Boreal moss communities: succession and implications for

establishment after fire in Alberta’s spruce-dominated forests

Michael SimpsonDepartment of Biological Sciences, University of Alberta

Supervisor: Dr Mark Dale

Polytrichum juniperinum

Funaria hygrometrica

Ceratodon purpureus

Bryum argenteum

Hylocomium splendens

Pleurozium schreberi

Ptilium crista-castrensis

RESEARCH OBJECTIVES

1. Successional change in boreal moss communities – characteristics and controls

A. Describe short-term variations in composition, diversity and species distribution in early-successional communities

B. Test hypotheses about controls on timing of establishment of late-successional feather mosses

C. Generate a model of species change over time

2. Implications for wider forest community• Effects of moss on post-fire recruitment of selected

conifer species

HYPOTHESES

Establishment and growth of feather mosses is controlled by:

• Available substrates– Early successional: mineral-based; high pH, low nutrients, dry

c.f. Late successional: high OM, low pH, high nutrients, moist

• Limited tolerance for low humidity, increased water loss– High exposure in early successional (open) stands

• Reproduction primarily asexual (vegetative propagation); delays dispersal of propagules

• Interactions between substrate, stand age, reproductive strategy

HYPOTHESIS 1: Establishment and growth of feather mosses is controlled by available substrates

1. Compare the establishment potential and growth of fragments of 2 feather mosses on burned and unburned substrates

Pleurozium schreberi

Ptiliumcrista-castrensis

Ash

Humus

Burned moss

Burned mineral soil

2 FRAGMENT SIZES

Small: unbranched, mean lengths: Ptilium5.6 mm Pleurozium 8.2 mm, dislodged using a soil sieve

Large: branching, ~ 4 cm long, cut with scissors

• 2.5” square plastic pots – 24 or 36 = 1 ‘block’

• 5 blocks per stand in:– SMALL frags: 3 early- &

1 late-successional stand

– LARGE frags: 1 late-successional stand

• Sunk into humus on forest floor

• Fragments tied to paper clips

• SMALL - 12 monthsLARGE - 3 months

12221018N =

SUBTYPE

Humus

Mineral soil

CONTROL

Burned moss

Mea

n +-

1 S

E SQ

RT(

leng

th)

5.0

4.5

4.0

3.5

3.0

2.5

SubstrateMea

n to

tal l

engt

h (s

quar

e-ro

ot tr

ans.

dat

a)

12221018N =

SUBTYPE

Humus

Mineral soil

CONTROL

Burned moss

Mea

n +-

1 S

E SQ

RT(

leng

th)

5.0

4.5

4.0

3.5

3.0

2.5

SubstrateMea

n to

tal l

engt

h (s

quar

e-ro

ot tr

ans.

dat

a)

12221018N =

SUBTYPE

Humus

Mineral soil

CONTROL

Burned moss

Mea

n +-

1 S

E SQ

RT(

leng

th)

5.0

4.5

4.0

3.5

3.0

2.5

SubstrateMea

n to

tal l

engt

h (s

quar

e-ro

ot tr

ans.

dat

a)

a aa

b

132220N =

Substrate

Humus

Mineral soil

Burned moss

#SHO

OTS

10

8

6

4

2

0

399

327

Med

ian

num

ber o

f sho

ots

per f

ragm

ent

Substrate

132220N =

Substrate

Humus

Mineral soil

Burned moss

#SHO

OTS

10

8

6

4

2

0

399

327

Med

ian

num

ber o

f sho

ots

per f

ragm

ent

Substrate

132220N =

Substrate

Humus

Mineral soil

Burned moss

#SHO

OTS

10

8

6

4

2

0

399

327

Med

ian

num

ber o

f sho

ots

per f

ragm

ent

Substrate

# shoots per fragment– Few shoots; no difference

between substrates

SMALL: Total length of fragments with living shoots– Only 2 Pleurozium fragments on

ash and 2 Ptilium fragments total with growth

– Fragments on all substrates significantly longer than initial length (P<0.05)

