Seasonal bryophyte productivity in the sub‐Arctic: a comparison with vascular plants

Abstract

Summary1. Arctic ecosystems are experiencing rapid climate change, which could result in positive feedbacks on climate warming if ecosystem carbon (C) loss exceeds C uptake through plant growth. Bryophytes (mosses, liverworts and hornworts) are important components of Arctic vegetation, but are currently not well represented in terrestrial C models; in particular, seasonal patterns in bryophyte C metabolism compared to vascular plant vegetation are poorly understood. 2. Our objective was to quantify land-surface CO 2 fluxes for common sub-Arctic bryophyte patches (dominated by Polytrichum piliferum and Sphagnum fuscum) in spring (March-May) and during the summer growing season (June-August) and to develop a simple model of bryophyte gross primary productivity fluxes (P B ). We use the model to explore the key environmental controls over P B for P. piliferum and S. fuscum and compare seasonal patterns of productivity with those of typical vascular plant communities at the same site. 3. The modelled total gross primary productivity (RP B ) over 1 year (March -November) for P. piliferum was c. 360 g C m )2 ground and for S. fuscum c. 112 g C m )2 ground, c. 90% and 30% of total gross primary productivity for typical vascular plant communities (RP V ) over the same year. In spring (March-May), when vascular plant leaves are not fully developed, RP B for P. piliferum was 3 · RP V . 4. Model sensitivity analysis indicated that bryophyte turf water content does not significantly affect (March-November) RP B for P. piliferum and S. fuscum, at least for periods without sustained lack of precipitation. However, we find that seasonal changes in bryophyte photosynthetic capacity are important in determining RP B for both bryophyte species. 5. Our study implies that models of C dynamics in the Arctic must include a bryophyte component if they are intended to predict the effects of changes in the timing of the growing season, or of changes in vegetation composition, on Arctic C balance.

Improving a plot-scale methane emission model and its performance at a northeastern Siberian tundra site

“…We attribute this to the fact that FW1 and TW3 are groups with a very low vegetation canopy, with mossdominated vegetation and low vegetation total biomass, under which conditions the photosynthesis is driven more by soil water and temperature than by light. Similar results can be found from recent studies (Zona et al, 2011;Street et al, 2012). The results from two GPP calculation methods do not differ significantly except for FW2.…”

Pan-Arctic modelling of net ecosystem exchange of CO 2

“…We also underestimate LAI when the canopy includes a high proportion of closely appressed, overlapping leaves, especially Cassiope tetragona [31]. Finally, our estimate of LAI assumes that mosses do not contribute to the photosynthetic surface area despite the important contributions of moss photosynthesis to NEE [32,33]. Most of these errors in estimation of leaf area would vary in relation to species composition, and thus would appear as 'species effects' on estimates of NEE.…”

Parameter Sensitivity of the Arctic Biome–BGC Model for Estimating Evapotranspiration in the Arctic Coastal Plain

“…For example, Euskirchen et al (2009) forcing if these changes occur on the same time scales as those studied by Euskirchen et al (2009). Bryophyte and lichen species composition may also play an important role in snow capture and melt; Street et al (2011a) observed that patches of Polytrichum spp. at Abisko were the first to thaw in the spring on account of their microtopographical position on the tops of small ridges and their low albedo (Fig.…”