1. 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

2. 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

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

4. 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 – m2 ha-1
Site 2 – m2 ha-1
Site 5 – m2 ha-1

5. Weather from Isobel site ~ 1000 m

6. Weather from Isobel site ~ 1000 m

7. 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

8. Late summer 2015
Winter
Summer & fall 2016

9. Snow measurements at Isobel Lake – 2017
Peak snow

11. August 10, 2015

12. August 10, 2015
August 8, 2016

13. 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

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

15. Partial cut

16. 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.

17. Soil texture and plant available water

18. 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 Seedling micro-climate.