11715109N =

Substrate

Humus

Mineral soil

CONTROL

Burned moss

Ash

Squa

re ro

ot o

f mea

n LM

A8.0

7.5

7.0

6.5

6.0

5.5

91115108N =

Substrate

Humus

Mineral soil

CONTROL

Burned moss

Ash

Squa

re ro

ot o

f mea

n LM

A

7.4

7.2

7.0

6.8

6.6

6.4

6.2

6.0

5.8

Ptilium

Pleurozium

Mea

n le

ngth

of m

ain

axis

(mm

) (sq

uare

-root

tran

sfor

med

dat

a)

Substrate

b

a

a a a

a

bb

ab ab

11715109N =

Substrate

Humus

Mineral soil

CONTROL

Burned moss

Ash

Squa

re ro

ot o

f mea

n LM

A8.0

7.5

7.0

6.5

6.0

5.5

91115108N =

Substrate

Humus

Mineral soil

CONTROL

Burned moss

Ash

Squa

re ro

ot o

f mea

n LM

A

7.4

7.2

7.0

6.8

6.6

6.4

6.2

6.0

5.8

Ptilium

Pleurozium

Mea

n le

ngth

of m

ain

axis

(mm

) (sq

uare

-root

tran

sfor

med

dat

a)

Substrate

b

a

a a a

a

bb

ab ab

11715109N =

Substrate

Humus

Mineral soil

CONTROL

Burned moss

Ash

Num

ber o

f firs

t-ord

er s

ide

shoo

ts

7

6

5

4

3

2

1

0

-1

3117

168

162

185

91115108N =

Substrate

Humus

Mineral soil

CONTROL

Burned moss

Ash

Num

ber o

f firs

t-ord

er s

ide

shoo

ts

4.6

4.4

4.2

4.0

3.8

3.6

3.4

3.2

3.0

40

169

Ptilium

Pleurozium

Med

ian

num

ber o

f firs

t-ord

er s

ide

shoo

ts

Substrate

a

bbcdc

d

a

bc ab c ab

HYPOTHESIS 2: Establishment and growth of feather mosses is controlled by limited tolerance for exposure (low humidity, increased water loss)

1. Compare the establishment potential and growth of fragments of 2 species sown in recently burned (open) stands

2. Test for differences between 3 fragment sizes

• LARGE, SMALL, MULCH

• Soil surface excavated to ~ 2.5 cm and replaced with humus

• 5 blocks in 5 stands– 4 recently burned (open)– 1 late-successional

• 4 x 4 blocks marked out using plastic frame

• Fragments pinned/spread within squares

• Number of fragments with living shoots recorded after 12 months

Number of Pleurozium fragments recovered, and number of fragments found with shoots across all stands (August 2004)

38

4

46

43

15

40

5

10

15

20

25

30

35

40

45

50

BRANCHES MULCH SHOOT TIPS

Fragment size

Num

ber o

f fra

gmen

ts

0

5

10

15

20

25

30

35

40

45

50Number of fragments recovered

Number of fragments with shoots

Number of Ptilium fragments recovered, and number of fragments found with shoots (August 2004)

39

46

0

40

0 10

5

10

15

20

25

30

35

40

45

50

BRANCHES MULCH SHOOT TIPS

Fragment size

Num

ber o

f fra

gmen

ts

0

5

10

15

20

25

30

35

40

45

Number of fragments recovered

Number of fragments with shoots

43

15

4

40

1

46

4

38

46

39

0

Number of Ptilium fragments recovered, and number of fragments found with shoots (August 2004)

39

46

0

40

0 10

5

10

15

20

25

30

35

40

45

50

BRANCHES MULCH SHOOT TIPS

Fragment size

Num

ber o

f fra

gmen

ts

0

5

10

15

20

25

30

35

40

45

Number of fragments recovered

Number of fragments with shoots

39

46

0

40

0 10

5

10

15

20

25

30

35

40

45

BRANCHES MULCH SHOOT TIPS

Fragment size

Num

ber o

f fra

gmen

ts

0

5

10

15

20

25

30

35

40

Number of fragments recovered

Number of fragments with shootsNumber of Pleurozium fragments recovered after 12 months

and number of recovered fragments with living shoots

Number of Ptilium fragments recovered after 12 months and number of recovered fragments with living shoots

