Bert Tanner Student Presentation Award
Taurai Matengu (University of Manitoba) and Erin Nicholls (McMaster University)

Weather-based models for forecasting and managing Fusarium head blight risk in western Canadian cereal production

T.T. Matengu, P. Bullock, M.S. Mkhabela, F. Zvomuya, M.A. Henriquez, T. Ojo, R. Picard, R. Avila and M. Harding

Predicting the risk of Fusarium Head Blight (FHB) disease occurrence in cereal crops is critical for determining the need for and timing of fungicide sprays. Existing models for predicting FHB risk developed many years ago may no longer be suitable for the current Fusarium species complex that has evolved in Canada. Therefore, this study aims to develop and validate weather-based risk models around flowering for predicting FHB index (FHBi), Fusarium damaged kernels (FDK), and deoxynivalenol (DON) in spring wheat, winter wheat, barley, and durum across three Canadian Prairie provinces. Data collected from 15 sites in western Canada in 2019 and 2020 were used to classify an epidemic at a 5% FHBi (all crops), or 1 mg kg-1 DON (all crops) or 0.2, 0.3, 0.8, and 2% FDK thresholds for barley, spring wheat, winter wheat, and durum, respectively, to develop weather-based models for Fusarium epidemics. Kendall correlation and stepwise logistic regression analysis identified suitable combinations of temperature (temp), relative humidity (RH), precipitation (prec), and solar radiation (SR) at 4, 7, 10, 14 days pre-anthesis, and 3 days pre to 3 days post-anthesis for predicting FHB risk. The weather variables chosen across crop types for the FHBi models were RH, temp, and prec, and for the FDK and DON models RH was selected. Prediction accuracy of the models ranged from 74.6 to 80.6, 76.5 to 78.1 and 78.3 to 79.3% for FHBi, FDK, and DON, respectively. Fusarium head blight pressure was low in 2019 and 2020, most likely due to drier than normal weather conditions, which were unfavorable for the disease. The models will be used to power an interactive, online digital viewer and provide early warning of potential FHBi, FDK, and DON epidemics in prairie cereal crops.

Soil-stomata-sky: How forests and shrubs control evaporative partitioning in a subarctic, alpine catchment, Yukon Territory, Canada

Erin M. Nicholls, Sean K. Carey

As a result of altitude and latitude amplified climate change, widespread alterations in vegetation composition, density and distribution have been observed across northern latitudes. While there has been considerable focus on the ecological, thermal and climate impacts of these changes, how shifting vegetation will affect catchment hydrology is unclear in the face of a projected warmer and wetter future. To understand future water yield from northern watersheds, resolving the role of vegetation on evaporative partitioning and quantifying transpiration (T) and total evapotranspiration (ET) across ecozones is critical. This is challenging in alpine watersheds that have complex terrain and heterogeneous land cover driven by altitude and aspect. Here, we present several years of eddy covariance and sap flow data along an elevation gradient with distinct thermal and vegetation characteristics; providing a space-for-time comparison. We seek to answer the question: what hydrological changes will occur with a shift in treeline and increased shrub abundance? The three sites include: 1) a low-elevation boreal white spruce forest (~20 m), 2) a mid-elevation subalpine taiga comprised of tall willow (Salix) and birch (Betula) shrubs (~1-3 m) and 3) a high-elevation subalpine taiga with shorter shrub cover (< 0.75 m) and moss, lichen, and bare rock. Specifically, we: 1) compare contributions of T to ET among sites and between wet and dry years, and 2) assess the primary meteorological, phenological, and soil controls on T and ET. Overall, mean ET rates declined with increasing elevation, with the highest ET at the forest site. Differences in ET rates between shrubs sites were primarily in the mid-growing season when T was high. In the peak growing season, mean T rates and contributions to total ET were greater at the dense shrub site (2.0 ± 0.75 mm/day, T:ET = 0.80) than the forest (1.47 ± 0.52 mm/day, T:ET = 0.48). However, over the entire growing season, T:ET was similar at both sites, with mean contributions of 0.50 at the forest and 0.55 at the shrub sites. The cool, wet season in 2020 suppressed total T at the shrub sites more than the forest. With respect to environmental controls, net radiation was the dominant driver of ET at the forest. At the shrub sites, drivers of ET varied throughout the season, primarily driven by net radiation in the peak growing season, and stomatal resistance in the shoulder seasons. Soil moisture was a primary control on T at the forest, but not at the shrub sites, indicating the potential for moisture stress at lower elevations with higher ET and lower rainfall. Our results suggest treeline advance will increase total ET and result in a net drying of catchments. However, changing air temperatures, growing season length, and precipitation regimes will result in complex feedbacks that vary with vegetation cover.

CSAFM-SCMAF Student Presentation Award

Patrick Pow, University of British Columbia

Measurements of CO2, N2O and CH4 exchange over a Conventionally Managed Highbush Blueberry Field in BC, Canada

Patrick Pow, T. Andrew Black, Rachhpal (Paul) Jassal, Sean Smukler, Mark Johnson, Zoran Nesic.

Agricultural fields are significant sources of greenhouse gases (GHGs) including carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4), with implications for climate change. In Canada, studies using micrometeorological methods to measure all three GHGs in agricultural settings are limited to Ontario, Quebec and the Prairies. This study reports year-round (January 1, 2018 – December 31, 2018), continuous half-hourly measurements of CO2, N2O and CH4 exchange over a conventionally-managed highbush blueberry field on Westham Island in Delta, BC, Canada using the eddy-covariance (EC) method. Field management including fertilization using ammonium nitrate and mowing inter-row grass was associated with substantial changes in GHG exchange, suggesting that management strategies can be targeted for GHG mitigation, especially for CO2. The annual net ecosystem exchange (NEE) was 171 g C m-2 year-1 (627 g CO2 m-2 year-1). With emissions of 175 and 28 g CO2 equivalent (CO2e) m-2 year-1 from N2O and CH4, respectively, the field was a net source of all measured GHGs of 830 g CO2e m-2 year-1. After accounting for inputs and outputs of carbon the field gained a net of 233 g C m-2 year-1 largely controlled by the regular import of sawdust mulch. Soil water content was an important factor controlling N2O emissions, with higher N2O emissions being associated with the sudden onset of precipitation following prolonged drying during the growing season. Soil temperature and water content were the main factors controlling CO2 emissions. These findings have important implications for future feedback cycles and climate change.