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Lichens and bryophytes are abundant primary producers in high latitude and high elevation ecosystems, and they play an important role in ecosystem processes such as decomposition and nutrient cycling. Despite their importance, little is known about the decomposability of lichens and bryophytes either among or within species, at the whole community level, or how this decomposability is affected by their functional traits. Here, we studied decomposability of lichens and bryophytes at the community‐level and individual species‐level (using 21 species and genera) collected from an elevational gradient in alpine Norway. In order to isolate the elevation effect on litter quality, we used a standardized laboratory bioassay to measure decomposability. In contrast to our expectations, we found that community‐level decomposability of lichens and bryophytes increased with elevation and thus decreasing temperature. In contrast, phosphorus release from the litter decreased with elevation while nitrogen release was unresponsive. Decomposability was explained by nutrient concentrations, litter pH and primary producer group identity (lichens versus bryophytes) at both the individual species and community levels. Species turnover (changes in species composition and abundance) was the main driver of decomposability across elevation at the community level, despite some of the traits explaining decomposability showing high intraspecific variability. Our study highlights the importance of among‐species variation in determining lichen and bryophyte decomposability. Further, the higher decomposability that we found for higher elevations suggests that global warming might result in a shift towards slower decomposable lichen and bryophyte species. [ABSTRACT FROM AUTHOR]

Across environmental gradients, community‐level functional traits of plants can change due to species turnover, intraspecific variation and their covariation. Studies on vascular plants suggest that species turnover is the main driver of trait variation across gradients, although intraspecific variation can also be important. However, there is limited knowledge about whether this holds for non‐vascular primary producers such as lichens and bryophytes. We hypothesized that intraspecific variation is more important for non‐vascular than for vascular primary producers because they lack specialized structures to maintain homeostasis and should therefore be more responsive to extrinsic factors.To assess the relative importance of species turnover versus intraspecific variation for vascular plants, lichens and bryophytes, we estimated species abundance and measured chemical (tissue nitrogen (N) and phosphorous (P) content, N:P ratio and pH) and non‐chemical (specific leaf or thallus area, dry matter content and water holding capacity) functional traits along an elevational gradient in alpine southern Norway. We calculated community‐weighted mean traits and quantified the relative contribution of species turnover, intraspecific variation and their covariation to total trait variation across the gradient.We found mixed support for our hypothesis: the contribution of intraspecific variation to total trait variation for N and N:P was higher in lichens than in vascular plants and bryophytes, but in general the contribution of intraspecific variation differed among functional traits and producer groups. Nutrient variables (N, P and N:P) were significantly impacted by intraspecific variation for vascular plants and lichens but not for bryophytes. Non‐chemical traits and pH were mainly driven by species turnover effects in all primary producer groups.Our results highlight that while nearly all studies on primary producer trait variation across environments have focused on vascular plants, trait variation of other largely neglected but ecologically important producer groups, such as lichens and bryophytes, may show very different responses to the same environmental factors. In order to fully understand how future environmental changes impact on community‐ and ecosystem‐level processes, traits of primary producers other than vascular plants—and their within‐species variation—need to be considered in systems where these groups are abundant. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

We studied the effects of different mat-forming lichens on microclimate and litter decomposition in an alpine ecosystem where lichens constitute a major part of the vegetation. We used four lichens with contrasting colour and water-holding capacity. We recorded soil temperature and moisture, and decomposition rate of plant litter under the different lichen mats and in bare soil. While soil temperature and freeze-thaw cycles were reduced under all lichen mats compared to bare soil, Cladonia rangiferina/ Cladonia stygia insulated stronger than other lichens. Litter decomposition was faster under Flavocetraria nivalis than under Alectoria ochroleuca , but this was not related to lichen traits or microclimate. We conclude that insulation by lichen mats is stronger with higher water-holding capacity, and we suggest that microbial communities associated with different lichens have a larger effect on litter decomposition than soil conditions. Our findings highlight the importance of mat-forming lichens on microclimate and ecosystem processes in alpine environments. [ABSTRACT FROM AUTHOR]