Living shoots (all stands)• Growth found in few

MULCH replicates• Few SMALL fragments

had living shoots• Almost all LARGE

fragments had living shoots

Number of fragments recovered

Number of fragments with shoots

OBJECTIVE 1: PRELIMINARY CONCLUSIONS

• Establishment and growth on burned/mineral substrates and in open stands possible

Therefore…• Timing of establishment of feather mosses

primarily a function of dispersal limitation, but…• Exposure and substrate influence timing

thorough interactions with fragment size– Larger fragments likely to be more successful, but…– Fewer of them– Long distance saltation dispersal = long process

(which may be accompanied by loss of viability)– Other vectors may be quicker – rare event?

OBJECTIVE 1 – PRELIMINARY CONCLUSIONS

• Suggests establishment by fragments is increasingly rare at greater distances from fire boundary– Spread from boundaries of fire and residuals limited– In the middle of large burns, post-fire recolonisation

likely to be slow• Do distant colonies establish from fragments?

– may occur primarily through spores• Recolonisation likely to be faster post-logging

– source of propagules in situ– would compress intermediate successional stages

and constrain opportunities of species associated with them

RESEARCH OBJECTIVES

1. Successional dynamics in boreal moss communities

A. Describe short-term variations in composition, diversity and species distribution in early-successional communities

B. Test hypotheses about controls on timing of establishment of late-successional feather mosses

C. Generate a model of species change over time

2. Implications for wider forest community• Effects of moss on post-fire recruitment of selected

conifer species

RESEARCH OBJECTIVES

Post-fire recruitment is influenced by early successional conditions

• Burned feather moss remains = ‘biological legacy’• ‘persisting living and dead structures’ left by disturbances’

(Franklin et al. 2002)

RESEARCH OBJECTIVES

Post-fire recruitment is influenced by early successional conditions

• Burned feather moss remains = ‘biological legacy’• ‘persisting living and dead structures’ left by disturbances’

(Franklin et al. 2002)• Dry; elevate seeds and seedlings

RESEARCH OBJECTIVES

Post-fire recruitment is influenced by early successional conditions

• Burned feather moss remains = ‘biological legacy’• ‘persisting living and dead structures’ left by disturbances

(Franklin et al. 2002)• Dry; elevate seeds and seedlings

• Previous studies indicate living moss carpets can enhance seed germination and seedling survival

• Moist; cover; moss-cyanobacteria associations might enhance seedling growth compared with open soil – N fixation

• Potential influence on understory and canopy spatial structure and composition

Assess the impact of:– BURNED MOSS– LIVING CARPETS OF EARLY SUCCESSIONAL MOSS

…on seed germination, and short-term survival and growth of seedlings of selected boreal tree species

BURNED MOSS - METHODS (SEEDLINGS)

• Seeds of Picea glauca and Larix laricina pre-germinated on moist filter paper in Petri plates.

• 10 germinants per species planted in 20 4-inch pots of burned moss, mineral soil or humus subsoil

• Pots in a growth chamber, watered every 3 days.

• Survival recorded periodically; mean dry weight and height after 97 days

Surviving Picea glauca and Larix laricina seedlings 92-97 days after sowing, as a proportion of seeds sown (N=150)

0.71

0.64

0.530.48

0.73

0.20

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

BURNED MINERAL SOIL SUB-SOIL BURNED MOSS

Substrate

Prop

ortio

n of

see

ds s

own

Picea glaucaLarix laricina

0.49

0.73

0.20

0.710.64

0.53

Surviving P. glauca and L. laricina seedlings 92-97 days after sowing, as a proportion of seeds sown (N=150)

Surviving Picea glauca and Larix laricina seedlings 23-28 days after sowing, as a proportion of seeds sown (N=150)

