Soil moisture in a recent opening and mature forest within the IDFxh2 Soil factors influencing moisture & productivity: Soil moisture in a recent opening and mature forest within the IDFxh2 Brian Wallace and Chuck Bulmer Soil Scientists Thompson Okanagan Region 21 April 2017

The availability of soil moisture becomes a function of soil and vegetation characteristics controlled by year to year differences in weather Harvest type and degree of site preparation will modify the early, and possibly the long-term vegetation characteristics In dry forest ecosystems, H2O inputs to the upper soil layer as snow and rain would be nearly equal

Stemflow & interception? Soil Water Balance Inputs = snow and rain Outputs = evaporation transpiration runoff drainage Stemflow & interception?

Isobel Lake tree seedling survival trial (2015) ~15-20 km north of Kamloops Elevation 1050 m; IDFxh2/dk1 South-east aspect, sloping 19% MAT = 5oC MAP = 609mm Moisture deficit = 356mm Factors Cattle exclusion Planting delay after harvest (1st, 2nd, 3rd year) 4 species (Fd, Py, Pl, Lw) 2 site prep (screef, raw) 4 H2O treatments (water, grass+, water & grass+, control) Mature Forest Basal Area Site 1 – 32.25 m2 ha-1 Site 2 – 11.47 m2 ha-1 Site 5 – 30.65 m2 ha-1

Weather from Isobel site ~ 1000 m

Weather from Isobel site ~ 1000 m

Precipitation (mm) Open 2015 2016 June 15-30 48 22 July 20 72 August 44 27 Sub-total 112 121 September 41 46 October 29 83 November 25 40 Total 207 290 Precipitation (mm) Forest 2015 2016 June 10** July 7 28 August 16 9 Sub-total 23 47 September 14 37 October 8 35 November 11 Total 57 135

Late summer 2015 Winter2015-16 Summer & fall 2016

Snow measurements at Isobel Lake – 2017 Peak snow

August 10, 2015

August 10, 2015 August 8, 2016

Conclusions Snow accumulation and melt – critical H2O input The pattern and intensity of rain events seem to be more important than total precipitation amount Competition for moisture increases with time after harvest Vegetation control through active cattle management could improve conditions for seedling survival

Acknowledgments: Walt Klenner – FLNRO Chuck Bulmer – FLNRO Rita Winkler – FLNRO Tom Pypker – TRU BCTS Numerous contractors and students

Partial cut - 2016

Frost and tree seedlings  Radiation frost occurs on calm, clear nights when the ground surface cools to <0°C. Bare soil reduces this risk while grassy vegetation increases the risk. Advection frost occurs when cool air flows or is blown (advected) onto a site.

Soil texture and plant available water

Spittlehouse and Stathers. 1990. Seedling micro-climate. Self mulching Fine textured (clay) soils allow greater water movement toward the surface from deeper layers. It takes about 15 days with little rain to dry the top 5 to 10 cm of an exposed mineral surface to the permanent wilting point. If there is no vegetation, the soil at the 15 to 20 cm depth will still be moist. Spittlehouse and Stathers. 1990. Seedling micro-climate.