Moss lore
• Moss NPP is inversely proportional to vascular plant production
• Moss NPP ≥ black spruce in boreal forest
Hypotheses
1. Moss NPP and vascular NPP are inversely related
2. Moss NPP increases positively with vascular ANPP up to a critical value (e.g., canopy closure), and then decrease.
Vascular ANPP (g m-2 yr-1)
Mos
s N
PP
(g
m-2 y
r-1)
Mos
s N
PP
(g
m-2 y
r-1)
The first step: published moss NPP values for tundra and boreal forest
Boreal AK and CN = 39Tundra AK = 8Total studies = 47
Moss NPP (g m-2 yr-1)0 50 100 150 200
0
5
10
15
20
Cou
nt
0.0
0.1
0.2
0.3
0.4
Proportion per B
ar
TundraBoreal
BIOME
Boreal TundraBIOME
0
50
100
150
200
Mo
ss N
PP
(g
m-2 y
r-1)
Alaska: upland tundra and boreal forest
0 100 200 300 400 5000
50
100
150
200
TundraBoreal
BIOME
Mos
s N
PP
(g
m-2 y
r-1)
Vascular ANPP (g m-2 yr-1)
Alaska: upland tundra and boreal forest
0 100 200 300 400 5000
50
100
150
200
TundraBoreal
BIOME
Mos
s N
PP
(g
m-2 y
r-1)
Vascular ANPP (g m-2 yr-1)
Tundra slope = 0.5 (R2=0.51)Boreal slope = 0.1 (R2=0.40)Slopes sig. diff. @ P = 0.02
Why?
Alaska: upland tundra and boreal forest
0 100 200 300 400 5000
50
100
150
200
TundraBoreal
BIOME
Mos
s N
PP
(g
m-2 y
r-1)
Vascular ANPP (g m-2 yr-1)
Ruess et al. 2007 (most precise?)
Shaver and Chapin 1991(boreal multiplier?)
Canada: wetlands and uplands
WetlandUpland
Position
U
W
0 100 200 300 400Understory ANPP (g m-2 yr-1)
0
50
100
150
200
Mo
ss N
PP
(g
m-2 y
r-1)
U
U
U
W
W
W
W
What about wetlands?
Alaska: moss vs. spruce
0 100 200 300 40010
20
30
40
50
60
70
80
Mos
s N
PP
(g
m-2 y
r-1)
Spruce ANPP (g m-2 yr-1)
No relationship, but spruce is generally > moss
Conclusions
• Positive relationship between moss and vascular NPP
• More support for H2 than H1, but…– Small sample size; missing wetlands, other
veg. types– Variation in methods of measuring moss NPP
may make comparisons difficult– Future: find more data, explore methods for
measuring moss NPP, use meta-analytical techniques