Site Climatic Conditions during the Study Period
Average air temperature at the wetland over the study period was 9 °C (±4.1), with a daily maximum of 18.6 °C on 10 August and a daily minimum of 0.8 °C on 11 June (Figure 2b). The soil surface remained frozen until 20 June and then rapidly increased in temperature from -0.3 °C to 7.4 °C over a three-day period (Figure 2b). The spring thaw aligned with the appearance of snow-free areas around the tower. Snowfall was captured on the site’s time-lapse camera as late as 2 July and began again on 29 August. Precipitation was frequent and intense at the beginning of the study period, when two individual days received upwards of 33 mm (Figure 2c). Overall, rainfall from June to August reached 339 mm at Bonsai (Figure 2c), similar to the historic seasonal average across Marmot Creek Research Basin (342mm), located 14 km North of the study site in the Kananaskis Range (DeBeer & Pomeroy, 2009).
During the 2018 study period at Bonsai, air temperature and precipitation values were similar to the 30-year (1981 – 2010) normals reported by an Environment and Climate Change Canada (ECCC) monitoring station (ID 3053600: 51.03 N, 115.03 W, 1,391 m.a.s.l.), located 28 km North of the study site. Average monthly air temperatures at the ECCC station in 2018 were within 2 standard deviations (except for September) of the respective monthly ECCC normals with 11.4 °C (±1.1), 14.5 °C (±1.5), 13.8 °C (±1.5), and 9.4 °C (±1.9) in June, July, August, and September, respectively. The 30-year average annual precipitation at the ECCC station was 639.3 mm, with 119.4 mm, 64.9 mm, 70.8 mm, and 72.8 mm falling over the months of June, July, August, and September, respectively.
When environmental variables were analyzed for differences between the two shade periods during Peak Growing Season , it was clear that the amount of incoming radiation was substantially lower duringDynamic shade compared to Steady shade (Figure 2a). Both incoming radiation and net radiation were reduced by about 25%. The period of Dynamic shade during Peak Growing season had warmer (by about 11%) air temperatures compared to Steady shade, but this did not result in much change in soil temperatures (Figure 2).Dynamic shade had lower soil moisture and higher vapour pressure deficit, suggesting there was somewhat less moisture in the system at the time.