Boreal moss communities: succession and implications for establishment after fire in Alberta’s spruce-dominated forests Michael Simpson Department of Biological Sciences, University of Alberta Supervisor: Dr Mark Dale
Funaria hygrometrica Hylocomium splendens
Ceratodon purpureus Ptilium cristacastrensis Bryum argenteum
Pleurozium schreberi Polytrichum juniperinum
RESEARCH OBJECTIVES 1. Successional change in boreal moss communities – characteristics and controls A. Describe short-term variations in composition, diversity and species distribution in earlysuccessional 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 Ptilium crista-castrensis
Pleurozium schreberi
Ash
Burned mineral soil
Burned moss
Humus
2 FRAGMENT SIZES
Large: branching, ~ 4 cm long, cut with scissors
Small: unbranched, mean lengths: Ptilium 5.6 mm Pleurozium 8.2 mm, dislodged using a soil sieve
• 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 latesuccessional stand
• Sunk into humus on forest floor • Fragments tied to paper clips • SMALL - 12 months LARGE - 3 months
– Only 2 Pleurozium fragments on ash and 2 Ptilium fragments total with growth
a
4.0
3.5
b
3.0
2.5 N=
18
10
22
12
l oi
Substrate
327
6
4
399
# shoots per fragment
2
0 N=
20
22
13
us m Hu
s al er in M l oi
s os m
Substrate Substrate
– Few shoots; no difference between substrates
us m Hu
s al er in M
SUBTYPE
L RO NT CO
s os m
8
a
a
4.5
ed rn Bu
10
ed rn Bu
#SHOOTSof shoots per fragment Median number
– Fragments on all substrates significantly longer than initial length (P<0.05)
Mean total length trans. data) Mean +- (square-root 1 SE SQRT(length)
SMALL: Total length of fragments with living shoots
5.0
7.5
7.0
a
a
a
6.5
b
6.0
5.5 10
5.8 N=
c
2 1
185
d
0
117 3
-1 N=
4.6
9
10
Pleurozium
4.4 4.2
bc
15
ab
c Substrate
7
11
a
us m Hu
6.0
b
l oi
6.2
bcd
3
L RO NT CO
b
168
s os m
b
4
ed rn Bu
6.6
162
5
sh
ab
ab
a
6
A
us m Hu
a
Substrate
6.8
6.4
11
l oi
7.0
7
s al er in M
7.2
L RO NT CO
s os m
Pleurozium
15
ed rn Bu
sh
7.4
9
Ptilium
s al er in M
N=
Medianside number Number of first-order shoots
a
of first-order side shoots side shoots Number of first-order
7
Ptilium
A
Mean length axis (mm) (square-root data) Square rootof of main mean LMA Square transformed root of mean LMA
8.0
ab
4.0 3.8 3.6
40 169
3.4 3.2 3.0
8
10
15
9
N=
8
10
15
9
us m Hu
l oi
Substrate Substrate
11
s al er in M
s os m
l oi
L RO NT CO
sh
ed rn Bu
A
us m Hu
s al er in M
s os m
L RO NT CO
sh
ed rn Bu
A
Substrate Substrate
11
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 â&#x20AC;˘ 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
46
5040
46 46
4535
Number of fragments Number of fragments
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 Pleurozium fragments recovered after 12 months 45 Number of Pleurozium fragments recovered, and number of fragments found with shoots Number of fragments with shoots 40 of recovered across all stands (August 2004) with living shoots and number fragments 39
4030
Number of fragments recovered
50 35 45 30
Number of fragments with shoots 43 43
40
38 38
40 25
3525
35
3020
30
2515
25
2010
10 20
20
15
15 5 10 0
0
BRANCHES
5
MULCH
44
15 1 15
0 10
SHOOT TIPS 5
Fragment size 4 4
0
5 15
0
BRANCHES MULCH SHOOT TIPS Number of Ptilium fragments recovered, and number of fragments found with Fragment size shoots (August 2004)
50
45
46 Numberrecovered of fragments recovered Number ofofPtilium fragments after 12 months Ptilium fragments Number recovered, and number of fragments found with and 45 Number of fragments with shoots shoots (August 2004)with living shoots number40of recovered fragments
