Absence of snow cover reduces understory plant cover and alters plant community composition in boreal forests

Abstract

Snow regimes affect biogeochemistry of boreal ecosystems and are altered by climate change. The effects on plant communities, however, are largely unexplored despite their influence on relevant processes. Here, the impact of snow cover on understory community composition and below-ground production in a boreal Picea abies forest was investigated using a long-term (8-year) snow cover manipulation experiment consisting of the treatments: snow removal, increased insulation (styrofoam pellets), and control. The snow removal treatment caused longer (118 vs. 57 days) and deeper soil frost (mean minimum temperature -5.5 vs. -2.2°C) at 10 cm soil depth in comparison to control. Understory species composition was strongly altered by the snow cover manipulations; vegetation cover declined by more than 50% in the snow removal treatment. In particular, the dominant dwarf shrub Vaccinium myrtillus (-82%) and the most abundant mosses Pleurozium schreberi (-74%) and Dicranum scoparium (-60%) declined strongly. The C:N ratio in V. myrtillus leaves and plant available N in the soil indicated no altered nitrogen nutrition. Fine-root biomass in summer, however, was negatively affected by the reduced snow cover (-50%). Observed effects are attributed to direct frost damage of roots and/ or shoots. Besides the obvious relevance of winter processes on plant ecology and distribution, we propose that shifts in the vegetation caused by frost damage may be an important driver of the reported alterations in biogeochemistry in response to altered snow cover. Understory plant performance clearly needs to be considered in the biogeochemistry of boreal systems in the face of climate change.

Complex Changes in Plant Communities across a Subarctic Alpine Tree Line in Labrador, Canada + Supplementary Appendix Table (See Article Tools)

“…Wind transport of snow is expected to be greatly reduced in a warmer winter (as happened in this region in 2010), when wetter snowfall and more frequent icing occur, implying that snow distribution patterns could become more uniform at higher elevations under a warmer climate. More uniformity in snow distribution patterns could influence plant communities by favouring the establishment of individuals in exposed areas that would previously have been relatively snow-free throughout the winter and by potentially shifting away from species that benefited from longlasting snow-cover in depressions or snow berms (Kreyling et al, 2012). Recent temperature increases, as drivers of snow pattern change as well as possible soil moisture deficits, are expected to have contrasting effects on the trajectories of plant communities (Crimmins et al, 2011).…”

Impacts of Climate Change on Vegetation Distribution No. 1 -- Climate Change Induced Vegetation Shifts in the Palearctic Region

“…Thus, the study demonstrates that both bryophytes and vascular plants at boreal mires exhibit a time lag of more than five years in response to nitrogen and temperature rise. The slow and gradual shift from Kreyling et al (2012) showed in an experiment conducted in a boreal Picea abies forest that understory species composition was strongly altered by snow cover manipulations and vegetation cover, in particular the dominant dwarf shrub Vaccinium myrtillus (bilberry) and the most abundant mosses, significantly declined in the snow removal treatment. As a conclusion, shifts are caused in vegetation by frost damage as well.…”

Canopy cover and understory composition determine abundance of Vaccinium myrtillus L., a key plant for capercaillie (Tetrao urogallus), in subalpine forests in the Pyrenees

“…V. myrtillus cover was positively correlated with precipitation and longitude (geographic location). Both factors may reflect the important influence of climate and microclimate on this species as reported in boreal and high mountain forests (Löffler 2007;Rasmus et al 2011;Kreyling et al 2012). For instance, the greatest annual precipitation was found in the Atalaiador and Vila sites, which also showed the greatest covers of V. myrtillus and mosses in the study area, and a high floristic similarity among both sites.…”