Spatial and temporal variability of soil freeze-thaw cycling across Southern Alberta, Canada

Abstract

Soil freeze-thaw cycles play an important role in all aspects of agro-ecosystems, such as crop productivity, the evolution of the soil matrix, including trace-gas emissions. In regions that experience synoptic weather conditions throughout the winter, freeze-thaw cycles generally occur in one of two categories; seasonal or winter cycles. Current soil vegetation atmosphere models (SVAT's) often include a heat-transport soil freeze-thaw algorithm, but lack detail on complex interactions between the main driving variables. Boundary conditions for these models are often based only on a few climate variables and typically lack regional context. A nested statistical analysis was applied to identify the optimal set of environmental variables (via a stepwise regression selection procedure) to track soil freeze-thaw dynamics. Historical data collected between the years 2006-2009, for 17 long-term climate stations distributed across southern Alberta Canada was utilized. Cross-correlation between wind speed and maximum air temperature identified Chinook-driven freeze-thaw events, with such interaction varying significantly across the region and by soil depth. Climate-soil interactions were most significant predictors of soil temperature during winter months. The seasonal freeze-thaw cycle is estimated to vary between 112 -131 days, consisting of 12 -20 winter cycles (1 cm depth), and 1-5 winter cycles (5 cm depth) with average lag time of 26 -112 days. Freeze-thaw prediction was greatly improved when higher-order climate interaction terms were considered. Our findings highlight the importance of soil-water assumeptions within complex ecosystem SVAT models in resolving regional-driven climatic trends. Alongside improved representation of regional trends aimed at reducing model-based uncertainty, such efforts are expected to, in tandem, help advance the geostatistical design, and implementation of agroenvironmental monitoring systems that combine in-situ and satellite/remotesensing derived estimates of near-surface soil moisture.

Soil C and N response to changes in winter precipitation in a subalpine forest ecosystem, NW Italy

“…Soil temperature (15 cm depth) was measured with an accuracy of ±0.1 °C by means of temperature sensors (PT100) connected to a central data logger (QuadrTD). Soil temperature data were also used to calculate the number of soil freeze/thaws episodes, as the number of times the daily mean soil temperature dropped below 0 °C and rose again above freezing, as suggested by Phillips and Newlands ().…”

Abiotic Parameters and Pedogenesis as Controlling Factors for Soil C and N Cycling Along an Elevational Gradient in a Subalpine Larch Forest (NW Italy)

“…The SCD was calculated as the sum of the snow-covered days. Soil temperature data were also used to calculate the number of soil freeze/thaws cycles (FTCs), which represented the number of times the daily mean soil temperature dropped below 0 • C and raised again above freezing, as suggested by Phillips and Newlands [49]. The intensity of soil freezing (ISF), which represented minimum soil temperature when soil is frozen, was classified as "mild freezing", "mild/hard freezing", or "hard freezing" when soil temperature was between 0 • C and −5 • C, −5 • C and −13 • C, or lower than −13 • C, respectively, as suggested by Tierney et al [24] and Neilsen et al [50].…”

Model-Based Forecasting of Agricultural Crop Disease Risk at the Regional Scale, Integrating Airborne Inoculum, Environmental, and Satellite-Based Monitoring Data

“…Snow cover is beneficial to urediniospore survival during the winter, whereby areas in the vicinity of Olds are more conducive for spore survival than areas near Lethbridge. This enables Pst to overwinter in this region, and cause outbreaks in early spring when the weather is cool and wet (Conner et al, 1988;Phillips and Newlands, 2011;Xi et al, 2015). Significant snow cover (>7.6 cm) has an insulative effect, enabling Pst to infect wheat within 4-6 h and survive at temperatures down to −10 • C. With no snow cover and with temperatures less than −5 • C, Pst goes dormant (Sharma-Poudyal et al, 2014).…”