5040
39
46 46
Number of fragments Number of fragments
4535 4030
40 40
40 45
Number of fragments recovered Number of fragments with shoots
40
39 39
35
3525
30
3020
25
2515 20
2010 15
15 5
Number of fragments recovered Number of fragments with shoots
10 0 5
BRANCHES
0
1
MULCH
SHOOT TIPS
Fragment size 00
0 BRANCHES
MULCH Fragment size
10
5
1
1 SHOOT TIPS
0
35
30
25
20
15
10
5
0
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 earlysuccessional 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 â&#x20AC;˘
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’ • •
•
Previous studies indicate living moss carpets can enhance seed germination and seedling survival •
•
‘persisting living and dead structures’ left by disturbances (Franklin et al. 2002) Dry; elevate seeds and seedlings
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
•
For both species, survival declined most on burned moss – L. laricina 51% to 20% – P. glauca 70% to 53%
1.00 0.90
0.70
Picea glauca Larix laricina
0.93 0.93
0.80
Proportion of seeds sown
SEEDLING SURVIVAL Between 28 and 97 days after sowing:
Surviving P. glauca and L. laricina seedlings 23-28 days after Surviving Picea glauca and Larix laricina seedlings 23-28 days after sowing, as aasproportion ofseeds seeds sown (N=150) sowing, a proportion of sown (N=150)
0.78 0.78
0.77 0.77
0.79 0.79 0.70 0.70
0.60 0.50
0.51 0.51
0.40 0.30 0.20 0.10 0.00 BURNED MINERAL SOIL
SUB-SOIL
BURNED MOSS
Substrate
At 97 days:
•
L. laricina survival lowest on burned moss, highest on humus P. glauca survival lowest on burned moss, highest on mineral soil
1.00
Picea glauca Larix laricina
0.90 0.80 0.70 Proportion of seeds sown
•
Surviving P. glauca and L. laricina seedlings 92-97 days after Surviving Picea glauca and Larix laricina seedlings 92-97 days after sowing, as a proportion of seeds sown (N=150) sowing, as a proportion of seeds sown (N=150)
0.73 0.73
0.71 0.71 0.64 0.64
0.60
0.53 0.53
0.50
0.48 0.49 0.40 0.30 0.20
0.20 0.20
0.10 0.00 BURNED MINERAL SOIL
SUB-SOIL Substrate
BURNED MOSS
-2.0
Picea glauca
SEEDLING GROWTH Mean dry weight (g) (log95% transformed CI log(Wt) data)
Mean height • P. glauca - no significant difference between substrates • L. laricina: burned moss significantly different from humus but not mineral soil (P<0.01)
-2.1
95% CI log(Wt)
Mean dry weight • Both species: burned moss significantly different from humus but not mineral soil (P<0.01)
a
ab b
-2.2
-2.3 N=
-1.8
124
138
126
Burned moss
Mineral soil
Humus
Larix Treatment
a
laricina
-1.9
-2.0
-2.1
b
-2.2
b
-2.3
-2.4 -2.5 N=
42
98
148
Burned moss
Mineral soil
Humus
Treatment
Substrate
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)
1 0.9 0.8 0.7
Proportion
Germination – All species • Very high on all treatments • Little difference between treatments
Survival of L. laricina seedlings up to 84 days after sowing as a Survival of Larix laricina seedlings as a proportion of seeds sown proportion of seeds sown
0.6 0.5 0.4 0.3
Moss removed Moss present Open soil Control 2 (JP)
0.2 0.1 0 7
14
21
28
35
42
49
56
63
70
77
84
Time since sowing (days)
Survival ofSurvival P. mariana seedlings up to 84 days after sowing as a of Picea mariana seedlings as a proportion of seeds sown proportion of seeds sown 1 0.9 0.8 0.7
Proportion
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
0.6 0.5 0.4 0.3
Moss removed Moss present Open soil Control 2 (JP)
0.2 0.1 0 7
14
21
28
35
42
49
56
Time since sowing (days)
63
70
77
84
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