The influence of soil drainage and moss species composition on carbon budgets of contrasting boreal black spruce forest communities

Mature black spruce forests (Picea mariana) store more carbon (C) than other forest types Oack pine, aspen) in the central North American boreal forest. At least two contrasting black spruce forest communities exist: closed-canopy black spruce overstory with a continuous feathermoss (Pleurozium schreberi and Hylocomium splendens) ground cover, and open-canopy black spruce overstory with a Sphagnum spp. ground cover.; 1 focused my research on the two contrasting black spruce communities—black spruce with feathermoss (BSFM) and black spruce with sphagnum (BSSP)—to better understand (1) factors controlling the distribution of ground cover species in black spruce forests, (2) C and light use dynamics of black spruce forests, and (3) soil surface CO₂ flux and net ecosystem production (NEP).; Sphagnum presence was related to the position of the water table relative to the peat layer, and it was restricted to growing in poorly-drained areas. In comparison, feathermoss occurred in a wider range of microenvironments and was not related to depth of the water table. Average net primary production (NPP) for 1998 was over three times greater for sphagnum than feathermoss (171 g m−2 yr−1 vs. 53 g m −2 yr−1).; The BSFM community had significantly greater (p = 0.04) NPP (446 g m −2 yr−1) than the BSSP community (276 g m−2 yr−1). Bryophytes comprised the greatest fraction of total NPP (42%) in the BSSP community whereas fine root NPP was the largest component of total NPP (50%) in the BSFM community. Light use efficiency was significantly greater (p = 0.001) for the BSFM community (0.2 g MJ−1 annual APAR) than the BSSP community (0.15 g MJ−1 annual APAR). The NEP of the BSFM community (259 ± 35 g C m−2 yr−1) was a significantly greater (p = 0.03) source of CO₂ to the atmosphere than the BSSP community (−151 + 15 g C m−2 yr −1).; The results of this study illustrate the need to accurately measure and model ground cover species composition of boreal forests. The different C budgets of the two black spruce communities suggest that the two communities should be distinguished when simulating C dynamics for boreal black spruce forests.