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