, tree diameter, and organic layer thickness (OLT) were major factors involved in stand development ten years following these partial harvesting treatments. Depending on pre-harvest structure and site characteristics, partial harvesting can result in either an increase in post-harvest tree recruitment and growth or a loss of stand volume because of standing tree mortality. To increase the chances of partial harvesting success in ensuring an increase in decennial stand yield after harvest in black spruce forest stands, sites prone to paludification (i.e., where OLT >17 cm) should be left unharvested. This study illustrates the importance of taking into account pre-existing structure and site characteristics in the selection of management strategies to maximize the potential of partial harvesting to achieve sustainable forest management in black spruce stands. [ABSTRACT FROM AUTHOR]