Effects of Regeneration Abundance on Predicted Development of Interior Douglas-fir Stands

By

Cornel LencarGraduate Student, Faculty of Forestry

University of British Columbia

Objectives

The objectives of my thesis are:

To calibrate the small tree height increment component of PrognosisBC.

To determine regeneration levels and their effect in the development of Interior Douglas-fir stands from the IDFdk1, IDFdk2, and IDFdk3 subzone variants.

To develop working guidelines for natural regeneration stocking levels in IDFdk1, IDFdk2, and IDFdk3.

Interior Douglas Fir Zone in the Kamloops Forest District

IDF Zone In BC, the IDF dominates the low to mid-

elevation landscape of the southern Interior Plateau and southern Rocky Mountain trench.

Much of the IDF landscape is occupied by stands of pure Douglas-fir, however mixed stands with lodgepole pine and spruce do occur.

The intricate landscape mozaic that comprise IDF are also characterized by stands with one to four age cohorts.

Irregular size distributions with varying amounts of regeneration, poles and large stems are very frequent.

Stands volume range widely, but reach 250 to 300 m3/ha.

Sampling Design Sampling took place in partially cut stands.

The sample population was stratified based on time since

disturbance and residual basal area.

In each selected stand, between 2 and 9 plots were located

systematically.

Each plot had a fixed-area of 0.04 ha, with a nested cluster of 5

subplots, each with a radius of 2.07 m, for regeneration

measurements.

The cluster of 5 regeneration subplots consisted of 1 plot located in

the centre of the main plot and 4 other plots located at 11.28 m from

the centre of the main plot in the cardinal directions.

Measurements(large and small trees)

In the 0.04 ha plot, all trees > 7.5 cm (large trees) were measured for dbh.

Up to 2 trees per species were sampled for height.

All small trees (defined as trees with dbh between 2.0 and 7.5 cm), were measured for dbh in the 0.04 ha plot.

5 small trees per species per plot were sub-sampled for total height and 5 year height increment.

Measurements(regeneration trees)

In the regeneration subplots, all regeneration was counted by species and height class.

4 height classes were used: (1) 0 - 0.5 m; (2) 0.5 - 1.0 m; (3) 1.0 - 1.3 m; and (4) > 1.3 m.

Up to 2 “best” trees per species were sub-sampled for height and total age.

Present Data

335 Plots distributed in:

3 ecological zones

sites disturbed 4 to 21 years ago

an elevation range of 700 m

a range of basal area retention

a range of slopes, aspects and elevations

Methodology A matrix of stands was created,using residual basal area,

site conditions and species composition for each subzone. Average levels of regeneration were calculated for each

subzone and grouped by residual basal area and site conditions according to the stand matrix.

Stands disturbed more than 10 years ago were selected from each group of sampled stands defined in the matrix and tree lists were obtained.

For each sampled stand, different levels of regeneration were used as input in the PrognosisBC tree list.

These stands were then projected for 40 years and compared across regeneration levels.

Example of Matrix of Stands

Types of Stands as a function of Species Composition, Residual Basal Area Class and Site conditions (Numbers represent sample stands)

COMPOSITION

BGC SITE RESIDUALBASALAREA

FD_lead HD_lead Mix No_Trees PL_lead SX_lead ALL

dens 13 . . . . . 13mod. 23 . . . . . 23

dry

open 10 . . 2 . . 12dens 2 . . . 2 . 4mod. 13 . . . 1 . 14

mesic

open 1 1 1 . 8 . 11dens 11 . . . 1 3 15mod. 15 1 . . 1 3 20

IDFdk1

wet

open 4 . . . 2 2 8TOTAL 92 2 1 2 15 8 120

Regeneration Summary: Average Regeneration Levels in IDFdk1

PrognosisBC Runs

Input tree list

Select Treatment

Input the regeneration levels

Run the model

Compare results

Draw conclusions

(Project must be completed)

IDFdk1-Predicted Volume over a 40 Years Cycle for Different Levels of Basal Area and Regeneration

IDFdk1- Dry Site Series, Low Initial Basal Area and Low, Medium, and High Regeneration Levels

DFdk1don (2039): StandTable

PL

FD

Density (

SP

H)

DBH Class (cm)

0

50

100

150

200

250

300

350

400

5 15 25 35 45 55 65 75 85 95

DFdk1dod (2039): StandTable

PL

FD

Density (

SP

H)

DBH Class (cm)

0

50

100

150

200

250

300

350

400

5 15 25 35 45 55 65 75 85 95

DFdk1dox (2039): StandTable

PL

FD

Density (

SP

H)

DBH Class (cm)

0

100

200

300

400

500

600

5 15 25 35 45 55 65 75 85 95

IDFdk1- Dry Site Series, Medium Initial Basal Area and Low, Medium, and High Regeneration Levels

DFdk1dmd (2039): StandTable

PL

FD

Density (

SP

H)

DBH Class (cm)

0

50

100

150

200

250

300

350

400

5 15 25 35 45 55 65 75 85 95

DFdk1dmn (2039): StandTable

PL

FD

Density (

SP

H)

DBH Class (cm)

0

50

100

150

200

250

300

5 15 25 35 45 55 65 75 85 95

DFdk1dmx (2039): StandTable

PL

FD

Densi

ty (

SP

H)

DBH Class (cm)

0

200

400

600

800

1000

1200

5 15 25 35 45 55 65 75 85 95

IDFdk1- Dry Site Series, High Initial Basal Area and Low, Medium, and High Regeneration Levels

DFdk1ddn (2039): StandTable

FD

Density (

SP

H)

DBH Class (cm)

0

20

40

60

80

100

120

5 15 25 35 45 55 65 75 85 95

DFdk1ddd (2039): StandTable

FD

Density (

SP

H)

DBH Class (cm)

0

20

40

60

80

100

120

140

5 15 25 35 45 55 65 75 85 95

DFdk1ddx (2039): StandTable

FD

Density (

SP

H)

DBH Class (cm)

0

50

100

150

200

250

300

5 15 25 35 45 55 65 75 85 95

Conclusions

Little difference was found for the total volumes at different levels of regeneration.

There were considerable differences in the stand structures associated with the different regeneration assumptions.

Species composition and stand structures varied somewhat among subzones and moisture levels, but the trends illustrated here were repeated.

Acknowledgments

This research was funded by the BC Ministry of Forests using FRBC funds.

Many people, including my supervisory committee, B.C. Ministry of Forests employees, and some of my graduate student colleagues at UBC made this work possible, and more important enjoyable.