1. Moss lore Moss NPP is inversely proportional to vascular plant production Moss NPP ≥ black spruce in boreal forest

2. 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 ) Moss NPP (g m -2 yr -1 )

3. The first step: published moss NPP values for tundra and boreal forest Boreal AK and CN = 39 Tundra AK = 8 Total studies = 47 Moss NPP (g m -2 yr -1 ) 050100150200 0 5 10 15 20 Count 0.0 0.1 0.2 0.3 0.4 Proportion per Bar Tundra Boreal BIOME BorealTundra BIOME 0 50 100 150 200 Moss NPP (g m -2 yr -1 )

4. Alaska: upland tundra and boreal forest 0100200300400500 0 50 100 150 200 Tundra Boreal BIOME Moss NPP (g m -2 yr -1 ) Vascular ANPP (g m -2 yr -1 )

5. Alaska: upland tundra and boreal forest 0100200300400500 0 50 100 150 200 Tundra Boreal BIOME Moss NPP (g m -2 yr -1 ) Vascular ANPP (g m -2 yr -1 ) Tundra slope = 0.5 (R 2 =0.51) Boreal slope = 0.1 (R 2 =0.40) Slopes sig. diff. @ P = 0.02 Why?

6. Alaska: upland tundra and boreal forest 0100200300400500 0 50 100 150 200 Tundra Boreal BIOME Moss NPP (g m -2 yr -1 ) Vascular ANPP (g m -2 yr -1 ) Ruess et al. 2007 (most precise?) Shaver and Chapin 1991 (boreal multiplier?)

7. Canada: wetlands and uplands Wetland Upland Position U W 0100200300400 Understory ANPP (g m -2 yr -1 ) 0 50 100 150 200 Moss NPP (g m -2 yr -1 ) U U U W W W W What about wetlands?

8. Alaska: moss vs. spruce 0100200300400 10 20 30 40 50 60 70 80 Moss NPP (g m -2 yr -1 ) Spruce ANPP (g m -2 yr -1 ) No relationship, but spruce is generally > moss

9. 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