0.78 0.79

0.70

0.77

0.93

0.51

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

BURNED MINERAL SOIL SUB-SOIL BURNED MOSS

Substrate

Prop

ortio

n of

see

ds s

own

Picea glaucaLarix laricina

0.77

0.93

0.51

0.78 0.79

0.70

Surviving P. glauca and L. laricina seedlings 23-28 days after sowing, as a proportion of seeds sown (N=150)

SEEDLING SURVIVALBetween 28 and 97 days

after sowing:• For both species, survival

declined most on burned moss– L. laricina 51% to 20%– P. glauca 70% to 53%

At 97 days:• L. laricina survival lowest on

burned moss, highest on humus

• P. glauca survival lowest on burned moss, highest on mineral soil

126138124N =

Treatment

HumusMineral soilBurned moss

95%

CI l

og(W

t)

-2.0

-2.1

-2.2

-2.3

Picea glaucaa

ab

b

1489842N =

Treatment

HumusMineral soilBurned moss

95%

CI l

og(W

t)

-1.8

-1.9

-2.0

-2.1

-2.2

-2.3

-2.4

-2.5

Mea

n dr

y w

eigh

t (g)

(log

tran

sfor

med

dat

a)

Substrate

a

bb

Larix laricina

SEEDLING GROWTH

Mean dry weight• Both species: burned moss

significantly different from humus but not mineral soil (P<0.01)

Mean height• P. glauca - no significant

difference between substrates• L. laricina: burned moss

significantly different from humus but not mineral soil (P<0.01)

PRELIMINARY CONCLUSIONS

• Burned feather mosses are a poor substrate for survival of seedlings, esp. of L. laricina.– Conditions more amenable in growth

chamber?– NO SEEDLINGS on burned moss in field

trial!• Optimum growth of successful germinants will

not occur on burned moss • L. laricina likely to form minor component of

canopy in stands where burned moss had high cover

LIVE MOSS - METHODS

• Pilot study in field – low germination• Seeds of P. glauca, L. laricina and P. mariana

(black spruce) sown in trays on 3 treatments:– Moss present– Moss cleared– Open soil

• Controls sown on filter paper and Jiffy Pots©

• Germination and survival data collected weekly (ongoing)

Survival of Picea mariana seedlings as a proportion of seeds sown

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

7 14 21 28 35 42 49 56 63 70 77 84

Time since sowing (days)

Prop

ortio

n

Moss removedMoss presentOpen soilControl 2 (JP)

Survival of Larix laricina seedlings as a proportion of seeds sown

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

7 14 21 28 35 42 49 56 63 70 77 84

Time since sowing (days)

Prop

ortio

n

Moss removedMoss presentOpen soilControl 2 (JP)

Survival of L. laricina seedlings up to 84 days after sowing as a proportion of seeds sown

Survival of P. mariana seedlings up to 84 days after sowing as a proportion of seeds sown

Germination – All species• Very high on all treatments• Little difference between

treatments

Seedling survival• Little difference between

treatments for P. glauca• L. laricina – germination

highest but survival lowest on Open soil

• P. mariana – germination highest but survival lowest on Moss present

PRELIMINARY CONCLUSIONS

• Little difference between treatments– No effect on germination and survival?– Differences moderated in growth chamber?

• Effects on growth to be determined…• Mortality of L. laricina seedlings might be

lower in presence of early successional moss carpets?

• Mortality of P. mariana seedlings might be greater in moss patches?

ACKNOWLEDGEMENTS

• Dr. Mark Dale, Dr. J. F. Cahill, Dr. Dennis Gignac

• Chisholm-Dogrib Fire Research Initiative (Foothills Model Forest, Alberta), Alberta Conservation Association Grants for Biodiversity Research

• Alberta Sustainable Resource Development (Alberta Tree Improvement & Seed Centre)

• Devonian Botanic Garden• Steve Morse, Lindsay Elliot,

Alexandra Rutherford, Chris Drake, Jess Leatherdale, Rose Muto