Preliminary Findings on Canopy and Bryophyte Forest Floor Interception Loss of Growing-Season Rainfall at Mayson Lake. Darryl Carlyle-Moses, Ph.

Transcription

1 Preliminary Findings on Canopy and Bryophyte Forest Floor Interception Loss of Growing-Season Rainfall at Mayson Lake Darryl Carlyle-Moses, Ph.D Department of Geography & Graduate Program in Environmental Science Thompson Rivers University

2 Presentation Outline Introduction Study Objectives Study Methodology Results to Date and Discussion Management Implications Conclusions and What s s Next?

3 Introduction Importance of and factors controlling interception loss.

4 Study Methodology In 2006 four stands near Mayson Lake were selected and instrumented with throughfall and stemflow gauges. Ic = R (TF+SF)

5 Four stands Mature pine spruce fir (Green / Red Attack) Mature stand with MPB infested trees selectively cut. Juvenile stand (Green Attack) Juvenile stand (healthy)

6 D

7 Rainfall tipping bucket rain gauges located in nearby clearings. Throughfall 30 manually read gauges in each stand. Stemflow 3 to 6 manually read collectors in each stand.

8 10 bryophyte floor lysimeters (0.05 m 2 ) in each of 3 stands. 20 additional samples from each site taken to derive dry mass versus water storage capacity relationships.

9 Results Canopy Interception Loss: Relationship between canopy interception loss depth and rainfall depth was found to be linear for each of the four stands in 2006.

10 Canopy Interception Loss Depth Versus Rainfall Depth (mm) Site Slope Intercept R 2 Mature (Green / Red Attack) Mature (Select Cut) Juvenile (Green Attack) Juvenile (Healthy)

11 Canopy Cover and Storage Capacities Site Mature (Green / Red Attack) Mature (Select Cut) Juvenile (Green Attack) Juvenile (Healthy) Canopy Storage Cover (%) (mm) (2.7) (3.5) (2.6) (1.4)

12 Rainfall Frequency Distribution at Mayson Lake Frequency < 2 < 4 < 6 < 8 < 10 < 12 < 14 < 16 < 18 < 20 < 22 < 24 Rainfall (mm)

13 Canopy Interception Loss (%) as a Function of Rainfall Depth (mm) 70 Canopy Interception Loss (%) Rainfall (mm)

14 Expected Season-Long Canopy Interception Loss % Mature Mature (Select Cut) Juvenile (Green Attack) Juvenile (Healthy) Canopy Interception Loss Throughfall Stemflow

15 Mature Stand

16 Juvenile (Attacked)

17 Juvenile (Healthy)

18 25 Yr-Old Bole 13 Yr-Old Bole

19 Canopy Interception Loss from a Dead Stand Spring / Early Summer 2007 Interception loss = 3.3 mm for 25.3 mm of rainfall (7 events).

20 Linear equation + rainfall frequency distribution suggests seasonal canopy interception of ~13 % Canopy Interception Loss (mm) Ic = 0.12R R 2 = Rainfall (mm)

21 Role of the Bryophyte Dominated Floor Cover

22 Bryophyte Turf Sample 20 cm

23 Mature (Red / Green Attack) Mature (Select Cut) Juvenile (Green Attack) Total Depth (x 10-2 m) 3.4 ± ± ± ± 1.0 Area (x 10-2 m 2 ) 5.5 ± ± ± ± 0.6 Dry Mass (kg m - 2 ) 1.2 ± ± ± ± 0.7 Storage (mm) 7.5 ± ± ± ± 2.1

24 Storage Capacity Versus Dry Weight (Individual Samples) Minimum Storage Capacity (mm) R 2 = Bryophyte Turf Dry Weight (kg) / m^2

25 Storage Capacity Versus Dry Weight (Grouped Samples) Minim um Storage Capacity (mm) Storage = 1.84 M D ,, R 2 = Bryophyte Turf Dry Weight (kg) / m^2

26 Storage capacity values used to run a weekly water balance model: E = L i + TF L f D D = TF - SC Model run from mid June to mid August 2006 in the 3 study stands.

27 Water Balance Study Results Site Canopy Interception Loss (%) Mature 28 Bryophyte Layer Interception Loss (%) Total Interception Loss (%) Mature (Select Cut) Juvenile (Green Attack)

28 Cumulative Evaporation Loss from Forest Floor Cover 26/06/07 09/07/07 5 Cumulative Evaporation (mm) E cuml. = 1.44Ln (D) R 2 = Days after Saturating Rain

29 Management Implications 1. Summer / Fall soil moisture = important for Winter / Spring flows. 2. Total interception ~ 50 to 60 % of rainfall (and thus potential soil / groundwater) where bryophyte mats are present. 3. Dead stands still intercept a large amount of rainfall (guestimate( ~ % interception loss if bryophyte mats present, ~ 15 % if not).

30 4. Bryophyte mats need to be retained. Currently site preparation destroys this cover.

31 5. Select cut stands no difference in interception loss where other species present and canopy gaps not large. Riparian zones no no need to clear cut these areas. 6. Stands will recover to their pre-disturbance interception efficiency after ~? years (between 12 and 24 years).

32 What s s Next? Continued monitoring as stands go from green to red to grey attack. Interception modelling procedures re- evaluated, new models to be developed.

33 Interception loss by slash, very young stands, stands between 12 and 24 yrs, and pine needle litter to be quantified.

34 Relationship between interception loss, transpiration and soil moisture / deep drainage to be established. Investigate how different disturbance regimes impact forest water balances differently. Nutrient cycling??????

35 Thank You! Acknowledgements FIA Forest Science Program Projects M & M Thompson Rivers University Comprehensive University Enhancement Fund & Scholarly Activity Committee Funds