Saproxylic beetles and the cumulative ecological effects of

wildfire and forest harvesting

Saproxylic beetles and the cumulative ecological effects of

wildfire and forest harvesting

Tyler CobbPhD candidate

Dept. of Renewable ResourcesUniversity of Alberta

Tyler CobbPhD candidate

Dept. of Renewable ResourcesUniversity of Alberta

• background • hypotheses• study design• preliminary results• implications

• background • hypotheses• study design• preliminary results• implications

Talk Outline

Effects of disturbance combinations may be cumulative

1949

7 km

Swan Hills area, Alberta, CANADATwp. 63, Rge. 11, W5th

1964+ oil wells + access roads

1991oil wells

+ access roads+ logging

Source: Schneider 2002

ASRD 2001ASRD 2001

Welch&Rylander

Melanophila acuminata

Saproxylic Beetles?Saproxylic Beetles?

Hypotheses

1. Combined effects of wildfire and forest harvesting on saproxylic beetles are greater than eitherdisturbance alone. (Survey Approach)

2. Abundance of saproxylic beetle larvae is linked to changes in soil nutrients near burned trees. (Experimental Approach)

ChisholmFire

ChisholmFire

• May 23 - June 4, 2001• ~ 120,000 ha

H1: Combined effects of wildfire and forest harvesting on saproxylic beetles are greater than either disturbance alone.

Survey Design:1 Factor ANOVA (4 levels and 6 replicates = 24 sites)

Stand Treatments (age, density, plant composition, soil types, accessibility)

GRN BRN HAR SAL

1 Factor ANOVA (4 levels and 6 replicates = 24 sites)

Stand Treatments

GRN BRN HAR SAL

Undisturbed in > 100yrs

H1: Combined effects of wildfire and forest harvesting on saproxylic beetles are greater than either disturbance alone.

Survey Design:

1 Factor ANOVA (4 levels and 6 replicates = 24 sites)

Stand Treatments

GRN BRN HAR SAL

Burned by Chisholm fire 2001

H1: Combined effects of wildfire and forest harvesting on saproxylic beetles are greater than either disturbance alone.

Survey Design:

1 Factor ANOVA (4 levels and 6 replicates = 24 sites)

Stand Treatments

GRN BRN HAR SAL

Clear-cut harvested in 2001

H1: Combined effects of wildfire and forest harvesting on saproxylic beetles are greater than either disturbance alone.

Survey Design:

1 Factor ANOVA (4 levels and 6 replicates = 24 sites)

Stand Treatments

GRN BRN HAR SAL

Salvaged following the Chisholm fire

H1: Combined effects of wildfire and forest harvesting on saproxylic beetles are greater than either disturbance alone.

Survey Design:

Sampling Design

• summer months 2002 and 2003

• flight-intercept traps (4/site = 96 total)

• total beetles collected 15,326

• identification ~60% complete (187 species, 38 families so far!)

H1: Combined effects of wildfire and forest harvesting on saproxylic beetles are greater than either disturbance alone.

020406080

100120140

0 500 1000 1500 2000 2500Number of individuals

Estim

ated

num

ber o

f spe

cies

GRNBRNHARSAL

- diversity

H1: Combined effects of wildfire and forest harvesting on saproxylic beetles are greater than either disturbance alone.

GRNBRNHARSAL

-1.5

-1.5

-0.5 0.5 1.5

-0.5

0.5

1.5

Axis 1

Axis

2

NMS OrdinationFinal Stress = 15.08

Variance explainedAxis 1 = 0.342Axis 2 = 0.454Cumulative = 0.796

- community level

H1: Combined effects of wildfire and forest harvesting on saproxylic beetles are greater than either disturbance alone.

Abs

olut

e de

part

ure

from

und

istu

rbed

catc

h ra

te (i

div.

/trap

-day

)

Glischrochilus siepmanni W.J.Brown(Nitidulidae; total catch = 64)

0.1

0.2

0.3

Pediacus fuscus Erichson(Cucujidae; total catch = 173)

0.5

1.0

1.5

Caenoscelis antennalis (Casey)(Cryptophagidae; total catch = 681)

2.0

4.0

6.0

8.0

BRN HAR SAL

negative

negative

positive

species level

H1: Combined effects of wildfire and forest harvesting on saproxylic beetles are greater than either disturbance alone.

Photo: Matti Koivula 2002Photo: Matti Koivula 2002

H2: Abundance of saproxylic beetle larvae is linked to changes in soil nutrients in near burned trees.

0.000.00

0.050.05

0.100.10

0.150.15

0.200.20

GRNGRN BRNBRN HARHAR SALSAL

Stand treatmentStand treatment

Mea

n ca

tch

rate

M

ean

catc

h ra

te

(indi

vidu

als/

trap

-day

)(in

divi

dual

s/tr

ap-d

ay)

H2: Abundance of saproxylic beetle larvae is linked to changes in soil nutrients in near burned trees.

1 Factor ANOVA (6 levels and 4 replicates = 24 enclosures)1 Factor ANOVA (6 levels and 4 replicates = 24 enclosures)

Levels: larvae abundance 0,2,5,8,10, Method CTRLLarvae allowed to feed for 2 years, soil samples collected once per yr

Experimental Design:

H2: Abundance of saproxylic beetle larvae is linked to changes in soil nutrients in near burned trees.

H2: Abundance of saproxylic beetle larvae is linked to changes in soil nutrients in near burned trees.

- Both years combined- Larval abundance corrected for mortality

0.0

2.0

4.0

6.0

8.0

0 2 4 6 8 10

pH

0.0

4.0

8.0

12.0

16.0

0 2 4 6 8 10

Tota

l C (%

)

0.00

0.20

0.40

0.60

0 2 4 6 8 10

Number of Larvae (corrected)

Tota

l N (%

)

0

40

80

120

160

0 2 4 6 8 10

Number of Larvae (corrected)

Extr

acta

ble

P (p

pm)

R2 = 0.2747p = 0.0005n = 40

R2 = 0.2504p = 0.0010n = 40

Summary• early support for both hypotheses:

H1: Combined effects of fire and harvesting

Community-level- salvage logging reduced saproxylic diversity and altered species assemblages more either fire or harvesting alone

Species-level- combined effects of fire and harvesting were greater than either disturbance alone for several species (e.g. M. scutellatus absent from SAL stands)

H2: linking beetle abundance to soil nutrients

- increased abundance of larval M. scutellatus increased total C and total N in the soil

J.K.Bedrick 2002

Implications?Implications?

Woody Debris Decomposition Soil ChemistryForest Regeneration

Woody Debris Decomposition Soil ChemistryForest Regeneration

Fire + HarvestingFire + Harvesting

Acknowledgements

Supervisors:Dr. John Spence (University of Alberta)Dr. Dave Langor (Canadian Forest Service)

Field Assistance:Iain Phillips (University of Alberta)Andrea Déchêne (University of Alberta)

Soil Chemistry:Dr. Barb Kishchuk (Canadian Forest Service)Martin Blank (Canadian Forest Service)Dr. Leonie Nadeau (Canadian Forest Service)

Taxonomic Assistance:Josh Jacobs (University of Alberta)

Funding and Logistical Support: